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Reexamination of $^{6}$Li scattering as a Probe to Investigate the
Isoscalar Giant Resonances in Nuclei: Inelastic ${}^{6}$Li scattering at 100 MeV/u on ${}^{12}$C and ${}^{93}$Nb
have been measured with the high-resolution magnetic spectrometer Grand Raiden.
The magnetic-rigidity settings of the spectrometer covered excitation energies
from 10 to 40 MeV and scattering angles in the range $0^\circ <
\theta_{\text{lab.}}< 2^\circ$. The isoscalar giant monopole resonance was
selectively excited in the present data. Measurements free of instrumental
background and the very favorable resonance-to-continuum ratio of ${}^{6}$Li
scattering allowed for precise determination of the $E0$ strengths in
${}^{12}$C and ${}^{93}$Nb. It was found that the monopole strength in
${}^{12}$C exhausts $52 \pm 3^\text{(stat.)} \pm 8 ^\text{(sys.)}$\% of the
energy-weighted sum rule (EWSR), which is considerably higher than results from
previous $\alpha$-scattering experiments. The monopole strength in ${}^{93}$Nb
exhausts $92 \pm 4^\text{(stat.)} \pm 10 ^\text{(sys.)}$\% of the EWSR, and it
is consistent with measurements of nuclei with mass number of $A\approx90$.
Such comparison indicates that the isoscalar giant monopole resonance
distributions in these nuclei are very similar, and no influence due to nuclear
structure was observed. | nucl-ex |
"QM19 summary talk": Outlook and future of heavy-ion collisions: A summary of the QM19 conference is given by highlighting a few selected
results. These are discussed as examples to illustrate the exciting future of
heavy-ion collisions and the need for further instrumentation. (The arXiv
version is significantly longer than the printed proceedings, with more
figures.) | nucl-ex |
Highlights of Crystal Ball Physics: Differential and total cross sections are presented for pi- - and K- -induced
reactions on a proton target leading to all-neutral final states. Also shown
are rates for rare and upper limits for forbidden eta-meson decays to test
Chiral Perturbation Theory, the pi0-pi0 interactions and C and CP invariance. | nucl-ex |
Moments of Spin Structure Functions: Sum Rules and Polarizabilities: Nucleon structure study is one of the most important research areas in modern
physics and has challenged us for decades. Spin has played an essential role
and often brought surprises and puzzles to the investigation of the nucleon
structure and the strong interaction. New experimental data on nucleon spin
structure at low to intermediate momentum transfers combined with existing high
momentum transfer data offer a comprehensive picture in the strong region of
the interaction and of the transition region from the strong to the
asymptotic-free region. Insight for some aspects of the theory for the strong
interaction, Quantum Chromodynamics (QCD), is gained by exploring lower moments
of spin structure functions and their corresponding sum rules. These moments
are expressed in terms of an operator-product expansion using quark and gluon
degrees of freedom at moderately large momentum transfers. The higher-twist
contributions have been examined through the evolution of these moments as the
momentum transfer varies from higher to lower values. Furthermore, QCD-inspired
low-energy effective theories, which explicitly include chiral symmetry
breaking, are tested at low momentum transfers. The validity of these theories
is further examined as the momentum transfer increases to moderate values. It
is found that chiral perturbation theory calculations agree reasonably well
with the first moment of the spin structure function g_1 at low momentum
transfer of 0.05 - 0.1 GeV^2 but fail to reproduce some of the higher moments,
noticeably, the neutron data in the case of the generalized polarizability
Delta_LT. The Burkhardt-Cottingham sum rule has been verified with good
accuracy in a wide range of Q^2 assuming that no singular behavior of the
structure functions is present at very high excitation energies. | nucl-ex |
The PHOBOS Glauber Monte Carlo: ``Glauber'' models are used to calculate geometric quantities in the initial
state of heavy ion collisions, such as impact parameter, number of
participating nucleons and initial eccentricity. The four RHIC experiments have
different methods for Glauber Model calculations, leading to similar results
for various geometric observables. In this document, we describe an
implementation of the Monte Carlo based Glauber Model calculation used by the
PHOBOS experiment. The assumptions that go in the calculation are described. A
user's guide is provided for running various calculations. | nucl-ex |
Towards the Quark Gluon Plasma: We discuss recent experimental results in the field of ultra-relativistic
nuclear collisions. The emerging ``picture'' is a collectively expanding,
initially hot and dense fireball in which strangeness- and low-mass di-lepton
pair production are enhanced and J/$\Psi$ production is suppressed compared to
expectations from nucleon-nucleon collisions. It is argued that, taken
together, these data provide circumstantial evidence that a (at least partly)
partonic phase was produced in such collisions. | nucl-ex |
Searching for three-nucleon short-range correlations: Electron scattering measurements from high-momentum nucleons in nuclei at
SLAC and Jefferson Lab (JLab) have shown that these nucleons are generally
associated with two-nucleon short-range correlations (2N-SRCs). These SRCs are
formed when two nucleons in the nucleus interact at short distance via the
strong tensor attraction or repulsive core of the NN potential. A series of
measurements at JLab have mapped out the A dependence and isospin dependence of
2N-SRCs, and have begun to map out their momentum structure. However, we do not
yet know if 3N-SRCs, similar high-momentum configurations of three nucleons,
play an important role in nuclei. We summarize here previous attempts to
isolate 3N-SRCs, go over the limitations of these previous attempts, and
discuss the present and near-term prospects for searching for 3N-SRCs, mapping
out their A dependence in nuclei, and constraining their isospin and momentum
structure. | nucl-ex |
A new method for the experimental study of topological effects in the
quark-gluon plasma: A new method is presented for the quantitative measurement of charge
separation about the reaction plane. A correlation function is obtained whose
shape is concave when there is a net separation of positive and negative
charges. Correlations not specifically associated with charge, from flow, jets
and momentum conservation, do not influence the shape or magnitude of the
correlation function. Detailed simulations are used to demonstrate the
effectiveness of the method for the quantitative measurement of charge
separation. Such measurements are a pre-requisite to the investigation of
topological charge effects in the QGP as derived from the "strong $\cal{CP}$
problem". | nucl-ex |
Nuclear track emulsion in search for the Hoyle-state in dissociation of
relativistic ${}^{12}$C nuclei: Production of ensembles of $\alpha$-particle triples associated with the
Hoyle state (the second excited state of the ${}^{12}$C nucleus) in peripheral
dissociation of relativistic ${}^{12}$C nuclei is studied. Stacks of nuclear
track emulsion pellicles exposed to ${}^{12}$C with an energy from hundreds MeV
to a few GeV per nucleon serve as the material for studies. The Hoyle state
decays are reconstructed via measurement of emission angles of $\alpha$
particles with the precision sufficient for identification of the unstable
${}^{8}$Be nucleus. The estimate of the contribution of Hoyle's state to the
${}^{12}$C $\to$ 3$\alpha$ dissociation is 10-15\%. | nucl-ex |
Potential for measurement of the tensor electric and magnetic
polarizabilities of the deuteron in storage-ring experiments with polarized
beams: Measurement of the tensor electric and magnetic polarizabilities of the
deuteron is of great interest, especially in connection with the possibilities
of COSY and GSI. These polarizabilities can be measured in storage rings by the
frozen spin method providing a disappearance of g-2 precession. This method
will be used in the planned deuteron electric-dipole-moment experiment in
storage rings. The tensor electric polarizability of the deuteron significantly
influences the buildup of the vertical polarization in the above experiment.
The spin interactions depending on the electric dipole moment, the tensor
electric polarizability, and main systematical errors caused by field
misalignments have very different symmetries. For the considered experimental
conditions, the sensitivity to the deuteron EDM of $1\times10^{-29} e\cdot$cm
corresponds to measuring the both of tensor polarizabilities with an accuracy
of $\delta\alpha_T\approx\delta\beta_T\approx5\times10^{-42}$ cm$^3$. This
conservative estimate can be improved by excluding the systematical error
caused by the field instability which is negligible for the measurement of the
tensor polarizabilities. To find the tensor magnetic polarizability, the
horizontal components of the polarization vector should be measured. | nucl-ex |
Bulk Properties of the System Formed in Au+Au Collisions at
$\sqrt{s_{\mathrm{NN}}}$ = 14.5 GeV: We report systematic measurements of bulk properties of the system created in
Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 14.5 GeV recorded by the STAR
detector at the Relativistic Heavy Ion Collider (RHIC).The transverse momentum
spectra of $\pi^{\pm}$, $K^{\pm}$ and $p(\bar{p})$ are studied at mid-rapidity
($|y| < 0.1$) for nine centrality intervals. The centrality, transverse
momentum ($p_T$),and pseudorapidity ($\eta$) dependence of inclusive charged
particle elliptic flow ($v_2$), and rapidity-odd charged particles directed
flow ($v_{1}$) results near mid-rapidity are also presented. These measurements
are compared with the published results from Au+Au collisions at other
energies, and from Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. The
results at $\sqrt{s_{\mathrm{NN}}}$ = 14.5 GeV show similar behavior as
established at other energies and fit well in the energy dependence trend.
These results are important as the 14.5 GeV energy fills the gap in $\mu_B$,
which is of the order of 100 MeV,between $\sqrt{s_{\mathrm{NN}}}$ =11.5 and
19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor
agreement in general. | nucl-ex |
Optical Alignment System for the PHENIX Muon Tracking Chambers: A micron-precision optical alignment system (OASys) for the PHENIX muon
tracking chambers is developed. To ensure the required mass resolution of
vector meson detection, the relative alignment between three tracking station
chambers must be monitored with a precision of 25$\mu$m. The OASys is a
straightness monitoring system comprised of a light source, lens and CCD
camera, used for determining the initial placement as well as for monitoring
the time dependent movement of the chambers on a micron scale. | nucl-ex |
Reactions of a Be-10 beam on proton and deuteron targets: The extraction of detailed nuclear structure information from transfer
reactions requires reliable, well-normalized data as well as optical potentials
and a theoretical framework demonstrated to work well in the relevant mass and
beam energy ranges. It is rare that the theoretical ingredients can be tested
well for exotic nuclei owing to the paucity of data. The halo nucleus Be-11 has
been examined through the 10Be(d,p) reaction in inverse kinematics at
equivalent deuteron energies of 12,15,18, and 21.4 MeV. Elastic scattering of
Be-10 on protons was used to select optical potentials for the analysis of the
transfer data. Additionally, data from the elastic and inelastic scattering of
Be-10 on deuterons was used to fit optical potentials at the four measured
energies. Transfers to the two bound states and the first resonance in Be-11
were analyzed using the Finite Range ADiabatic Wave Approximation (FR-ADWA).
Consistent values of the spectroscopic factor of both the ground and first
excited states were extracted from the four measurements, with average values
of 0.71(5) and 0.62(4) respectively. The calculations for transfer to the first
resonance were found to be sensitive to the size of the energy bin used and
therefore could not be used to extract a spectroscopic factor. | nucl-ex |
Mid-rapidity anti-baryon to baryon ratios in pp collisions at $\sqrt{s}$
= 0.9, 2.76 and 7 TeV measured by ALICE: The ratios of yields of anti-baryons to baryons probes the mechanisms of
baryon-number transport. Results for $\bar{\rm p}/{\rm p}$, $\bar{\rm
\Lambda}/{\rm \Lambda}$, $\rm\bar{\Xi}$$^{+}/{\rm \Xi}^{-}$ and
$\rm\bar{\Omega}$$^{+}/{\rm \Omega}^{-}$ in pp collisions at $\sqrt{s} = 0.9$,
2.76 and 7 TeV, measured with the ALICE detector at the LHC, are reported.
