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Thermal dileptons in high-energy nuclear collisions: Clear signs of excess dileptons above the known sources were found at the SPS
since long. However, a real clarification of these observations was only
recently achieved by NA60, measuring dimuons with unprecedented precision in
158A GeV In-In collisions. The excess mass spectrum in the region M<1 GeV is
consistent with a dominant contribution from pi+pi- -> rho -> mu+mu-
annihilation. The associated rho spectral function shows a strong broadening,
but essentially no shift in mass. In the region M>1 GeV, the excess is found to
be prompt, not due to enhanced charm production. The inverse slope parameter
Teff associated with the transverse momentum spectra rises with mass up to the
rho, followed by a sudden decline above. While the initial rise, coupled to a
hierarchy in hadron freeze-out, points to radial flow of a hadronic decay
source, the decline above signals a transition to a low-flow source, presumably
of partonic origin. The mass spectra show the steep rise towards low masses
characteristic for Planck-like radiation. The polarization of the excess
referred to the Collins Soper frame is found to be isotropic. All observations
are consistent with a global interpretation of the excess as thermal radiation.
We conclude with a short discussion of a possible link to direct photons. | nucl-ex |
Production of light flavour hadrons at intermediate and high pT in pp,
p-Pb and Pb-Pb collisions measured with ALICE: Light flavour transverse momentum spectra at intermediate and high pT provide
an important baseline for the measurement of perturbative QCD processes in pp,
for the evaluation of initial state effects in p-Pb, and for investigating the
suppression from parton energy loss in Pb-Pb collisions. The measurement of the
nuclear modification factor RpPb for inclusive charged particles is extended up
to 50 GeV/c in pT compared to our previous measurement and remains consistent
with unity up the largest momenta. Results on RpPb of charged pions, kaons and
protons that cover up to 14 GeV/c in pT are presented and compared to RpPb of
inclusive charged particles. On the production of charged pions, kaons, and
protons up to pT = 20 GeV/c in Pb-Pb collisions final results for RAA are
presented. | nucl-ex |
Hypernuclei - the next decade: We are at the verge of a new impact from hypernuclear experiments planned or
already operative at various laboratories all over the world. The complementary
of these different experimental approaches to hypernuclei provides a wide basis
for a comprehensive understanding of strange hadrons in cold hadronic matter.
High precision studies of light $\Lambda$ hypernuclei, spectroscopy of double
$\Lambda\Lambda$ nuclei and the properties of antihyperons in nuclei are
examples for the outstanding challenges for hypernuclei research in the next
decade. | nucl-ex |
Resonant Formation of $dμt$ Molecules in Deuterium: An Atomic Beam
Measurement of Muon Catalyzed dt Fusion: Resonant formation of $d\mu t$ molecules in collisions of muonic tritium
($\mu t$) on D$_2$ was investigated using a beam of $\mu t$ atoms,
demonstrating a new direct approach in muon catalyzed fusion studies. Strong
epithermal resonances in $d\mu t$ formation were directly revealed for the
first time. From the time-of-flight analysis of $2036\pm 116$ $dt$ fusion
events, a formation rate consistent with $0.73\pm (0.16)_{meas} \pm
(0.09)_{model}$ times the theoretical prediction was obtained. For the largest
peak at a resonance energy of $0.423 \pm 0.037$ eV, this corresponds to a rate
of $(7.1 \pm 1.8) \times 10^9$ s$^{-1}$, more than an order of magnitude larger
than those at low energies. | nucl-ex |
The Jefferson Lab 12 GeV Program: The Jefferson Lab facilities have undergone a substantial upgrade, both of
accelerator, CEBAF, and of the experimental installations. We will discuss the
progress to completion of these facilities, the status of accelerator
commissioning, and the recent first operations for physics. We will then flesh
out the anticipated exciting physics program of the next several years. | nucl-ex |
Measurements of azimuthal anisotropies in $^{16}$O+$^{16}$O and
$γ$+Au collisions from STAR: In this proceeding, we present the first measurements of azimuthal
anisotropies, $v_2$ and $v_3$, in $^{16}$O+$^{16}$O collisions at 200 GeV as a
function of transverse momentum and multiplicity, by using two- and
four-particle correlation methods. We compare our measurements with STAR
