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Nuclei with enhanced Schiff moments in practical elements for atomic and
molecular EDM measurements: This is a resource paper concerning enhancement of observable time-reversal
breaking effects by nuclear structure, aimed at AMO experimentalists. It's
intended to support a white paper by providing some orientation on what can be
said about some particular isotopes. Any conclusions are qualitative, and the
reader should consult and cite the primary references and reviews rather than
this arXiv alone. | nucl-ex |
Charm and beauty isolation from heavy flavor decay electrons in Au+Au
collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV at RHIC: We present a study of charm and beauty isolation based on a data-driven
method with recent measurements on heavy flavor hadrons and their decay
electrons in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV at RHIC. The
individual electron $p_{\rm T}$ spectra, $R_{\rm AA}$ and $v_2$ distributions
from charmed and beauty hadron decays are obtained. We find that the electron
$R_{\rm AA}$ from beauty hadron decays ($R_{\rm AA}^{\rm b\rightarrow e}$) is
suppressed in minimum bias Au+Au collisions but less suppressed compared with
that from charmed hadron decays at $p_{\rm T}$ $>$ 3.5 GeV/$c$, which indicates
that beauty quark interacts with the hot-dense medium with depositing its
energy and is consistent with the mass-dependent energy loss scenario. For the
first time, the non-zero electron $v_2$ from beauty hadron decays ($v_2^{\rm
b\rightarrow e}$) at $p_{\rm T}$ $>$ 3.0 GeV/$c$ is observed and shows smaller
elliptic flow compared with that from charmed hadron decays at $p_{\rm T}$ $<$
4.0 GeV/$c$. At 2.5 GeV/$c$ $<$ $p_{\rm T}$ $<$ 4.5 GeV/$c$, $v_2^{\rm
b\rightarrow e}$ is smaller than a number-of-constituent-quark (NCQ) scaling
hypothesis. This suggests that beauty quark is unlikely thermalized and too
heavy to be moved in a partonic collectivity in heavy-ion collisions at the
RHIC energy. | nucl-ex |
High Resolution Hypernuclear Spectroscopy at Jefferson Lab Hall A: The characteristics of the Jefferson Lab electron beam, together with those
of the experimental equipment, offer a unique opportunity to study hypernuclear
spectroscopy via electromagnetic induced reactions. Experiment 94-107 started a
systematic study on 1p-shell targets, $^{12}C$, $^{9}Be$ and $^{16}O$. For
$^{12}C$ for the first time measurable strength in the core-excited part of the
spectrum between the ground state and the p state was shown in
$^{12}_{\Lambda}B$ spectrum. A high-quality $^{16}_{\Lambda}N$ spectrum was
produced for the first time with sub-MeV energy resolution. A very precise
$\Lambda$ binding energy value for $^{16}_{\Lambda}N$, calibrated against the
elementary $(e,e'K^+)$ reaction on hydrogen, has also been obtained.
$^{9}_{\Lambda}Li$ spectrum shows some disagreement in strength for the second
and third doublet with respect to the theory. | nucl-ex |
Improved precision on the experimental E0 decay branching ratio of the
Hoyle state: Stellar carbon synthesis occurs exclusively via the $3\alpha$ process, in
which three $\alpha$ particles fuse to form $^{12}$C in the excited Hoyle
state, followed by electromagnetic decay to the ground state. The Hoyle state
is above the $\alpha$ threshold, and the rate of stellar carbon production
depends on the radiative width of this state. The radiative width cannot be
measured directly, and must instead be deduced by combining three separately
measured quantities. One of these quantities is the $E0$ decay branching ratio
of the Hoyle state, and the current $10$\% uncertainty on the radiative width
stems mainly from the uncertainty on this ratio. The $E0$ branching ratio was
deduced from a series of pair conversion measurements of the $E0$ and $E2$
transitions depopulating the $0^+_2$ Hoyle state and $2^+_1$ state in $^{12}$C,
respectively. The excited states were populated by the $^{12}$C$(p,p^\prime)$
reaction at 10.5 MeV beam energy, and the pairs were detected with the
electron-positron pair spectrometer, Super-e, at the Australian National
University. The deduced branching ratio required knowledge of the proton
population of the two states, as well as the alignment of the $2^+_1$ state in
the reaction. For this purpose, proton scattering and $\gamma$-ray angular
distribution experiments were also performed. An $E0$ branching ratio of
$\Gamma^{E0}_{\pi}/\Gamma=8.2(5)\times10^{-6}$ was deduced in the current work,
and an adopted value of $\Gamma^{E0}_{\pi}/\Gamma=7.6(4)\times10^{-6}$ is
recommended based on a weighted average of previous literature values and the
new result. The new recommended value for the $E0$ branching ratio is about 14%
larger than the previous adopted value of
$\Gamma^{E0}_{\pi}/\Gamma=6.7(6)\times10^{-6}$, while the uncertainty has been
reduced from 9% to 5%. | nucl-ex |
Event-by-event mean p_T fluctuations in pp and Pb-Pb collisions at the
LHC: The ALICE detector at the LHC is used to study the properties of the
Quark-Gluon Plasma produced in heavy-ion collisions. As a reference
measurement, also the analysis of proton-proton (pp) collisions is very
important. In the study presented here, event-by-event fluctuations of the mean
transverse momentum are analysed in pp collisions at sqrt(s) = 0.9, 2.76 and 7
TeV, and Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV as a function of the
charged-particle multiplicity. In both systems, dynamical fluctuations beyond
the statistical expectation are observed. In pp collisions, no significant
dependence on collision energy is found, even in comparison to inclusive
results at much lower collision energies. Likewise, central A-A collisions show
only little dependence on collision energy. The multiplicity dependence
observed in peripheral Pb-Pb data is in agreement with that in pp collisions.
Going to more central Pb-Pb collisions, a clear deviation from this trend is
found, reaching a significant reduction of the fluctuations in most central
collisions. Comparisons to Monte Carlo event generators show good agreement in
pp, but rather large differences in Pb-Pb collisions. | nucl-ex |
Measurement of global polarization of Λ hyperons in few-GeV
heavy-ion collisions: The global polarization of {\Lambda} hyperons along the total orbital angular
momentum of a relativistic heavy-ion collision is presented based on the high
statistics data samples collected in Au+Au collisions at \sqrt{s_{NN}} = 2.4
GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer
(HADES) at GSI, Darmstadt. This is the first measurement below the strangeness
production threshold in nucleon-nucleon collisions. Results are reported as a
function of the collision centrality as well as a function of the hyperon
transverse momentum (p_T) and rapidity (y_{CM}) for the range of centrality
0--40%. We observe a strong centrality dependence of the polarization with an
increasing signal towards peripheral collisions. For mid-central (20--40%)
collisions the polarization magnitudes are <P_{\Lambda}>(%) = 6.8 \pm 1.3
(stat.) \pm 2.1 (syst.) for Au+Au and <P_{\Lambda}>(%) = 6.2 \pm 0.4 (stat.)
\pm 0.6 (syst.) for Ag+Ag, which are the largest values observed so far. This
observation thus provides a continuation of the increasing trend previously
observed by STAR and contrasts expectations from recent theoretical
calculations predicting a maximum in the region of collision energies about 3
GeV. The observed polarization is of a similar magnitude as predicted by 3D
fluid dynamics and the UrQMD plus thermal vorticity model and significantly
above results from the AMPT model. | nucl-ex |
Characterizing the mechanism(s) of heavy element synthesis: A review of the current state of our understanding of complete fusion
reaction mechanisms is presented, from the perspective of an experimentalist.
For complete fusion reactions, the overall uncertainties in predicting heavy
element synthesis cross sections are examined in terms of the uncertainties
associated with the calculations of capture cross sections, fusion
probabilities and survival probabilities. | nucl-ex |
Two-particle transverse momentum correlations in pp and p-Pb collisions
at energies available at the CERN Large Hadron Collider: Two-particle transverse momentum differential correlators, recently measured
in Pb--Pb collisions at energies available at the CERN Large Hadron Collider
(LHC), provide an additional tool to gain insights into particle production
mechanisms and infer transport properties, such as the ratio of shear viscosity
to entropy density, of the medium created in Pb-Pb collisions. The longitudinal
long-range correlations and the large azimuthal anisotropy measured at low
transverse momenta in small collision systems, namely pp and p-Pb, at LHC
energies resemble manifestations of collective behaviour. This suggests that
locally equilibrated matter may be produced in these small collision systems,
similar to what is observed in Pb-Pb collisions. In this work, the same
two-particle transverse momentum differential correlators are exploited in pp
and p-Pb collisions at $\sqrt{s} = 7$ TeV and $\sqrt{s_{\rm NN}} = 5.02$ TeV,
respectively, to seek evidence for viscous effects. Specifically, the strength
and shape of the correlators are studied as a function of the produced particle
multiplicity to identify evidence for longitudinal broadening that might reveal
the presence of viscous effects in these smaller systems. The measured
correlators and their evolution from pp and p--Pb to Pb--Pb collisions are
additionally compared to predictions from Monte Carlo event generators, and the
potential presence of viscous effects is discussed. | nucl-ex |
PHENIX Direct Photons in 200 GeV p+p and Au+Au Collisions: We present the first positive direct photon results in Au+Au at sqrt{s_NN} =
200 GeV along with initial p+p results at the same energy. The p+p result is
found to be consistent with NLO perturbative QCD predictions within its large
uncertainties. In central Au+Au collisions, an excess over expected background
as large as 200-300% is observed from p_T = 4-12 GeV/c. This large signal is
shown to be consistent with the scaled pQCD photon prediction, together with
suppression of meson background sources. | nucl-ex |
Statistical sensitivity of the nEDM apparatus at PSI to neutron
mirror-neutron oscillations: The neutron and its hypothetical mirror counterpart, a sterile state
degenerate in mass, could spontaneously mix in a process much faster than the
neutron $\beta$-decay. Two groups have performed a series of experiments in
search of neutron - mirror-neutron ($n-n'$) oscillations. They reported no
evidence, thereby setting stringent limits on the oscillation time
$\tau_{nn'}$. Later, these data sets have been further analyzed by Berezhiani
et al.(2009-2017), and signals, compatible with $n-n'$ oscillations in the
presence of mirror magnetic fields, have been reported. The Neutron Electric
Dipole Moment Collaboration based at the Paul Scherrer Institute performed a
new series of experiments to further test these signals. In this paper, we
describe and motivate our choice of run configurations with an optimal filling
time of $29~$s, storage times of $180~$s and $380~$s, and applied magnetic
fields of $10~\mu$T and $20~\mu$T. The choice of these run configurations
ensures a reliable overlap in settings with the previous efforts and also
improves the sensitivity to test the signals. We also elaborate on the
technique of normalizing the neutron counts, making such a counting experiment
at the ultra-cold neutron source at the Paul Scherrer Institute possible.