Within the experimental uncertainties and ranges covered by our measurement,
these ratios are independent of rapidity, transverse momentum and multiplicity
for all measured energies. The results are compared to expectations from event
generators, such as PYTHIA and HIJING-B, that are used to model the particle
production in pp collisions. The energy dependence of $\bar{\rm p}/{\rm p}$,
$\bar{\rm \Lambda}/{\rm \Lambda}$, $\rm\bar{\Xi}$$^{+}/{\rm \Xi^{-}}$ and
$\rm\bar{\Omega}$$^{+}/{\rm \Omega^{-}}$, reaching values compatible with unity
for $\sqrt{s} = 7$ TeV, complement the earlier $\bar{\rm p}/{\rm p}$
measurement of ALICE. These dependencies can be described by exchanges with the
Regge-trajectory intercept of $\alpha_{\rm {J}} \approx 0.5$, which are
suppressed with increasing rapidity interval ${\rm \Delta} y$. Any significant
contribution of an exchange not suppressed at large ${\rm \Delta} y$ (reached
at LHC energies) is disfavoured. | nucl-ex |
Positrons at JLab - Advancing Nuclear Science in Hall B: In this talk I address two high impact physics programs that require the use
of polarized and unpolarized positron beams in addition to using electron beams
of the same energy. First, I address what will be gained from using positron
beams in addition to electron beams in the extraction of the Compton Form
Factors (CFFs) and generalized parton distributions (GPDs) from Deeply Virtual
Compton Scattering (DVCS) on a proton target. As a second high impact science
program I discuss an experimental scenario using unpolarized positrons to
measure elastic scattering on protons in an effort to determine definitively
the 2-photon exchange contributions in order to resolve a longstanding
discrepancy in the determination of the proton's electric and magnetic form
factors. | nucl-ex |
On the Microscopic Level Density Models for Nuclei Near Z=28 Shell
Closure: A comprehensive test of level density models for explaining the decay of
excited compound nuclei, 54 Mn, 56 Fe, 58 Co, 60 Ni, 61 Ni and 63 Cu, in the
energy range of 28 - 36 MeV has been performed. The compound nuclei of interest
in the desired ranges are populated using 6 Li based transfer reactions. The
proton decay spectrum for each excitation energy bins has been measured. The
measured proton spectrum has been reproduced using statistical model
calculations with different level density models. A variance minimised approach
has been employed for analysing the prediction capability of different level
density models. This approach has been converged to Gogny
Hartree-Fock-Bogoliubov(HFB) microscopic level density model and which is
attributed as the most accurate model for the desired nuclei. | nucl-ex |
J/$ψ$ and $ψ$(2S) Production in Small Systems with PHENIX: The suppression of the $\psi$(2S) nuclear modification factor has been seen
as a trademark signature of final state effects in large collision systems for
decades. In small systems, deviations of the nuclear modification from unity
had been attributed to cold nuclear matter effects until the observation of
strong differential suppression of the $\psi$(2S) state in $p/d+$A collisions,
which suggests the presence of final state effects. In this paper, we present
results of J/$\psi$ and $\psi$(2S) measurements in the dimuon decay channel for
$p+p$, $p+$Al, and $p+$Au collision systems at $\sqrt{s_{_{NN}}}$ = 200 GeV.
Key results include the nuclear modification factors $R_{pA}$ as a function of
centrality and rapidity. The measurements are compared with shadowing and
transport model predictions, as well as to complementary measurements at LHC
energies. | nucl-ex |
Elliptic flow of charged pions, protons and strange particles emitted in
Pb+Au collisions at top SPS energy: Differential elliptic flow spectra v2(pT) of \pi-, K0short, p, \Lambda have
been measured at \sqrt(s NN)= 17.3 GeV around midrapidity by the
CERN-CERES/NA45 experiment in mid-central Pb+Au collisions (10% of
\sigma(geo)). The pT range extends from about 0.1 GeV/c (0.55 GeV/c for
\Lambda) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified
by dE/dx. At higher pT, proton elliptic flow v2(pT) is derived as a
constituent, besides \pi+ and K+, of the elliptic flow of positive pion
candidates. The retrieval requires additional inputs: (i) of the particle
composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios
obtained by NA49 were adapted to CERES conditions; for (ii), the measured
v2(pT) of negative pions is substituted, assuming \pi+ and \pi- elliptic flow
magnitudes to be sufficiently close. The v2(pT) spectra are compared to
ideal-hydrodynamics calculations. In synopsis of the series \pi- - K0short - p
- \Lambda, flow magnitudes are seen to fall with decreasing pT progressively
even below hydro calculations with early kinetic freeze-out (Tf= 160 MeV)
leaving not much time for hadronic evolution. The proton v2(pT) data show a
downward swing towards low pT with excursions into negative v2 values. The
pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in
principle our working assumption, is found in its impact on proton flow
bracketed from above by the direct proton flow data, and not to alter any of
our conclusions. Results are discussed in perspective of recent viscous
dynamics studies which focus on late hadronic stages. | nucl-ex |
Energy scan of correlations in p+p and Be+Be from NA61/SHINE: The existence of the critical point (CP) of strongly interacting matter is
still an open problem. An extensive strong interactions program including a
search of the CP and the study of the onset of deconfinement was started by the
NA61/SHINE experiment at the CERN SPS. A two dimensional scan of the phase
diagram scan is performed to search for the CP and to shed light on the phase
transition region. This program includes studies of hadron production in
proton-proton, proton-nucleus and nucleus-nucleus interactions measured in a
wide range of colliding energy and system size. Correlations between various
observables measured at midrapidity as well as in separated rapidity intervals
are considered as additional and sensitive tools of this phase diagram scan. We
present NA61/SHINE results of studies of energy dependence of two-particle
correlations of pseudo-rapidity and azimuthal angle in p+p collisions at the
SPS and the first results on correlations between multiplicity and mean
transverse momentum in 7Be+9Be collisions at 150A GeV/c obtained for separated
pseudo-rapidity intervals (so called long-range correlations). Comparison with
data calculations using the EPOS 1.99 model are also discussed. | nucl-ex |
Measuring the lepton sign asymmetry in elastic electron-proton
scattering with OLYMPUS: OLYMPUS is a particle physics experiment that collected data in 2012 at DESY,
in Hamburg, Germany, on the asymmetry between positron-proton and
electron-proton elastic scattering cross sections. A non-zero asymmetry is
evidence of hard two-photon exchange, which has been hypothesized to cause the
discrepancy in measurements of the proton's electromagnetic form factors.
Alternating electron and positron beams, accelerated to 2 GeV, were directed
through a windowless, gaseous, hydrogen target, and the scattered lepton and
recoiling proton were detected in coincidence using a large acceptance magnetic
spectrometer. Determining the relative integrated luminosity between the
electron and positron data sets was critical, and a new technique, involving
multi-interaction events, was developed to achieve the desired sub-percent
accuracy. A detailed Monte Carlo simulation was built in order to reproduce the
convolution of systematic effects at every stage of the experiment. The first
stage in the simulation was new radiative event generator, which permitted the
full simulation of the non-trivial, radiative corrections to the measurement.
The analysis of the data and simulation showed that the lepton sign asymmetry
rises by several percent between a momentum transfer of 0.5 GeV$^2/c^2$ and
2.25 GeV$^2/c^2$. This rise as a function of increasing momentum transfer
confirms that two photon exchange at least partially contributes to the proton
form factor discrepancy. | nucl-ex |
Single- and Double-Pion Production in Nucleon Collisions on the Nucleon
and on Nuclei -- the ABC Effect and its Possible Origin in a Dibaryonic
Resonance: The ABC effect -- an intriguing low-mass enhancement in the $\pi\pi$
invariant mass spectrum -- is known from inclusive measurements of two-pion
production in nuclear fusion reactions. First exclusive measurements carried
out at CELSIUS-WASA for the fusion reactions leading to d or $^3$He reveal this
effect to be a $\sigma$ channel phenomenon associated with the formation of a
$\Delta\Delta$ system in the intermediate state and combined with a
resonance-like behavior in the total cross section. Together with the
observation that the differential distributions do not change in shape over the
resonance region the features fulfill the criteria of an isoscalar s-channel
resonance in $pn$ and $NN\pi\pi$ systems, if the two emitted nucleons are
bound. It obviously is robust enough to survive in nuclei as a dibaryonic
resonance configuration. In this context also the phenomenon of $N\Delta$
resonances is reexamined. | nucl-ex |
Using Nab to determine correlations in unpolarized neutron decay: The Nab experiment will measure the ratio of the weak axial-vector and vector
coupling constants $\lambda=g_A/g_V$ with precision
$\delta\lambda/\lambda\sim3\times10^{-4}$ and search for a Fierz term $b_F$ at
a level $\Delta b_F<10^{-3}$. The Nab detection system uses thick, large area,
segmented silicon detectors to very precisely determine the decay proton's time
of flight and the decay electron's energy in coincidence and reconstruct the
correlation between the antineutrino and electron momenta. Excellent
understanding of systematic effects affecting timing and energy reconstruction
using this detection system are required. To explore these effects, a series of
ex situ studies have been undertaken, including a search for a Fierz term at a
less sensitive level of $\Delta b_F<10^{-2}$ in the beta decay of $^{45}$Ca
using the UCNA spectrometer. | nucl-ex |
Dual Magnetic Separator for TRI$μ$P: The TRI$\mu$P facility, under construction at KVI, requires the production
and separation of short-lived and rare isotopes. Direct reactions,
fragmentation and fusion-evaporation reactions in normal and inverse kinematics
are foreseen to produce nuclides of interest with a variety of heavy-ion beams
from the superconducting cyclotron AGOR. For this purpose, we have designed,
constructed and commissioned a versatile magnetic separator that allows
efficient injection into an ion catcher, i.e., gas-filled stopper/cooler or
thermal ionizer, from which a low energy radioactive beam will be extracted.