measurements of $v_n$ in \dau and \heau collisions to provide insight into the
impact of system symmetry on initial condition for small systems. We also
investigate the ratio $v_2\{4\}/v_2\{2\}$ as a function of centrality, which is
expected to be sensitive to nucleon-nucleon correlation in the $^{16}$O
nucleus. | nucl-ex |
Dielectron production in proton-proton and proton-lead collisions at
$\sqrt{s_{\rm{NN}}}$ = 5.02 TeV: The first measurements of dielectron production at midrapidity
($|\eta_{c}|<0.8$) in proton-proton and proton-lead collisions at
$\sqrt{s_{\rm{NN}}}$ = 5.02 TeV at the LHC are presented. The dielectron cross
section is measured with the ALICE detector as a function of the invariant mass
$m_{\rm{ee}}$ and the pair transverse momentum $p_{\rm{T,ee}}$ in the ranges
$m_{\rm{ee}}$ < 3.5 GeV/$c^{2}$ and $p_{\rm{T,ee}}$ < 8.0 GeV/$c^{2}$, in both
collision systems. In proton-proton collisions, the charm and beauty cross
sections are determined at midrapidity from a fit to the data with two
different event generators. This complements the existing dielectron
measurements performed at $\sqrt{s}$ = 7 and 13 TeV. The slope of the
$\sqrt{s}$ dependence of the three measurements is described by FONLL
calculations. The dielectron cross section measured in proton-lead collisions
is in agreement, within the current precision, with the expected dielectron
production without any nuclear matter effects for $\rm{e}^{+}\rm{e}^{-}$ pairs
from open heavy-flavor hadron decays. For the first time at LHC energies, the
dielectron production in proton-lead and proton-proton collisions are directly
compared at the same $\sqrt{s_{\rm{NN}}}$ via the dielectron nuclear
modification factor $R_{\rm{pPb}}$. The measurements are compared to model
calculations including cold nuclear matter effects, or additional sources of
dielectrons from thermal radiation. | nucl-ex |
Another look at anomalous J/Psi suppression in Pb+Pb collisions at P/A =
158 GeV/c: A new data presentation is proposed to consider anomalous $J/\Psi$
suppression in Pb + Pb collisions at $P/A=158$ GeV/c. If the inclusive
differential cross section with respect to a centrality variable is available,
one can plot the yield of J/Psi events per Pb-Pb collision as a function of an
estimated squared impact parameter. Both quantities are raw experimental data
and have a clear physical meaning. As compared to the usual J/Psi over
Drell-Yan ratio, there is a huge gain in statistical accuracy. This
presentation could be applied advantageously to many processes in the field of
nucleus-nucleus collisions at various energies. | nucl-ex |
Intensities of the $γ$-ray emissions following the $^{111}Sn$ decay
determined via photonuclear reaction yield measurements: The intensities of the ten strongest $\gamma$-ray transitions following the
$^{111}Sn$ ($T_{1/2}$=35.3 m) decay have been determined via comparison of the
two sets of the experimental photonucleon reaction yields driven using the
traditional activation equation and the activation equation for the genetically
coupled radioactive nuclei. The found absolute intensities of the $\gamma$-ray
transitions in question were happened to be noticeably different from the
currently recommended values. | nucl-ex |
Phenomenology of the $ppK^+K^-$ system near threshold: In this article studies of the near threshold $pp\to ppK^+K^-$ reaction
conducted with the COSY-11 and the ANKE detectors are reviewed. In particular
recent investigations on the $K^+K^-$ final state interaction are revisited
taking into account updated cross sections of the COSY-11 experiment. These
studies resulted in the new value of $K^+K^-$ effective range amounting to:
$\mathrm{Re}(b_{K^{+}K^{-}}) =
-0.2^{+0.8_{stat}~+0.4_{sys}}_{-0.6_{stat}~-0.4_{sys}}~\mathrm{fm}$ and
$\mathrm{Im}(b_{K^{+}K^{-}}) =
1.2^{~+0.5_{stat}~+0.3_{sys}}_{~-0.3_{stat}~-0.3_{sys}}~\mathrm{fm}$. The
determined real and imaginary parts of the $K^+K^-$ scattering length were
estimated to be: $\left|\mathrm{Re}(a_{K^{+}K^{-}})\right| =
10^{~+17_{stat}}_{~-10_{stat}}~\mathrm{fm}$ and $\mathrm{Im}(a_{K^{+}K^{-}}) =
0^{~+37_{stat}}_{~-10_{stat}}~\mathrm{fm}$. | nucl-ex |
\textsc{MaGe} - a {\sc Geant4}-based Monte Carlo Application Framework
for Low-background Germanium Experiments: We describe a physics simulation software framework, MAGE, that is based on
the GEANT4 simulation toolkit. MAGE is used to simulate the response of
ultra-low radioactive background radiation detectors to ionizing radiation,
specifically the MAJORANA and GERDA neutrinoless double-beta decay experiments.
