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Cross section for $b\bar{b}$ production via dielectrons in d$+$Au
collisions at $\sqrt{s_{_{NN}}}=200$ GeV: We report a measurement of $e^+e^-$ pairs from semileptonic heavy-flavor
decays in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. Exploring the mass
and transverse-momentum dependence of the yield, the bottom decay contribution
can be isolated from charm, and quantified by comparison to {\sc pythia} and
{\sc mc@nlo} simulations. The resulting $b\bar{b}$-production cross section is
$\sigma^{d{\rm Au}}_{b\bar{b}}=1.37{\pm}0.28({\rm stat}){\pm}0.46({\rm
syst})$~mb, which is equivalent to a nucleon-nucleon cross section of
$\sigma^{NN}_{bb}=3.4\pm0.8({\rm stat}){\pm}1.1({\rm syst})\ \mu$b. | nucl-ex |
Inclusive pion and eta production in p+Nb collisions at 3.5 GeV beam
energy: Data on inclusive pion and eta production measured with the dielectron
spectrometer HADES in the reaction p+93Nb at a kinetic beam energy of 3.5 GeV
are presented. Our results, obtained with the photon conversion method,
supplement the rather sparse information on neutral meson production in
proton-nucleus reactions existing for this bombarding energy regime. The
reconstructed e+e-e+e- transverse-momentum and rapidity distributions are
confronted with transport model calculations, which account fairly well for
both pi0 and eta production. | nucl-ex |
Production and Flow of Identified Hadrons at RHIC: We review the production and flow of identified hadrons at RHIC with a main
emphasis on the intermediate transverse momentum region ($2< p_{T} <5$
GeV/$c$). The goal is to unravel the dynamics of baryon production and resolve
the anomalously large baryon yields and elliptic flow observed in the
experiments. | nucl-ex |
A Facility for Low-energy Antiproton and Ion Research: The future accelerator facility for beams of ions and antiprotons at
Darmstadt will provide antiproton beams of intensities that are two orders of
magnitude higher than currently available. Within the foreseen scheme,
antiprotons can be decelerated to 30 MeV. The low-energy antiproton community
has recently formed a users group to make use of this opportunity to create a
next-generation low-energy antiproton facility called FLAIR, which will be able
to provide cooled antiproton beams well below 100 keV kinetic energy. This talk
gives an overview of the layout and physics program of the proposed facility. | nucl-ex |
A solenoidal electron spectrometer for a precision measurement of the
neutron $β$-asymmetry with ultracold neutrons: We describe an electron spectrometer designed for a precision measurement of
the neutron $\beta$-asymmetry with spin-polarized ultracold neutrons. The
spectrometer consists of a 1.0-Tesla solenoidal field with two identical
multiwire proportional chamber and plastic scintillator electron detector
packages situated within 0.6-Tesla field-expansion regions. Select results from
performance studies of the spectrometer with calibration sources are reported. | nucl-ex |
Electroweak probes with ATLAS: Measuring electroweak bosons in relativistic heavy ion collisions at high
energy provide an opportunity to understand temporal evolution of the
quark-gluon plasma created in such collisions by constraining the initial state
of the interaction. Due to lack of color charges the bosons and or particles
produced in their leptonic decays are unaffected by the quark-gluon plasma and
therefore preserve the information about the very early stage of the collision
when they were born. This singles electroweak bosons as a unique and very
interesting class of observables in heavy ion collisions. The ATLAS experiment
at LHC measures production of electroweak bosons in pp, p+Pb, and Pb + Pb
collisions systems. A review of the existing results is given in this
proceeding that includes studies made with isolated photons to constraint
kinematic properties and flavour composition of associated jets, measurements
of W and Z bosons used to estimate nuclear modification of parton distribution
function and the production rates of the bosons used to verify geometric models
implied to estimate event centrality. A novel analysis on measuring
two-particle correlations in pp collisions where the Z boson is registered is
also discussed in the proceeding. This is the first attempt to break into the
initial geometry of the pp collisions by constraining the impact parameter with
a hard scattering process. It shows that the strength of the two particle
correlations in such collision is 1.08+/-0.06 above the inclusive. To make the
measurement ATLAS solves the technical problem of measuring the underlying
event in high pileup condition. | nucl-ex |
Polarization in Hyperon Photo- and Electro- Production: Multiple polarization observables must be measured to access the amplitude
structure of pseudoscalar meson photoproduction off the proton. The
hyperon-producing reactions are especially attractive to study, since the weak
decays allow straightforward measurement of the induced and recoil polarization
observables. In this paper we emphasize $\gamma + p \to K^+ + \Lambda$,
discussing recent measurements of $C_x$, $C_z$, and $P$ for this reaction. An
empirical constraint on the helicity amplitudes is obtained. A simplified model
involving spin-flip and spin non-flip amplitudes is presented. Finally, a
semi-classical model of how the polarization may arise is presented. | nucl-ex |
Non-equilibrium emission of complex fragments from p+Au collisions at
2.5 GeV proton beam energy: Energy and angular dependence of double differential cross sections
d$^2\sigma$/d$\Omega$dE was measured for reactions induced by 2.5 GeV protons
on Au target with isotopic identification of light products (H, He, Li, Be, and
B) and with elemental identification of heavier intermediate mass fragments (C,
N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction
mechanisms give comparable contributions to the cross sections. The
intranuclear cascade of nucleon-nucleon collisions followed by evaporation from
an equilibrated residuum describes low energy part of the energy distributions
whereas another reaction mechanism is responsible for high energy part of the
spectra of composite particles. Phenomenological model description of the
differential cross sections by isotropic emission from two moving sources led
to a very good description of all measured data. Values of the extracted
parameters of the emitting sources are compatible with the hypothesis claiming
that the high energy particles emerge from pre-equilibrium processes consisting
in a breakup of the target into three groups of nucleons; small, fast and hot
fireball of $\sim$ 8 nucleons, and two larger, excited prefragments, which
emits the light charged particles and intermediate mass fragments. The smaller
of them contains $\sim$ 20 nucleons and moves with velocity larger than the CM
velocity of the proton projectile and the target. The heavier prefragment
behaves similarly as the heavy residuum of the intranuclear cascade of
nucleon-nucleon collisions. %The mass and charge dependence of the total
production cross %sections was extracted from the above analysis for all
observed %reaction products. This dependence follows the power low behavior
%(A$^{-\tau}$ or Z$^{-\tau}$). | nucl-ex |
Study of jet quenching with Z+jet correlations in PbPb and pp collisions
at sqrt(s[NN]) = 5.02 TeV: The production of jets in association with Z bosons, reconstructed via the
mu+mu- and e+e- decay channels, is studied in pp and, for the first time, in
PbPb collisions. Both data samples were collected by the CMS experiment at the
LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The PbPb
collisions were analyzed in the 0-30% centrality range. The back-to-back
azimuthal alignment was studied in both pp and PbPb collisions for Z bosons
with transverse momentum p[tz] > 60 GeV/c and a recoiling jet with p[tj] > 30
GeV/c. The pt imbalance, x[jz] = p[tj] / p[tz], as well as the average number
of jet partners per Z, R[jz], were studied in intervals of p[tz], in both pp
and PbPb collisions. The R[jz] is found to be smaller in PbPb than in pp
collisions, which suggests that in PbPb collisions a larger fraction of
partons, associated with the Z bosons, lose energy and fall below the 30 GeV/c
p[tj] threshold. | nucl-ex |
Recent Progress in Double Beta Decay: At least one neutrino has a mass of about 50 meV or larger. However, the
absolute mass scale for the neutrino remains unknown. Studies of double beta
decay offer hope for determining the absolute mass scale. Furthermore, the
critical question: Is the neutrino its own antiparticle? is unanswered. In
particular, zero-neutrino double beta decay can address the issues of lepton
number conservation, the particle-antiparticle nature of the neutrino, and its
mass. A summary of the recent progress in double beta decay, and the related
technologies will be discussed in the context of the future double beta decay
program. | nucl-ex |
Measurement of the $^{14}$N(n,p)$^{14}$C cross section at the CERN n_TOF
facility from sub-thermal energy to 800 keV: Background: The $^{14}$N(n,p)$^{14}$C reaction is of interest in neutron
capture therapy, where nitrogen-related dose is the main component due to
low-energy neutrons, and in astrophysics, where 14N acts as a neutron poison in
the s-process. Several discrepancies remain between the existing data obtained
in partial energy ranges: thermal energy, keV region and resonance region.
Purpose: Measuring the 14N(n,p)14C cross section from thermal to the resonance
region in a single measurement for the first time, including characterization
of the first resonances, and providing calculations of Maxwellian averaged
cross sections (MACS). Method: Time-of-flight technique. Experimental Area 2
(EAR-2) of the neutron time-of-flight (n_TOF) facility at CERN.
$^{10}$B(n,${\alpha}$)$^7$Li and $^{235}$U(n,f) reactions as references. Two
detection systems running simultaneously, one on-beam and another off-beam.
Description of the resonances with the R-matrix code sammy. Results: The cross
section has been measured from sub-thermal energy to 800 keV resolving the two
first resonances (at 492.7 and 644 keV). A thermal cross-section
(1.809$\pm$0.045 b) lower than the two most recent measurements by slightly
more than one standard deviation, but in line with the ENDF/B-VIII.0 and
JEFF-3.3 evaluations has been obtained. A 1/v energy dependence of the cross
section has been confirmed up to tens of keV neutron energy. The low energy
tail of the first resonance at 492.7 keV is lower than suggested by evaluated
values, while the overall resonance strength agrees with evaluations.
Conclusions: Our measurement has allowed to determine the $^{14}$N(n,p)
cross-section over a wide energy range for the first time. We have obtained
cross-sections with high accuracy (2.5 %) from sub-thermal energy to 800 keV
and used these data to calculate the MACS for kT = 5 to kT = 100 keV. | nucl-ex |
Improved search for two-neutrino double electron capture on $^{124}$Xe
and $^{126}$Xe using particle identification in XMASS-I: We conducted an improved search for the simultaneous capture of two $K$-shell
electrons on the $^{124}$Xe and $^{126}$Xe nuclei with emission of two
neutrinos using 800.0 days of data from the XMASS-I detector. A novel method to
discriminate $\gamma$-ray/$X$-ray or double electron capture signals from
$\beta$-ray background using scintillation time profiles was developed for this
search. No significant signal was found when fitting the observed energy
spectra with the expected signal and background. Therefore, we set the most
stringent lower limits on the half-lives at $2.1 \times 10^{22}$ and $1.9
\times 10^{22}$ years for $^{124}$Xe and $^{126}$Xe, respectively, with 90%
confidence level. These limits improve upon previously reported values by a
factor of 4.5. | nucl-ex |
Comment on "Search for new particles decaying into electron pairs of
mass below 100 MeV/c^2": A re-analysis of data from electron-pair production following 160 A GeV 207Pb
bombardment of nuclear emulsions indicates the production and decay of neutral
particles of significantly lower invariant mass and shorter lifetimes than
previously claimed (J. Phys. G: Nucl. Part. Phys. 34 (2007) 129-138). | nucl-ex |
Breakup Conditions of Projectile Spectators from Dynamical Observables: Momenta and masses of heavy projectile fragments (Z >= 8), produced in
collisions of 197Au with C, Al, Cu and Pb targets at E/A = 600 MeV, were
determined with the ALADIN magnetic spectrometer at SIS. An analysis of
kinematic correlations between the two and three heaviest projectile fragments
in their rest frame was performed. The sensitivity of these correlations to the
conditions at breakup was verified within the schematic SOS-model. The data
were compared to calculations with statistical multifragmentation models and to
classical three-body calculations. Classical trajectory calculations reproduce
the dynamical observables. The deduced breakup parameters, however, differ
considerably from those assumed in the statistical multifragmentation models
which describe the charge correlations. If, on the other hand, the analysis of
kinematic and charge correlations is performed for events with two and three
heavy fragments produced by statistical multifragmentation codes, a good
agreement with the data is found with the exception that the fluctuation widths
of the intrinsic fragment energies are significantly underestimated. A new
version of the multifragmentation code MCFRAG was therefore used to investigate
the potential role of angular momentum at the breakup stage. If a mean angular
momentum of 0.75$\hbar$/nucleon is added to the system, the energy fluctuations
can be reproduced, but at the same time the charge partitions are modified and
deviate from the data.
PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.Ld, 25.75.-q | nucl-ex |
Neutral meson production in d+Au and p+p collisions at sqrt(s_NN) = 200
GeV in STAR: The high centre-of-mass energy of 200 GeV available at the Relativistic Heavy
Ion Collider (RHIC) at Brookhaven opens up the hard scattering regime in
heavy-ion collisions. Particles at large transverse momentum originate from the
early stage of the interaction and, therefore, probe the medium produced in
these collisions. To quantitatively understand the medium induced modification
of hadron production, precise measurements of identified hadrons in p+p and
d+Au systems are required. This thesis presents the high transverse momentum
measurements of neutral pions and eta mesons through their di-photon decay
channel, performed with STAR Barrel Electromagnetic Calorimeter. The medium
induced spectrum modification in d+Au collisions is also measured in comparison
to the most peripheral d+Au and to the p+p collisions. The results are
consistent with the previous STAR charged hadron measurements and with the
theory (QCD) calculations, as well as with measurements from PHENIX, another
RHIC experiment. | nucl-ex |
Quark participants and global observables: We show that the centrality dependence of charged particle and photon
pseudorapidity density at midrapidity along with the transverse energy
pseudorapidity density at SPS and RHIC energies scales with the number of
participating constituent quarks. The number of charged particles and
transverse energy per participant constituent quark is found to increase with
increase in beam energy. | nucl-ex |
Sideward Flow in Au + Au Collisions Between 2A GeV and 8A GeV: Using the large acceptance Time Projection Chamber of experiment E895 at
Brookhaven, measurements of collective sideward flow in Au + Au collisions at
beam energies of 2, 4, 6 and 8A GeV are presented in the form of in-plane
transverse momentum <Px> and the first Fourier coefficient of azimuthal
anisotropy v_1. These measurements indicate a smooth variation of sideward flow
as a function of beam energy. The data are compared with four nuclear transport
models which have an orientation towards this energy range. All four exhibit
some qualitative trends similar to those found in the data, although none shows
a consistent pattern of agreement within experimental uncertainties. | nucl-ex |
Single-nucleon experiments: We discuss the Jefferson Lab low momentum transfer data on moments of the
nucleon spin structure functions $g_1$ and $g_2$ and on single charged pion
electroproduction off polarized proton and polarized neutron. A wealth of data
is now available, while more is being analyzed or expected to be taken in the
upcoming years. Given the low momentum transfer selected by the experiments,
these data can be compared to calculations from Chiral Perturbation theory, the
effective theory of strong force that should describe it at low momentum
transfer. The data on various moments and the respective calculations do not
consistently agree. In particular, experimental data for higher moments
disagree with the calculations.The absence of contribution from the $\Delta$
resonance in the various observables was expected to facilitate the
calculations and hence make the theory predictions either more robust or valid
over a larger $Q^2$ range. Such expectation is verified only for the Bjorken
sum, but not for other observables in which the $\Delta$ is suppressed.
Preliminary results on pion electroproduction off polarized nucleons are also
presented and compared to phenomenological models for which contributions from
different resonances are varied. Chiral Perturbation calculations of these
observables, while not yet available, would be valuable and, together with
these data, would provide an extensive test of the effective theory. | nucl-ex |
First measurement of the $|t|$-dependence of incoherent J/$ψ$
photonuclear production: The first measurement of the cross section for incoherent photonuclear
production of J/$\psi$ vector meson as a function of the Mandelstam $|t|$
variable is presented. The measurement was carried out with the ALICE detector
at midrapidity, $|y|<0.8$, using ultra-peripheral collisions of Pb nuclei at a
centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV.
This rapidity interval corresponds to a Bjorken-$x$ range $(0.3$$-$$1.4)\times
10^{-3}$. Cross sections are reported in five $|t|$ intervals in the range
$0.04<|t|<1$~GeV$^2$ and compared to the predictions of different models.
Models that ignore quantum fluctuations of the gluon density in the colliding
hadron predict a $|t|$-dependence of the cross section much steeper than in
data. The inclusion of such fluctuations in the same models provides a better
description of the data. | nucl-ex |
Is $\hat{q}$ a physical quantity or just a parameter? and other
unanswered questions in High-$p_T$ Physics: The many different theoretical studies of energy loss of a quark or gluon
traversing a medium have one thing in common: the transport coefficient of a
gluon in the medium, $\hat{q}$, which is defined as the mean 4-momentum
transfer$^2$, $\left<q^2\right>$, by a gluon to the medium per gluon mean free
path, $\lambda_{\rm mfp}$. In the original BDMPSZ formalism, the energy loss of
an outgoing parton, $-dE/dx$, per unit length ($x$) of a medium with total
length $L$, due to coherent gluon bremsstrahlung, is proportional to the
$\left< q^2\right>$ and takes the form: ${-dE/dx }\simeq \alpha_s
\left<{q^2(L)}\right>=\alpha_s\, \mu^2\, L/\lambda_{\rm mfp} =\alpha_s\,
\hat{q}\, L\ $ , where $\mu$, is the mean momentum transfer per collision.
Thus, the total energy loss in the medium goes like $L^2$. Additionally, the
accumulated momentum$^2$, $\left<{k_{\perp}^2}\right>$, transverse to a gluon
traversing a length $L$ in the medium is well approximated by
$\left<{k_{\perp}^2}\right>\approx\left<{q^2(L)}\right>=\hat{q}\, L$.
A simple estimate shows that the
$\left<{k_{\perp}^2}\right>\approx\hat{q}\,L$ should be observable at RHIC at
$\sqrt{s_{NN}}=200$ GeV via the broadening of di-hadron azimuthal correlations
resulting in an azimuthal width $\sim\sqrt{2}$ larger in Au$+$Au than in $p+p$
collisions . Measurements relevant to this issue will be discussed as well as
recent STAR jet results presented at QM2014. Other topics to be discussed
include the danger of using forward energy to define centrality in $p(d)+$A
collisions for high $p_T$ measurements, the danger of not using comparison
$p+p$ data at the same $\sqrt{s}$ in the same detector for $R_{AA}$ or lately
for $R_{pA}$ measurements. | nucl-ex |
Photoneutron Reactions $^{181}\rm{Ta}(γ,\textit{x}n; \textit{x} = 1
÷8)^{181-\textit{x}}\rm{Ta}$ AT $E_{\rm{γmax}}$ = 80 $÷$ 95 MeV: The bremsstrahlung flux-averaged cross-sections $\langle{\sigma(E_{\rm{\gamma
max}})}\rangle$ for the $^{181}\rm{Ta}(\gamma,\textit{x}n; \textit{x} = 1 \div
8)^{181-\textit{x}}\rm{Ta}$ photoneutron reactions have been measured at
end-point bremsstrahlung energies ranging from 80 MeV to 95 MeV. The
measurements were performed with the beam from the NSC KIPT electron linear
accelerator LUE-40 using the residual $\gamma$-activity method. The theoretical
$\langle{\sigma(E_{\rm{\gamma max}})}\rangle$ values were computed using the
cross-sections $\sigma(E)$ from TALYS1.9 code. A comparison between the
measured cross-sections $\langle{\sigma(E_{\rm{\gamma max}})}\rangle$ and the
theoretical values has demostrated their good agreement for the reactions with
escape of up to 6 neutrons, and substantial differences for the
$(\gamma,7\rm{n})$ and $(\gamma,8\rm{n})$ reactions. Isomeric ratios of the
average cross-sections $d(E_{\rm{\gamma max}})$ have been found for the
$^{181}\rm{Ta}(\gamma,3n)^{178g,m}\rm{Ta}$ reaction products. The results have
been compared with the literature data and the computations based on TALYS1.9
code. | nucl-ex |
Determination of luminosity for in-ring reactions: A new approach for
the low-energy domain: Luminosity is a measure of the colliding frequency between beam and target
and it is a crucial parameter for the measurement of absolute values, such as
reaction cross sections. In this paper, we make use of experimental data from
the ESR storage ring to demonstrate that the luminosity can be precisely
determined by modelling the measured Rutherford scattering distribution. The
obtained results are in good agreement with an independent measurement based on
the x-ray normalization method. Our new method provides an alternative way to
precisely measure the luminosity in low-energy stored-beam configurations. This
can be of great value in particular in dedicated low-energy storage rings where
established methods are difficult or impossible to apply. | nucl-ex |
Measurements of the γ* p --> Δ(1232) reaction at low Q2: We report new p$(\vec{e},e^\prime p)\pi^\circ$ measurements in the
$\Delta^{+}(1232)$ resonance at the low momentum transfer region utilizing the
magnetic spectrometers of the A1 Collaboration at MAMI. The mesonic cloud
dynamics are predicted to be dominant and appreciably changing in this region
while the momentum transfer is sufficiently low to be able to test chiral
effective calculations. The results disagree with predictions of constituent
quark models and are in reasonable agreement with dynamical calculations with
pion cloud effects, chiral effective field theory and lattice calculations. The
reported measurements suggest that improvement is required to the theoretical
calculations and provide valuable input that will allow their refinements. | nucl-ex |
Experimental Evidence of Large Collective Enhancement of Nuclear Level
Density and its Significance in Radiative Neutron Capture: The collective enhancement of nuclear level density and its fade out with
excitation energy in deformed $^{171}$Yb nucleus has been inferred through an
exclusive measurement of neutron spectra.The statistical model analysis of
neutron spectra demonstrated a large collective enhancement factor of 40$\pm$3
for the first time, which corroborates with the recent microscopic model
predictions but is an anomalous result compared with the measurements in the
nearby deformed nuclei. The complete picture of the energy dependent collective
enhancement has been obtained by combining with Oslo data below neutron binding
energy. The significance of large collective enhancement in radiative neutron
capture cross section of astrophysical interest is highlighted. | nucl-ex |
Measurement of substructure-dependent jet suppression in Pb+Pb
collisions at 5.02 TeV with the ATLAS detector: The ATLAS detector at the Large Hadron Collider has been used to measure jet
substructure modification and suppression in Pb+Pb collisions at a
nucleon-nucleon center-of-mass energy
$\sqrt{s_{_\mathrm{NN}}}=5.02~\mathrm{TeV}$ in comparison with $pp$ collisions
at $\sqrt{s}=5.02~\mathrm{TeV}$. The Pb+Pb data, collected in 2018, have an
integrated luminosity of $1.72~\mathrm{nb^{-1}}$, while the $pp$ data,
collected in 2017, have an integrated luminosity of $260~\mathrm{pb}^{-1}$.