Furthermore, the magnetic field characterization to meet the requirements of
this $n-n'$ oscillation search is demonstrated. Finally, we show that this
effort has a statistical sensitivity comparable to the current leading
constraints for $n-n'$ oscillations. | nucl-ex |
Experimental conditions for the gamma optical scattering: This work discusses the possibility of observation of nuclear multiphoton
processes in which the interaction of a gamma ray photon with a nucleus takes
place simultaneously with the interaction of a radio-frequency photon. | nucl-ex |
Prototype Performance of Novel Muon Telescope Detector at STAR: Research on a large-area, cost-effective Muon Telescope Detector has been
carried out for RHIC and for next generation detectors at future QCD Lab. We
utilize state-of-the-art multi-gap resistive plate chambers with large modules
and long readout strips in detector design \cite{MTDLDRD}. The results from
cosmic ray and beam test will be presented to address intrinsic timing and
spatial resolution for a Long-MRPC. The prototype performance of a novel muon
telescope detector at STAR will be reported, including muon identification
capability, timing and spatial resolution. | nucl-ex |
Data on neutron-neutron scattering length extracted in the n+2H-->n+n+p
reaction at 60 MeV: $^{1}S_{0}$ \textit{nn}-scattering length has been measured in the
\textit{nd}-breakup reaction at 60 MeV. The experiment was performed in the
final state interaction geometry with registration of all three secondary
particles. The scattering length $a_{nn} = -16.3 \pm 0.5$~fm was obtained from
a comparison of the experimental dependence of the \textit{nd}-breakup yield on
the relative energy of \textit{nn}-pair with the simulation results. An
analysis of this value of scattering length together with the data obtained in
other experiments on \textit{nd}- and \textit{dd}-breakup confirms the
hypothesis about the influence of $3N$-forces on the values of
\textit{nn}-interaction parameters extracted in these reactions. | nucl-ex |
Measurement of Open Heavy Flavor Production with Single Muons in p+p and
d+Au Collisions at RHIC: Heavy flavor production in hadronic collisions is dominated by gluonic
processes and so is a sensitive probe of the gluon structure function in the
nucleon and its modification in nuclei. A study of heavy flavor production in
p+p and d+Au collisions in various kinematic regions presents an opportunity to
probe cold nuclear medium effects; parton shadowing, color glass condensate,
initial state energy loss, and coherent multiple scattering in final state
interactions. The PHENIX muon arms cover both forward and backward directions
in the rapidity range of $1.2 < |\eta| < 2.4$. We investigate single muon
production from open heavy flavor and light mesons decay in p+p and d+Au
collisions at forward and backward rapidity. | nucl-ex |
Open heavy flavour production via semi-leptonic decay muons in lead lead
collisions at $\sqrtsnn = 2.76$ \TeV with the ATLAS detector at the LHC: Measurements of heavy quark production and suppression in ultra-relativistic
nuclear collisions probe the interactions of heavy quarks with the hot, dense
medium created in the collisions. ATLAS has measured heavy quark production in
$\sqrtsnn = 2.76$ \TeV \PbPb collisions via semi-leptonic decays of open heavy
flavour hadrons to muons. Results are presented for the per-event muon yield as
a function of muon transverse momentum, \pT, over the range of $4 < \pT < 14$
\GeV. The centrality dependence of the muon yields is characterized by the
"central to peripheral" ratio, \Rcp. Muon production is suppressed by
approximately a factor of two in central collisions relative to peripheral
collisions. Within the experimental errors, the observed suppression is
independent of muon \pT for all centralities. | nucl-ex |
Fusion excitation function revisited: We report on a comprehensive systematics of fusion-evaporation and/or
fusion-fission cross sections for a very large variety of systems over an
energy range 4-155 A.MeV. Scaled by the reaction cross sections, fusion cross
sections do not show a universal behavior valid for all systems although a high
degree of correlation is present when data are ordered by the system mass
asymmetry.For the rather light and close to mass-symmetric systems the main
characteristics of the complete and incomplete fusion excitation functions can
be precisely determined. Despite an evident lack of data above 15A.MeV for all
heavy systems the available data suggests that geometrical effects could
explain the persistence of incomplete fusion at incident energies as high as
155A.MeV. | nucl-ex |
Inclusive Jet Spectra in p-Pb Collisions at ALICE: Jet suppression has been observed in central heavy ion collisions. This
suppression is attributed to partonic energy loss in the Quark Gluon Plasma
(QGP) formed in such collisions. However, this measurement is influenced by all
stages of the collision. It is expected that in p-Pb collisions similar initial
conditions occur as in Pb-Pb collisions without creating a QGP, allowing
modification to the jet spectra due to cold nuclear matter effects to be
quantified. Inclusive jet spectra in p-Pb collisions at $\sqrt{s_{\rm NN}} =
5.02$ TeV measured by ALICE are presented. Jets are reconstructed via the
anti-k$_{\rm T}$ algorithm with different resolution parameters by combining
charged tracks measured in the ALICE tracking system with the neutral energy
deposited in the electromagnetic calorimeter. The jet spectra can be used to
determine a nuclear modification factor $R_{\rm pPb}$ while the jet profile in
p-Pb is studied by dividing spectra measured with different resolution
parameters and comparing to the same ratio measured in pp collisions. | nucl-ex |
Charged pion form factor between Q^2=0.60 and 2.45 GeV^2. II.
Determination of, and results for, the pion form factor: The charged pion form factor, Fpi(Q^2), is an important quantity which can be
used to advance our knowledge of hadronic structure. However, the extraction of
Fpi from data requires a model of the 1H(e,e'pi+)n reaction, and thus is
inherently model dependent. Therefore, a detailed description of the extraction
of the charged pion form factor from electroproduction data obtained recently
at Jefferson Lab is presented, with particular focus given to the dominant
uncertainties in this procedure. Results for Fpi are presented for
Q^2=0.60-2.45 GeV^2. Above Q^2=1.5 GeV^2, the Fpi values are systematically
below the monopole parameterization that describes the low Q^2 data used to
determine the pion charge radius. The pion form factor can be calculated in a
wide variety of theoretical approaches, and the experimental results are
compared to a number of calculations. This comparison is helpful in
understanding the role of soft versus hard contributions to hadronic structure
in the intermediate Q^2 regime. | nucl-ex |
Nuclear excitation functions from 40-200 MeV proton irradiation of
terbium: Nuclear formation cross sections are reported for 26 radionuclides, measured
with 40 to 200 MeV proton irradiations of terbium foils. These data are
relevant to the production of medically relevant radionuclides (e.g., 152Tb,
155Tb, 155Eu, and 156Eu) and to ongoing efforts to characterize stellar
nucleosynthesis routes passing through long-lived intermediaries (e.g., 153Gd).
Computational predictions from the ALICE2011, CEM03.03, Bertini, and INCL+ABLA
codes are compared with newly measured data to contribute to the ongoing
process of code development, and yields are calculated for selected
radionuclides using measured data. | nucl-ex |
Nonextensive statistics in spin precession: Many experiments utilize the precession of trapped particles in magnetic
fields to perform high precision measurements. It had been presumed that after
free precession, initially polarized particles will form a Gaussian phase
distribution in the plane of precession. We show that trapped particles in the
presence of magnetic field gradients and electric fields will often form a
non-Gaussian distribution with power-law tails which are consistent with
nonextensive statistics. As the exact shape of the distribution depends upon
many experimental parameters, it provides a potential new technique to directly
measure them. | nucl-ex |
Direct observation of dijets in central Au+Au collisions at sqrt(s_NN) =
200 GeV: The STAR Collaboration at RHIC reports measurements of azimuthal correlations
of high transverse momentum (p_T) charged hadrons in Au+Au collisions at higher
p_T than reported previously. As p_T is increased, a narrow, back-to-back peak
emerges above the decreasing background, providing a clear dijet signal for all
collision centralities studied. Using these correlations, we perform a
systematic study of dijet production and suppression in nuclear collisions,
providing new constraints on the mechanisms underlying partonic energy loss in
dense matter. | nucl-ex |
Shell Evolutions and Nuclear Forces: During the last 30 years, and more specifically during the last 10 years,
many experiments have been carried out worldwide using different techniques to
study the shell evolution of nuclei far from stability. What seemed not
conceivable some decades ago became rather common: all known magic numbers that
are present in the valley of stability disappear far from stability and are
replaced by new ones at the drip line. By gathering selected experimental
results, beautifully consistent pictures emerge, that very likely take root in
the properties of the nuclear forces.The present manuscript describes some of
these discoveries and proposes an intuitive understanding of these shell
evolutions derived from observations. Extrapolations to yet unstudied regions,
as where the explosive r-process nucleosynthesis occurs, are proposed. Some
remaining challenges and puzzling questions are also addressed. | nucl-ex |
The ALICE experiment -- A journey through QCD: The ALICE experiment was proposed in 1993, to study strongly interacting
matter at extreme energy densities via a comprehensive investigation of nuclear
collisions at the LHC. Its physics programme initially focused on the
determination of the properties of the Quark-Gluon Plasma (QGP), a deconfined
state of quarks and gluons and was extended along the years, covering a diverse
ensemble of observables related to Quantum Chromodynamics (QCD), the theory of
strong interactions. The experiment has studied Pb-Pb, Xe-Xe, p-Pb and pp
collisions in the multi-TeV energy range, during the Run 1 and Run 2 data
taking periods at the LHC (2009-2018). The aim of this review article is to
gather and summarise a selection of ALICE physics results and to discuss their
implications on the current understanding of the macroscopic and microscopic
properties of strongly interacting matter at the highest temperature reached in
the laboratory. It will be shown that it is possible to have a quantitative
description of the properties of the QGP produced in Pb--Pb collisions. We also
show that various features, commonly ascribed to QGP formation, are detected
for a wide range of interacting system sizes. Precision measurements of
QCD-related observables not directly connected to the study of the QGP will
also be discussed. Prospects for future measurements with the ALICE detector
and its foreseen upgrades will also be briefly described. | nucl-ex |
Two-particle azimuthal correlations in photonuclear ultraperipheral
Pb+Pb collisions at 5.02 TeV with ATLAS: Two-particle long-range azimuthal correlations are measured in photonuclear
collisions using 1.7 nb$^{-1}$ of 5.02 TeV Pb+Pb collision data collected by
the ATLAS experiment at the LHC. Candidate events are selected using a
dedicated high-multiplicity photonuclear event trigger, a combination of
information from the zero-degree calorimeters and forward calorimeters, and
from pseudorapidity gaps constructed using calorimeter energy clusters and
charged-particle tracks. Distributions of event properties are compared between
data and Monte Carlo simulations of photonuclear processes. Two-particle
correlation functions are formed using charged-particle tracks in the selected
events, and a template-fitting method is employed to subtract the non-flow
contribution to the correlation. Significant nonzero values of the second- and
third-order flow coefficients are observed and presented as a function of
charged-particle multiplicity and transverse momentum. The results are compared
with flow coefficients obtained in proton-proton and proton-lead collisions in
similar multiplicity ranges, and with theoretical expectations. The unique
initial conditions present in this measurement provide a new way to probe the
origin of the collective signatures previously observed only in hadronic
collisions. | nucl-ex |
Peculiarities of isotopic temperatures obtained from p+A collisions at 1
GeV: Nuclear temperatures obtained from inclusive measurements of double isotopic
yield ratios of fragments produced in 1 GeV p + A collisions amount to about 4
MeV nearly independent from the target mass. | nucl-ex |
Reexamination of phenomenological two-photon exchange corrections to the
proton form factors and e+-p scattering: We extract the two-photon exchange (TPE) contributions to electron--proton
elastic scattering using two parametrizations and compare the results to
different phenomenological extractions and direct calculations of the TPE
effects. We find that many of the extractions give similar results, and
highlight the common assumptions and the impact of not including such
assumptions. We provide a simple parametrization of the TPE contribution to the
unpolarized cross section, along with an estimate of the fit uncertainties and
the uncertainties associated with the assumptions made in the extraction. We
look at the contributions as extracted from various e--p elastic scattering
observables, and make predictions for ratio $R^{e^{+} e^{-}}$ of
positron-proton to electron-proton elastic scattering cross sections. | nucl-ex |
Photons and low-mass dileptons: results from PHENIX: Most recent PHENIX results on electromagnetic probes are presented including
first preliminary results obtained with the Hadron Blind Detector (HBD) on e+e-
invariant mass spectra from Au+Au collisions at sqrt(s_NN) = 200 GeV. | nucl-ex |
LAMBDA: Large Area Modular BaF2 Detector Array for the measurement of
high energy gamma rays: A large BaF2 detector array along with its dedicated CAMAC electronics and
VME based data acquisition system has been designed, constructed and installed
successfully at VECC, Kolkata for studying high energy gamma rays (E>8 MeV).