The separator performance was tested with the production and clean separation
of $^{21}$Na ions, where a beam purity of 99.5% could be achieved. For
fusion-evaporation products, some of the features of its operation as a
gas-filled recoil separator were tested. | nucl-ex |
Photoneutron emission cross sections for $^{13}$C: Photoneutron emission cross sections were measured for $^{13}$C below $2n$
threshold using quasi-monochromatic $\gamma$-ray beams produced in laser
Compton-scattering at the NewSUBARU synchrotron radiation facility. The data
show fine structures in the low-energy tail of the giant-dipole resonance; the
integrated strength of the fine structure below 18~MeV is intermediate among
the past measurements with bremsstrahlung and the positron annihilation
$\gamma$ rays. We compare the photoneutron emission data with the {\sf TALYS}
statistical model calculation implemented with the simple modified Lorentzian
model of $E1$ and $M1$ strengths. We also compare the total photoabsorption
cross sections for $^{13}$C with the shell model and antisymmetrized molecular
dynamics calculations as well as the statistical model calculation. We further
investigate the consistency between the present photoneutron emission and the
reverse $^{12}$C(n,$\gamma$) cross sections through their corresponding
astrophysical rate. | nucl-ex |
Statistical analysis of experimental multifragmentation events in
$^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon: A statistical multifragmentation model (SMM) is applied to the experimentally
observed multifragmentation events in an intermediate heavy ion reaction.Using
the temperature and symmetry energy extracted from the isobaric yield ratio
(IYR) method based on the Modified Fisher Model (MFM), SMM is applied to the
reaction $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon. The experimental isotope
distribution and mass distribution of the primary reconstructed fragments are
compared without afterburner and they are well reproduced. The extracted
temperature $T$ and symmetry energy coefficient $a_{sym}$ from SMM simulated
events, using the IYR method, are also consistent with those from the
experiment. These results strongly suggest that in the multifragmentation
process there is a freezeout volume, in which the thermal and chemical
equilibrium is established before or at the time of the intermediate-mass
fragments emission. | nucl-ex |
Electroexcitation of the Roper resonance for 1.7 < Q2 < 4.5 GeV2 in ep
-> enpi+: The helicity amplitudes of the electroexcitation of the Roper resonance are
extracted for 1.7 < Q2 < 4.5 GeV2 from recent high precision JLab-CLAS cross
section and longitudinally polarized beam asymmetry data for pi+
electroproduction on protons at W=1.15-1.69 GeV. The analysis is made using two
approaches, dispersion relations and a unitary isobar model, which give
consistent results. It is found that the transverse helicity amplitude A_{1/2}
for the gamma* p -> N(1440)P11 transition, which is large and negative at Q2=0,
becomes large and positive at Q2 ~ 2 GeV2, and then drops slowly with Q2. The
longitudinal helicity amplitude S_{1/2}, which was previously found from CLAS
ep -> eppi0,enpi+ data to be large and positive at Q2=0.4,0.65 GeV2, drops with
Q2. Available model predictions for gamma* p -> N(1440)P11 allow us to conclude
that these results provide strong evidence in favor of N(1440)P11 as a first
radial excitation of the 3q ground state. The results of the present paper also
confirm the conclusion of our previous analysis for Q2 < 1 GeV2 that the
presentation of N(1440)P11 as a 3qG hybrid state is ruled out. | nucl-ex |
First test of a cryogenic scintillation module with a CaWO4 scintillator
and a low-temperature photomultiplier down to 6 K: Future cryogenic experiments searching for rare events require reliable,
efficient and robust techniques for the detection of photons at temperatures
well below that to which low-temperature photomultipliers (PMT) were
characterised. Motivated by this we investigated the feasibility of a
low-temperature PMT for the detection of scintillation from crystalline
scintillators at T = 6 K. The scintillation module was composed of a CaWO4
scintillator and a low-temperature PMT D745B from ET Enterprises. The PMT
responsivity was studied at T=290, 77 and 6 K using gamma-quanta from 241Am (60
keV) and 57Co (122 and 136 keV) sources. We have shown that the low-temperature
PMT retains its single photon counting ability even at cryogenic temperatures.
At T = 6 K, the response of the PMT decreases to 51 +- 13 % and 27 +- 6 % when
assessed in photon counting and pulse height mode, respectively. Due to the
light yield increase of the CaWO4 scintillating crystal the overall
responsivity of the scintillation modules CaWO4+PMT is 94 +- 15 % (photon
counting) and 48 +- 8 % (pulse height) when cooling to T = 6 K. The dark count
rate was found to be 20 s-1. The energy resolution of the module remains
similar to that measured at room temperature using either detection mode. It is
concluded that commercially available low-temperature PMT are well suited for
detection of scintillation light at cryogenic temperatures. | nucl-ex |
Searching for the critical point of strongly interacting matter in
nucleus-nucleus collisions at CERN SPS: The search for experimental signatures of the critical point (CP) of strongly
interacting matter is one of the main objectives of the NA61/SHINE experiment
at CERN SPS. In the course of the experiment, a beam momentum and system size
scan is performed. Local proton density fluctuations in transverse momentum
space represent an order parameter of the chiral phase transition and are
expected to scale according to a universal power-law in the vicinity of the CP;
we probe their behavior through an intermittency analysis of the proton second
scaled factorial moments (SSFMs) in transverse momentum space. Previous such
analyses revealed power-law behavior in NA49 Si+Si collisions at 158$A$
GeV/$c$, with no intermittency observed in lighter or heavier NA49 & NA61/SHINE
systems at the same energy. We now extend the analysis to NA61/SHINE Ar+Sc
collisions at 150$A$ GeV/$c$, similar in size and baryochemical potential to
NA49 Si+Si. We employ statistical techniques to subtract non-critical
background and estimate statistical and systematic uncertainties. Subsequently,
we use Monte Carlo simulations to assess the statistical significance of the
observed intermittency effect. | nucl-ex |
Hard photon and neutral pion production in cold nuclear matter: The production of hard photons and neutral pions in 190 MeV proton induced
reactions on C, Ca, Ni, and W targets has been for the first time concurrently
studied. Angular distributions and energy spectra up to the kinematical limit
are discussed and the production cross-sections are presented. From the target
mass dependence of the cross-sections the propagation of pions through nuclear
matter is analyzed and the production mechanisms of hard photons and primordial
pions are derived. It is found that the production of subthreshold particles
proceeds mainly through first chance nucleon-nucleon collisions. For the most
energetic particles the mass scaling evidences the effect of multiple
collisions. | nucl-ex |
Measurements of strange and multi-strange hadrons elliptic flow in
isobar collisions at RHIC by STAR: We present measurements of elliptic flow ($v_{2}$) of $K_{s}^{0}$, $\Lambda$,
$\bar{\Lambda}$, $\phi$, $\Xi^{-}$, $\overline{\Xi}^{+}$, and
$\Omega^{-}$+$\overline{\Omega}^{+}$ at mid-rapidity ($|\eta| <$ 1.0) in isobar
collisions ($^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr) at
$\sqrt{s_{\mathrm{NN}}}$ = 200 GeV. The centrality and transverse momentum
($p_{\mathrm{T}}$) dependence of elliptic flow is presented. The number of
constituent quark (NCQ) scaling of $v_{2}$ in isobar collisions is discussed.
$p_{T}$-integrated elliptic flow ($\left\langle v_{2}\right\rangle$) is
observed to increase from central to peripheral collisions. The ratio of
$\left\langle v_{2}\right\rangle$ between the two isobars shows a deviation
from unity for strange hadrons ($K_{s}^{0}$, $\Lambda$ and $\bar{\Lambda}$)
indicating a difference in nuclear structure and deformation. A system size
dependence of strange hadron $v_{2}$ at high $p_{T}$ is observed among Ru+Ru,
Zr+Zr, Cu+Cu, Au+Au, and U+U systems. A multi-phase transport (AMPT) model with
string melting (SM) describes the experimental data well in the measured
$p_{\mathrm{T}}$ range for isobar collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200
GeV. | nucl-ex |
Characterization of electroless nickel-phosphorus plating for
ultracold-neutron storage: Electroless nickel plating is an established industrial process that provides
a robust and relatively low-cost coating suitable for transporting and storing
ultracold neutrons (UCN). Using roughness measurements and UCN-storage
experiments we characterized UCN guides made from polished aluminum or
stainless-steel tubes plated by several vendors. All electroless nickel
platings were similarly suited for UCN storage with an average loss probability
per wall bounce of $2.8\cdot10^{-4}$ to $4.1\cdot10^{-4}$ for energies between
90 neV and 190 neV, or a ratio of imaginary to real Fermi potential $\eta$ of
$1.7\cdot10^{-4}$ to $3.3\cdot10^{-4}$. Measurements at different elevations
indicate that the energy dependence of UCN losses is well described by the
imaginary Fermi potential. Some special considerations are required to avoid an
increase in surface roughness during the plating process and hence a reduction
in UCN transmission. Increased roughness had only a minor impact on storage
properties. Based on these findings we chose a vendor to plate the
UCN-production vessel that will contain the superfluid-helium converter for the
new TRIUMF UltraCold Advanced Neutron (TUCAN) source, achieving acceptable
UCN-storage properties with ${\eta=3.5(5)\cdot10^{-4}}$. | nucl-ex |
Recent results on Light Flavor from STAR: These proceedings present an overview of the recent results on light flavor
by the STAR experiment at RHIC. | nucl-ex |
Fragment Kinetic Energies and Modes of Fragment Formation: Kinetic energies of light fragments A <= 10 from the decay of target
spectators in 197Au 197Au collisions at 1000 MeV per nucleon have been measured
with high-resolution telescopes at backward angles. Except for protons and
apart from the observed evaporation components, the kinetic-energy spectra
exhibit slope temperatures of about 17 MeV, independent of the particle
species, but not corresponding to the thermal or chemical degrees of freedom at
breakup. It is suggested that these slope temperatures may reflect the
intrinsic Fermi motion and thus the bulk density of the spectator system at the
instant of becoming unstable.
PACS numbers: 25.70.Pq, 21.65.+f, 25.70.Mn | nucl-ex |
A new precision measurement of the α-decay half-life of 190Pt: A laboratory measurement of the $\alpha$-decay half-life of $^{190}$Pt has
been performed using a low background Frisch grid ionisation chamber. A total
amount of 216.60(17) mg of natural platinum has been measured for 75.9 days.