Jets used in this analysis are clustered using the anti-$k_{t}$ algorithm with
a radius parameter $R=0.4$. The jet constituents, defined by both tracking and
calorimeter information, are used to determine the angular scale $r_\mathrm{g}$
of the first hard splitting inside the jet by reclustering them using the
Cambridge-Aachen algorithm and employing the soft-drop grooming technique. The
nuclear modification factor, $R_\mathrm{AA}$, used to characterize jet
suppression in Pb+Pb collisions, is presented differentially in $r_\mathrm{g}$,
jet transverse momentum, and in intervals of collision centrality. The
$R_\mathrm{AA}$ value is observed to depend significantly on jet
$r_\mathrm{g}$. Jets produced with the largest measured $r_\mathrm{g}$ are
found to be twice as suppressed as those with the smallest $r_\mathrm{g}$ in
central Pb+Pb collisions. The $R_\mathrm{AA}$ values do not exhibit a strong
variation with jet $p_\mathrm{T}$ in any of the $r_\mathrm{g}$ intervals. The
$r_\mathrm{g}$ and $p_\mathrm{T}$ dependence of jet $R_\mathrm{AA}$ is
qualitatively consistent with a picture of jet quenching arising from coherence
and provides the most direct evidence in support of this approach. | nucl-ex |
Mixed-symmetry octupole and hexadecapole excitations in the N=52
isotones: Background: Excitations with mixed proton-neutron symmetry have been
previously observed in the $N=52$ isotones. Besides the well established
quadrupole mixed-symmetry states (MSS), octupole and hexadecapole MSS have been
recently proposed for the nuclei $^{92}$Zr and $^{94}$Mo.
Purpose: The heaviest stable $N=52$ isotone $^{96}$Ru was investigated to
study the evolution of octupole and hexadecapole MSS with increasing proton
number.
Methods: Two inelastic proton-scattering experiments on $^{96}$Ru were
performed to extract branching ratios, multipole mixing ratios, and level
lifetimes. From the combined data, absolute transition strengths were
calculated.
Results: Strong $M1$ transitions between the lowest-lying $3^-$ and $4^+$
states were observed, providing evidence for a one-phonon mixed-symmetry
character of the $3^{(-)}_2$ and $4^+_2$ states.
Conclusions: $sdg$-IBM-2 calculations were performed for $^{96}$Ru. The
results are in excellent agreement with the experimental data, pointing out a
one-phonon hexadecapole mixed-symmetry character of the $4^+_2$ state. The
$\big< 3^-_1||M1||3^{(-)}_2\big>$ matrix element is found to scale with the
$<2^+_{\mathrm{s}}||M1||2^+_{\mathrm{ms}}>$ matrix element. | nucl-ex |
Interpretations of Elastic Electron Scattering: Elastic scattering of relativistic electrons from the nucleon yields Lorentz
invariant form factors that describe the fundamental distribution of charge and
magnetism. The spatial dependence of the nucleon's charge and magnetism is
typically interpreted in the Breit reference frame which is related by a
Lorentz boost from the laboratory frame, where the nucleon is at rest. We
construct a toy model to estimate how the charge and magnetic radii of the
nucleon are modified between the Breit and lab. frames. This has implications
for the ratio of the proton electric to magnetic elastic form factors as a
function of momentum transfer as well as for determinations of the proton
charge radius. Predicted corrections based on the model are provided for the
rms charge radii of the deuteron, the triton, and the helium isotopes. | nucl-ex |
Antinucleus Production at RHIC: Light antinuclei may be formed in relativistic heavy ion collisions via final
state coalescence of antinucleons. The yields of antinuclei are sensitive to
primordial antinucleon production, the volume of the system at kinetic
freeze-out, and space-momentum correlations among antinucleons at freeze-out.
We report here preliminary STAR results on antideuteron and antihelion
production in 130A GeV Au+Au collisions. These results are examined in a
coalescence framework to elucidate the space-time structure of the antinucleon
source. | nucl-ex |
High pT correlations with strange particles in STAR: We present the highlights of the current identified strange particles
DeltaPhi and DeltaEta correlations analyses, including system-size and
trigger-pT of the jet and ridge, jet, ridge and away-side meson/baryon ratios,
and the current state of the multi-strange baryon analysis. We see clear
azimuthal peaks of comparable strength for all strange baryons and K0-short
mesons. We see no observable species dependence on the same-side jet or ridge
yields as a function of pT. However, while the away side and the ridge have
Lambda to K0-short ratio similar to that of the bulk, the jet-only ratio is
similar to that in $p+p$. The implications of these findings on current
in-medium jet theoretical explanations are discussed. | nucl-ex |
Centrality dependence of the thermal excitation-energy deposition in
8-15 GeV/c hadron-Au reactions: The excitation energy per residue nucleon (E*/A) and fast and thermal light
particle multiplicities are studied as a function of centrality defined as the
number of grey tracks emitted N_grey and by the mean number of primary
hadron-nucleon scatterings <nu> and mean impact parameter <b> extracted from
it. The value of E*/A and the multiplicities show an increase with centrality
for all systems, 14.6 GeV p-Au and 8.0 GeV pi-Au and pbar-Au collisions, and
the excitation energy per residue nucleon exhibits a uniform dependence on
N_grey. | nucl-ex |
Inclusive Studies of Short-Range Correlations: Overview and New Results: We present an overview of Short-Range Correlations (SRC) studies using the
inclusive measurement of the electron scattering off nuclei. A brief
introduction of the origin of the SRC is given, followed by the survey of the
two-nucleon SRC (2N-SRC) study and its interesting connection to the EMC
effect. A discussion of the three-nucleon SRC study (3N-SRC) measured by the
Jefferson Lab's Hall B and Hall C experiments which showed contradictory
results is given and, most importantly, we report a new result from the Hall A
E08-014 experiment which was dedicated on studying 3N-SRC. Our high precision
4He/3He cross section ratios at the x > 2 region do not show a 3N-SRC plateau
as predicted by the naive SRC model. To further investigate the 3N-SRC as well
as the Isospin effect of the SRC, we have designed several approved experiments
in Hall A and in Hall C, including the Tritium experiments using the mirror
nuclei (3H and 3He) which are currently running in Hall A. | nucl-ex |
The Evolution of Nuclear Multifragmentation in the Temperature-Density
Plane: The mean transverse kinetic energies of the fragments formed in the
interaction of 1 A GeV Au+C have been determined. An energy balance argument
indicates the presence of a collective energy which increases in magnitude with
increasing multiplicity and accounts for nearly half of the measured mean
transverse kinetic energy. The radial flow velocity associated with the
collective energy yields estimates for the time required to expand to the
freeze-out volume. Isentropic trajectories in the temperature-density plane are
shown for the expansion and indicate that the system goes through the critical
region at the same multiplicities as deduced from a statistical analysis. Here,
the expansion time is approximately 70 fm/c. | nucl-ex |
Flavor Decomposition of Nucleon Form Factors: The nucleon form factors provide fundamental knowledge about the strong
interaction. We review the flavor composition of the nucleon form factors and
focus on an analysis of the possible impact of the s-quark contribution. A
future experiment is presented to measure the strange form factor at large
momentum transfer. | nucl-ex |
Jefferson Lab Science, Past and Future: The Continuous Electron Beam Accelerator Facility (CEBAF) and associated
experimental equipment at Jefferson Lab comprise a unique facility for
experimental nuclear physics. This facility is presently being upgraded, which
will enable a new experimental program with substantial discovery potential to
address important topics in nuclear, hadronic, and electroweak physics. Further
in the future, it is envisioned that the Laboratory will evolve into an
electron-ion colliding beam facility. | nucl-ex |
Separated Response Functions in Exclusive, Forward $π^{\pm}$
Electroproduction on Deuterium: Background: Measurements of forward exclusive meson production at different
squared four-momenta of the exchanged virtual photon, $Q^2$, and at different
four-momentum transfer, t, can be used to probe QCD's transition from
meson-nucleon degrees of freedom at long distances to quark-gluon degrees of
freedom at short scales. Ratios of separated response functions in $\pi^-$ and
$\pi^+$ electroproduction are particularly informative. The ratio for
transverse photons may allow this transition to be more easily observed, while
the ratio for longitudinal photons provides a crucial verification of the
assumed pole dominance, needed for reliable extraction of the pion form factor
from electroproduction data. Method: Data were acquired with 2.6-5.2 GeV
electron beams and the HMS+SOS spectrometers in Jefferson Lab Hall C, at
central $Q^2$ values of 0.6, 1.0, 1.6 GeV$^2$ at W=1.95 GeV, and $Q^2$=2.45
GeV$^2$ at W=2.22 GeV. There was significant coverage in $\phi$ and $\epsilon$,
which allowed separation of $\sigma_{L,T,LT,TT}$. Results: $\sigma_L$ shows a
clear signature of the pion pole, with a sharp rise at small -t. In contrast,
$\sigma_T$ is much flatter versus t. The longitudinal/transverse ratios evolve
with $Q^2$ and t, and at the highest $Q^2$=2.45 GeV$^2$ show a slight
enhancement for $\pi^-$ production compared to $\pi^+$. The $\pi^-/\pi^+$ ratio
for transverse photons exhibits only a small $Q^2$-dependence, following a
nearly universal curve with t, with a steep transition to a value of about
0.25, consistent with s-channel quark knockout. The $\sigma_{TT}/\sigma_T$
ratio also drops rapidly with $Q^2$, qualitatively consistent with s-channel
helicity conservation. The $\pi^-/\pi^+$ ratio for longitudinal photons
indicates a small isoscalar contamination at W=1.95 GeV, consistent with what
was observed in our earlier determination of the pion form factor at these
kinematics. | nucl-ex |
Charged-particle jet spectra in event-shape engineered Pb--Pb collisions
at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE: The path-length dependence of jet quenching can help to constrain different
jet quenching mechanisms in heavy-ion collisions. However, measuring an
explicit value for this dependence has proven challenging. Traditional
approaches, which consider anisotropic jet suppression arising from geometric
asymmetries, have successfully measured a non-zero azimuthal dependence of jet
modification with respect to the event-plane angle of the collision. While such
signals improve our qualitative understanding of this topic, extraction of an
explicit dependence from these results is limited by fluctuations in the
initial state and jet--medium interactions. A new approach to characterize the
geometry of the collision is to use event-shape engineering, a technique that
classifies events within a centrality class according to their elliptical
anisotropies. By doing so, we gain an improved knowledge of the initial-state
medium, consequently enabling better constraints on the average path length
traversed by the jet. In these proceedings, new results of jet spectra from
event-shape-engineered collisions at ALICE will be presented. | nucl-ex |
On the transverse momentum distribution of strange hadrons produced in
relativistic heavy ion collisions: Particles with strange quark content produced in the system 1.93 AGeV
$^{58}$Ni on $^{58}$Ni have been investigated at GSI Darmstadt with the FOPI
detector system. The correlation of these produced particles was analyzed with
respect to the reaction plane. Lambda baryons exhibit a very pronounced
sideward flow pattern which is qualitatively similar to the proton flow.