The array consists of 162 detector elements. The detectors were fabricated from
bare barium fluoride crystals (each measuring 35 cm in length and having
cross-sectional area of 3.5 cm X 3.5 cm X 35.0 cm). The basic properties of the
detectors (energy resolution, time resolution, efficiency, uniformity, fast to
slow ratio etc.) were studied exhaustively. Complete GEANT3 monte carlo
simulations were performed to optimize the detector design and also to generate
the response function. The detector system has been used successfully to
measure high energy photons from 113Sb, formed by bombarding 145 and 160 MeV
20Ne beams on a 93Nb target. The measured experimental spectra are in good
agreement with those from a modified version of the statistical model code
CASCADE. In this paper, we present the complete description of this detector
array along with its in-beam performance. | nucl-ex |
Low-lying states in 8B: Excitation functions of elastic and inelastic 7Be+p scattering were measured
in the energy range between 1.6 and 2.8 MeV in the c.m. An R-matrix analysis of
the excitation functions provides strong evidence for new positive parity
states in 8B. A new 2+ state at an excitation energy of 2.55 MeV was observed
and a new 0+ state at 1.9 MeV is tentatively suggested. The R-matrix and Time
Dependent Continuum Shell Model were used in the analysis of the excitation
functions. The new results are compared to the calculations of contemporary
theoretical models. | nucl-ex |
Study of Z production in PbPb and pp collisions at sqrt(s[NN]) = 2.76
TeV in the dimuon and dielectron decay channels: The production of Z bosons is studied in the dimuon and dielectron decay
channels in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV, using data
collected by the CMS experiment at the LHC. The PbPb data sample corresponds to
an integrated luminosity of about 150 inverse microbarns, while the pp data
sample collected in 2013 at the same nucleon-nucleon centre-of-mass energy has
an integrated luminosity of 5.4 inverse picobarns. The Z boson yield is
measured as a function of rapidity, transverse momentum, and collision
centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic
nucleon-nucleon collisions, is found to be 1.06 +/- 0.05 (stat) +/- 0.08 (syst)
in the dimuon channel and 1.02 +/- 0.08 (stat) +/- 0.15 (syst) in the
dielectron channel, for centrality-integrated Z boson production. This binary
collision scaling is seen to hold in the entire kinematic region studied, as
expected for a colourless probe that is unaffected by the hot and dense QCD
medium produced in heavy ion collisions. | nucl-ex |
The LHC as a Nucleus-Nucleus Collider: This paper begins with a summary of the status of the Large Hadron Collider
at CERN, including the lead-ion injector chain and the plans for the first
phases of commissioning and operation with colliding proton beams. In a later
phase, the LHC will collide lead nuclei at centre-of-mass energies of 5.5 TeV
per colliding nucleon pair. This leap to 28 times beyond what is presently
accessible will open up a new regime, not only in the experimental study of
nuclear matter, but also in the beam physics of hadron colliders.
Ultraperipheral and hadronic interactions of highly-charged beam nuclei will
cause beam losses that dominate the luminosity decay and may quench
superconducting magnets, setting upper limits on luminosity and stored beam
current. Lower limits are set by beam instrumentation. On the other hand,
coherent radiation by the nuclear charges should provide natural cooling to
overcome intra-beam scattering. As with protons, a flexible, staged approach to
full performance will test the limits and make optimal use of scheduled beam
time. | nucl-ex |
Strange Meson Enhancement in PbPb Collisions: The NA44 Collaboration has measured yields and differential distributions of
K+, K-, pi+, pi- in transverse kinetic energy and rapidity, around the
center-of-mass rapidity in 158 A GeV/c Pb+Pb collisions at the CERN SPS. A
considerable enhancement of K+ production per pi is observed, as compared to
p+p collisions at this energy. To illustrate the importance of secondary hadron
rescattering as an enhancement mechanism, we compare strangeness production at
the SPS and AGS with predictions of the transport model RQMD. | nucl-ex |
New data strengthen the connection between Short Range Correlations and
the EMC effect: Recently published measurements of the two nucleon short range correlation
($NN$-SRC) scaling factors, $a_2(A/d)$, strengthen the previously observed
correlation between the magnitude of the EMC effect measured in electron deep
inelastic scattering at $0.35\le x_B\le 0.7$ and the SRC scaling factor
measured at $x_B \ge 1$. The new results have improved precision and include
previously unmeasured nuclei. The measurements of $a_2(A/d)$ for $^9$Be and
$^{197}$Au agree with published predictions based on the EMC-SRC correlation.
This paper examines the effects of the new data and of different corrections to
the data on the slope and quality of the EMC-SRC correlation, the size of the
extracted deuteron IMC effect, and the free neutron structure function. The
results show that the linear EMC-SRC correlation is robust and that the slope
of the correlation is insensitive to most combinations of corrections examined
in this work. This strengthens the interpretation that both $NN$-SRC and the
EMC effect are related to high momentum nucleons in the nucleus. | nucl-ex |
Evidence for Spinodal Decomposition in Nuclear Multifragmentation: Multifragmentation of a ``fused system'' was observed for central collisions
between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products
were well identified thanks to the high performances of the INDRA 4pi array.
Experimental higher-order charge correlations for fragments show a weak but non
ambiguous enhancement of events with nearly equal-sized fragments. Supported by
dynamical calculations in which spinodal decomposition is simulated, this
observed enhancement is interpreted as a ``fossil'' signal of spinodal
instabilities in finite nuclear systems. | nucl-ex |
Feasibility study of the quasi-free creation of the eta-prime meson in
the reaction pn --> pn eta-prime: The feasibility of an investigation of the pn --> pn eta-prime reaction by
means of the COSY-11 internal target facility is discussed. Appraisals are
based on the assumption of the quasi-free reactions of beam protons,
circulating in the cooler synchrotron COSY, with neutrons from a windowless
deuteron cluster target. | nucl-ex |
The study of heavy flavors via non-photonic electrons in STAR: The strong suppression of hadrons with high transverse momenta in central
Au+Au collisions observed at RHIC is generally interpreted as a consequence of
energy loss of energetic partons in the hot and dense matter before
fragmenting. The study of heavy quark production tests our understanding of
energy loss mechanisms.
Heavy quarks were expected to lose less energy in the medium than light
quarks and gluons due to the suppression of small-angle gluon radiation.
However, the high transverse momentum non-photonic electron spectra, which are
dominated by semi-leptonic decays of heavy quarks, show a strong suppression in
central Au+Au collisions as well. Current theoretical models do not
satisfactory explain this observation.
Preliminary non-photonic electron spectra are being extracted for Cu+Cu
collisions at $\sqrt{s_{NN}}$ = 200 GeV. They are compared to the non-photonic
electron yields from p+p and Au+Au collisions at the same collision energy.
This provides a direct experimental test of the dependence of the non-photonic
electron yield on collision system size. | nucl-ex |
A precise measurement of the deuteron elastic structure function A(Q^2): The A(Q^2) structure function in elastic electron-deuteron scattering was
measured at six momentum transfers Q^2 between 0.66 and 1.80 (GeV/c)^2 in Hall
C at Jefferson Laboratory. The scattered electrons and recoil deuterons were
detected in coincidence, at a fixed deuteron angle of 60.5 degrees. These new
precise measurements resolve discrepancies between older sets of data. They put
significant constraints on existing models of the deuteron electromagnetic
structure, and on the strength of isoscalar meson exchange currents. | nucl-ex |
Study of the gp-->etap reaction with the Crystal Ball detector at the
Mainz Microtron(MAMI-C): The gp-->etap reaction has been measured with the Crystal Ball and TAPS
multiphoton spectrometers in the energy range from the production threshold of
707 MeV to 1.4 GeV (1.49 =< W >= 1.87 GeV). Bremsstrahlung photons produced by
the 1.5-GeV electron beam of the Mainz Microtron MAMI-C and momentum analyzed
by the Glasgow Tagging Spectrometer were used for the eta-meson production. Our
accumulation of 3.8 x 10^6 gp-->etap-->3pi0p-->6gp events allows a detailed
study of the reaction dynamics. The gp-->etap differential cross sections were
determined for 120 energy bins and the full range of the production angles. Our
data show a dip near W = 1680 MeV in the total cross section caused by a
substantial dip in eta production at forward angles. The data are compared to
predictions of previous SAID and MAID partial-wave analyses and to thelatest
SAID and MAID fits that have included our data. | nucl-ex |
The Importance of Correlations and Fluctuations on the Initial Source
Eccentricity in High-Energy Nucleus-Nucleus Collisions: In this paper, we investigate various ways of defining the initial source
eccentricity using the Monte Carlo Glauber (MCG) approach. In particular, we
examine the participant eccentricity, which quantifies the eccentricity of the
initial source shape by the major axes of the ellipse formed by the interaction
points of the participating nucleons. We show that reasonable variation of the
density parameters in the Glauber calculation, as well as variations in how
matter production is modeled, do not significantly modify the already
established behavior of the participant eccentricity as a function of collision
centrality. Focusing on event-by-event fluctuations and correlations of the
distributions of participating nucleons we demonstrate that, depending on the
achieved event-plane resolution, fluctuations in the elliptic flow magnitude
$v_2$ lead to most measurements being sensitive to the root-mean-square, rather
than the mean of the $v_2$ distribution. Neglecting correlations among
participants, we derive analytical expressions for the participant eccentricity
cumulants as a function of the number of participating nucleons,
$\Npart$,keeping non-negligible contributions up to $\ordof{1/\Npart^3}$. We
find that the derived expressions yield the same results as obtained from
mixed-event MCG calculations which remove the correlations stemming from the
nuclear collision process. Most importantly, we conclude from the comparison
with MCG calculations that the fourth order participant eccentricity cumulant
does not approach the spatial anisotropy obtained assuming a smooth nuclear
matter distribution. In particular, for the Cu+Cu system, these quantities
deviate from each other by almost a factor of two over a wide range in
centrality. | nucl-ex |
Charged jet cross sections and properties in proton-proton collisions at
$\sqrt{s}=7$ TeV: The differential charged jet cross sections, jet fragmentation distributions,
and jet shapes are measured in minimum bias proton-proton collisions at
centre-of-mass energy $\sqrt{s}=7$ TeV using the ALICE detector at the LHC.