The resulting half-life is $(4.97\pm0.16)\times 10^{11}$ years, with a total
uncertainty of 3.2%. This number is in good agreement with the half-life
obtained using the geological comparison method. | nucl-ex |
Beam Energy Dependence of Clan Multiplicity at RHIC: In this paper, STAR's measurement of clan multiplicity is presented for AuAu
collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200
GeV, for a variety of centrality classes. The mean number of particles per clan
is found to decrease with decreasing centrality. Within the same centrality
class, the mean number of particles per clan exhibits a reduction between 19.6
GeV and 62 GeV, with the minimum around 27 GeV. The structure is visible for
most centralities, and most prominent for central collisions. | nucl-ex |
Simulations of the nEDM@SNS light collection system efficiency: A system for collecting the scintillation light produced by the capture
process of ultra-cold neutrons (UCN) on polarized $^{3}$He is discussed and
results from simulations of its performance are presented. This system will be
implemented in nEDM@SNS, the experiment searching for the neutron electric
dipole moment (nEDM) at the Spallation Neutron Source (SNS) at Oak Ridge
National Laboratory. Simulation results show that the light collection system
collects on average 17 photoelectrons per UCN-$^{3}$He capture event
(sufficient to generate a robust signal), reconstructs the event location in
the beam direction to approximately 3 cm accuracy, detects capture events with
a high and spatially uniform efficiency (0.95 with 1% variation), and rejects
greater than 50% of beta decay background events. | nucl-ex |
Response of CdWO4 crystal scintillator for few MeV ions and low energy
electrons: The response of a CdWO4 crystal scintillator to protons, alpha particles, Li,
C, O and Ti ions with energies in the range 1 - 10 MeV was measured. The
non-proportionality of CdWO4 for low energy electrons (4 - 110 keV) was studied
with the Compton Coincidence Technique. The energy dependence of the quenching
factors for ions and the relative light yield for low energy electrons was
calculated using a semi-empirical approach. Pulse-shape discrimination ability
between gamma quanta, protons, alpha particles and ions was investigated. | nucl-ex |
Tracing the Evolution of Temperature in Near Fermi Energy Heavy Ion
Collisions: The kinetic energy variation of emitted light clusters has been employed as a
clock to explore the time evolution of the temperature for thermalizing
composite systems produced in the reactions of 26A, 35A and 47A MeV $^{64}$Zn
with $^{58}$Ni, $^{92}$Mo and $^{197}$Au. For each system investigated, the
double isotope ratio temperature curve exhibits a high maximum apparent
temperature, in the range of 10-25 MeV, at high ejectile velocity. These
maximum values increase with increasing projectile energy and decrease with
increasing target mass. The time at which the maximum in the temperature curve
is reached ranges from 80 to 130 fm/c after contact. For each different target,
the subsequent cooling curves for all three projectile energies are quite
similar. Temperatures comparable to those of limiting temperature systematics
are reached 30 to 40 fm/c after the times corresponding to the maxima, at a
time when AMD-V transport model calculations predict entry into the final
evaporative or fragmentation stage of de-excitation of the hot composite
systems. Evidence for the establishment of thermal and chemical equilibrium is
discussed. | nucl-ex |
Recent Heavy-Flavor results at STAR: We present the recent results on non-photonic electron (NPE) yields from RHIC
run8 p+p collisions. The $e/\pi$ ratio as a function of $p_T$ in run8 with a
factor of 10 reduction of the inner detector material at STAR is found to be
consistent with those results from run3 taking into account the NPE from charm
leptonic decay and the difference of photonic electron yield from photon
conversion in detector material. \Jpsi spectra in \pp and \cucu collisions at
\sNN = 200 GeV with high sampled luminosity \Jpsi spectrum at high-\pT follows
$x_T$ scaling, but the scaling is violated at low \pT. $J/\psi$-hadron
correlations in \pp collisions are studied to understand the \Jpsi production
mechanism at high $p_T$. We observed an absence of charged hadrons accompanying
\Jpsi on the near-side, in contrast to the strong correlation peak in the
di-hadron correlations. This constrains the $B$-meson contribution and jet
fragmentation to inclusive \Jpsi to be ${}^{<}_{\sim}17%$. Yields in
minimum-bias \cucu collisions are consistent with those in \pp collisions
scaled by the underlying binary nucleon-nucleon collisions in the measured \pT
range. Other measurements and future projects related to heavy-flavors are
discussed. | nucl-ex |
Analysis of various projectile interactions with Nuclear Emulsion
Detector nuclei at ~ 1 GeV per nucleon using Coulomb modified Glauber model: The total nuclear reaction cross-section is calculated considering with and
without medium effect by employing Coulomb Modified Glauber Model (CMGM) for
interactions of projectiles 56^Fe_26, 84^Kr_36, 132^Xe_54, 197^Au_79 and
238^U_92 with nuclear emulsion detector (NED) nuclei at around 1 GeV per
nucleon incident kinetic energy. These calculated reaction cross-sections are
correlated with the different target groups of the NED nuclei. The average
value of various parameters are also calculated and compared with the
corresponding experimental results. The number of shower particles emitted in
an interaction is also calculated and showed good agreement with the
experimental result. We observed that the total reaction cross-section
increases with increasing the target mass number in case of all the considered
projectiles. In addition, it shows that the average value of reaction
cross-section with nuclear medium effect is in good agreement with the
experimental results for projectiles 56^Fe, 84^Kr, 132^Xe, although results of
projectiles 197^Au and 238^U are not in agreement with the experimental
observations. This study sheds some light on the energy dependence of the
nuclear reaction cross-section. | nucl-ex |
Properties of the fast fission and the coincident emissions of light
charged particles in $^{40}$Ar + $^{197}$Au reactions at 30 MeV/u: The experiment of Ar+Au reactions at 30 MeV/u have been performed using the
Compact Spectrometer for Heavy IoN Experiments (CSHINE) in phase I. The
light-charged particles are measured by the silicon stripe telescopes in
coincidence with the fission fragments recorded by the parallel plate avalanche
counters. The distribution properties of the azimuth difference $\Delta \phi$
and the time-of-flight difference $\Delta TOF$ of the fission fragments are
presented varying the folding angles which represents the linear momentum
transfer from the projectile to the reaction system. The relative abundance of
the light charged particles in the fission events to the inclusive events is
compared as a function of the laboratory angle $\theta_{\rm lab}$ ranging from
$18^\circ$ to $60^\circ$ in various folding angle windows. The angular
evolution of the yield ratios of p/d and t/d in coincidence with fission
fragments is investigated. In a relative comparison, tritons are more
abundantly emitted at small angles, while protons are more abundant at large
angles. The angular evolution of the neutron richness of the light-charged
particles is consistent with the results obtained in previous inclusive
experiments. | nucl-ex |
Multifragmentation at Intermediate Energy: Dynamics or Statistics?: To make a statement about the nature and mechanism of fragmentation, it is
necessary to probe directly any competition, or lack thereof, between the
emission of various particle species as a function of excitation energy. The
task is then to find a global observable that best follows the increase in
excitation energy or dissipated energy. In the following, we will consider two
contradictory claims that have been advanced recently: 1) the claim for a
predominantly dynamical fragment production mechanism; and 2) the claim for a
dominant statistical and thermal process. We will present a new analysis in
terms of Poissonian reducibility and thermal scaling, which addresses some of
the criticisms of the binomial analysis. | nucl-ex |
Event-plane flow analysis without non-flow effects: The event-plane method, which is widely used to analyze anisotropic flow in
nucleus-nucleus collisions, is known to be biased by nonflow effects,especially
at high $p_t$. Various methods (cumulants, Lee-Yang zeroes) have been proposed
to eliminate nonflow effects, but their implementation is tedious, which has
limited their application so far. In this paper, we show that the
Lee-Yang-zeroes method can be recast in a form similar to the standard
event-plane analysis. Nonflow correlations are strongly suppressed by using the
information from the length of the flow vector, in addition to the event-plane
angle. This opens the way to improved analyses of elliptic flow and
azimuthally-sensitive observables at RHIC and LHC. | nucl-ex |
System-size dependence of the viscous attenuation of anisotropic flow in
p+Pb and Pb+Pb collisions at LHC energies: The elliptic and triangular flow coefficients ($\mathrm{v_n, \, n=2,3}$)
measured in Pb+Pb ($\sqrt{s_{_{\rm NN}}} = 2.76$ TeV) and p+Pb ($\sqrt{s_{_{\rm
NN}}} = 5.02$ TeV) collisions, are studied as a function of initial-state
eccentricity ($\varepsilon_n$), and dimensionless size characterized by the
cube root of the mid-rapidity charged hadron multiplicity density
$\mathrm{\left< N_{ch} \right>^{1/3}}$. The results indicate that the influence
of eccentricity ($\mathrm{v_n} \propto \varepsilon_n$) observed for large
$\mathrm{\left< N_{ch} \right>}$, is superseded by the effects of viscous
attenuation for small $\mathrm{\left< N_{ch} \right>}$, irrespective of the
colliding species. Strikingly similar acoustic scaling patterns of exponential
viscous modulation, with a damping rate proportional to $\mathrm{n^2}$ and
inversely proportional to the dimensionless size, are observed for the
eccentricity-scaled coefficients for the two sets of colliding species. The
resulting scaling parameters suggest that, contrary to current predilections,
the patterns of viscous attenuation, as well as the specific shear viscosity
$\left<\frac{\eta}{s}(\text{T})\right>$ for the matter created in p+Pb and
Pb+Pb collisions, are comparable. | nucl-ex |
Dominance of tensor correlations in high-momentum nucleon pairs studied
by (p,pd) reaction: The isospin character of p-n pairs at large relative momentum has been
observed for the first time in the 16O ground state. A strong population of the
J,T=1,0 state and a very weak population of the J,T=0,1 state were observed in
neutron pick up domain of 16O(p,pd) at 392 MeV. This strong isospin dependence
at large momentum transfer is not reproduced by the distorted-wave impulse
approximation calculations with known spectroscopic amplitudes. The results
indicate the presence of high-momentum protons and neutrons induced by the
tensor interactions in ground state of 16O. | nucl-ex |
Solid State Systems for Electron Electric Dipole Moment and other
Fundamental Measurements: In 1968, F.L. Shapiro published the suggestion that one could search for an
electron EDM by applying a strong electric field to a substance that has an
unpaired electron spin; at low temperature, the EDM interaction would lead to a
net sample magnetization that can be detected with a SQUID magnetometer. One
experimental EDM search based on this technique was published, and for a number
of reasons including high sample conductivity, high operating temperature, and
limited SQUID technology, the result was not particularly sensitive compared to
other experiments in the late 1970's.
Advances in SQUID and conventional magnetometery had led us to reconsider
this type of experiment, which can be extended to searches and tests other than
EDMs (e.g., test of Lorentz invariance). In addition, the complementary
measurement of an EDM-induced sample electric polarization due to application
of a magnetic field to a paramagnetic sample might be effective using modern
ultrasensitive charge measurement techniques. A possible paramagnetic material
is Gd-substituted YIG which has very low conductivity and a net enhancement
(atomic enhancement times crystal screening) of order unity. Use of a
reasonable volume (100's of cc) sample of this material at 50 mK and 10 kV/cm
might yield an electron EDM sensitivity of $10^{-33}$ e cm or better, a factor
of $10^6$ improvement over current experimental limits. | nucl-ex |
Multiplicity Fluctuations in Au+Au Collisions at RHIC: In the PHOBOS experiment, charged particles are measured in almost the full
solid angle. This enables the study of fluctuations and correlations in the
particle production over a very wide kinematic range. In this paper, we show
results of a direct search for fluctuations identified by an unusual shape of
the pseudorapidity distribution. In addition, we use analysis of correlations
of the multiplicity in similar pseudorapidity bins, placed symmetrically in the
forward and backward hemispheres, to test the hypothesis of production of
particles in clusters. | nucl-ex |
Measurement of the Target-Normal Single-Spin Asymmetry in Quasi-Elastic
Scattering from the Reaction $^3$He$^\uparrow(e,e^\prime)$: We report the first measurement of the target single-spin asymmetry, $A_y$,
in quasi-elastic scattering from the inclusive reaction
$^3$He$^{\uparrow}(e,e^\prime)$ on a $^3$He gas target polarized normal to the
lepton scattering plane. Assuming time-reversal invariance, this asymmetry is
strictly zero for one-photon exchange. A non-zero $A_y$ can arise from the
interference between the one- and two-photon exchange processes which is
sensitive to the details of the sub-structure of the nucleon. An experiment
recently completed at Jefferson Lab yielded asymmetries with high statistical
precision at $Q^{2}=$ 0.13, 0.46 and 0.97 GeV$^{2}$. These measurements
demonstrate, for the first time, that the $^3$He asymmetry is clearly non-zero
and negative with a statistical significance of (8-10)$\sigma$. Using measured
proton-to-$^{3}$He cross-section ratios and the effective polarization
approximation, neutron asymmetries of $-$(1-3)% were obtained. The neutron
asymmetry at high $Q^2$ is related to moments of the Generalized Parton
Distributions (GPDs). Our measured neutron asymmetry at $Q^2=0.97$ GeV$^2$
agrees well with a prediction based on two-photon exchange using a GPD model
and thus provides a new, independent constraint on these distributions. | nucl-ex |
Structure in the Event-by-Event Energy-Dependent Neutron-Gamma
Multiplicity Correlations in $^{252}\text{Cf}$(sf): The emission of neutrons and gamma rays by fission fragments reveal important
information about the properties of fragments immediately following scission.
The initial fragment properties, correlations between fragments, and emission
competition give rise to correlations in neutron-gamma emission. Neutron-gamma
correlations are important in nonproliferation applications because the
characterization of fissionable samples relies on the identification of
signatures in the measured radiation. Furthermore, recent theoretical and
experimental advances have proposed to explain the mechanism of angular
momentum generation in fission. In this paper, we present a novel analysis
method of neutrons and gamma rays emitted by fission fragments that allows us
to discern structure in the observed correlations. We have analyzed data
collected on \ce{^{252}Cf}(sf) at the Chi-Nu array at the Los Alamos Neutron
Science Center. Through our analysis of the energy-differential neutron-gamma
multiplicity covariance, we have observed enhanced neutron-gamma correlations,
corresponding to rotational band gamma-ray transitions, at gamma-ray energies
of $0.7$ and $1.2$ MeV. To shed light on the origin of this structure, we
compare the experimental data with the predictions of three model calculations.