However, the kaon ($K^+$,$K^0_S$) flow patterns are significantly different
from that of the protons, and their form may be useful to restrict theoretical
models on the form of the kaon potential in the nuclear medium. | nucl-ex |
Exploring the Partonic Structure of Hadrons through the Drell-Yan
Process: The Drell-Yan process is a standard tool for probing the partonic structure
of hadrons. Since the process proceeds through a quark-antiquark annihilation,
Drell-Yan scattering possesses a unique ability to selectively probe sea
distributions. This review examines the application of Drell-Yan scattering to
elucidating the flavor asymmetry of the nucleon's sea and nuclear modifications
to the sea quark distributions in unpolarized scattering. Polarized beams and
targets add an exciting new dimension to Drell-Yan scattering. In particular,
the two initial-state hadrons give Drell-Yan sensitivity to chirally-odd
transversity distributions. | nucl-ex |
Weak interaction studies at SARAF: We review the current status of the radioisotopes program at the Soreq
Applied Research Accelerator Facility (SARAF), where we utilize an
electrostatic-ion-beam trap and a magneto-optical trap for studying the nuclear
$\beta$-decay from trapped radioactive atoms and ions. The differential energy
spectra of $\beta$'s and recoil ions emerging from the decay is sensitive to
beyond standard model interactions and is complementary to high energy
searches. The completed facility SARAF-II will be one of the world's most
powerful deuteron, proton and fast neutron sources, producing light radioactive
isotopes in unprecedented amounts, needed for obtaining enough statistics for a
high precision measurement. | nucl-ex |
Measurement of long-range two-particle azimuthal correlations in
$Z$-boson tagged $pp$ collisions at $\sqrt{s}{=}8$ and 13 TeV: Results are presented from the measurement by ATLAS of long-range
($|\Delta\eta|>2$)dihadron angular correlations in $\sqrt{s}=8$ and 13 TeV $pp$
collisions containing a $Z$ boson. The analysis is performed using 19.4
$\mathrm{fb}^{-1}$ of $\sqrt{s}=8$ TeV data recorded during Run 1 of the LHC
and 36.1 $\mathrm{fb}^{-1}$ of $\sqrt{s}=13$ TeV data recorded during Run 2.
Two-particle correlation functions are measured as a function of relative
azimuthal angle over the relative pseudorapidity range $2<|\Delta\eta|<5$ for
different intervals of charged-particle multiplicity and transverse momentum.
The measurements are corrected for the presence of background charged particles
generated by collisions that occur during one passage of two colliding proton
bunches in the LHC. Contributions to the two-particle correlation functions
from hard processes are removed using a template-fitting procedure. Sinusoidal
modulation in the correlation functions is observed and quantified by the
second Fourier coefficient of the correlation function, $v_{2,2}$, which in
turn is used to obtain the single-particle anisotropy coefficient $v_{2}$. The
$v_{2}$ values in the $Z$-tagged events, integrated over $0.5<p_{\mathrm{T}}<5$
GeV, are found to be independent of multiplicity and $\sqrt{s}$, and consistent
within uncertainties with previous measurements in inclusive $pp$ collisions.
As a function of charged-particle $p_{\mathrm{T}}$, the $Z$-tagged and
inclusive $v_{2}$ values are consistent within uncertainties for
$p_{\mathrm{T}}<3$ GeV. | nucl-ex |
Beta decay of 115-In to the first excited level of 115-Sn: Potential
outcome for neutrino mass: Recent observation of beta decay of 115-In to the first excited level of
115-Sn with an extremely low Q_beta value (Q_beta ~ 1 keV) could be used to set
a limit on neutrino mass. To give restriction potentially competitive with
those extracted from experiments with 3-H (~2 eV) and 187-Re (~15 eV), atomic
mass difference between 115-In and 115-Sn and energy of the first 115-Sn level
should be remeasured with higher accuracy (possibly of the order of ~1 eV). | nucl-ex |
Design of a High Intensity Neutron Source for Neutron-Induced Fission
Yield Studies: The upgraded IGISOL facility with JYFLTRAP, at the accelerator laboratory of
the University of Jyv\"askyl\"a, has been supplied with a new cyclotron which
will provide protons of the order of 100 {\mu}A with up to 30 MeV energy, or
deuterons with half the energy and intensity. This makes it an ideal place for
measurements of neutron-induced fission products from various actinides, in
view of proposed future nuclear fuel cycles. The groups at Uppsala University
and University of Jyv\"askyl\"a are working on the design of a neutron
converter that will be used as neutron source in fission yield studies. The
design is based on simulations with Monte Carlo codes and a benchmark
measurement that was recently performed at The Svedberg Laboratory in Uppsala.
In order to obtain a competitive count rate the fission targets will be placed
very close to the neutron converter. The goal is to have a flexible design that
will enable the use of neutron fields with different energy distributions. In
the present paper, some considerations for the design of the neutron converter
will be discussed, together with different scenarios for which fission targets
and neutron energies to focus on. | nucl-ex |
Moments of the Spin Structure Functions g_1^p and g_1^d for 0.05 < Q^2 <
3.0 GeV^2: The spin structure functions g_1 for the proton and the deuteron have been
measured over a wide kinematic range in x and Q2 using 1.6 and 5.7 GeV
longitudinally polarized electrons incident upon polarized NH_3 and ND_3
targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large
Acceptance Spectrometer, for 0.05 < Q^2 < 5 GeV^2 and W < 3 GeV. The first
moments of g_1 for the proton and deuteron are presented -- both have a
negative slope at low Q^2, as predicted by the extended Gerasimov-Drell-Hearn
sum rule. The first result for the generalized forward spin polarizability of
the proton gamma_0^p is also reported. This quantity shows strong Q^2
dependence at low Q^2, while Q^6\gamma_0^p seems to flatten out at the highest
Q^2 accessed by our experiment. Although the first moments of g_1 are
consistent with Chiral Perturbation Theory (ChPT) calculations up to
approximately Q^2 = 0.06 GeV^2, a significant discrepancy is observed between
the \gamma_0^p data and ChPT for gamma_0^p, even at the lowest Q2. | nucl-ex |
Coherent Dissociation of Relativistic C-9 Nuclei: Results on the coherent dissociation of relativistic $^9$C nuclei in a
nuclear track emulsion are described. These results include the charge topology
and kinematical features of final states. Events of C-9 to 3He-3 coherent
dissociation are identified. | nucl-ex |
Photoproduction of eta mesons from the neutron: cross sections and
double polarization observable E: Photoproduction of $\eta$ mesons from neutrons} \abstract{Results from
measurements of the photoproduction of $\eta$ mesons from quasifree protons and
neutrons are summarized. The experiments were performed with the CBELSA/TAPS
detector at the electron accelerator ELSA in Bonn using the
$\eta\to3\pi^{0}\to6\gamma$ decay. A liquid deuterium target was used for the
measurement of total cross sections and angular distributions. The results
confirm earlier measurements from Bonn and the MAMI facility in Mainz about the
existence of a narrow structure in the excitation function of $\gamma
n\rightarrow n\eta$. The current angular distributions show a forward-backward
asymmetry, which was previously not seen, but was predicted by model
calculations including an additional narrow $P_{11}$ state. Furthermore, data
obtained with a longitudinally polarized, deuterated butanol target and a
circularly polarized photon beam were analyzed to determine the double
polarization observable $E$. Both data sets together were also used to extract
the helicity dependent cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$. The
narrow structure in the excitation function of $\gamma n\rightarrow n\eta$
appears associated with the helicity-1/2 component of the reaction. | nucl-ex |
Photo-disintegration cross section measurements on $^{186}$W, $^{187}$Re
and $^{188}$Os: Implications for the Re-Os cosmochronology: Cross sections of the $^{186}$W, $^{187}$Re, $^{188}$Os($\gamma,n$) reactions
were measured using quasi-monochromatic photon beams from laser Compton
scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are
compared with the predictions of Hauser-Feshbach statistical calculations using
four different sets of input parameters. In addition, the inverse neutron
capture cross sections were evaluated by constraining the model parameters,
especially the $E1$ strength function, on the basis of the experimental data.
The present experiment helps to further constrain the correction factor
$F_{\sigma}$ for the neutron capture on the 9.75 keV state in $^{187}$Os.