Jets are reconstructed from charged particle momenta in the mid-rapidity region
using the sequential recombination $k_{\rm T}$ and anti-$k_{\rm T}$ as well as
the SISCone jet finding algorithms with several resolution parameters in the
range $R=0.2$ to $0.6$. Differential jet production cross sections measured
with the three jet finders are in agreement in the transverse momentum ($p_{\rm
T}$) interval $20<p_{\rm T}^{\rm jet,ch}<100$ GeV/$c$. They are also consistent
with prior measurements carried out at the LHC by the ATLAS collaboration. The
jet charged particle multiplicity rises monotonically with increasing jet
$p_{\rm T}$, in qualitative agreement with prior observations at lower
energies. The transverse profiles of leading jets are investigated using radial
momentum density distributions as well as distributions of the average radius
containing 80% ($\langle R_{\rm 80} \rangle$) of the reconstructed jet $p_{\rm
T}$. The fragmentation of leading jets with $R=0.4$ using scaled $p_{\rm T}$
spectra of the jet constituents is studied. The measurements are compared to
model calculations from event generators (PYTHIA, PHOJET, HERWIG). The measured
radial density distributions and $\langle R_{\rm 80} \rangle$ distributions are
well described by the PYTHIA model (tune Perugia-2011). The fragmentation
distributions are better described by HERWIG. | nucl-ex |
Nuclear Charge Radii of the Nickel Isotopes $^{58-68,70}$Ni: Collinear laser spectroscopy is performed on the nickel isotopes
$^{58-68,70}$Ni, using a time-resolved photon counting system. From the
measured isotope shifts, nuclear charge radii $R_c$ are extracted and compared
to theoretical results. Three ab initio approaches all employ, among others,
the chiral interaction NNLO$_{\rm sat}$, which allows an assessment of their
accuracy. We find agreement with experiment in differential radii $\delta
\left\langle r_\mathrm{c}^2 \right\rangle$ for all employed ab initio methods
and interactions, while the absolute radii are consistent with data only for
NNLO$_{\rm sat}$. Within nuclear density functional theory, the Skyrme
functional SV-min matches experiment more closely than the Fayans functional
Fy($\Delta r$,HFB). | nucl-ex |
The Proton Form Factor Ratio Measurements at Jefferson Lab: The ratio of the proton form factors, GEp/GMp, has been measured from Q2 of
0.5 GeV2 to 8.5 GeV2, at the Jefferson Laboratory, using the polarization
transfer method. This ratio is extracted directly from the measured ratio of
the transverse and longitudinal polarization components of the recoiling proton
in elastic electron-proton scattering. The discovery that the proton form
factor ratio measured in these experiments decreases approximately linearly
with four-momentum transfer, Q2, for values above ? 1 GeV2, is one of the most
significant results to come out of JLab. These results have had a large impact
on progress in hadronic physics; and have required a significant rethinking of
nucleon structure. The increasingly common use of the double-polarization
technique to measure the nucleon form factors, in the last 15 years, has
resulted in a dramatic improvement of the quality of all four nucleon
electromagnetic form factors, GEp, GMp, GEn and GMn. There is an approved
experiment at JLab, GEP(V), to continue the ratio measurements to 12 GeV2. A
dedicated experimental setup, the Super Bigbite Spectrometer (SBS), will be
built for this purpose. It will be equipped with a focal plane polarimeter to
measure the polarization of the recoil protons. The scattered electrons will be
detected in an electromagnetic calorimeter. In this presentation, I will review
the status of the proton elastic electromagnetic form factors and discuss a
number of theoretical approaches to describe nucleon form factors. | nucl-ex |
Strength of the $E_{\text{cm}} = 1113$ keV resonance in $^{20}${Ne}$(p,
γ)^{21}${Na}: The $^{20}$Ne$(p, \gamma)^{21}$Na reaction is the starting point of the NeNa
cycle, which is an important process for the production of intermediate mass
elements. The $E_{\text{cm}} = 1113$ keV resonance plays an important role in
the determination of stellar rates for this reaction since it is used to
normalize experimental direct capture yields at lower energies. The commonly
accepted strength of this resonance, $\omega \gamma = 1.13 \pm 0.07$ eV, has
been misinterpreted as the strength in the center-of-mass frame when it is
actually the strength in the laboratory frame. This has motivated a new
measurement of the $E_{\text{cm}} = 1113$ keV resonance strength in
$^{20}$Ne$(p, \gamma)^{21}$Na using the DRAGON recoil mass spectrometer. The
DRAGON result, $0.972 \pm 0.11$ eV, is in good agreement with the accepted
value when both are calculated in the same frame of reference. | nucl-ex |
Target-Normal Single Spin Asymmetries Measured with Positrons: Two-photon exchange and the larger class of hadronic box diagrams are
difficult to calculate without a large degree of model-dependence. At the same
time, these processes are significant radiative corrections in parity-violating
electron scattering, in neutron decay, and may even be responsible for the
proton's form factor ratio discrepancy. New kinds of experimental data are
needed to help constrain models and guide future box-diagram calculations. The
target-normal single spin asymmetry, $A_n$, formed with an unpolarized beam
scattering from a target that is polarized normal to the scattering plane, is
sensitive to the imaginary part of the two-photon exchange amplitude, and can
provide a valuable constraint. A measurement with both electrons and positrons
can reduce sources of experimental error, and distinguish between the effects
of two-photon exchange and those of time-reversal symmetry violation. This
article describes a proposed experiment in Hall A, using the new Super Big-Bite
Spectrometer that can cover a momentum transfer range in the critical zone of
uncertainty between where hadronic calculations and those based on partonic
degrees of freedom are expected to be accurate. | nucl-ex |
Anisotropic Flow from RHIC to the LHC: Anisotropic flow is recognized as one of the main observables providing
information on the early stage of a heavy-ion collision. At RHIC the large
observed anisotropic flow and its successful description by ideal hydrodynamics
is considered evidence for an early onset of thermalization and almost ideal
fluid properties of the produced strongly coupled Quark Gluon Plasma. This
write-up discusses some key RHIC anisotropic flow measurements and for
anisotropic flow at the LHC some predictions. | nucl-ex |
HBT in Relativisitic Heavy Ion Collisions: A summary of current interferometry data in relativistic heavy ions is
presented. At sqrt{s}=17GeV a sudden increase in the pion source volume is
observed for central PbPb collisions.
This seems to imply that the pion phase density has reached a limit.
The source size of different particles decreases with mass when the
transverse velocity is held constant but increases with mass when the
transverse mass is held constant. The antiproton source radius is larger than
the proton source radius. So far no long lived source has been seen. The pion
source size varies slowly with rapidity but more rapidly with transverse mass
implying strong transverse flow. There is very slow increase of pion radii with
sqrt{s}. | nucl-ex |
Baseline for the cumulants of net-proton distributions at STAR: We present a systematic comparison between the recently measured cumulants of
the net-proton distributions by STAR for 0-5% central Au+Au collisions at
$\sqrt{s_{NN}}$=7.7-200 GeV and two kinds of possible baseline measures, the
Poisson and Binomial baselines. These baseline measures are assuming that the
proton and anti-proton distributions independently follow Poisson statistics or
Binomial statistics. The higher order cumulant net-proton data are observed to
deviate from all the baseline measures studied at 19.6 and 27 GeV. We also
compare the net-proton with net-baryon fluctuations in UrQMD and AMPT model,
and convert the net-proton fluctuations to net-baryon fluctuations in AMPT
model by using a set of formula. | nucl-ex |
Measurement of Hadron Production in $π^-$-C Interactions at 158 and
350 GeV/c with NA61/SHINE at the CERN SPS: We present a measurement of the momentum spectra of $\pi^\pm$, K$^\pm$,
p$^\pm$, $\Lambda$, $\bar{\Lambda}$ and K$^{0}_{S}$ produced in interactions of
negatively charged pions with carbon nuclei at beam momenta of 158 and 350
GeV/c. The total production cross sections are measured as well. The data were
collected with the large-acceptance spectrometer of the fixed target experiment
NA61/SHINE at the CERN SPS. The obtained double-differential $p$-$p_T$ spectra
provide a unique reference data set with unprecedented precision and large
phase-space coverage to tune models used for the simulation of particle
production in extensive air showers in which pions are the most numerous
projectiles. | nucl-ex |
Transverse-momentum dependent modification of dynamic texture in central
Au+Au collisions at sqrt(S_NN)=200 GeV: Correlations in the hadron distributions produced in relativistic Au+Au
collisions are studied in the discrete wavelet expansion method. The analysis
is performed in the space of pseudorapidity (|eta| < 1) and azimuth (full 2 pi)
in bins of transverse momentum (p_t) from 0.14 < p_t < 2.1 GeV/c. In peripheral
Au+Au collisions a correlation structure ascribed to mini-jet fragmentation is
observed. It evolves with collision centrality and p_t in a way not seen before
which suggests strong dissipation of minijet fragmentation in the
longitudinally-expanding medium. | nucl-ex |
First observation of low-energy γ-ray enhancement in the
rare-earth region: The {\gamma}-ray strength function and level density in the quasi-continuum
of 151,153Sm have been measured using BGO shielded Ge clover detectors of the
STARLiTeR system. The Compton shields allow for an extraction of the {\gamma}
strength down to unprecedentedly low {\gamma} energies of about 500 keV. For
the first time an enhanced low- energy {\gamma}-ray strength has been observed
in the rare-earth region. In addition, for the first time both the upbend and
the well known scissors resonance have been observed simultaneously for the
same nucleus. Hauser-Feshbach calculations show that this strength enhancement
at low {\gamma} energies could have an impact of 2-3 orders of magnitude on the
(n,{\gamma}) reaction rates for the r-process nucleosynthesis. | nucl-ex |
Semi-inclusive jets recoiling from $γ_{dir}$ and $π^{0}$ triggers
in central Au+Au collisions at $\sqrt {s_{\rm NN}}$ = 200 GeV in STAR: We report the first measurement of fully corrected semi-inclusive charged
recoil jets for both direct-photon ($\gamma_{dir}$) and $\pi^{0}$ triggers,
within two trigger transverse energy ranges between 9 GeV and 15 GeV, in
central Au+Au collisions at $\sqrt {s_{\rm NN}}$ = 200 GeV using data with an
integrated luminosity of 13 $\rm nb^{-1}$ collected by the STAR experiment. A
comparison between $\pi^{0}$-triggered recoil jets in p+p collisions and PYTHIA
is discussed. A comparison is also presented between the suppression of
$\gamma_{dir}$- and $\pi^{0}$-triggered recoil jets in central Au+Au collisions
with respect to their corresponding PYTHIA references. A strong and similar
level of suppression is observed in recoil-jet yields as a function of jet
transverse momentum for $\gamma_{dir}$+jet and $\pi^{0}$+jet. | nucl-ex |
First search for $2\varepsilon$ and $\varepsilonβ^+$ decay of
$^{162}$Er and new limit on $2β^{-}$ decay of $^{170}$Er to the first
excited level of $^{170}$Yb: The first search for double electron capture ($2\varepsilon$) and electron
capture with positron emission ($\varepsilon\beta^+$) of $^{162}$Er to the
ground state and to several excited levels of $^{162}$Dy was realized with 326
g of highly purified erbium oxide. The sample was measured over 1934 h by the
ultra-low background HP Ge $\gamma$ spectrometer GeCris (465 cm$^3$) at the
Gran Sasso underground laboratory. No effect was observed, the half-life limits
were estimated at the level of $\lim T_{1/2}\sim 10^{15}-10^{18}$ yr. A
possible resonant $0\nu KL_1$ capture in $^{162}$Er to the $2^+$ 1782.7 keV
excited state of $^{162}$Dy is restricted as $T_{1/2}\geq5.0\times 10^{17}$ yr
at 90% C.L. A new improved half-life limit $T_{1/2}\geq4.1\times 10^{17}$ yr
was set on the $2\beta^-$ decay of $^{170}$Er to the $2^+$ 84.3 keV first
excited state of $^{170}$Yb. | nucl-ex |
Intermediate-energy inverse-kinematics one-proton pickup reactions on
neutron-deficient $fp$-shell nuclei: Background: Thick-target-induced nucleon-adding transfer reactions onto
energetic rare-isotope beams are an emerging spectroscopic tool. Their
sensitivity to single-particle structure complements one-nucleon removal
reaction capabilities in the quest to reveal the evolution of nuclear shell
structure in very exotic nuclei. Purpose: To add intermediate-energy,
carbon-target-induced one-proton pickup reactions to the arsenal of
$\gamma$-ray tagged direct reactions applicable in the regime of low beam
intensities and to apply these for the first time to $fp$-shell nuclei.