MAJORANA and GERDA use high-purity germanium detectors to search for the
neutrinoless double-beta decay of 76Ge, and MAGE is jointly developed between
these two collaborations. The MAGE framework contains the geometry models of
common objects, prototypes, test stands, and the actual experiments. It also
implements customized event generators, GEANT4 physics lists, and output
formats. All of these features are available as class libraries that are
typically compiled into a single executable. The user selects the particular
experimental setup implementation at run-time via macros. The combination of
all these common classes into one framework reduces duplication of efforts,
eases comparison between simulated data and experiment, and simplifies the
addition of new detectors to be simulated. This paper focuses on the software
framework, custom event generators, and physics lists. | nucl-ex |
Determining $g_{A}/g_{V}$ with High Resolution Spectral Measurements
Using an LiInSe$_2$ Bolometer: Neutrinoless Double-Beta decay (0$\nu\beta\beta$) processes sample a wide
range of intermediate forbidden nuclear transitions, which may be impacted by
quenching of the axial vector coupling constant ($g_A/g_V$), the uncertainty of
which plays a pivotal role in determining the sensitivity reach of
0$\nu\beta\beta$ experiments. In this Letter, we present measurements performed
on a high-resolution LiInSe$_{2}$~ bolometer in a ''source=detector''
configuration to measure the spectral shape of the 4-fold forbidden
$\beta$-decay of $^{115}$In. The value of $g_A/g_V$ is determined by comparing
the spectral shape of theoretical predictions to the experimental $\beta$
spectrum taking into account various simulated background components as well as
a variety of detector effects. We find evidence of quenching of $g_A/g_V$ at
$>5\sigma$ with a model-dependent quenching factor of $0.655\pm0.002$ as
compared to the free-nucleon value for the Interacting Shell Model. We also
measured the $^{115}$In half-life to be
[$5.18\pm0.06(\text{stat.})^{+0.005}_{-0.015}(\text{sys.})]\times{10}^{14}$ yr
within the Interacting Shell Model framework. This work demonstrates the power
of the bolometeric technique to perform precision nuclear physics
single-$\beta$ decay measurements, which can help reduce the uncertainties in
the calculation of $0\nu\beta\beta$ nuclear matrix elements. | nucl-ex |
Open heavy flavour production in ALICE: After a short review of the physics motivations for the study of open heavy
flavour production in proton-proton, proton-nucleus and nucleus-nucleus
collisions at the LHC, we present results on the expected performance of the
ALICE experiment for charm and beauty production measurements. | nucl-ex |
Measurements of $π^\pm$, $K^\pm$, $p$ and $\bar{p}$ spectra in
$^{40}$Ar+$^{45}$Sc collisions at 13$A$ to 150$A$ GeV/$c$: The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the
onset of deconfinement in strongly interacting matter through a beam energy
scan of particle production in collisions of nuclei of varied sizes. This paper
presents results on inclusive double-differential spectra, transverse momentum
and rapidity distributions and mean multiplicities of $\pi^\pm$, $K^\pm$, $p$
and $\bar{p}$ produced in $^{40}$Ar+$^{45}$Sc collisions at beam momenta of
13$A$, 19$A$, 30$A$, 40$A$, 75$A$ and 150$A$~\GeVc. The analysis uses the 10\%
most central collisions, where the observed forward energy defines centrality.