Implications of $F_{\sigma}$ to the Re-Os cosmochronology are discussed with a
focus on the uncertainty in the estimate of the age of the Galaxy. | nucl-ex |
Preparation for heavy-flavour measurements with ALICE at the LHC: ALICE will study nucleus-nucleus and proton-proton collisions at the LHC. The
main goal of the experiment is to investigate the properties of QCD matter at
the extreme energy densities that will be reached in Pb-Pb collisions. Heavy
quarks (charm and beauty) are regarded as powerful tools for this study. After
briefly reviewing the ALICE heavy-flavour program, we will describe the
preparation for the first measurements to be performed with pp collisions. | nucl-ex |
Factorization of Short- and Long-range Interactions in Charged Meson
Production: Meson production data play an important role in our understanding of nucleon
structure. The combination of reaction channels is sensitive to gluon and
charge and flavor non-singlet quark densities and has the potential to provide
detailed images of the QCD quark structure of the nucleon. Quark imaging
requires a good understanding of the reaction mechanism, and in particular
rigorous tests of factorization of long- and short-distance physics. The higher
energies after the Jefferson Lab 12 GeV upgrade provide ideal conditions for
such studies, which are an essential prerequisite for studies of valence quark
distributions. An electron-ion collider would allow to extend these studies to
detailed imaging of sea quarks and gluons. | nucl-ex |
Discovery of the Arsenic Isotopes: Twenty-nine arsenic isotopes have so far been observed; the discovery of
these isotopes is discussed. For each isotope a brief summary of the first
refereed publication, including the production and identification method, is
presented. | nucl-ex |
Heavy quark and J/psi production at RHIC/PHENIX: Single electrons from open heavy quarks and di-leptons from J/psi mesons have
been studied systematically at RHIC/PHENIX using data from p + p, d + Au and Au
+ Au collisions at $\sqrt{s_{NN}}$ = 62.4 GeV, 130 GeV and 200 GeV. From the
single electron study, the charm quark yield is found to scale with the number
of binary collisions. This scaling has recently been confirmed using Au+Au
collisions at 62.4 GeV. A new analysis shows that a high p_T suppression of
single electrons is observed in Au + Au collisions at 200 GeV. This suppression
suggests that heavy quarks lose significant energy in the medium. A weak
rapidity dependence is seen in J/psi yields from d + Au data, which can be
interpreted as a cold matter effect. We report also the results of a
measurement of the spin alignment of the J/psi in the p_T range around 1.5
GeV/c. | nucl-ex |
Hard scattering and jets--from p-p collisions in the 1970's to Au+Au
collisions at RHIC: Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the
method of leading particles, proved that the partons of Deeply Inelastic
Scattering strongly interacted with each other. Further ISR measurements
utilizing inclusive single or pairs of hadrons established that high pT
particles are produced from states with two roughly back-to-back jets which are
the result of scattering of constituents of the nucleons as described by
Quantum Chromodynamics (QCD), which was developed during the course of these
measurements. These techniques, which are the only practical method to study
hard-scattering and jet phenomena in Au+Au central collisions, are reviewed,
with application to measurements at RHIC. | nucl-ex |
Light Nuclei and Hyper Nuclei Collectivity Measurements at High Baryon
Density Region: High energy heavy-ion collisions produce large amounts of light nuclei and
hype nuclei, especially at high baryon density around collision energy of
several GeV. These light nuclei and hyper nuclei carry the information of
nucleon-nucleon and hyperon-nucleon interactions and affect the chemical
composition and properties of the collision system. This proceeding is a brief
review for the recent measurements on light nuclei collective flow, including
directed flow $v_1$, elliptic flow $v_2$, and high order flow coefficients, at
finite and high baryon densities from different experiments. The light nuclei
production mechanism is discussed based on comparisons of the measurements and
model calculations. The first measurement for hyper nuclei $v_1$ at 3 GeV by
STAR is also reported, which may imply the hyper nuclei are formed via the
coalescence of nucleons and hyperon. | nucl-ex |
Measurement of the 2$νββ$ Decay Half-Life of Se-82 with the
Global CUPID-0 Background Model: We report on the results obtained with the global CUPID-0 background model,
which combines the data collected in the two measurement campaigns for a total
exposure of 8.82~kg$\times$yr of $^{82}$Se. We identify with improved precision
the background sources within the 3 MeV energy region, where neutrinoless
double $\beta$-decay of $^{82}$Se and $^{100}$Mo is expected, making more solid
the foundations for the background budget of the next-generation CUPID
experiment. Relying on the excellent data reconstruction, we measure the
two-neutrino double $\beta$-decay half-life of $^{82}$Se with unprecedented
accuracy: $T_{1/2}^{2\nu} = [8.69 \pm 0.05 \textrm{(stat.)}~^{+0.09}_{-0.06}
\textrm{(syst.)}] \times 10^{19}~\textrm{yr}$. | nucl-ex |
No correlation between Solar flares and the decay rate of several
$β$-decaying isotopes: We report on finding no correlation between the two strongest observed Solar
flares in September 2017 and the decay rates of $^{60}$Co, $^{44}$Ti and
$^{137}$Cs sources, which are continuously measured by two independent NaI(Tl)
detector setups. We test for variations in the number of observed counts with
respect to the number of expected counts over multiple periods with timescales
varying from 1 to 109 hours around the Solar flare. No excess or deficit
exceeds the 2$\sigma$ global significance. We set a conservative lower limit on
the decay rate deviation over an 84-hour period around the two correlated Solar
flares in September 2017 to $0.044\%$ with 2$\sigma$ confidence. A fractional
change of $~0.1\%$ in the decay rate of $^{54}$Mn over a period of 84 hours was
claimed with 7$\sigma$ significance during multiple Solar flares in December
2006. We exclude such an effect at 4.7$\sigma$ significance. | nucl-ex |
Nuclear multifragmentation time-scale and fluctuations of largest
fragment size: Distributions of the largest fragment charge, Zmax, in multifragmentation
reactions around the Fermi energy can be decomposed into a sum of a Gaussian
and a Gumbel distribution, whereas at much higher or lower energies one or the
other distribution is asymptotically dominant. We demonstrate the same generic
behavior for the largest cluster size in critical aggregation models for small
systems, in or out of equilibrium, around the critical point. By analogy with
the time-dependent irreversible aggregation model, we infer that Zmax
distributions are characteristic of the multifragmentation time-scale, which is
largely determined by the onset of radial expansion in this energy range. | nucl-ex |
Acceptance and resolution simulation studies for the dielectron
spectrometer HADES at GSI: Design studies for a second generation Dilepton Spectrometer to be built at
the SIS accelerator of GSI are presented. The basic design parameters of this
system are specified and the different detector components for charged particle
tracking and for lepton identification are described. The geometrical
acceptance for lepton pairs is given. Results on single track momentum
resolution and on lepton pair mass resolution are reported. | nucl-ex |
Polarization and spin correlation parameters in proton knockout
reactions from s1/2 - orbits at 1 GeV: The polarization of the secondary protons (P1,2) in the (p,2p) reaction with
the S - shell protons of nuclei 4He, 6Li, 12C, 28Si, 40Ca was measured at 1 GeV
unpolarized proton beam. The spin correlation parameters Cij for the 4He and
12C targets also were for the first time obtained. The polarization
measurements were performed by means of a two - arm magnetic spectrometer each
arm of which was equipped with multiwire - proportional chambers polarimeter. | nucl-ex |
The MAJORANA Experiment: The MAJORANA collaboration is actively pursuing research and development
aimed at a tonne-scale 76Ge neutrinoless double-beta decay) experiment. The
current, primary focus is the construction of the MAJORANA DEMONSTRATOR
experiment, an R&D effort that will field approximately 40kg of germanium
detectors with mixed enrichment levels. This article provides a status update
on the construction of the DEMONSTRATOR. | nucl-ex |
Search for jet quenching effects in high multiplicity pp collisions at
$\sqrt{\mathrm{s}}$=13 TeV: The ALICE Collaboration reports a search for jet quenching effects in pp
collisions at $\sqrt{\mathrm{s}}$=13 TeV, in events selected on high
multiplicity compared to the minimum bias population. The measurement is based
on the semi-inclusive acoplanarity distribution of jets recoiling from a
high-$p_\mathrm{T}$ trigger hadron. Significant broadening of the recoil jet
acoplanarity distribution is observed in high multiplicity pp collisions, in
both data and in simulations based on the PYTHIA model. Analysis is ongoing to
elucidate the origin of this effect. | nucl-ex |
$\rm Λ_{c}^{+}$ production and baryon-to-meson ratios in pp and
p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV at the LHC: The prompt production of the charm baryon $\rm \Lambda_{c}^{+}$ and the $\rm
\Lambda_{c}^{+}/\mathrm {D^0}$ production ratios were measured at midrapidity
with the ALICE detector in pp and p-Pb collisions at $\sqrt{s_\mathrm{NN}} =
5.02$TeV. These new measurements show a clear decrease of the $\rm
\Lambda_{c}^{+}/\mathrm {D^0}$ ratio with increasing transverse momentum
($p_{\rm T}$) in both collision systems in the range $2<p_{\rm T}<12$ GeV/$c$,
exhibiting similarities with the light-flavour baryon-to-meson ratios ${\rm
p}/\pi$ and $\Lambda/\mathrm {K^0_S}$. At low $p_{\rm T}$, predictions that
include additional colour-reconnection mechanisms beyond the leading-colour
approximation; assume the existence of additional higher-mass charm-baryon
states; or include hadronisation via coalescence can describe the data, while
predictions driven by charm-quark fragmentation processes measured in $\mathrm
{e^+e^-}$ and $\mathrm {e^-p}$ collisions significantly underestimate the data.
The results presented in this letter provide significant evidence that the
established assumption of universality (colliding-system independence) of
parton-to-hadron fragmentation is not sufficient to describe charm-baryon
production in hadronic collisions at LHC energies. | nucl-ex |
Entropy Production at High Energy and mu_B: The systematics of bulk entropy production in experimental data on A+A, p+p
and e+e- interactions at high energies and large mu_B is discussed. It is
proposed that scenarios with very early thermalization, such as Landau's
hydrodynamical model, capture several essential features of the experimental
results. It is also pointed out that the dynamics of systems which reach the
hydrodynamic regime give similar multiplicities and angular distributions as
those calculated in weak-coupling approximations (e.g. pQCD) over a wide range
of beam energies. Finally, it is shown that the dynamics of baryon stopping are
relevant to the physics of total entropy production, explaining why A+A and
e+e- multiplicities are different at low beam energies. | nucl-ex |
Directed flow of quarks from the RHIC Beam Energy Scan measured by STAR: Directed flow ($v_1$) is a good probe of the early-stage dynamics of
collision systems, and the $v_1$ slope at midrapidity ($dv_1/dy|_{y=0}$) is
sensitive to the system's equation of state. STAR has published $v_1(y)$
measurements for ten particle species ($\pi^\pm$, $p$, $\bar{p}$, $\Lambda$,
$\bar{\Lambda}$, $\phi$, $K^\pm$ and $K^0_{S}$) in Au+Au collisions at eight
beam energies from $\sqrt{s_{NN}} = 7.7$ GeV to 200 GeV. In this study, we
employ a simple coalescence idea to decompose $v_1$ of hadrons into $v_1$ of
constituent quarks. The $dv_1/dy$ values of $\bar{p}$, $K^-$ and
$\bar{\Lambda}$ are used to test the coalescence sum rule for produced quarks.