Methods: Inclusive and partial cross sections were measured for the
$\nuc{12}{C}(\nuc{48}{Cr},\nuc{49}{Mn}+\gamma)$X and
$\nuc{12}{C}(\nuc{50}{Fe},\nuc{51}{Co}+\gamma)$X proton pickup reactions at
56.7 and 61.2 MeV/nucleon, respectively, using coincident particle-$\gamma$
spectroscopy at the NSCL. The results are compared to reaction theory
calculations using $fp$-shell-model nuclear structure input. For comparison
with our previous work, the same reactions were measured on \nuc{9}{Be}
targets. Results: The measured partial cross sections confirm the specific
population pattern predicted by theory, with pickup into high-$\ell$ orbitals
being strongly favored; driven by linear and angular momentum matching.
Conclusion: Carbon target-induced pickup reactions are well-suited, in the
regime of modest beam intensity, to study the evolution of nuclear structure,
with specific sensitivities that are well described by theory. | nucl-ex |
System Size Dependence of Particle Production at the SPS: Recent results on the system size dependence of net-baryon and hyperon
production as measured at the CERN SPS are discussed. The observed Npart
dependences of yields, but also of dynamical properties, such as average
transverse momenta, can be described in the context of the core corona
approach. Other observables, such as antiproton yields and net-protons at
forward rapidities, do not follow the predictions of this model. Possible
implications for a search for a critical point in the QCD phase diagram are
discussed. Event-by-event fluctuations of the relative core to corona source
contributions might influence fluctuation observables (e.g. multiplicity
fluctuations). The magnitude of this effect is investigated. | nucl-ex |
A Precise Measurement of the Neutron Magnetic Form Factor GMn in the
Few-GeV2 Region: The neutron elastic magnetic form factor GMn has been extracted from
quasielastic electron scattering data on deuterium with the CEBAF Large
Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic coverage of the
measurement is continuous from Q2=1 GeV2 to 4.8 GeV2. High precision was
achieved by employing a ratio technique in which many uncertainties cancel, and
by a simultaneous in-situ calibration of the neutron detection efficiency, the
largest correction to the data. Neutrons were detected using the CLAS
electromagnetic calorimeters and the time-of-flight scintillators. Data were
taken at two different electron beam energies, allowing up to four
semi-independent measurements of GMn to be made at each value of Q2. The dipole
parameterization is found to provide a good description of the data over the
measured Q2 range. | nucl-ex |
Measurement of the $^{12}$C($n,p$)$^{12}$B cross section at n_TOF (CERN)
by in-beam activation analysis: The integral cross section of the $^{12}$C($n,p$)$^{12}$B reaction has been
determined for the first time in the neutron energy range from threshold to
several GeV at the n_TOF facility at CERN. The measurement relies on the
activation technique, with the $\beta$-decay of $^{12}$B measured over a period
of four half-lives within the same neutron bunch in which the reaction occurs.
The results indicate that model predictions, used in a variety of applications,
are mostly inadequate. The value of the integral cross section reported here
can be used as a benchmark for verifying or tuning model calculations. | nucl-ex |
Search for Neutrinoless Double-Beta Decay of $^{130}$Te with CUORE-0: We report the results of a search for neutrinoless double-beta decay in a
9.8~kg$\cdot$yr exposure of $^{130}$Te using a bolometric detector array,
CUORE-0. The characteristic detector energy resolution and background level in
the region of interest are $5.1\pm 0.3{\rm~keV}$ FWHM and $0.058 \pm
0.004\,(\mathrm{stat.})\pm
0.002\,(\mathrm{syst.})$~counts/(keV$\cdot$kg$\cdot$yr), respectively. The
median 90%~C.L. lower-limit sensitivity of the experiment is $2.9\times
10^{24}~{\rm yr}$ and surpasses the sensitivity of previous searches. We find
no evidence for neutrinoless double-beta decay of $^{130}$Te and place a
Bayesian lower bound on the decay half-life, $T^{0\nu}_{1/2}>$~$ 2.7\times
10^{24}~{\rm yr}$ at 90%~C.L. Combining CUORE-0 data with the 19.75~kg$\cdot$yr
exposure of $^{130}$Te from the Cuoricino experiment we obtain $T^{0\nu}_{1/2}
> 4.0\times 10^{24}~\mathrm{yr}$ at 90%~C.L.~(Bayesian), the most stringent
limit to date on this half-life. Using a range of nuclear matrix element
estimates we interpret this as a limit on the effective Majorana neutrino mass,
$m_{\beta\beta}< 270$ -- $760~\mathrm{meV}$. | nucl-ex |
First search for $2\varepsilon$ and $\varepsilonβ^+$ decay of
$^{174}$Hf: The first ever search for $2\varepsilon$ and $\varepsilon\beta^+$ decay of
$^{174}$Hf was realized using a high-pure sample of hafnium (with mass 179.8 g)
and the ultra low-background HPGe-detector system located 225 m underground.
After 75 days of data taking no indication of the double beta decay transitions
could be detected but lower limits for the half-lives of the different channels
and modes of the decays were set on the level of $\lim T_{1/2}\sim
10^{16}-10^{18}$ a. | nucl-ex |
"$\mathbf{{\textit K^-}{\textit p}{\textit p}}$", a
${\overline{K}}$-Meson Nuclear Bound State, Observed in $^{3}{\rm He}({K^-},
Λ p)n$ Reactions: We observed a distinct peak in the $\Lambda p$ invariant mass spectrum of
$^{3}{\rm He}(K^-, \, \Lambda p)n$, well below the mass threshold of $m_K + 2
m_p$. By selecting a relatively large momentum-transfer region $q = 350 \sim
650$ MeV/$c$, one can clearly separate the peak from the quasi-free process,
$\overline{K}N \rightarrow \overline{K}N$ followed by the non-resonant
absorption by the two spectator-nucleons $\overline{K}NN \rightarrow \Lambda N
$. We found that the simplest fit to the observed peak gives us a Breit-Wigner
pole position at $B_{\rm {\it Kpp}} = 47 \pm 3 \, (stat.) \,^{+3}_{-6}
\,(sys.)$ MeV having a width $\Gamma_{\rm {\it Kpp}} = 115 \pm 7 \, (stat.)