The origin of the observed correlation structure is understood in terms of a
positive spin-energy correlation in the generation of angular momentum in
fission. | nucl-ex |
Q_EC values of the Superallowed beta Emitters 50Mn and 54Co: Using a new fast cleaning procedure to prepare isomerically pure ion samples,
we have measured the beta-decay Q_EC values of the superallowed beta-emitters
50Mn and 54Co to be 7634.48(7) keV and 8244.54(10) keV, respectively, results
which differ significantly from the previously accepted values. The corrected
Ft values derived from our results strongly support new
isospin-symmetry-breaking corrections that lead to a higher value of the
up-down quark mixing element, Vud, and improved confirmation of the unitarity
of the Cabibbo-Kobayashi-Maskawa matrix. | nucl-ex |
Leading Modes of the 3pi0 production in proton-proton collisions at
incident proton momentum 3.35GeV/c: This work deals with the prompt pp-->pp3pi0 reaction where the 3pi0 do not
origin from the decay of narrow resonances like \eta(547), \omega(782),
\eta'(958). The reaction was measured for the proton beam momentum of 3.35GeV/c
with the WASA-at-COSY detector setup. The dynamics of the reaction is
investigated by Dalitz and Nyborg plots studies. The reaction is described by
the model assuming simultaneous excitation of two baryon resonances
\Delta(1232) and N*(1440) where resonances are identified by their unique
decays topology on the missing mass of two protons MMpp dependent Dalitz and
Nyborg plots. The ratio
R=\Gamma(N*(1440)->N\pi\pi)/\Gamma(N*(1440)->\Delta(1232)\pi->N\pi\pi)= 0.039
+- 0.011(stat.) +- 0.008(sys.) is measured for the first time in a direct way.
It shows that the {N*(1440)->\Delta(1232)\pi->N\pi\pi} decay is a leading mode
of 3pi0 production. It is also shown that the MMpp is very sensitive to the
structure of the spectral line shape of the N*(1440) resonance as well as on
the interaction between the \Delta(1232) and N*(1440) resonances. The multipion
spectroscopy - a precision tool to directly access the properties of baryon
resonances is considered.
The pp-->pp\eta(3pi0) reaction was also measured simultaneously. It is shown
that the {\eta} production mechanism via N*(1535) is 43.4 +- 0.8(stat.) +-
2.0(sys.) of the total production, for the {\eta} momentum in the CM system
q_\eta^CM=0.45-0.7GeV/c. First time momentum dependence of the {\eta} angular
distribution is seen, the strongest effect is observed for the
cos(\theta_\eta^CM) distribution. | nucl-ex |
Photon production from gluon mediated quark-anti-quark annihilation at
confinement: Heavy ion collisions at RHIC produce direct photons at low transverse
momentum, $p_{T}$ from 1-3 GeV/c, in excess of the $p$$+$$p$ spectra scaled by
the nuclear overlap factor, $T_{AA}$. These low $p_{T}$ photons have a large
azimuthal anisotropy, $v_{2}$. Theoretical models, including hydrodynamic
models, struggle to quantitatively reproduce the large low $p_{T}$ direct
photon excess and $v_{2}$ in a self-consistent manner. This paper presents a
description of the low $p_{T}$ photon flow as the result of increased photon
production from soft-gluon mediated $q$-$\bar{q}$ interactions as the system
becomes color-neutral. This production mechanism will generate photons that
follow constituent quark number, $n_{q}$, scaling of $v_{2}$ with an $n_{q}$
value of two for direct photons. $\chi^{2}$ comparisons of the published PHENIX
direct photon and identified particle $v_{2}$ measurements finds that
$n_{q}$-scaling applied to the direct photon $v_{2}$ data prefers the value
$n_{q}=1.8$ and agrees with $n_{q}=2$ within errors in most cases. The 0-20%
and 20-40% Au$+$Au direct photon data are compared to a coalescence-like Monte
Carlo simulation that calculates the direct photon $v_{2}$ while describing the
shape of the direct photon $p_{T}$ spectra in a consistent manner. The
simulation, while systematically low compared to the data, is in agreement with
the Au$+$Au measurement at $p_{T}<3$ GeV/c in both centrality bins.
Furthermore, this model predicts that higher order flow harmonics, $v_{n}$, in
direct photons will follow the modified $n_{q}$-scaling laws seen in identified
hadron $v_{n}$ with an $n_{q}$ value of two. | nucl-ex |
Precision mass measurements of radioactive nuclei at JYFLTRAP: The Penning trap mass spectrometer JYFLTRAP was used to measure the atomic
masses of radioactive nuclei with an uncertainty better than 10 keV. The atomic
masses of the neutron-deficient nuclei around the N = Z line were measured to
improve the understanding of the rp-process path and the SbSnTe cycle.
Furthermore, the masses of the neutron-rich gallium (Z = 31) to palladium (Z =
46) nuclei have been measured. The physics impacts on the nuclear structure and
the r-process paths are reviewed. A better understanding of the nuclear
deformation is presented by studying the pairing energy around A = 100. | nucl-ex |
Low Energy Analyzing Powers in Pion-Proton Elastic Scattering: Analyzing powers of pion-proton elastic scattering have been measured at PSI
with the Low Energy Pion Spectrometer LEPS as well as a novel polarized
scintillator target. Angular distributions between 40 and 120 deg (c.m.) were
taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic
energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering.
These new measurements constitute a substantial extension of the polarization
data base at low energies. Predictions from phase shift analyses are compared
with the experimental results, and deviations are observed at low energies. | nucl-ex |
Imperfect World of $ββ$-decay Nuclear Data Sets?: The precision of double-beta ($\beta\beta$) decay experimental half-lives and
their uncertainties is reevaluated. A complementary analysis of the decay
uncertainties indicates deficiencies due to small size of statistical samples,
and incomplete collection of experimental information. Further experimental and
theoretical efforts would lead toward more precise values of $\beta\beta$-decay
half-lives and nuclear matrix elements. | nucl-ex |
Astrophysical factor for the neutron generator 13C(alpha,n)16O reaction
in the AGB stars: The reaction 13C(alpha,n) is considered to be the main source of neutrons for
the s-process in AGB stars. At low energies the cross section is dominated by
the 1/2+ 6.356 MeV sub-threshold resonance in 17O whose contribution is
determined with a very large uncertainty of ~1000% at stellar temperatures. In
this work we performed the most precise determination of the low-energy
astrophysical S factor using the indirect asymptotic normalization (ANC)
technique. The alpha-particle ANC for the sub-threshold state has been measured
using the sub-Coulomb alpha-transfer reaction (6Li,d). Using the determined ANC
we calculated S(0), which turns out to be an order of magnitude smaller than in
the NACRE compilation. | nucl-ex |
Search for particle-stable tetraneutrons in thermal fission of $^{235}$U: Background: The existence of a tetraneutron comprising four neutrons has long
been debated.
Purpose: Motivated by a recent observation of particle-stable tetraneutrons,
we investigated potential particle-stable tetraneutron emission in thermal
neutron-induced $^{235}$U fission using a nuclear research reactor.
Methods: We performed $\gamma$-ray spectroscopy for a $^{88}$SrCO$_3$ sample
irradiated in a reactor core. Stable $^{88}$Sr was expected to produce
$^{91}$Sr by a tetraneutron-induced ($^4n$,n) reaction; hence, observation of
$\gamma$-rays followed by $\beta$ decay of $^{91}$Sr would indicate
particle-stable tetraneutron emission.
Results: The $\gamma$-ray spectrum of an irradiated $^{88}$SrCO$_3$ sample
did not show any photopeak for $^{91}$Sr.
Conclusion: The emission rate of particle-stable tetraneutrons, if they
exist, is estimated to be lower than $8\times 10^{-7}$ per fission at the 95%
confidence level, assuming the cross-sections of reactions induced by
hypothetical particle-stable tetraneutrons. | nucl-ex |
Measurement of the pn -> dK^+K^- total cross section close to threshold: Measurements of the pn -> p_spec dK^+K^- reaction, where p_spec is a
spectator proton, have been undertaken at the Cooler Synchrotron COSY-Juelich
by detecting a fast deuteron in coincidence with a K^+K^- pair in the ANKE
facility. Although the proton beam energy was fixed, the moving target neutron
allowed values of the non-resonant quasi-free pn -> dK^+K^- total cross section
to be deduced up to an excess energy epsilon ~ 100 MeV. Evidence is found for
the effects of K^-d and KKbar final state interactions. The comparison of these
data with those of pp -> ppK^+K^- and pp -> dK^+Kbar shows that all the total
cross sections are very similar in magnitude. | nucl-ex |
Energy and system dependence of high-$p_T$ triggered two-particle
near-side correlations: Previous studies have indicated that the near-side peak of high-$p_T$
triggered correlations can be decomposed into two parts, the \textit{Jet} and
the \textit{Ridge}. We present data on the yield per trigger of the
\textit{Jet} and the \textit{Ridge} from $d+Au$, $Cu+Cu$ and $Au+Au$ collisions
at $\sqrt{s_{NN}}$ = 62.4 GeV and 200 GeV and compare data on the \textit{Jet}
to PYTHIA 8.1 simulations for $p+p$. PYTHIA describes the \textit{Jet}
component up to a scaling factor, meaning that PYTHIA can provide a better
understanding of the \textit{Ridge} by giving insight into the effects of the
kinematic cuts. We present collision energy and system dependence of the
\textit{Ridge} yield, which should help distinguish models for the production
mechanism of the \textit{Ridge}. | nucl-ex |
Fast-neutron induced pre-equilibrium reactions on 55Mn and 63,65Cu at
energies up to 40 MeV: Excitation functions were measured for the $^{55}$Mn(n,2n)$^{54}$Mn,
$^{55}$Mn(n,$\alpha$)$^{52}$V, $^{63}$Cu(n,$\alpha$)$^{60}$Co,
$^{65}$Cu(n,2n)$^{64}$Cu, and $^{65}$Cu(n,p)$^{65}$Ni reactions from 13.47 to
14.83 MeV. The experimental cross sections are compared with the results of
calculations including all activation channels for the stable isotopes of Mn
and Cu, for neutron incident energies up to 50 MeV. Within the energy range up
to 20 MeV the model calculations are most sensitive to the parameters related
to nuclei in the early stages of the reaction, while the model assumptions are
better established by analysis of the data in the energy range 20-40 MeV. While
the present analysis has taken advantage of both a new set of accurate measured
cross sections around 14 MeV and the larger data basis fortunately available
between 20 and 40 MeV for the Mn and Cu isotopes, the need of additional
measurements below as well as above 40 MeV is pointed out. Keywords: 55Mn,
63,65Cu, E$\leq$40 MeV, Neutron activation cross section measurements, Nuclear
reactions, Model calculations, Manganese, Copper | nucl-ex |
Some Striking New STAR Results: Recent high-statistics Au+Au and Cu+Cu runs at RHIC have provided a wealth of
new data that allow STAR to answer several outstanding questions regarding the
nature of the hot, dense medium that is created in ultrarelativistic heavy-ion
collisions. However, the new data also raise new questions that require further
study. Here, we focus on a few qualitatively new results presented by STAR for
the first time at Quark Matter `05. | nucl-ex |
System size dependence of associated yields in hadron-triggered jets: We present results on the system size dependence of high transverse momentum
di-hadron correlations at $\sqrt{s_{NN}}$ = 200 GeV as measured by STAR at
RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like
correlation yields at small angular separation ($\Delta\phi\sim0$,
$\Delta\eta\sim0$) for all systems and centralities. Previous measurements have
shown that the away-side yield is suppressed in heavy-ion collisions. We
present measurements of the away-side suppression as a function of transverse
momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found
to be similar in Cu+Cu and Au+Au collisions at a similar number of
participants. The results are compared to theoretical calculations based on the
parton quenching model and the modified fragmentation model. The observed
differences between data and theory indicate that the correlated yields
presented here will provide important constraints on medium density profile and
energy loss model parameters. | nucl-ex |
Cosmic-ray Monte Carlo predictions for forward particle production in
p-p, p-Pb, and Pb-Pb collisions at the LHC: We present and compare the predictions of various cosmic-ray Monte Carlo
models for the energy (dE/deta) and particle (dN/deta) flows in p-p, p-Pb and
Pb-Pb collisions at sqrt(s) = 14, 8.8, and 5.5 TeV respectively, in the range
covered by forward LHC detectors like CASTOR or TOTEM (5.2<|eta|<6.6) and ZDC
or LHCf (|eta|>8.1 for neutrals). | nucl-ex |
NA61/SHINE results on Bose-Einstein correlations: One of the main goals of NA61/SHINE is the investigation of the phase diagram
of strongly interacting matter. NA61/SHINE observes collisions of various
nuclei at different energies, allowing to study the same phenomena and
observables in vastly different conditions. One of the observables related to
the quark-hadron transition is the Bose-Einstein momentum correlation function
of identical pions, related to the space-time structure of pion emission. In
this paper we report on such measurements in Be+Be collisions at an SPS beam
momentum of 150A GeV/c. Our correlation functions can be statistically well
described with Levy-distributed sources, hence we also study the mT dependence
of the Levy source parameters, and discuss their possible interpretations. | nucl-ex |
The study of light nuclei production in different interactions at 4.2
AGeV/c: Average multiplicity of light nuclei produced in different interactions at
4.2A GeVc is studied as a function of centrality. A change in multiplicity is
observed with increase in the mass of projectile. In 12CC-interactions an
unexpected increase in the multiplicity is seen for the most central events.