Data involving produced quarks support the coalescence picture at
$\sqrt{s_{NN}} = 11.5$ GeV to 200 GeV, and a sharp deviation from this picture
is observed at 7.7 GeV. The $dv_1/dy$ of transported quarks is studied via net
particles (net $p$ and net $\Lambda$). In these proceedings, we further extract
the $v_1$ slopes of produced and transported quarks, assuming that the
coalescence sum rule is valid. | nucl-ex |
Contemporary presence of dynamical and statistical production of
intermediate mass fragments in midperipheral $^{58}$Ni+$^{58}$Ni collisions
at 30 MeV/nucleon: The $^{58}Ni+^{58}Ni$ reaction at 30 MeV/nucleon has been experimentally
investigated at the Superconducting Cyclotron of the INFN Laboratori Nazionali
del Sud. In midperipheral collisions the production of massive fragments
(4$\le$Z$\le$12), consistent with the statistical fragmentation of the
projectile-like residue and the dynamical formation of a neck, joining
projectile-like and target-like residues, has been observed. The fragments
coming from these different processes differ both in charge distribution and
isotopic composition. In particular it is shown that these mechanisms leading
to fragment production act contemporarily inside the same event. | nucl-ex |
Two-pion and two-kaon femtoscopic correlations in Au+Au collisions at
$\sqrt{s_{NN}}$=200 GeV from STAR: Measurement of femtoscopic correlations in heavy-ion collisions can provide
information about spatial and temporal parameters of the particle emission
region at kinetic freeze-out. In this work we present the measurement of
two-pion and two-kaon femtoscopic correlations in 200 GeV Au+Au collisions at
RHIC. The collision centrality and transverse momentum dependence of the
three-dimensional radii, $R_{out}$, $R_{side}$ and $R_{long}$ is discussed. | nucl-ex |
Energy dependence of pbar/p ratio in p+p collisions: We have compiled the experimentally measured pbar/p ratio at midrapidity in
p+p collisions from \sqrt{s} = 23 to 7000 GeV and compared it to various
mechanisms of baryon production as implemented in PYTHIA, PHOJET and
HIJING/B-Bbar models. For the models studied with default settings, PHOJET has
the best agreement with the measurements, PYTHIA gives a higher value for
\sqrt{s} < 200 GeV and the ratios from HIJING/B-Bbar are consistently lower for
all the \sqrt{s} studied. Comparison of the data to different mechanisms of
baryon production as implemented in PYTHIA shows that through a suitable tuning
of the suppression of diquark-antidiquark pair production in the color field
relative to quark-antiquark production and allowing the diquarks to split
according to the popcorn scheme gives a fairly reasonable description of the
measured pbar/p ratio for \sqrt{s} < 200 GeV. Comparison of the beam energy
dependence of the pbar/p ratio in p+p and nucleus-nucleus (A+A) collisions at
midrapidity shows that the baryon production is significantly more for A+A
collisions relative to p+p collisions for \sqrt{s} < 200 GeV. We also carry out
a phenomenological fit to the y_beam dependence of the pbar/p ratio. | nucl-ex |
Underlying-event properties in pp and p$-$Pb collisions at $\sqrt{s_{\rm
NN}} = 5.02$ TeV: We report about the properties of the underlying event measured with ALICE at
the LHC in pp and p$-$Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. The event
activity, quantified by charged-particle number and summed-$p_{\rm T}$
densities, is measured as a function of the leading-particle transverse
momentum ($p_{\rm T}^{\rm trig}$). These quantities are studied in three
azimuthal-angle regions relative to the leading particle in the event: toward,
away, and transverse. Results are presented for three different $p_{\rm T}$
thresholds (0.15, 0.5, and 1 GeV/$c$) at mid-pseudorapidity ($|\eta|<0.8$). The
event activity in the transverse region, which is the most sensitive to the
underlying event, exhibits similar behaviour in both pp and p$-$Pb collisions,
namely, a steep increase with $p_{\rm T}^{\rm trig}$ for low $p_{\rm T}^{\rm
trig}$, followed by a saturation at $p_{\rm T}^{\rm trig} \approx 5$ GeV/$c$.
The results from pp collisions are compared with existing measurements at other
centre-of-mass energies. The quantities in the toward and away regions are also
analyzed after the subtraction of the contribution measured in the transverse
region. The remaining jet-like particle densities are consistent in pp and
p$-$Pb collisions for $p_{\rm T}^{\rm trig}>10$ GeV/$c$, whereas for lower
$p_{\rm T}^{\rm trig}$ values the event activity is slightly higher in p$-$Pb
than in pp collisions. The measurements are compared with predictions from the
PYTHIA 8 and EPOS LHC Monte Carlo event generators. | nucl-ex |
Inelastic Scatterings of Entangled Mossbauer Gammas: We report the observation of the temperature-dependent inelastic scattering
of three entangled Mossbauer gammas in the time-resolved Mossbauer
spectroscopy. Recently, the long-lived E3 Mossbauer transition of rhodium
generated by bremsstrahlung irradiation has been reported. Two kinds of X-rays
with the fast decay are attributed to the tri-photon effect. They are
tri-photon pile-up of rhodium K X-rays and the high-Z impurity K X-rays. Energy
of the particular K emission is higher than the sum energy of two Mossbauer
gammas. This letter reports new discoveries by cooling down the sample using
liquid nitrogen, namely the collective anomalous emission of entangled
Mossbauer gammas. The enhancement of inelastic scatterings at low temperature
such as rhodium K satellites is attributed to this entanglement. | nucl-ex |
Evidence on the absence of critical transition in AMPT for Pb-Pb
collisions at $sqrt{s_{\rm{NN}}}$ = 2.76 TeV: Event-by-event fluctuations in the spatial patterns in charged particles
generated in Pb--Pb collisions at the center-of-mass energy
$\sqrt{S_{\rm{NN}}}$ = 2.76 TeV are studied within A MultiPhase Transport
(AMPT) model. The spatial patterns of the particles generated in the ($\eta,
\phi$) space for $|\eta| \le 0.8$ are studied using the methodology of
intermittency and erraticity analysis. We find negative intermittency for
charged particles generated in a range of $p_{\rm{T}}$ windows. This result
contrasts sharply from what is expected for a quark-gluon plasma undergoing
hadronization by a second-order phase transition. Appropriate scaling behavior
is examined, resulting in definitive scaling exponent $\nu_{-}$. Event-by-event
fluctuations in the spatial patterns quantified by an index, named erraticity
index are determined for different $p_{\rm{T}}$ bins $\leq 1$ GeV/c, for AMPT
model. This is the first time that the intermittency and erraticity indices are
determined for any model at such high energies. The results presented here can
be used for comparison with the fluctuation properties of the experimental data
and hence can help the development of a wider scope of understanding of
validity of the particle production process by AMPT at these energies on the
one hand, and of the true nature of the real data on the other. | nucl-ex |
Direct determination of the excitation energy of quasi-stable isomer
$^{180m}$Ta: $^{180m}$Ta is a naturally abundant quasi-stable nuclide and the
longest-lived nuclear isomer known to date. It is of interest for, among
others, the search for dark matter, for the development of a gamma laser and
for astrophysics. So far, its excitation energy has not been measured directly
but has been based on an evaluation of available nuclear reaction data. We have
determined the excitation energy of this isomer with high accuracy using the
Penning-trap mass spectrometer JYFLTRAP. The determined mass difference between
the ground and isomeric states of $^{180}$Ta yields an excitation energy of
76.79(55) keV for $^{180m}$Ta. This is the first direct measurement of the
excitation energy and provides a better accuracy than the previous evaluation
value, 75.3(14) keV. | nucl-ex |
Observation of flow angle and flow magnitude fluctuations in Pb-Pb
collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the CERN Large Hadron
Collider: This Letter reports on the first measurements of transverse momentum
dependent flow angle $\Psi_n$ and flow magnitude $v_n$ fluctuations, determined
using new four-particle correlators. The measurements are performed for various
centralities in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of
$\sqrt{s_{\rm NN}}$ = 5.02 TeV with ALICE at the CERN Large Hadron Collider.
Both flow angle and flow magnitude fluctuations are observed in the presented
centrality ranges and are strongest in the most central collisions and for a
transverse momentum $p_{\rm T}>2$ GeV/$c$. Comparison with theoretical models,
including iEBE-VISHNU, MUSIC, and AMPT, show that the measurements exhibit
unique sensitivities to the initial state of heavy-ion collisions. | nucl-ex |
Neutron capture of 26Mg at thermonuclear energies: The neutron capture cross section of 26Mg was measured relative to the known
gold cross section at thermonuclear energies using the fast cyclic activation
technique. The experiment was performed at the 3.75 MV Van-de-Graaff
accelerator, Forschungszentrum Karlsruhe. The experimental capture cross
section is the sum of resonant and direct contributions. For the resonance at
E(n,lab) = 220 keV our new results are in disagreement with the data from
Weigmann et al. An improved Maxwellian averaged capture cross section is
derived from the new experimental data taking into account s- and p-wave
capture and resonant contributions. The properties of so-called potential
resonances which influence the p-wave neutron capture of 26}Mg are discussed in
detail. | nucl-ex |
Event anisotropy $v_{2}$ in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7 -
62.4 GeV with STAR: We present the $v_2$ measurement at midrapidity from Au+Au collisions at
$\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 62.4 GeV for inclusive charged
hadrons and identified hadrons ($\pi^{\pm}$, $K^{\pm}$, $K_{S}^{0}$, $p$,
$\bar{p}$, $\phi$, $\Lambda$, $\bar{\Lambda}$, $\Xi^{-}$, $\bar{\Xi}^{+}$,
$\Omega^{-}$, $\bar{\Omega}^{+}$) up to 4 GeV/$c$ in $p_{T}$. The beam energy
and centrality dependence of charged hadron $v_2$ are presented with comparison
to higher energies at RHIC and LHC. The identified hadron $v_{2}$ are used to
discuss the NCQ scaling for different beam energies. Significant difference in
$v_{2}(p_{T})$ is observed between particles and corresponding anti-particles
for $\sqrt{s_{NN}} <$ 39 GeV. These differences are more pronounced for baryons
compared to mesons and they increase with decreasing energy. | nucl-ex |
Identified particle transverse momentum spectra in p+p and d+Au
collisions at sqrt{s_NN} = 200 GeV: The transverse momentum ($p_{\mathrm T}$) spectra for identified charged
pions, protons and anti-protons from $p$+$p$ and $d$+Au collisions are measured
around midrapidity ($\mid$y$\mid$ $<$ 0.5) over the range of 0.3 $<$
$p_{\mathrm T}$ $<$ 10 GeV/$c$ at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV. The
charged pion and proton+anti-proton spectra at high p_{T} in p+p collisions
have been compared with the next-to-leading order perturbative quantum
chromodynamic (NLO pQCD) calculations with a specific fragmentation scheme. The
p/pi^{+} and pbar/pi^{-}has been studied at high p_{T}. The nuclear
modification factor (R_{dAu}) shows that the identified particle Cronin effects
around midrapidity are significantly non-zero for charged pions and to be even
larger for protons at intermediate p_{T} (2 < p_{T} < 5 GeV/c). | nucl-ex |
Magnetic and antimagnetic rotational bands data tables: The experimental results of 252 magnetic rotational bands reported in 123
nuclei and 38 antimagnetic rotational bands reported in 27 nuclei are collected
and listed in the present work, including energy, spin, parity, magnetic dipole
reduced transition probability B(M1), electric quadrupole reduced transition
probability B(E2), B(M1)/B(E2) ratio, and the ratio of the dynamic moment of
inertia to the electric quadrupole reduced transition probability J(2)/B(E2).
Following the presentation of the kinematic moment of inertia J(1), dynamic
moment of inertia J(2), and I versus rotational frequency, as well as energy
staggering parameter S(I), B(M1), B(E2), B(M1)/B(E2), and J(2)/B(E2) versus I
in A 60, 80, 110, 140, and 190 mass regions, a brief discussion is provided.