\,^{+10}_{-9} \,(sys.)$ MeV, and the $S$-wave Gaussian reaction form-factor
parameter $Q_{\rm {\it Kpp}} = 381 \pm 14 \, (stat.)\,^{+57}_{-0} \,(sys.)$
MeV/$c$, as a new form of the nuclear bound system with strangeness --
"$K^-pp$". | nucl-ex |
Improved Limit on Tensor Currents in the Weak Interaction from $^8$Li
$β$ Decay: The electroweak interaction in the Standard Model (SM) is described by a pure
vector-axial-vector structure, though any Lorentz-invariant component could
contribute. In this work, we present the most precise measurement of tensor
currents in the low-energy regime by examining the $\beta$-$\bar{\nu}$
correlation of trapped $^{8}$Li ions with the Beta-decay Paul Trap. We find
$a_{\beta\nu} = -0.3325 \pm 0.0013_{stat} \pm 0.0019_{syst}$ at $1\sigma$ for
the case of coupling to right-handed neutrinos $(C_T=-C_T')$, which is
consistent with the SM prediction. | nucl-ex |
Machine studies for the development of storage cells at the ANKE
facility of COSY: We present a measurement of the transverse intensity distributions of the
COSY proton beam at the target interaction point at ANKE at the injection
energy of 45 MeV, and after acceleration at 2.65 GeV. At 2.65 GeV, the machine
acceptance was determined as well. From the intensity distributions the beam
size is determined, and together with the measured machine acceptance, the
dimensions of a storage cell for the double-polarized experiments with the
polarized internal gas target at the ANKE spectrometer are specified. An
optimum storage cell for the ANKE experiments should have dimensions of 15mm x
20mm x 390mm (vertical x horizontal x longitudinal), whereby a luminosity of
about 2.5*10^29 cm^-2*s^-1 with beams of 10^10 particles stored in COSY could
be reached. | nucl-ex |
Charged antiparticle to particle ratios near midrapidity in p+p
collisions at sqrt(s_NN)=200 GeV: The ratios of the yields of primary charged antiparticles to particles have
been obtained for pions, kaons, and protons near midrapidity for p+p collisions
at sqrt(s_NN) = 200 GeV. Ratios of <pi-/pi+>=1.000 +/- 0.012 (stat.) +/- 0.019
(syst.), <K-/K+>=0.93 +/- 0.05 (stat.) +/- 0.03 (syst.), and <pbar/p>=0.85 +/-
0.04 (stat.) +/- 0.03 (syst.) have been measured. The reported values represent
the ratio of the yields averaged over the rapidity range of 0.1<y_{pi}<1.3 and
0<y_{K,p}<0.8, and for transverse momenta of 0.1<p_T^{pi,K}<1.0 GeV/c and
0.3<p_T^{p}<1.0 GeV/c. Within the uncertainties, all three ratios are
consistent with the values measured in d+Au collisions at the same energy. The
data are compared to results from other collision systems and energies. | nucl-ex |
New results in rare allowed muon and pion decays: Simple dynamics, few available decay channels, and highly controlled
radiative and loop corrections, make pion and muon decays a sensitive means of
exploring details of the underlying symmetries. We review the current status of
the rare decays: pi+ -> e+ nu, pi+ -> e+ nu gamma, pi+ -> pi0 e+ nu, and mu+ ->
e+ nu nu-bar gamma. For the latter we report new preliminary values for the
branching ratio B(E_gamma >10 MeV, theta_(e-gamma) > 30deg) = 4.365 (9)_stat
(42)_syst x 10^{-3}, and the decay parameter eta-bar = 0.006 (17)_stat
(18)_syst, both in excellent agreement with standard model predictions. We
review recent measurements, particularly by the PIBETA and PEN experiments, and
near-term prospects for improvement. These and other similar precise low energy
studies complement modern collider results materially. | nucl-ex |
First Application of Pulse-Shape Analysis to Silicon Micro-Strip
Detectors: The method of pulse-shape analysis (PSA) for particle identification (PID)
was applied to a double-sided silicon strip detector (DSSD) with a strip pitch
of 300 \{mu}m. We present the results of test measurements with particles from
the reactions of a 70 MeV 12C beam impinging on a mylar target. Good separation
between protons and alpha particles down to 3 MeV has been obtained when
excluding the interstrip events of the DSSD from the analysis. | nucl-ex |
Searching for Jets in Heavy Ion Collisions: Jet quenching measurements using leading particles and their correlations
suffer from known biases, which can be removed via direct reconstruction of
jets in central heavy ion collisions. In this talk, we discuss several modern
jet reconstruction algorithms and background subtraction techniques that are
appropriate to heavy ion collisions. | nucl-ex |
Measurement of the $ν_e$ and Total $^{8}$B Solar Neutrino Fluxes with
the Sudbury Neutrino Observatory Phase-III Data Set: This paper details the solar neutrino analysis of the 385.17-day Phase-III
data set acquired by the Sudbury Neutrino Observatory (SNO). An array of $^3$He
proportional counters was installed in the heavy-water target to measure
precisely the rate of neutrino-deuteron neutral-current interactions. This
technique to determine the total active $^8$B solar neutrino flux was largely
independent of the methods employed in previous phases. The total flux of
active neutrinos was measured to be
$5.54^{+0.33}_{-0.31}(stat.)^{+0.36}_{-0.34}(syst.)\times 10^{6}$ cm$^{-2}$
s$^{-1}$, consistent with previous measurements and standard solar models. A
global analysis of solar and reactor neutrino mixing parameters yielded the
best-fit values of $\Delta m^2 = 7.59^{+0.19}_{-0.21}\times 10^{-5}{eV}^2$ and
$\theta = 34.4^{+1.3}_{-1.2}$ degrees. | nucl-ex |
Studies of nuclear equation of state with the HIRFL-CSR external-target
experiment: The HIRFL-CSR external-target experiment (CEE) under construction is expected
to provide novel opportunities to the studies of the thermodynamic properties,
namely the equation of state of nuclear matter (nEOS) with heavy ion collisions
at a few hundreds MeV/u beam energies. Based on Geant 4 packages, the fast
simulations of the detector responses to the collision events generated using
transport model are conducted. The overall performance of CEE, including
spatial resolution of hits, momentum resolution of tracks and particle
identification ability has been investigated. Various observables proposed to
probe the nEOS, such as the production of light clusters, $\rm t/^3He$ yield
ratio, the radial flow, $\pi^{-}/\pi^{+}$ yield ratio and the neutral kaon
yields, have been reconstructed. The feasibility of studying nEOS beyond the
saturation density via the aforementioned observables to be measured with CEE
has been demonstrated. | nucl-ex |
Suppression of soft nuclear bremsstrahlung in proton-nucleus collisions: Photon energy spectra up to the kinematic limit have been measured in 190 MeV
proton reactions with light and heavy nuclei to investigate the influence of
the multiple-scattering process on the photon production. Relative to the
predictions of models based on a quasi-free production mechanism a strong
suppression of bremsstrahlung is observed in the low-energy region of the
photon spectrum. We attribute this effect to the interference of photon
amplitudes due to multiple scattering of nucleons in the nuclear medium. | nucl-ex |
Bulk hadron production at high rapidities: Recent experimental observations on the `bulk' features of particle
production at high (pseudo)rapidities will be reviewed. This kinematic region
is of interest mostly because of its relevance to the theoretical description
of initial state effects of nuclei at ultra-relativistic energies. Measurements
of the charged hadron multiplicity density as well as the pseudorapidity
dependence of the elliptic and directed flow exhibit a remarkable scaling
property as a function of collision energy. This scaling seems to hold for
pions and even photons and J/Psi-s, but is violated for protons. The special
role of baryons will be discussed using selected results on nuclear
transparency and baryon stopping. | nucl-ex |
High-precision measurement of total fission cross sections in spallation
reactions of 208Pb and 238U: Total cross sections for proton- and deuteron-induced-fission of 208Pb and
238U have been determined in the energy range between 500 MeV and 1 GeV. The
experiment has been performed in inverse kinematics at GSI Darmstadt,
facilitating the counting of the projectiles and the identification of the
reaction products. High precision between 5 and 7 percent has been achieved by
individually counting the beam particles and by registering both fission
fragments in coincidence with high efficiency and full Z resolution. Fission
was clearly distinguished from other reaction channels. The results were found
to deviate by up to 30 percent from Prokofiev's systematics on total fission
cross sections. There is good agreement with an elaborate experiment performed
in direct kinematics. | nucl-ex |
Centrality and pseudorapidity dependence of the charged-particle
multiplicity density in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV: In this Letter, the ALICE Collaboration presents the first measurements of
the charged-particle multiplicity density, $\rm{d}N_{\rm{ch}}/\rm{d}\eta$, and
total charged-particle multiplicity, $N_{\rm{ch}}^{\rm{tot}}$, in Xe-Xe
collisions at a centre-of-mass energy per nucleon--nucleon pair of
$\sqrt{s_{\rm NN}}$ = 5.44 TeV. The measurements are performed as a function of
collision centrality over a wide pseudorapidity range of $-3.5 < \eta < 5$. The
values of $\rm{d}N_{\rm{ch}}/\rm{d}\eta$ at mid-rapidity and
$N_{\rm{ch}}^{\rm{tot}}$ for central collisions, normalised to the number of
nucleons participating in the collision ($N_{\rm{part}}$) as a function of
$\sqrt{s_{\rm NN}}$, follow the trends established in previous heavy-ion
measurements. The same quantities are also found to increase as a function of
$N_{\rm{part}}$, and up to the 5% most central collisions the trends are the
same as the ones observed in Pb-Pb at a similar energy. For more central
collisions, the Xe-Xe scaled multiplicities exceed those in Pb-Pb for a similar
$N_{\rm{part}}$. The results are compared to phenomenological models and
theoretical calculations based on different mechanisms for particle production
in nuclear collisions. All considered models describe the data reasonably well
within 15%. | nucl-ex |
$φ$ meson production at forward rapidity in Pb-Pb collisions at
$\sqrt{s_\mathrm{NN}}=2.76$ TeV: $\phi$ meson measurements provide insight into strangeness production, which
is one of the key observables for the hot medium formed in high-energy
heavy-ion collisions. ALICE measured $\phi$ production through its decay in
muon pairs in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV in the
intermediate transverse momentum range $2 < p_{\rm T} < 5$ GeV/$c$ and in the
rapidity interval $2.5<y<4$. The $\phi$ yield was measured as a function of the
transverse momentum and collision centrality. The nuclear modification factor
was obtained as a function of the average number of participating nucleons.
Results were compared with the ones obtained via the kaon decay channel in the
same $p_{\rm T}$ range at midrapidity. The values of the nuclear modification
factor in the two rapidity regions are in agreement within uncertainties. | nucl-ex |
Mass measurements and superallowed beta decay: A recent Penning-trap measurement of the masses of 46V and 46Ti leads to a
Qec value that disagrees significantly with the previously accepted value, and
destroys overall consistency among the nine most precisely characterized T=1
superallowed beta emitters. This raises the possibility of a systematic
discrepancy between Penning-trap measurements and the reaction-based
measurements upon which the Qec values depended in the past. We carefully
re-analyze (n,gamma) and (p,gamma) reaction measurements in the 24 \leq A \leq
28 mass region, and compare the results to very precise Penning-trap
measurements of the stable nuclei 24Mg, 26Mg and 28Si. We thus determine upper
limits to possible systematic effects in the reaction results, and go on to
establish limits for the mass of radioactive 26Al, to which future on-line
Penning-trap measurements can be compared. We stress the urgency of identifying
or ruling-out possible systematic effects. | nucl-ex |
Evidence of a new state in $^{11}$Be observed in the $^{11}$Li
$β$-decay: Coincidences between charged particles emitted in the $\beta$-decay of
$^{11}$Li were observed using highly segmented detectors. The breakup channels
involving three particles were studied in full kinematics allowing for the
reconstruction of the excitation energy of the $^{11}$Be states participating
in the decay. In particular, the contribution of a previously unobserved state
at 16.3 MeV in $^{11}$Be has been identified selecting the $\alpha$ +
$^7$He$\to\alpha$ + $^6$He+n channel. The angular correlations between the
$\alpha$ particle and the center of mass of the $^6$He+n system favors spin and
parity assignment of 3/2$^-$ for this state as well as for the previously known
state at 18 MeV. | nucl-ex |
Studies of systematic uncertainties of polarization estimation for
experiments with WASA detector at COSY: In November 2010, the azimuthally symmetric WASA detector and the polarized
proton beam of COSY, have been used to collect a high statistics sample of
$\vec{p}p \rightarrow pp\eta$ reactions in order to determine the analyzing
power as a function of the invariant mass spectra of the two particle
subsystems. Here, we show studies of the influence of the beam and target
characteristics such as location and direction on the determination of the
polarization. | nucl-ex |
Fine structure of the isovector giant dipole resonance in 208Pb:
Characteristic scales and level densities: The IVGDR in 208Pb has been measured with high energy resolution with the
(p,p') reaction under extreme forward angles and shows considerable fine
structure. Characteristic scales are extracted from the spectra with a wavelet
analysis based on continuous wavelet transforms. Comparison with corresponding
analyses of B(E1) strength distributions from microscopic model calculations in
the framework of the QPM and relativistic RPA allow to identify giant resonance
decay mechanisms responsible for the fine structure. The level density of 1-
states can be related to local fluctuations of the cross sections in the energy
region of the IVGDR. The magnitude of the fluctuations is determined by the
autocorrelation function. Scales in the fine structure of the IVGDR in 208Pb
are found at 80, 130, 220, 430, 640, 960 keV, and at 1.75 MeV. The values of
the most prominent scales can be reasonably well reproduced by the microscopic
calculations although they generally yield a smaller number of scales. In both
models the major scales are already present at the one-particle one-hole level
indicating Landau damping as a dominant mechanism responsible for the fine
structure of the IVGDR in contrast to the isoscalar giant quadrupole resonance,
where fine structure arises from the coupling to low-lying surface vibrations.