These measurements are compared with the predictions of Cascade and Fritiof
Models which fail to account for the experimentally observed effects. In case
of 12CC it is suggested that the inclusion of nuclear coalescence effect can be
an explanatory reason for the differences between the experimental measurements
and the models predictions. | nucl-ex |
Dynamical fission of the quasiprojectile and isospin equilibration for
the system 80Kr+ 48 Ca at 35 MeV/nucleon: Experimental results concerning the dynamical fission of quasiprojectiles in
semiperipheral collisions for the system 80 Kr+ 48 Ca at 35 MeV/nucleon are
presented. Data have been collected with four blocks of the FAZIA setup in the
first physics experiment of the FAZIA Collaboration. The degree of isospin
equilibration between the two fission fragments and its dependence on their
charge asymmetry is investigated. The data are compared with the results of the
AMD model coupled to GEMINI as an afterburner, in order to get hints about the
timescale of the process. | nucl-ex |
Total and nuclear photoabsorption cross section of 52Cr in the energy
range of 8 - 70 MeV: Total (atomic+nuclear) photoabsorption cross section of $^{52}Cr$ was for the
first time measured in the energy range of 8-70 MeV. Experimental data was
produced with small statistic and systematic errors. The results deviate from
calculations of atomic cross section at photon energies above 40 MeV.
Photonuclear cross section in the region of the E1 giant dipole resonance (GDR)
clearly exhibits three peaks at 18.9, 20.9 and 23.1 MeV. At higher energies,
the measured cross section hints a dip-peak structure at 40-48 MeV. | nucl-ex |
Meson Production in p+d Reactions: The production of neutral and charged pions as well as eta mesons is studied
in the Delta and N* resonance region, respectively. Heavy A=3 recoils were
measured with the GEM detector. The differential cross sections covering the
full angular range are compared with model calculations. | nucl-ex |
Backward-angle Exclusive pi0 Production above the Resonance Region: The proposed measurement is a dedicated study of the exclusive
electroproduction process,1H(e,e'p)pi0, in the backward-angle regime (u-channel
process) above the resonance region. The produced pi0 is emitted 180 degrees
opposite to the virtual-photon momentum. This study also aims to apply the
well-known Rosenbluth separation technique that provides the model-independent
differential cross-sections at the never explored u-channel kinematics region.
Currently, the "soft-hard transition" in u-channel meson production remains an
interesting and unexplored subject. The available theoretical frameworks offer
competing interpretations for the observed backward-angle cross section peaks.
In a "soft" hadronic Regge exchange description, the backward meson production
comes from the interference between nucleon exchange and the meson produced via
re-scattering within the nucleon. Whereas in the "hard" GPD-like backward
collinear factorization regime, the scattering amplitude factorizes into a hard
subprocess amplitude and baryon to meson transition distribution amplitudes
(TDAs), otherwise known as super skewed parton distributions (SuperSPDs). Both
TDAs and SPDs are universal non-perturbative objects of nucleon structure
accessible only through backward-angle kinematics. The separated cross
sections:sigma_T,sigma_L and T/L ratio at Q2=2-6 GeV2, provide a direct test of
two predictions from the TDA model. The magnitude and u-dependence of the
separated cross sections also provide a direct connection to the re-scattering
Regge picture. The extracted interaction radius (from u-dependence) at
different Q2 can be used to study the soft-hard transition in the u-channel
kinematics. The acquisition of these data will be an important step forward in
validating the existence of a backward factorization scheme of the nucleon
structure function and establishing its applicable kinematic range. | nucl-ex |
Di-lepton production in p+p collisions at $\sqrt{s_{_{NN}}} = 200$ GeV
from STAR: The di-electron analysis for 200 GeV p+p collisions is presented in this
article. The cocktail simulations of di-eletrons from light flavor meson decays
and heavy flavor decays are reported and compared with data. The perspectives
for di-lepton measurements in Au+Au collisions are discussed. | nucl-ex |
Production of deuterium, tritium, and $^3$He in central Pb+Pb collisions
at 20A, 30A, 40A, 80A, and 158A GeV at the CERN SPS: Production of $d$, $t$, and $^3$He nuclei in central Pb+Pb interactions was
studied at five collision energies ($\sqrt{s_{NN}}=$ 6.3, 7.6, 8.8, 12.3, and
17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum spectra,
rapidity distributions, and particle ratios were measured. Yields are compared
to predictions of statistical models. Phase-space distributions of light nuclei
are discussed and compared to those of protons in the context of a coalescence
approach. The coalescence parameters $B_2$ and $B_3$, as well as coalescence
radii for $d$ and $^3$He were determined as a function of transverse mass at
all energies. | nucl-ex |
Verification of detailed balance for $γ$ absorption and emission in
Dy isotopes: The photo-neutron cross sections of $^{162,163}\rm{Dy}$ have been measured
for the first time in an energy region from the neutron threshold ($S_n$) up to
$\approx$ $13$~MeV. The ($\gamma$,n) reaction was induced with
quasi-monochromatic laser Compton-scattered $\gamma$ rays, produced at the
NewSUBARU laboratory. The corresponding $\gamma$-ray strength functions
($\gamma$SF) have been calculated from the photo-neutron cross sections. The
data are compared to reanalyzed $\gamma$SFs of $^{160-164}\rm{Dy}$, which are
measured below $S_n$. The excellent agreement with the photo-neutron data at
$S_n$ confirms the principle of detailed balance. Thus, a complete $\gamma$SF
is established covering in total the energy region of 1 MeV $\leq$ E$_{\gamma}$
$\leq$ 13 MeV. These mid-shell well-deformed dysprosium isotopes all show
scissors resonances with very similar structures. We find that our data predict
the same integrated scissors strength as ($\gamma,\gamma^\prime$) data when
integrated over the same energy range, which shows that the scissors mode very
likely is consistent with the generalized Brink hypothesis. Finally, using the
$\gamma$SFs as input in the reaction code TALYS, we have deduced radiative
neutron-capture cross sections and compared them to direct measurements. We
find a very good agreement within the uncertainties, which gives further
support to the experimentally determined $\gamma$SFs. | nucl-ex |
K*(892)$^{0}$ and $Φ$(1020) production in Pb-Pb collisions at
$\sqrt{s_{\rm NN}}$ = 2.76 TeV: The yields of the K*(892)$^{0}$ and $\Phi$(1020) resonances are measured in
Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV through their hadronic
decays using the ALICE detector. The measurements are performed in multiple
centrality intervals at mid-rapidity (|$y$|<0.5) in the transverse-momentum
ranges 0.3 < $p_{\rm T}$ < 5 GeV/$c$ for the K*(892)$^{0}$ and 0.5 < $p_{\rm
T}$ < 5 GeV/$c$ for the $\Phi$(1020). The yields of K*(892)$^{0}$ are
suppressed in central Pb-Pb collisions with respect to pp and peripheral Pb-Pb
collisions (perhaps due to rescattering of its decay products in the hadronic
medium), while the longer lived $\Phi$(1020) meson is not suppressed. These
particles are also used as probes to study the mechanisms of particle
production. The shape of the $p_{\rm T}$ distribution of the $\Phi$(1020)
meson, but not its yield, is reproduced fairly well by hydrodynamic models for
central Pb-Pb collisions. In central Pb-Pb collisions at low and intermediate
$p_{\rm T}$, the p/$\Phi$(1020) ratio is flat in $p_{\rm T}$, while the p/$\pi$
and $\Phi$(1020)/$\pi$ ratios show a pronounced increase and have similar
shapes to each other. These results indicate that the shapes of the $p_{\rm T}$
distributions of these particles in central Pb-Pb collisions are determined
predominantly by the particle masses and radial flow. Finally, $\Phi$(1020)
production in Pb-Pb collisions is enhanced, with respect to the yield in pp
collisions and the yield of charged pions, by an amount similar to the
$\Lambda$ and $\Xi$. | nucl-ex |
Centrality and transverse momentum dependence of inclusive J/$ψ$
production at midrapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02
TeV: The inclusive J/$\psi$ meson production in Pb-Pb collisions at a
center-of-mass energy per nucleon-nucleon collision of $\sqrt{s_{\rm NN}}$ =
5.02 TeV at midrapidity ($|y|$ < 0.9) is reported by the ALICE Collaboration.
The measurements are performed in the dielectron decay channel, as a function
of event centrality and J/$\psi$ transverse momentum $p_{\rm T}$, down to
$p_{\rm T}$ = 0 GeV/$c$. The J/$\psi$ mean transverse momentum $\langle p_{\rm
T} \rangle$ and $r_{\rm AA}$ ratio, defined as $\langle p^{\rm 2}_{\rm T}
\rangle_{\rm PbPb}/\langle p^{\rm 2}_{\rm T} \rangle_{\rm pp}$, are evaluated.