Based on the systematic studies, some nuclei are predicted to be candidates for
magnetic or antimagnetic rotation. | nucl-ex |
High Precision Measurement of the Proton Elastic Form Factor Ratio at
Low $Q^2$: Jefferson Lab experiment E08-007 measured the proton elastic form factor
ratio $\mu_pG_E/G_M$ in the range of $Q^2=0.3-0.7(\mathrm{GeV}/c)^2$ by recoil
polarimetry. Data were taken in 2008 at the Thomas Jefferson National
Accelerator Facility in Virginia, USA. A 1.2 GeV polarized electron beam was
scattered off a cryogenic hydrogen target. The recoil proton was detected in
the left HRS in coincidence with the elasticly scattered electrons tagged by
the BigBite spectrometer. The proton polarization was measured by the focal
plane polarimeter (FPP). In this low $Q^2$ region, previous measurement from
Jefferson Lab Hall A (LEDEX) along with various fits and calculations indicate
substantial deviations of the ratio from unity. For this new measurement, the
proposed statistical uncertainty ($<1%$) was achieved. These new results are a
few percent lower than expected from previous world data and fits, which
indicate a smaller $G_{Ep}$ at this region. Beyond the intrinsic interest in
nucleon structure, the new results also have implications in determining the
proton Zemach radius and the strangeness form factors from parity violation
experiments. | nucl-ex |
Search for $η$-mesic nuclei in recoil-free transfer reaction: We have studied the reaction $p+{^{27}Al}\to {^3{He}}+p+\pi^-+X$ at
recoil-free kinematics. An $\eta$ meson possibly produced in this reaction
would be thus almost at rest in the laboratory system and could therefore be
bound with high probability, if nuclear $\eta$ states exist. The decay of such
a state through the $N^*(1535)$ resonance would lead to a proton-$\pi^-$ pair
emitted in opposite directions. For these conditions we find some indication of
such a bound state. An upper limit of $\approx$ 0.5 nb is found. | nucl-ex |
The Challenge of the EMC Effect: existing data and future directions: Since the discovery that the ratio of inclusive charged lepton (per-nucleon)
cross sections from a nucleus A to the deuteron is not unity - even in deep
inelastic scattering kinematics - a great deal of experimental and theoretical
effort has gone into understanding the phenomenon. The EMC effect, as it is now
known, shows that even in the most extreme kinematic conditions the effects of
the nucleon being bound in a nucleus can not be ignored. In this paper we
collect the most precise data available for various nuclear to deuteron ratios,
as well as provide a commentary on the current status of the theoretical
understanding of this thirty year old effect. | nucl-ex |
Thermal photon measurements at PHENIX: Photons are emitted at all stages of relativistic heavy-ion collisions and do
not interact with the medium strongly. With access to the versatility of RHIC,
measurements of low momentum direct photons are made possible across different
system size and beam energies. An excess of direct photons, above prompt photon
production from hard scattering processes, is observed for a system size
corresponding to $dN_{ch}/d\eta$ of 20-30, with a large azimuthal anisotropy
and a characteristic dependence on collision centrality. After subtracting the
prompt photon component, the inverse slope of the spectrum is continuously
increasing with the effective temperature ranging from 250 MeV/c at $p_{T}$ of
1-2 GeV/c to about 400 MeV/c at 2-4 GeV/c. Within the experimental uncertainty,
there is no indication of a system size dependence of the inverse slope. In
this proceeding, results from Au+Au collisions from the PHENIX experiment will
be presented. | nucl-ex |
Noise Equivalent Counts Based Emission Image Reconstruction Algorithm of
Tomographic Gamma Scanning: Tomographic Gamma Scanning (TGS) is a technique used to assay the nuclide
distribution and radioactivity in nuclear waste drums. Both transmission and
emission scans are performed in TGS and the transmission image is used for the
attenuation correction in emission reconstructions. The error of the
transmission image, which is not considered by the existing reconstruction
algorithms, negatively affects the final results. An emission reconstruction
method based on Noise Equivalent Counts (NEC) is presented. Noises from the
attenuation image are concentrated to the projection data to apply the NEC
Maximum-Likelihood Expectation-Maximization algorithm. Experiments are
performed to verify the effectiveness of the proposed method. | nucl-ex |
Analysis of Experiments Exhibiting Time-Varying Nuclear Decay Rates:
Systematic Effects or New Physics?: Since the 1930s, and with very few exceptions, it has been assumed that the
process of radioactive decay is a random process, unaffected by the environment
in which the decaying nucleus resides. There have been instances within the
past few decades, however, where changes in the chemical environment or
physical environment brought about small changes in the decay rates. But even
in light of these instances, decaying nuclei that were undisturbed or
un-"pressured" were thought to behave in the expected random way, subject to
the normal decay probabilities which are specific to each nuclide. Moreover,
any "non-random" behavior was assumed automatically to be the fault of the
detection systems, the environment surrounding the detectors, or changes in the
background radiation to which the detector was exposed. Recently, however,
evidence has emerged from a variety of sources, including measurements taken by
independent groups at Brookhaven National Laboratory, Physikalisch-Technische
Bundesanstalt, and Purdue University, that indicate there may in fact be an
influence that is altering nuclear decay rates, albeit at levels on the order
of $10^{-3}$. In this paper, we will discuss some of these results, and examine
the evidence pointing to the conclusion that the intrinsic decay process is
being affected by a solar influence. | nucl-ex |
Study of the hadron gas phase using short-lived resonances with ALICE: Short-lived hadronic resonances are unique tools for studying the hadron-gas
phase that is created in the late stages of relativistic heavy-ion collisions.
Measurements of the yield ratios between resonances and the corresponding
stable particles are sensitive to the competing rescattering and regeneration
effects. These measurements in small collision systems, such as pp and p-Pb,
are a powerful method to reveal a possible short-lived hadronic phase. In
addition, resonance production in small systems is interesting to study the
onset of strangeness enhancement, collective effects,and the hadron production
mechanism. On this front, the $\phi$ meson is particularly relevant since its
yield is sensitive to different production models: no effect is expected by
strange number canonical suppression but its production is expected to be
enhanced in the rope-hadronization scenario. In this presentation, recent
measurements of hadronic resonances in different collision systems,going from
pp to Pb-Pb collisions, are presented. These include transverse momentum
spectra,yields, and yield ratios as a function of multiplicity. The presented
results are discussed in the context of state-of-the-art phenomenological
models of hadron production. The resonance yields measured in Pb-Pb collisions
are used as an experimental input in a partial chemical equilibrium-based
thermal model to constrain the kinetic freeze-out temperature. This is a novel
procedure that is independent of assumptions on the flow velocity profile and
the freeze-out hypersurface. | nucl-ex |
Enhanced Production of Low-Mass Electron Pairs in 40 AGeV Pb-Au
Collisions at the CERN SPS: We report on first measurements of low-mass electron pairs in Pb-Au
collisions at the lower SPS beam energy of 40 AGeV. The pair yield integrated
over the range of invariant masses 0.2<m<1 GeV/c^2 is enhanced by a factor of
5.1+-1.3(stat)+-1.0/1.5(syst data/decays) over the expectation from neutral
meson decays, more than previously observed at the higher energy of 158 AGeV.
The results are discussed with reference to model calculations based on pi+ pi-
-> e+ e- annihilation with a modified rho-propagator. They may be linked to
chiral symmetry restoration and support the notion that the in-medium
modifications of the rho are more driven by baryon density than by temperature. | nucl-ex |
The $^{15}$O($α$,$γ$)$^{19}$Ne Breakout Reaction and Impact on
X-Ray Bursts: The breakout reaction $^{15}$O($\alpha,\gamma$)$^{19}$Ne, which regulates the
flow between the hot CNO cycle and the rp-process, is critical for the
explanation of the burst amplitude and periodicity of X-ray bursters. We report
on the first successful measurement of the critical $\alpha$-decay branching
ratios of relevant states in $^{19}$Ne populated via
$^{19}$F($^3$He,t)$^{19}$Ne. Based on the experimental results and our previous
lifetime measurements of these states, we derive the first experimental rate of
$^{15}$O($\alpha,\gamma$)$^{19}$Ne. The impact of our experimental results on
the burst pattern and periodicity for a range of accretion rates is analyzed. | nucl-ex |
Higher-twist analysis of moments of spin structure function: Available analyses on moments of the spin structure function g_1 use
different methods and are barely consistent with each other. We present a
higher twist analysis of Gamma_1^p using a method consistent with the studies
of Gamma_1^n and Gamma_1^(p-n) already published. The twist-4 coefficient f_2
is extracted. One result is that the higher twist coefficients seem to
alternate signs: the relatively larger twist-6 contribution is partly
suppressed by the twist-4 and twist-8 contributions. The size of twist-6 can be
due to the elastic contribution to the moments. | nucl-ex |
Advances and new ideas for neutron-capture astrophysics experiments at
CERN n_TOF: This article presents a few selected developments and future ideas related to
the measurement of $(n,\gamma)$ data of astrophysical interest at CERN n_TOF.