The inclusion of complex configurations in the calculations changes the E1
strength distributions but the impact on the wavelet power spectra and
characteristic scales is limited. The level density of 1- states is extracted
in the excitation energy range 9-12.5 MeV and compared to a variety of
phenomenological and microscopic models. The back-shifted Fermi gas model
parameterization of Rauscher et al., Phys. Rev. C 56, 1613 (1997) describes the
level-density data well, while other phenomeological and microscopic approaches
fail to reproduce absolute values or the energy dependence or both. | nucl-ex |
Five Years of Tracking Heavy Ion Collisions at RHIC: Five years have passed since the first collisions of Au nuclei at the
Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL)
on Long Island. With nucleon-nucleon center-of-mass energies of up to
sqrt(s_NN)=200GeV RHIC provides the highest energy heavy ion collisions at any
existing collider. To study the dynamics of nuclear matter at extreme
temperatures and pressures hundreds of produced particles need to be tracked
and identified, which provides a sizable challenge to the four experiments.
This article tries to summarize these first years of RHIC operation from the
detector point of view and give a glimpse at the future of the accelerator and
its experiments. | nucl-ex |
Isospin dependence of the eta meson production in hadronic collisions: Based on recent COSY-11 results of measurements of total cross sections for
the quasi-free pn-->pn eta reaction we determine the isospin I=0 component of
the total cross section for the NN-->NN eta reaction down to the threshold. We
show that the energy dependence of the total cross section ratios
{\sigma_{I=0}(pn-->pn eta)}/{\sigma(pp-->pp eta)} and \sigma_{I=0}(pn-->pn
eta)}/{\sigma(pn-->d eta)} can be described using the Faldt and Wilkin
analitical parametrization of the nucleon-nucleon final state interaction. | nucl-ex |
Kaon Photoproduction and the $Λ$ Decay Parameter $α_-$: The weak decay parameter $\alpha_-$ of the $\Lambda$ is an important quantity
for the extraction of polarization observables in various experiments.
Moreover, in combination with $\alpha_+$ from $\bar\Lambda$ decay it provides a
measure for matter-antimatter asymmetry. The weak decay parameter also affects
the decay parameters of the $\Xi$ and $\Omega$ baryons and, in general, any
quantity in which the polarization of the $\Lambda$ is relevant. The recently
reported value by the BESIII collaboration of $0.750(9)(4)$ is significantly
larger than the previous PDG value of $0.642(13)$ that had been accepted and
used for over 40 years. In this work we make an independent estimate of
$\alpha_-$, using an extensive set of polarization data measured in kaon
photoproduction in the baryon resonance region and constraints set by spin
algebra. The obtained value is 0.721(6)(5). The result is corroborated by
multiple statistical tests as well as a modern phenomenological model, showing
that our new value yields the best description of the data in question. Our
analysis supports the new BESIII finding that $\alpha_-$ is significantly
larger than the previous PDG value. Any experimental quantity relying on the
value of $\alpha_-$ should therefore be re-considered. | nucl-ex |
Rare $^{40}$K decay with implications for fundamental physics and
geochronology: Potassium-40 is a widespread, naturally occurring isotope whose radioactivity
impacts subatomic rare-event searches, nuclear structure theory, and estimated
geological ages. A predicted electron-capture decay directly to the ground
state of argon-40 has never been observed. The KDK (potassium decay)
collaboration reports strong evidence of this rare decay mode. A blinded
analysis reveals a non-zero ratio of intensities of ground-state
electron-captures ($I_{\text{EC}^0}$) over excited-state ones ($I_\text{EC*}$)
of $ I_{\text{EC}^0} / I_\text{EC*} = 0.0095 \stackrel{\text{stat}}{\pm} 0.0022
\stackrel{\text{sys}}{\pm} 0.0010 $ (68% C.L.), with the null hypothesis
rejected at 4$\sigma$. In terms of branching ratio, this signal yields
$I_{\text{EC}^0} = 0.098\% \stackrel{\text{stat}}{\pm} 0.023\%
\stackrel{\text{sys}}{\pm} 0.010\% $, roughly half of the commonly used
prediction, with consequences for various fields [L. Hariasz et al., companion
paper, DOI: 10.1103/PhysRevC.108.014327]. | nucl-ex |
Measurement of prompt D$^0$ meson azimuthal anisotropy in PbPb
collisions at $\sqrt{s_\mathrm{NN}} = $5.02 TeV: The prompt D$^0$ meson azimuthal anisotropy coefficients, $v_2$ and $v_3$,
are measured at midrapidity ($|y| < 1.0$) in PbPb collisions at a
center-of-mass energy $\sqrt{s_\mathrm{NN}} = $5.02 TeV per nucleon pair with
data collected by the CMS experiment. The measurement is performed in the
transverse momentum ($p_\mathrm{T}$) range of 1 to 40 GeV/c, for central and
midcentral collisions. The $v_2$ coefficient is found to be positive throughout
the $p_\mathrm{T}$ range studied. The first measurement of the prompt D$^0$
meson $v_3$ coefficient is performed, and values up to 0.07 are observed for
$p_\mathrm{T}$ around 4 GeV/c. Compared to measurements of charged particles, a
similar $p_\mathrm{T}$ dependence, but smaller magnitude for $p_\mathrm{T} < $6
GeV/c, is found for prompt D$^0$ meson $v_2$ and $v_3$ coefficients. The
results are consistent with the presence of collective motion of charm quarks
at low $p_\mathrm{T}$ and a path length dependence of charm quark energy loss
at high $p_\mathrm{T}$, thereby providing new constraints on the theoretical
description of the interactions between charm quarks and the quark-gluon
plasma. | nucl-ex |
Results on flow from the ALICE Collaboration: This short overview includes recent results from the ALICE Collaboration on
anisotropic flow of charged and identified particles in sqrt(sNN) = 2.76 TeV
Pb-Pb collisions. We also discuss charge dependent and event plane dependent
azimuthal correlations that are important in tests of the chiral magnetic
effect, as well as understanding the dynamics of the system evolution and
hadronization process. Lastly, we present ALICE results obtained with a new
technique, the event shape engineering, which allows to perform a physical
analysis on events with very large or small flow. | nucl-ex |
Competing quasifission and asymmetric fusion-fission in
neutron-deficient sub-lead nuclei: To disentangle the role of shell effects and dynamics, fission fragment mass
distributions of $^{191}$Au, a nucleus in the newly identified island of mass
asymmetric fission in the sub-lead region, have been measured down to
excitation energy of $\approx$20 MeV above the fission barrier via two
different entrance channels, viz. $^{16}$O+$^{175}$Lu and $^{37}$Cl+$^{154}$Sm
reactions. Apart from having signature of the shell effects in both the cases,
clear experimental evidence of quasifission has been observed in the mass
distributions of the Cl induced reaction, that has also been substantiated by
the theoretical calculations. This crucial evidence along with a systematic
analysis of available experimental data has revealed that the dynamics in the
entrance channel has significant influence on most of the reactions used
earlier to explore the persistence of recently discovered mass asymmetry in
$\beta$-delayed fission at low energy in this mass region, ignoring which might
lead to ambiguity in interpreting the heavy-ion data. | nucl-ex |
Influence of nuclear structure on sub-barrier hindrance in Ni+Ni fusion: Fusion-evaporation cross sections for $^{64}$Ni+$^{64}$Ni have been measured
down to the 10 nb level. For fusion between two open-shell nuclei, this is the
first observation of a maximum in the $S$-factor, which signals a strong
sub-barrier hindrance. A comparison with the $^{58}$Ni+$^{58}$Ni,
$^{58}$Ni+$^{60}$Ni, and $^{58}$Ni+$^{64}$Ni systems indicates a strong
dependence of the energy where the hindrance occurs on the stiffness of the
interacting nuclei. | nucl-ex |
Systematics of the low-energy electric dipole strength in the Sn
isotopic chain: We present a systematic study of the mass dependence of the low-energy
electric dipole strength (LEDS) in Sn isotopes in the range $ A = 111 - 124$
based on data obtained with the Oslo method and with relativistic Coulomb
excitation in forward-angle ($p,p^\prime$) scattering. The combined data cover
an energy range of $2 - 20$ MeV which permits, with minimal assumptions, a
decomposition of the total strength into the contribution from the low-energy
tail of the isovector giant dipole resonance (IVGDR) and possible
resonance-like structures on top of it. In all cases, a resonance peaked at
about 8.3 MeV is observed, exhausting an approximately constant fraction of the
Thomas-Reiche-Kuhn (TRK) sum rule with a local maximum at $^{120}$Sn which
might be related to shell structure effects. For heavier isotopes ($A \geq
118$) a consistent description of the data requires the inclusion of a second
resonance centered at 6.5 MeV, representing the isovector response of the pygmy
dipole resonance (PDR). Its strength corresponds to a small fraction of the
total LEDS only and shows an approximately linear dependence on mass number.
The experimental results are also compared to ab initio-based microscopic
calculations to investigate the importance of an inclusion of quasiparticle
vibration coupling (qPVC) for a realistic description of the LEDS. | nucl-ex |
Jet splitting measurements in Pb--Pb and pp collisions at
$\sqrt{s}_{\mathrm{NN}} =$ 5.02 TeV with ALICE: Recent ALICE measurements of jet splittings in Pb--Pb and pp collisions at
$\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV are reported. These measurements scan the
phase space of jet emissions in search of medium-induced signals which are
expected to emerge at different scales. These include effects such as multiple
soft-radiation, single hard emissions, and color coherence. The Lund plane
diagram is shown, including projections onto distributions of the splitting
scale $k_{\mathrm{T}}$ in intervals of the splitting angle $R_{\mathrm{g}}$.
Soft Drop grooming is applied to access hard splittings within the jet,
enabling measurements of groomed substructure variables. These include the
shared momentum fraction $z_{\mathrm{g}}$ between the two hardest subjets and
the number of Soft Drop splittings $n_{\mathrm{SD}}$. The results in Pb--Pb
collisions are compared to PYTHIA events embedded into a Pb--Pb background to
separate out background from in-medium effects. Measurements of
$z_{\mathrm{g}}$ and the normalized splitting angle $\theta_{\mathrm{g}}$ will
also be shown in pp collisions at $\sqrt{s}$ = 5.02 TeV for different grooming
settings. | nucl-ex |
Comment on "Fission Mass Widths in $^{19}$F + $^{232}$Th, $^{16}$O +
$^{235,238}$ U reactions at near barrier energies: A critical re-analysis of the experimental data to reject transfer fission
component did not change the fragment mass widths and hence the conclusion
regarding abrupt rise in mass widths with decreasing energy around Coulomb
barrier remains unchanged | nucl-ex |
Characteristics of Parton Energy Loss Studied with High-p_T Particle
Spectra from PHENIX: In the first three years of the physics program at the Relativistic Heavy Ion
Collider (RHIC) a picture was established in which the suppression of hadrons
at high transverse momenta (p_T) in central Au+Au collisions is explained by
energy loss of quark and gluon jets in a medium of high color-charge density.