The energy dependence of the $K^\pm$/$\pi^\pm$ ratios as well as of inverse
slope parameters of the $K^\pm$ transverse mass distributions are placed in
between those found in inelastic $p$+$p$ and central Pb+Pb collisions. The
results obtained here establish a system-size dependence of hadron production
properties that so far cannot be explained either within statistical or
dynamical models. | nucl-ex |
J/$ψ$ production measurements by the PHENIX experiment at RHIC: Measurements of J/$\psi$ production by the PHENIX experiment in p+p, d+Au,
Cu+Cu and Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV are reviewed. The results
show a suppression beyond what can be explained by cold nuclear matter effects
in the most central Au+Au and to a lesser extent in Cu+Cu collisions. In
addition, the suppression observed at mid rapidity in Au+Au is smaller than at
forward rapidity, a tendency opposite to what is expected from the higher
energy density at mid rapidity. Regeneration, a possible explanation, can be
tested by measuring the elliptic flow parameter v$_2$ of J/$\psi$. | nucl-ex |
Direct photons in 200 GeV p+p, d+Au, and Au+Au from PHENIX: Direct photons were measured with the PHENIX experiment in p+p, d+Au, and
Au+Au at sqrt(s_NN) = 200 GeV. To tackle the p_T region below 5 GeV/c, direct
photons were measured through their internal conversion into e^+e^- in Au+Au
collisions. | nucl-ex |
The N = 16 spherical shell closure in 24O: The unbound excited states of the neutron drip-line isotope 24O have been
investigated via the 24O(p,p')23O+n reaction in inverse kinematics at a beam
energy of 62 MeV/nucleon. The decay energy spectrum of 24O* was reconstructed
from the momenta of 23O and the neutron. The spin-parity of the first excited
state, observed at Ex = 4.65 +/- 0.14 MeV, was determined to be Jpi = 2+ from
the angular distribution of the cross section. Higher lying states were also
observed. The quadrupole transition parameter beta2 of the 2+ state was
deduced, for the first time, to be 0.15 +/- 0.04. The relatively high
excitation energy and small beta2 value are indicative of the N = 16 shell
closure in 24O. | nucl-ex |
Characterization of a ballistic supermirror neutron guide: We describe the beam characteristics of the first ballistic supermirror
neutron guide H113 that feeds the neutron user facility for particle physics
PF1B of the Institute Laue-Langevin, Grenoble (ILL). At present, the neutron
capture flux density of H113 at its 20x6cm2 exit window is 1.35x10^10/cm^2/s,
and will soon be raised to above 2x10^10/cm^2/s. Beam divergence is no larger
than beam divergence from a conventional Ni coated guide. A model is developed
that permits rapid calculation of beam profiles and absolute event rates from
such a beam. We propose a procedure that permits inter-comparability of the
main features of beams emitted from ballistic or conventional neutron guides. | nucl-ex |
Are the Muonic Hydrogen and Electron Scattering Experiments Measuring
the Same Observable?: 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 model to estimate how the Sachs electric and magnetic form factors
can be corrected for the effects of relativistic recoil. When the corrections
are applied, the ratio of the proton's Sachs form factors is approximately flat
with $Q^2$, i.e. the spatial distributions of the proton's intrinsic charge and
magnetization are similar. Further, we estimate the correction due to recoil
that must be applied to the determination of the proton charge radius from
elastic electron scattering before it can be compared to the value determined
using the Lamb shift in hydrogen. Application of the correction brings the two
values of the proton charge radius into significantly closer agreement.