Both observables show a centrality dependence decreasing towards central
(head-on) collisions. The J/$\psi$ nuclear modification factor $R_{\rm AA}$
exhibits a strong $p_{\rm T}$ dependence with a large suppression at high
$p_{\rm T}$ and an increase to unity for decreasing $p_{\rm T}$. When
integrating over the measured momentum range $p_{\rm T}$ < 10 GeV/$c$, the
J/$\psi$ $R_{\rm AA}$ shows a weak centrality dependence. Each measurement is
compared with results at lower center-of-mass energies and with ALICE
measurements at forward rapidity, as well as to theory calculations. All
reported features of the J/$\psi$ production at low $p_{\rm T}$ are consistent
with a dominant contribution to the J/$\psi$ yield originating from charm quark
(re)combination. | nucl-ex |
Analysis of 2-Body Central Events for $^{129}Xe+^{nat}Sn$ from $8A$
$MeV$ up to $18A$ $MeV$ and for $^{129}Xe+^{197}Au$ at $15A$ $MeV$ and $18A$
$MeV$: A study of medium-mass heavy-ion reactions leading to two fragments in the
exit channel from barrier to 18A MeV is proposed. A special focus is made on
fission and quasi-fission for events with two fragments ($Z\geq10$) in the exit
channel selected. Reactions induced by $^{129}Xe$ projectiles on $^{nat}Sn$ and
on $^{197}Au$ at energies ranging from $8A$ MeV to $18A$ MeV were analyzed.
Using the fragment ($Z\geq10$) multiplicity equal to 2, fission and
quasi-fission events were studied for the lowest beam energies using the
fission fragment charge distributions, the total kinetic energy distribution
(TKE) and its standard deviation $\sigma_{TKE}$. For the lighter system it is
still possible to observe fission events from incomplete fusion. At variance,
for the heavier system, Xenon on gold target only quasi-fission is evidenced.
The study of the events characterized by two fragments in the final channel
shows that fission, related to fusion in the entrance channel, disappears
around 20A MeV for both systems. At lower energies (8A, 12A and 15A MeV) for
the Sn target, an evolution with increasing energies towards an asymmetric
fission mode is displayed in the fragment charge distributions. This trend can
be attributed to the increasing angular momentum as indicated by the
out-of-plane angular distribution for light charged particles. The same effect
is also observed in the case of the gold target at 15A MeV. However, for this
heavier system, a strong memory of the entrance channel leading to
quasi-fission is evidenced. A comparison with the Viola systematics, moreover,
shows a deviation, greater for the heavier system than for $^{129}Xe+^{nat}Sn$
system. A complete understanding of the above results would certainly require
precise model calculations at these energies. | nucl-ex |
Measurement of the beam-helicity asymmetry $I^{\odot}$ in the
photoproduction of $π^0π^{\pm}$-pairs off protons and off neutrons: Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz
for the photoproduction of mixed-charge pion pairs in the reactions
$\boldsymbol{\gamma}p\rightarrow n\pi^0\pi^+$ off free protons and
$\boldsymbol{\gamma}d\rightarrow (p)p\pi^0\pi^-$ and
$\boldsymbol{\gamma}d\rightarrow (n)n\pi^0\pi^+$ off quasi-free nucleons bound
in the deuteron for incident photon energies up to 1.4 GeV. Circularly
polarized photons were produced from bremsstrahlung of longitudinally polarized
electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged
pions, recoil protons, recoil neutrons, and decay photons from $\pi^0$ mesons
were detected in the 4$\pi$ electromagnetic calorimeter composed of the Crystal
Ball and TAPS detectors. Using a complete kinematic reconstruction of the final
state, excellent agreement was found between the results for free and
quasi-free protons, suggesting that the quasi-free neutron results are also a
close approximation of the free-neutron asymmetries. A comparison of the
results to the predictions of the Two-Pion-MAID reaction model shows that the
reaction mechanisms are still not well understood, in particular at low
incident photon energies in the second nucleon-resonance region. | nucl-ex |
The first candidate for chiral nuclei in the $A\sim80$ mass region:
$^{80}$Br: Excited states of $^{80}$Br have been investigated via the
$^{76}$Ge($^{11}$B, $\alpha$3n) and $^{76}$Ge($^{7}$Li, 3n) reactions and a new
$\Delta I$ = 1 band has been identified which resides $\sim$ 400 keV above the
yrast band. Based on the experimental results and their comparison with the
triaxial particle rotor model calculated ones, a chiral character of the two
bands within the $\pi g_{9/2}\otimes \nu g_{9/2}$ configuration is proposed,
which provides the first evidence for chirality in the $A\sim80$ region. | nucl-ex |
Polarisation of the omega meson in the pd-->3He+omega reaction at 1360
and 1450 MeV: The tensor polarisation of omega mesons produced in the pd-->3He+omega
reaction has been studied at two energies near threshold. The 3He nuclei were
detected in coincidence with the pi0pi+pi- or pi0gamma decay products of the
omega. In contrast to the case of phi meson production, the omega mesons are
found to be unpolarised. This brings into question the applicability of the
Okubo-Zweig-Iizuka rule when comparing the production of vector mesons in low
energy hadronic reactions. | nucl-ex |
Measurement of leading charged-particle jet properties in p--Pb
collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE: Jets are collimated sprays of particles produced from the fragmentation and
hadronization of hard-scattered partons in high energy hadronic and nuclear
collisions. Jet properties are sensitive to details of parton showering
processes and are expected to be modified in the presence of a dense partonic
medium. Measurement of intra-jet properties in p--Pb collisions will help to
investigate cold nuclear matter effects and enrich our current understanding of
particle production in such collision systems. In this work, we present the
measurement of leading charged-particle jet properties, namely the mean
charged-particle multiplicity and the fragmentation functions, in the range of
jet $p_{\rm T}$ 10 -- 100 GeV/c at midrapidity in minimum bias p--Pb collisions
at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE. Results are compared with
theoretical model predictions. | nucl-ex |
Coulomb excitation of 73Ga: The B(E2; Ii -> If) values for transitions in 71Ga and 73Ga were deduced from
a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using
post-accelerated beams of 71,73Ga at the REX-ISOLDE on-line isotope mass
separator facility. The emitted gamma rays were detected by the
MINIBALL-detector array and B(E2; Ii->If) values were obtained from the yields
normalized to the known strength of the 2+ -> 0+ transition in the 120Sn
target. The comparison of these new results with the data of less neutron-rich
gallium isotopes shows a shift of the E2 collectivity towards lower excitation
energy when adding neutrons beyond N = 40. This supports conclusions from
previous studies of the gallium isotopes which indicated a structural change in
this isotopical chain between N = 40 and N = 42. Combined with recent
measurements from collinear laser spectroscopy showing a 1/2- spin and parity
for the ground state, the extracted results revealed evidence for a 1/2-; 3/2-
doublet near the ground state in 73 31Ga42 differing by at most 0.8 keV in
energy. | nucl-ex |
Characterizing the initial conditions of heavy-ion collisions at the LHC
with mean transverse momentum and anisotropic flow correlations: Correlations between mean transverse momentum $[p_{\rm T}]$ and anisotropic
flow coefficients $v_{\rm 2}$ or $v_{\rm 3}$ are measured as a function of
centrality in Pb$-$Pb and Xe$-$Xe collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV
and 5.44 TeV, respectively, with ALICE. In addition, the recently proposed
higher-order correlation between $[p_{\rm T}]$, $v_{\rm 2}$, and $v_{\rm 3}$ is
measured for the first time, which shows an anticorrelation for the presented
centrality ranges. These measurements are compared with hydrodynamic
calculations using IP-Glasma and $\rm T_{R}ENTo$ initial-state shapes, the
former based on the Color Glass Condensate effective theory with gluon
saturation, and the latter a parameterized model with nucleons as the relevant
degrees of freedom. The data are better described by the IP-Glasma rather than
the $\rm T_{R}ENTo$ based calculations. In particular, Trajectum and JETSCAPE
predictions, both based on the $\rm T_{R}ENTo$ initial state model but with
different parameter settings, fail to describe the measurements. As the
correlations between $[p_{\rm T}]$ and $v_{\rm n}$ are mainly driven by the
correlations of the size and the shape of the system in the initial state,
these new studies pave a novel way to characterize the initial state and help
pin down the uncertainty of the extracted properties of the quark$-$gluon
plasma recreated in relativistic heavy-ion collisions. | nucl-ex |
Latest CMS Heavy-Ion Results on Jets: Jet studies provide an experimental method to explore the features of energy
loss in the strongly interacting quark-gluon plasma. Recent jet results from
2.76 TeV PbPb and pp collisions measured with the CMS detector are presented.
Jets in the most head-on (central) PbPb collisions are quenched in comparison
to pp, and the jets fragment in different ways in the two systems. Measurements
from pPb collisions at 5.02 TeV show that the jet and charged particle
suppression seen in central PbPb measurements are not due to initial state
nuclear effects. | nucl-ex |
Comparison of fragment partitions production in peripheral and central
collisions: Ensembles of single-source events, produced in peripheral and central
collisions and correponding respectively to quasi-projectile and quasi-fusion
sources, are analyzed. After selections on fragment kinematic properties,
excitation energies of the sources are derived using the calorimetric method
and the mean behaviour of fragments of the two ensembles are compared.
Differences observed in their partitions, especially the charge asymmetry, can
be related to collective energy deposited in the systems during the collisions. | nucl-ex |
Decay modes of $^{10}$C nuclei unbound state: Unbound states of $^{10}$C nuclei produced as quasi-projectiles in
$^{12}$C+$^{24}$Mg collisions at E/A = 53 and 95 MeV are studied with the Indra
detector array. Multi-particle correlation function analyses provide
experimental evidence of sequential de-excitation mechanisms through the
production of intermediate $^{9}$B, $^{6}$Be and $^{8}$Be unbound nuclei. The
relative contributions of different decay sequences to the total decay width of
the explored states is estimated semi-quantitatively. The obtained results show
that heavy-ion collisions can be used as a tool to access spectroscopic
information about exotic nuclei. | nucl-ex |
Shape and Angular Distribution of the 4.438-MeV Line from Proton
Inelastic Scattering off 12C: The emission of the 4.438-MeV gamma-ray line in proton inelastic scattering
off 12C has been investigated in detail. The correlated scattering and emission
process is described independently for the direct reaction mechanism and for
the compound-nucleus (CN) component. The inelastic scattering process for
direct reactions is treated with a coupled-channels nuclear reaction code,
while the CN component is described as a superposition of separate resonances
with definite spin and parity, treated with the angular momentum coupling
theory. The calculations are compared to a comprehensive data set on measured
line shapes and angular distributions in the proton energy range E_p = 5.44 -
25.0 MeV. In the range E_p ~ 12 - 25 MeV a good agreement is obtained in
calculations assuming direct reactions with only a negligible part of CN
reactions. At lower energy, the data are reproduced by incoherent sums of the
direct component with typically one CN resonance. Based on these results, the
prospectives for line shape calculations applied to solar flares and gamma-ray
emission in proton radiotherapy are discussed. | nucl-ex |
Forward-Backward Multiplicity Correlations in Au+Au Collisions at
$\sqrt{s_{NN}}$ = 200 Gev: The study of correlations among particles produced in different rapidity
regions may provide understanding of the mechanisms of particle production.
Correlations that extend over a longer range are observed in hadron-hadron
interactions only at higher energies. Results for short and long-range
multiplicity correlations (Forward-Backward) are presented for Au+Au collisions
at $\sqrt{s_{NN}}$ = 200 GeV. The growth of long range correlations are
observed as a function of the pseudorapidity gap in central Au+Au collisions.