Measurements of single particle spectra for a smaller nucleus (Cu), for
different center-of-mass energies and with higher statistics were performed in
the subsequent years and are used to test predictions and assumptions of jet
quenching models in more detail. The measurements presented here are consistent
with a parton energy loss scenario so that these models can be used to relate
the observed suppression to properties of the created medium. | nucl-ex |
Isospin Character of the Pygmy Dipole Resonance in 124Sn: The pygmy dipole resonance has been studied in the proton-magic nucleus 124Sn
with the (a,a'g) coincidence method at E=136 MeV. The comparison with results
of photon-scattering experiments reveals a splitting into two components with
different structure: one group of states which is excited in (a,a'g) as well as
in (g,g') reactions and a group of states at higher energies which is only
excited in (g,g') reactions. Calculations with the self-consistent relativistic
quasiparticle time-blocking approximation and the quasiparticle phonon model
are in qualitative agreement with the experimental results and predict a
low-lying isoscalar component dominated by neutron-skin oscillations and a
higher-lying more isovector component on the tail of the giant dipole
resonance. | nucl-ex |
Closing in on critical net-baryon fluctuations at LHC energies:
cumulants up to third order in Pb$-$Pb collisions: Fluctuation measurements are important sources of information on the
mechanism of particle production at LHC energies. This article reports the
first experimental results on third-order cumulants of the net-proton
distributions in Pb$-$Pb collisions at a center-of-mass energy $\sqrt{s_{\rm
NN}} = 5.02$ TeV recorded by the ALICE detector. The results on the
second-order cumulants of net-proton distributions at $\sqrt{s_{\rm NN}} =
2.76$ and $5.02$ TeV are also discussed in view of effects due to the global
and local baryon number conservation. The results demonstrate the presence of
long-range rapidity correlations between protons and antiprotons. Such
correlations originate from the early phase of the collision. The experimental
results are compared with HIJING and EPOS model calculations, and the
dependence of the fluctuation measurements on the phase-space coverage is
examined in the context of lattice quantum chromodynamics (LQCD) and hadron
resonance gas (HRG) model estimations. The measured third-order cumulants are
consistent with zero within experimental uncertainties of about 4% and are
described well by LQCD and HRG predictions. | nucl-ex |
Dielectron Production in Heavy Ion Collisions at 158 GeV/c per Nucleon: In this paper, the low-mass electron pair production in 158 AGeV/c Pb-Au
collisions is investigated with the Cherenkov Ring Electron Spectrometer
(CERES) at the Super Proton Synchrotron accelerator (SPS) at CERN. The main
goal is to search for modifications of hadron properties in hot and dense
nuclear matter. The presented re-analysis of the 1996 data set is focused on a
detailed study of the combinatorial-background subtraction by means of the
mixed-event technique. The results confirm previous findings of CERES. The
dielectron production in the mass range of 0.25<m(ee)<2GeV/c**2 is enhanced by
a factor of 3.0+-1.3(stat.)+-1.2(syst.) over the expectation from neutral meson
decays. The data is compared to transport model calculations and seem to favor
the version including in-medium effects.
Furthermore, the development of a new technology to manufacture
ultralightweight mirrors for Ring Imaging Cherenkov detectors (RICH) is
described. Replacement of the RICH-2 glass mirror by a mirror almost
transparent to electrons would considerably improve the performance of the
upgraded CERES detector system including a radial Time Projection Chamber
(TPC). | nucl-ex |
Strangeness photoproduction at the BGO-OD experiment: The BGO-OD experiment at the University of Bonn's ELSA accelerator facility
in Germany is ideally suited to investigate photoproduction at extreme forward
angles. It combines a highly segmented BGO electromagnetic calorimeter at
central angles and an open dipole magnetic spectrometer in the forward
direction. This allows the detection of forward going kaons, and complex final
states of mixed charge from hyperon decays. Current projects at the BGO-OD
experiment include strangeness production of $\gamma p \rightarrow K^+
\Lambda/\Sigma^0$ at forward angles, $K^0\Sigma^0$ with a deuteron target and
$K^+\Lambda(1405)$ line shape and cross section measurements. | nucl-ex |
Search for the chiral magnetic wave using anisotropic flow of identified
particles at RHIC: The chiral magnetic wave (CMW) has been theorized to propagate in the
deconfined nuclear medium formed in high-energy heavy-ion collisions, and to
cause a difference in elliptic flow ($v_{2}$) between negatively and positively
charged hadrons. Experimental data consistent with the CMW have been reported
by the STAR Collaboration at the Relativistic Heavy Ion Collider (RHIC), based
on the charge asymmetry dependence of the pion $v_{2}$ from Au+Au collisions at
$\sqrt{s_{\rm NN}}$ = 27 to 200 GeV. In this comprehensive study, we present
the STAR measurements of elliptic flow and triangular flow of charged pions,
along with the $v_{2}$ of charged kaons and protons, as a function of charge
asymmetry in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 27, 39, 62.4 and 200
GeV. The slope parameters extracted from the linear dependence of the $v_2$
difference on charge asymmetry for different particle species are reported and
compared in different centrality intervals. In addition, the slopes of $v_{2}$
for charged pions in small systems, \textit{i.e.}, $p$+Au and $d$+Au at
$\sqrt{s_{\rm NN}}$ = 200 GeV, are also presented and compared with those in
large systems, \textit{i.e.}, Au+Au at $\sqrt{s_{\rm NN}}$ = 200 GeV and U+U at
193 GeV. Our results provide new insights for the possible existence of the
CMW, and further constrain the background contributions in heavy-ion collisions
at RHIC energies. | nucl-ex |
Direct TPE Measurement via $e^+p/e^-p$ Scattering at low $\varepsilon$
in Hall A: The proton elastic form factor ratio can be measured either via Rosenbluth
separation in an experiment with unpolarized beam and target, or via the use of
polarization degrees of freedom. However, data produced by these two approaches
show a discrepancy, increasing with $Q^2$. The proposed explanation of this
discrepancy - two-photon exchange - has been tested recently by three
experiments. The results support the existence of a small two-photon exchange
effect but cannot establish that theoretical treatments at the measured
momentum transfers are valid. At larger momentum transfers, theory remains
untested, and without further data, it is impossible to resolve the
discrepancy. A positron beam at Jefferson Lab allows us to directly measure
two-photon exchange over an extended $Q^2$ and $\epsilon$ range with high
precision. With this, we can validate whether the effect reconciles the form
factor ratio measurements, and test several theoretical approaches, valid in
different parts of the tested $Q^2$ range. In this proposal, we describe a
measurement program in Hall A that combines the Super BigBite, BigBite, and
High Resolution Spectrometers to directly measure the two-photon effect. Though
the limited beam current of the positron beam will restrict the kinematic
reach, this measurement will have very small systematic uncertainties, making
it a clean probe of two photon exchange. | nucl-ex |
Even-odd effect in multifragmentation products: the footprints of
evaporation: The analysis of experimental production cross-sections of intermediate-mass
fragments (IMF) of several nuclear reactions at relativistic energy, measured
at the FRS, GSI Darmstadt, revealed a very strong and complex even-odd
staggering. The origin of this effect is related to the condensation process of
hot nuclei while cooling down by evaporation. The characteristics of the
staggering correlate strongly with the lowest particle separation energy of the
final experimentally observed nuclei, but not with the binding energy. The
study confirms the important role of the de-excitation process in
multifragmentation reactions, and indicates that sequential decay strongly
influences the yields of IMF, which are often used to extract information on
the nature of nuclear reactions at high energies. | nucl-ex |
Measurement of the intensity ratio of Auger and conversion electrons for
the electron capture decay of $^{125}$I: Auger electrons emitted after nuclear decay have potential application in
targeted cancer therapy. For this purpose it is important to know the Auger
electron yield per nuclear decay. In this work we describe a measurement of the
ratio of the number of conversion electrons (emitted as part of the nuclear
decay process) to the number of Auger electrons (emitted as part of the atomic
relaxation process after the nuclear decay) for the case of $^{125}$I. Results
are compared with Monte-Carlo type simulations of the relaxation cascade using
the BrIccEmis code. Our results indicate that for $^{125}$I the calculations
based on rates from the Evaluated Atomic Data Library (EADL) underestimate the
K Auger yields by 20\%. | nucl-ex |
Methodology for the study of modified jet-like topologies in heavy ion
collisions via three particle correlation functions: Methodology is presented for analysis of three-particle correlation functions
obtained in heavy ion collisions at ultra-relativistic energies. We show that
harmonic correlations can be removed and jet driven correlations reliably
extracted. Results from detailed Monte Carlo simulations are used to
demonstrate the efficacy of this technique for the study of modifications to
away-side jet topologies. Such modifications are an essential probe of the
properties of the quark gluon plasma produced in heavy ion collisions. | nucl-ex |
Detection and Imaging of He_2 Molecules in Superfluid Helium: We present data that show a cycling transition can be used to detect and
image metastable He$_2$ triplet molecules in superfluid helium. We demonstrate
that limitations on the cycling efficiency due to the vibrational structure of
the molecule can be mitigated by the use of repumping lasers. Images of the
molecules obtained using the method are also shown. This technique gives rise
to a new kind of ionizing radiation detector. The use of He$_2$ triplet
molecules as tracer particles in the superfluid promises to be a powerful tool
for visualization of both quantum and classical turbulence in liquid helium. | nucl-ex |
Testing claims of the GW170817 binary neutron star inspiral affecting
$β$-decay rates: On August 17, 2017, the first gravitational wave signal from a binary neutron
star inspiral (GW170817) was detected by Advanced LIGO and Advanced VIRGO. Here
we present radioactive $\beta$-decay rates of three independent sources
$^{44}$Ti, $^{60}$Co and $^{137}$Cs, monitored during the same period by a
precision experiment designed to investigate the decay of long-lived
radioactive sources. We do not find any significant correlations between decay
rates in a 5\,h time interval following the GW170817 observation. This
contradicts a previous claim published in this journal of an observed
2.5$\sigma$ Pearson Correlation between fluctuations in the number of observed
decays from two $\beta$-decaying isotopes ($^{32}$Si and $^{36}$Cl) in the same
time interval. By correcting for the choice of an arbitrary time interval, we
find no evidence of a correlation above 1.5$\sigma$ confidence. In addition, we
argue that such analyses on correlations in arbitrary time intervals should
always correct for the so-called Look-Elsewhere effect by quoting the global
significance. | nucl-ex |
Measurement of the azimuthal anisotropy of neutral pions in PbPb
collisions at sqrt(s(NN)) = 2.76 TeV: First measurements of the azimuthal anisotropy of neutral pions produced in
PbPb collisions at a center-of-mass energy of sqrt(s(NN)) = 2.76 TeV are
presented. The amplitudes of the second Fourier component (v2) of the neutral
pion azimuthal distributions are extracted using an event-plane technique. The
values of v2 are studied as a function of the neutral pion transverse momentum
(pt) for different classes of collision centrality in the kinematic range 1.6 <
pt < 8.0 GeV, within the pseudorapidity interval abs(eta) < 0.8. The CMS
measurements of v2(pt) are similar to previously reported neutral pion
azimuthal anisotropy results from sqrt(s(NN)) = 200 GeV AuAu collisions at
RHIC, despite a factor of about 14 increase in the center-of-mass energy. In
the momentum range 2.5 < pt < 5.0 GeV, the neutral pion anisotropies are found
to be smaller than those observed by CMS for inclusive charged particles. | nucl-ex |
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