The MC-aided analysis methodology for the use of low-efficiency radiation
detectors in time-of-flight neutron-capture measurements is discussed, with
particular emphasis on the systematic accuracy. Several recent instrumental
advances are also presented, such as the development of total-energy detectors
with $\gamma$-ray imaging capability for background suppression, and the
development of an array of small-volume organic scintillators aimed at
exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics
prospects related to the intermediate $i$ neutron-capture process of
nucleosynthesis are discussed in the context of the new NEAR activation area. | nucl-ex |
Identified particle measurements at RHIC: elucidating hadronization
mechanisms for bulk partonic matter: Measurements of identified particle momentum spectra at center of mass energy
200 GeV are reviewed. Emphasis is placed on the azimuthal dependence and the
centrality dependence of hadron yields at intermediate transverse momentum (1.5
< p_T < 5 GeV/c). The first measurements of the fourth harmonic term (v_4) in
the azimuthal variation of identified particle yields are shown. The
recombination mechanism of hadron formation provides a consistent description
of the dependence of these measurements on particle-type. | nucl-ex |
$π/K/p$ production and Cronin effect from p+p, d+Au and Au+Au
collisions at $\sqrt{s_{NN}}= 200$ GeV from the PHENIX experiment: We present results on identified particle production in p+p, d+Au and Au+Au
collisions at $\sqrt{s_{NN}} = 200$ GeV at mid-rapidity measured by the PHENIX
experiment. The centrality and flavor dependence of the Cronin effect in d+Au
collisions is measured. The Cronin effect for the protons in d+Au is larger
than that for the pions, but not large enough to account for the ``anomalous''
proton to pion ratio in central Au+Au collisions. | nucl-ex |
Hadrons in the Nuclear Medium -- Quarks, Nucleons, or a Bit of Both?: Quantum Chromodynamics (QCD) is the theory governing the strong interaction
of particles. It describes the interactions that bind quarks and gluons into
protons and neutrons, and binds these into nuclei. We believe QCD to be as
fundamental and complete as QED, the theory of electromagnetic interactions,
whose predictions have been tested to more than ten decimal places. If it were
possible to make calculations in QCD the same way we can in QED, we would have
removed one of the biggest obstacles in the way of understanding matter in the
universe. Unfortunately, the properties of QCD make such calculations
impossible at present. Historically, there have been two approaches to this
problem. First, we work to improve our ability to solve QCD, with the most
visible effort being the field of Lattice QCD. Second, we make models of QCD
that attempt to incorporate what we believe to be the most important
symmetries, dynamics, or degrees of freedom, and then test these models against
experimental measurements sensitive to these assumptions. Even the earliest
quark models of hadrons structure and the simplest bag models have had great
success, far beyond any reasonable expectation, indicating that these models
have isolated some of the key features of QCD. More detailed models and ever
more sophisticated experimental tests are significantly improving such details,
and helping to better identify the most relevant features of QCD, one of the
key missing pieces in our understanding of the nature of matter. | nucl-ex |
Nonfuel Antineutrino Contributions in the High Flux Isotope Reactor: Reactor neutrino experiments have seen major improvements in precision in
recent years. With the experimental uncertainties becoming lower than those
from theory, carefully considering all sources of $\overline{\nu}_{e}$ is
important when making theoretical predictions. One source of
$\overline{\nu}_{e}$ that is often neglected arises from the irradiation of the
nonfuel materials in reactors. The $\overline{\nu}_{e}$ rates and energies from
these sources vary widely based on the reactor type, configuration, and
sampling stage during the reactor cycle and have to be carefully considered for
each experiment independently. In this article, we present a formalism for
selecting the possible $\overline{\nu}_{e}$ sources arising from the neutron
captures on reactor and target materials. We apply this formalism to the High
Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the
$\overline{\nu}_{e}$ source for the the Precision Reactor Oscillation and
Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the
nonfuel $\overline{\nu}_{e}$ contributions from HFIR to PROSPECT amount to 1\%
above the inverse beta decay threshold with a maximum contribution of 9\% in
the 1.8--2.0~MeV range. Nonfuel contributions can be particularly high for
research reactors like HFIR because of the choice of structural and reflector
material in addition to the intentional irradiation of target material for
isotope production. We show that typical commercial pressurized water reactors
fueled with low-enriched uranium will have significantly smaller nonfuel
$\overline{\nu}_{e}$ contribution. | nucl-ex |
Quest for a Nuclear Georeactor: Knowledge about the interior of our planet is mainly based on the
interpretation of seismic data from earthquakes and nuclear explosions, and of
composition of meteorites. Additional observations have led to a wide range of
hypotheses on the heat flow from the interior to the crust, the abundance of
certain noble gases in gasses vented from volcanoes and the possibility of a
nuclear georeactor at the centre of the Earth. This paper focuses on a proposal
for an underground laboratory to further develop antineutrinos as a tool to map
the distribution of radiogenic heat sources, such as the natural radionuclides
and the hypothetical nuclear georeactor. | nucl-ex |
Observation of Pendellösung Fringes by Using Pulsed Neutrons: Pendell\"{o}sung interference fringes of a single silicon crystal were
observed by using pulsed cold neutrons. The nuclear scattering length of
silicon was obtained as (4.159\pm0.003(stat.)\pm0.028(syst.)) fm using the
observed Pendell\"{o}sung fringes. This indicates the applicability of pulsed
neutron beam to observe the Pendell\"{o}sung fringes by using the
time-of-flight analysis. | nucl-ex |
The 95zr(n, gamma)96zr cross section from the surrogate ratio method and
its effect on the s-process nucleosynthesis: The 95Zr(n,gamma)96Zr reaction cross section is crucial in the modelling of
s-process nucleosynthesis in asymptotic giant branch stars because it controls
the operation of the branching point at the unstable 95Zr and the subsequent
production of 96Zr. We have carried out the measurement of the 94Zr(18O,16O)
and 90Zr(18O,16O) reactions and obtained the gamma-decay probability ratio of
96Zr* and 92Zr* to determine the 95Zr(n,gamma)96Zr reaction cross sections with
the surrogate ratio method. Our deduced maxwellian-averaged cross section of
66+-16 mb at 30 keV is close to the value recommended by Bao et al. (2000), but
30% and more than a factor of two larger than the values proposed by Toukan &
Kappeler (1990) and Lugaro et al. (2014), respectively, and routinely used in
s-process models. We tested the new rate in stellar models with masses between
2 and 6 Msun and metallicities 0.014 and 0.03. The largest changes - up 80%
variations in 96Zr - are seen in models of mass 3-4 Msun, where the 22Ne
neutron source is mildly activated. The new rate can still provide a match to
data from meteoritic stardust silicon carbide grains, provided the maximum mass
of the parent stars is below 4 Msun, for a metallicity of 0.03. | nucl-ex |
Investigation of production cross sections, using stacked targets at the
88" Cyclotron with focus on $^{\rm nat}{\rm Fe}(\rm p,x)^{51}{\rm Mn}$: With the investigation of the production cross section of $\ ^{51}\rm Mn$ off
of $\ ^{\rm nat}\rm Fe$ in mind, two stacked target experiments were conducted
at the Berkeley Lab 88-Inch Cyclotron. Proton beams with energies of $25$ and
$55\,\rm MeV$ result in a total of 14 data points for various reactions. Gamma
spectra of the activated foils were taken and analyzed, then cross sections
calculated. | nucl-ex |
critRHIC: The RHIC Low Energy Program: Recent experimental and theoretical developments have motivated interest in a
more detailed exploration of heavy ion collisions in the range sqrt(sNN)=5-15
GeV. In contrast to interactions at the full RHIC energy of sqrt(sNN)=200 GeV,
such collisions result in systems characterized by much higher baryon chemical
potential, muB. Extensions of lattice QCD calculations to non-zero values of
muB suggest that a critical point may exist in this region of the QCD phase
diagram. Discovery of the critical point or, equivalently, determining the
location where the phase transition from partonic to hadronic matter switches
from a smooth crossover to 1st order would establish a major landmark in the
phase diagram. Initial studies of Pb+Pb collisions in this energy range have
revealed several unexpected features in the data. In response to these results,
it has been suggested that the existing RHIC accelerator and experiments can be
used to further the investigation of this important physics topic. This
proceeding briefly summarizes the theoretical and experimental situation with
particular emphasis on the conclusions from a RIKEN BNL workshop held in March
of 2006. | nucl-ex |
First Measurement of $Λ$ Electroproduction off Nuclei in the
Current and Target Fragmentation Regions: We report results of $\Lambda$ hyperon production in semi-inclusive
deep-inelastic scattering off deuterium, carbon, iron, and lead targets
obtained with the CLAS detector and the Continuous Electron Beam Accelerator
Facility 5.014~GeV electron beam. These results represent the first
measurements of the $\Lambda$ multiplicity ratio and transverse momentum
broadening as a function of the energy fraction~($z$) in the current and target
fragmentation regions. The multiplicity ratio exhibits a strong suppression at
high~$z$~and~an enhancement at~low~$z$. The measured transverse momentum
broadening is an order of magnitude greater than that seen for light mesons.
This indicates that the propagating entity interacts very strongly with the
nuclear medium, which suggests that propagation of diquark configurations in
the nuclear medium takes place at least part of the time, even at high~$z$. The
trends of these results are qualitatively described by the Giessen
Boltzmann-Uehling-Uhlenbeck transport model, particularly for the multiplicity
ratios. These observations will potentially open a new era of studies of the
structure of the nucleon as well as of strange baryons. | nucl-ex |
Anisotropic flow and flow fluctuations of identified hadrons in Pb$-$Pb
collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV: The first measurements of elliptic flow of $\pi^\pm$, ${\rm K}^\pm$,
p+$\overline{\rm p}$, ${\rm K_{S}^0}$, $\Lambda$+$\overline{\Lambda}$, $\phi$,
$\Xi^-$+$\Xi^+$, and $\Omega^-$+$\Omega^+$ using multiparticle cumulants in
Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV are presented. Results
obtained with two- ($v_2\{2\}$) and four-particle cumulants ($v_2\{4\}$) are
shown as a function of transverse momentum, $p_{\rm T}$, for various collision
centrality intervals. Combining the data for both $v_2\{2\}$ and $v_2\{4\}$
also allows us to report the first measurements of the mean elliptic flow,
elliptic flow fluctuations, and relative elliptic flow fluctuations for various
hadron species. These observables probe the event-by-event eccentricity
fluctuations in the initial state and the contributions from the dynamic
evolution of the expanding quark-gluon plasma. The characteristic features
observed in previous $p_{\rm T}$-differential anisotropic flow measurements for
identified hadrons with two-particle correlations, namely the mass ordering at
low $p_{\rm T}$ and the approximate scaling with the number of constituent
quarks at intermediate $p_{\rm T}$, are similarly present in the four-particle
correlations and the combinations of $v_2\{2\}$ and $v_2\{4\}$. In addition, a
particle species dependence of flow fluctuations is observed that could
indicate a significant contribution from final state hadronic interactions. The
comparison between experimental measurements and CoLBT model calculations,
which combine the various physics processes of hydrodynamics, quark
coalescence, and jet fragmentation, illustrates their importance over a wide
$p_{\rm T}$ range. | nucl-ex |
Quasifree Lambda, Sigma^0, and Sigma^- electroproduction from 1,2H,
3,4He, and carbon: Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He,
4He, and Carbon targets has been measured at Jefferson Laboratory. The
quasifree angular distributions of Lambda and Sigma hyperons were determined at
Q^2= 0.35(GeV/c)^2 and W= 1.91GeV. Electroproduction on hydrogen was measured
at the same kinematics for reference. | nucl-ex |
The KDK (potassium decay) experiment: Potassium-40 (${}^{40}$K) is a background in many rare-event searches and may
well play a role in interpreting results from the DAMA dark-matter search. The
electron-capture decay of ${}^{40}$K to the ground state of ${}^{40}$Ar has
never been measured and contributes an unknown amount of background. The KDK
(potassium decay) collaboration will measure this branching ratio using a
${}^{40}$K source, an X-ray detector, and the Modular Total Absorption
Spectrometer at Oak Ridge National Laboratory. | nucl-ex |
Search for Pentaquark Theta+ in Hadronic Reaction at J-PARC: A variety of nuclear and hadron physics experiments are being performed using
meson beams at the J-PARC Hadron Facility. As the first experiment at the
facility, the pentaquark Theta+ was searched for in the pi- p -> K- X reaction
with a missing-mass resolution of 2 MeV (FWHM). The number of accumulated beam
pions are 7.8x10^10 and 8.1x10^10 for different beam momenta of 1.92 and 2.01
GeV/c, respectively. No significant structure was observed in the missing mass
spectra. Upper limits of the production cross section are obtained to be
0.28ub/sr in the laboratory frame at 90% confidence level for each beam
momenta. With a help of theoretical models, an upper limit of the total decay
width of Theta+ was estimated to be 0.36 and 1.9 MeV for J^P = 1/2+ and 1/2-
states, respectively. | nucl-ex |
Measurement of helium-3 and deuterium stopping power ratio for negative
muons: The measurement method and results measuring of the stopping power ratio of
helium-3 and deuterium atoms for muons slowed down in the D/$^3$He mixture are
presented. Measurements were performed at four values of pure $^3$He gas target
densities, $\phi_{He} = 0.0337, 0.0355, 0.0359, 0.0363$ (normalized to the
liquid hydrogen density) and at a density 0.0585 of the D/$^3$He mixture. The
experiment was carried out at PSI muon beam $\mu$E4 with the momentum P$\mu
=34.0$ MeV/c. The measured value of the mean stopping ratio $S_{^3He/D}$ is
$1.66\pm 0.04$. This value can also be interpreted as the value of mean reduced
ratio of probabilities for muon capture by helium-3 and deuterium atoms. | nucl-ex |
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