The Dual Parton model and Color Glass Condensate phenomenology have been
explored to understand the origin of long range correlations. | nucl-ex |
Strong Multi-step Interference Effects in 12C(d,p) to the 9/2+ State in
13C: The population of the 9.50 MeV 9/2+ resonance in 13C by single neutron
transfer reactions is expected to be dominated by the two-step route through
the 12C 2+ (4.44 MeV) state, with another possible contribution via the
strongly excited 3- (9.64 MeV) resonance in 12C. However, we find that a good
description of the angular distribution for population of this state via the
12C(d,p)13C reaction is only possible when both direct 0+ x g_9/2 and two-step
(via the 4.44 MeV 12C 2+ state) 2+ x d_5/2 paths are included in a coupled
reaction channel calculation. While the calculated angular distribution is
almost insensitive to the presence of the two-step path via the 9.64 MeV 12C 3-
resonance, despite a much greater contribution to the wave function from the 3-
x f_7/2 configuration, its inclusion is required to fit the details of the
experimental angular distribution. The very large interference between the
various components of the calculations, even when these are small, arises
through the ``kinematic'' effect associated with the different transfer routes. | nucl-ex |
Impact of $^{16}$O($γ$,$α$)$^{12}$C measurements on the
$^{12}$C($α,γ$)$^{16}$O astrophysical reaction rate: The $^{12}$C($\alpha,\gamma$)$^{16}$O reaction, an important component of
stellar helium burning, plays a key role in nuclear astrophysics. It has direct
impact on the evolution and final state of massive stars, while also
influencing the elemental abundances resulting from nucleosynthesis in such
stars. Providing a reliable estimate for the energy dependence of this reaction
at stellar helium burning temperatures has been a major goal for the field. In
this work, we study the role of potential new measurements of the inverse
reaction, $^{16}$O($\gamma,\alpha$)$^{12}$C, in reducing the overall
uncertainty. A multilevel R-matrix analysis is used to make extrapolations of
the astrophysical S factor for this reaction to the stellar energy of 300 keV.
The statistical precision of the S-factor extrapolation is determined by
performing multiple fits to existing E1 and E2 ground state capture data,
including the impact of possible future measurements of the
$^{16}$O($\gamma,\alpha$)$^{12}$C reaction. In particular, we consider a
proposed JLab experiment that will make use of a high-intensity low-energy
bremsstrahlung beam that impinges on an oxygen-rich single-fluid bubble chamber
in order to measure the total cross section for the inverse reaction. The
importance of low energy data as well as high precision data is investigated. | nucl-ex |
Effects of centrality fluctuation and deuteron formation on proton
number cumulant in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 3 GeV from
JAM model: We studied the effects of centrality fluctuation and deuteron formation on
the cumulants ($C_n$) and correlation functions ($\kappa_n$) of protons up to
sixth order in most central ($b<3$ fm) Au+Au collisions at
$\sqrt{s_\mathrm{NN}}$ = 3 GeV from a microscopic transport model (JAM). The
results are presented as a function of rapidity acceptance within transverse
momentum $0.4<p_{T}<2 $ GeV/$c$. We compared the results obtained by centrality
bin width correction (CBWC) using charged reference particle multiplicity with
CBWC done using impact parameter bins. It was found that at low energies the
centrality resolution for determining the collision centrality using charged
particle multiplicities is not good enough to reduce the initial volume
fluctuations effect for higher-order cumulant analysis. New methods need to be
developed to classify events with high centrality resolution for heavy-ion
collisions at low energies. Finally, we observed that the formation of deuteron
will suppress the higher-order cumulants and correlation functions of protons
and is found to be similar to the efficiency effect. This work can serve as a
noncritical baseline for the QCD critical point search at the high baryon
density region. | nucl-ex |
Final Results of GERDA on the Two-Neutrino Double-$β$ Decay
Half-Life of $^{76}$Ge: We present the measurement of the two-neutrino double-$\beta$ decay rate of
$^{76}$Ge performed with the GERDA Phase II experiment. With a subset of the
entire GERDA exposure, 11.8 kg$\cdot$yr, the half-life of the process has been
determined: $T^{2\nu}_{1/2} = (2.022 \pm 0.018_{stat} \pm
0.038_{sys})\times10^{21}$ yr. This is the most precise determination of the
$^{76}$Ge two-neutrino double-$\beta$ decay half-life and one of the most
precise measurements of a double-$\beta$ decay process. The relevant nuclear
matrix element can be extracted: $M^{2\nu}_{\text{eff}} = (0.101\pm0.001).$ | nucl-ex |
Centrality dependence of the charged-particle multiplicity density at
mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV: The centrality dependence of the charged-particle multiplicity density at
mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is
presented. The charged-particle density normalized per participating nucleon
pair increases by about a factor 2 from peripheral (70-80%) to central (0-5%)
collisions. The centrality dependence is found to be similar to that observed
at lower collision energies. The data are compared with models based on
different mechanisms for particle production in nuclear collisions. | nucl-ex |
Fragment Isotope Distributions and the Isospin Dependent Equation of
State: Calculations predict a connection between the isotopic composition of
particles emitted during an energetic nucleus-nucleus collision and the density
dependence of the asymmetry term of the nuclear equation of state (EOS). This
connection is investigated for central 112Sn+112Sn and 124Sn+124Sn collisions
at E/A=50 MeV in the limit of an equilibrated freezeout condition. Comparisons
between measured isotopic yields ratios and theoretical predictions in the
equilibrium limit are used to assess the sensitivity to the density dependence
of the asymmetry term of the EOS. This analysis suggests that such comparisons
may provide an opportunity to constrain the asymmetry term of the EOS. | nucl-ex |
Measurements of heavy-flavor jets with ALICE at the LHC: Heavy quarks created in ultra-relativistic heavy-ion collisions are mostly
produced in hard QCD processes during the early stages of the reaction. They
interact with the hot and cold nuclear matter throughout the evolution of the
medium via semi-hard and soft processes such as energy loss via gluon
radiations and collisions. Nuclear modification of heavy flavors in p-A systems
provides insight into cold nuclear matter effects such as (anti)shadowing and
$k_{T}$-broadening, and serves as a baseline for A-A studies. In addition to
that the fully reconstructed heavy-flavor jets provide additional information
on the flavor (or mass) dependence of fragmentation, color charge effects as
well as insight into the contribution of late gluon splitting. In this
contribution, we present the measurements of $b$-jet production in p-Pb
collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV and $c$-jet production in pp, p-Pb
and Pb-Pb collisions measured by the ALICE experiment at the LHC. The
measurements of the nuclear modification factors for $c$-jet in p-Pb and Pb-Pb
collisions are also presented. The experimental measurements are compared with
the results from Monte Carlo event generators (PYTHIA 6, PYTHIA 8 and Herwig 7)
and the NLO pQCD calculations (POWHEG+PYTHIA6). We find good agreement of the
measurements with the results from Monte Carlo event generators and from NLO
pQCD calculations. | nucl-ex |
Emergence of Quark-Gluon Plasma Phenomena: The discovery of QGP phenomena in small collision systems like pp and p-Pb
collisions have challenged the basic paradigms of heavy-ion and high-energy
physics. These proceedings give a brief overview of the key findings and their
implications, as well as today's experimental and theoretical situation. An
outlook of future measurement is made. | nucl-ex |
The Next Decade of Physics with PHENIX: The first decade of RHIC physics and the first heavy ion running at the LHC
have produced a wealth of data and discoveries. It is timely to now evaluate
what has been learned and ask what compelling new questions have been raised.
In this talk, several key unanswered questions about the properties of the
strongly coupled quark gluon plasma and the distribution of partons inside
nucleons and nuclei will be discussed along with how they can be addressed
experimentally. The PHENIX Collaboration has developed a plan for upgrading the
experiment in order to address these new questions. The current status of these
plans will be presented. | nucl-ex |
Halos and related structures: The halo structure originated in nuclear physics but is now encountered more
widely. It appears in loosely bound, clustered systems where the spatial
extension of the system is significantly larger than that of the binding
potentials. A review is given on our current understanding of these structures,
with an emphasis on how the structures evolve as more cluster components are
added, and on the experimental situation concerning halo states in light
nuclei. | nucl-ex |
Advancement of Photospheric Radius Expansion and Clocked Type-I X-Ray
Burst Models with the New $^{22}$Mg$(α,p)^{25}$Al Reaction Rate
Determined at Gamow Energy: We report the first (in)elastic scattering measurement of
$^{25}\mathrm{Al}+p$ with the capability to select and measure in a broad
energy range the proton resonances in $^{26}$Si contributing to the
$^{22}$Mg$(\alpha,p)$ reaction at type I x-ray burst energies. We measured
spin-parities of four resonances above the $\alpha$ threshold of $^{26}$Si that
are found to strongly impact the $^{22}$Mg$(\alpha,p)$ rate. The new rate
advances a state-of-the-art model to remarkably reproduce light curves of the
GS 1826$-$24 clocked burster with mean deviation $<9$ % and permits us to
discover a strong correlation between the He abundance in the accreting
envelope of photospheric radius expansion burster and the dominance of
$^{22}$Mg$(\alpha,p)$ branch. | nucl-ex |
Higher harmonic flow coefficients of identified hadrons in Pb-Pb
collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV: The elliptic, triangular, quadrangular and pentagonal anisotropic flow
coefficients for $\pi^{\pm}$, $\mathrm{K}^{\pm}$ and p+$\overline{\mathrm{p}}$
in Pb-Pb collisions at $\sqrt{s_\mathrm{{NN}}} = 2.76$ TeV were measured with
the ALICE detector at the Large Hadron Collider. The results were obtained with
the Scalar Product method, correlating the identified hadrons with reference
particles from a different pseudorapidity region. Effects not related to the
common event symmetry planes (non-flow) were estimated using correlations in pp
collisions and were subtracted from the measurement. The obtained flow
coefficients exhibit a clear mass ordering for transverse momentum
($p_{\mathrm{T}}$) values below $\approx$ 3 GeV/$c$. In the intermediate
$p_{\mathrm{T}}$ region ($3 < p_{\mathrm{T}} < 6$ GeV/$c$), particles group at
an approximate level according to the number of constituent quarks, suggesting
that coalescence might be the relevant particle production mechanism in this
region. The results for $p_{\mathrm{T}} < 3$ GeV/$c$ are described fairly well
by a hydrodynamical model (iEBE-VISHNU) that uses initial conditions generated
by A Multi-Phase Transport model (AMPT) and describes the expansion of the
fireball using a value of 0.08 for the ratio of shear viscosity to entropy
density ($\eta/s$), coupled to a hadronic cascade model (UrQMD). Finally,
expectations from AMPT alone fail to quantitatively describe the measurements
for all harmonics throughout the measured transverse momentum region. However,
the comparison to the AMPT model highlights the importance of the late hadronic
rescattering stage to the development of the observed mass ordering at low
values of $p_{\mathrm{T}}$ and of coalescence as a particle production
mechanism for the particle type grouping at intermediate values of
$p_{\mathrm{T}}$ for all harmonics. | nucl-ex |
Probing Cold and Hot, Dense Nuclear Media Via High-p$_{T}$ Jets with
Di-hadron and gamma-hadron Correlations at PHENIX: With the recent high statistics Au+Au and Cu+Cu runs at RHIC, it has become
possible to systematically study jet properties in several different colliding
systems with potentially different final state interactions. In this talk we
present results from high-pT di-hadron and gamma-hadron correlations from p+p,
d+Au, Cu+Cu, and Au+Au collisions where jets in vacuum, cold nuclear matter,
and hot, dense nuclear matter are studied. | nucl-ex |
Detectors for Energy-Resolved Fast Neutron Imaging: Two detectors for energy-resolved fast-neutron imaging in pulsed broad-energy
neutron beams are presented. The first one is a neutron-counting detector based
on a solid neutron converter coupled to a gaseous electron multiplier (GEM).
The second is an integrating imaging technique, based on a scintillator for
neutron conversion and an optical imaging system with fast framing capability. | nucl-ex |
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