Predicted corrections based on the model are provided for the rms charge radii
of the deuteron, the triton, and the helium isotopes. | nucl-ex |
Prompt D$^{0}$, D$^{+}$, and D$^{*+}$ production in Pb-Pb collisions at
$\sqrt{s_{\rm NN}}$ = 5.02 TeV: The production of prompt D$^{0}$, D$^{+}$, and D$^{*+}$ mesons was measured
at midrapidity (|y|< 0.5) in Pb-Pb collisions at the centre-of-mass energy per
nucleon-nucleon pair $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at
the LHC. The D mesons were reconstructed via their hadronic decay channels and
their production yields were measured in central (0-10%) and semicentral
(30-50%) collisions. The measurement was performed up to a transverse momentum
($p_{\rm T}$) of 36 or 50 GeV/$c$ depending on the D meson species and the
centrality interval. For the first time in Pb-Pb collisions at the LHC, the
yield of D$^0$ mesons was measured down to $p_{\rm T}$ = 0, which allowed a
model-independent determination of the $p_{\rm T}$-integrated yield per unit of
rapidity (d$N$/d$y$). A maximum suppression by a factor 5 and 2.5 was observed
with the nuclear modification factor ($R_{\rm AA}$) of prompt D mesons at
$p_{\rm T}$ = 6-8 GeV/$c$ for the 0-10% and 30-50% centrality classes,
respectively. The D-meson $R_{\rm AA}$ is compared with that of charged pions,
charged hadrons, and J/$\psi$ mesons as well as with theoretical predictions.
The analysis of the agreement between the measured $R_{\rm AA}$, elliptic
($v_2$) and triangular ($v_3$) flow, and the model predictions allowed us to
constrain the charm spatial diffusion coefficient $D_s$. Furthermore the
comparison of $R_{\rm AA}$ and $v_2$ with different implementations of the same
models provides an important insight into the role of radiative energy loss as
well as charm quark recombination in the hadronisation mechanisms. | nucl-ex |
Physics case for a polarised target for AFTER@LHC: We review a number of ideas put forward in favour of the use of a polarised
target along with the proposed idea of a fixed-target experiment using the LHC
beams -- AFTER@LHC. A number of recent studies have shown that single
transverse-spin asymmetries (STSAs) are large enough to be precisely measured
in the region accessible with AFTER@LHC, in particular as regards the Drell-Yan
process as well as single-pion, isolated-photon and jet production. AFTER@LHC
with a polarised target would also be the ideal experimental set-up to measure
the gluon Sivers effect via a number of original quarkonium STSA studies. We
discuss first figures-of-merit based on simulations for AFTER@LHC with a
polarised target. | nucl-ex |
Spins and magnetic moments of 58;60;62;64Mn ground states and isomers: The odd-odd 54;56;58;60;62;64Mn isotopes (Z = 25) were studied using
bunched-beam collinear laser spectroscopy at ISOLDE, CERN. From the measured
hyperfine spectra the spins and magnetic moments of Mn isotopes up to N = 39
were extracted. The previous tentative ground state spin assignments of
58;60;62;64Mn are now firmly determined to be I = 1 along with an I = 4
assignment for the isomeric states in 58;60;62Mn. The I = 1 magnetic moments
show a decreasing trend with increasing neutron number while the I = 4 moments
remain quite constant between N = 33 and N = 37. The results are compared to
large-scale shell-model calculations using the GXPF1A and LNPS effective
interactions. The excellent agreement of the ground state moments with the
predictions from the LNPS calculations illustrates the need for an increasing
amount of proton excitations across Z = 28 and neutron excitations across N =
40 in the ground state wave functions from N = 37 onwards. | nucl-ex |
One-dimensional pion, kaon, and proton femtoscopy in Pb-Pb collisions at
$\sqrt{s_{\rm {NN}}}$ =2.76 TeV: The size of the particle emission region in high-energy collisions can be
deduced using the femtoscopic correlations of particle pairs at low relative
momentum. Such correlations arise due to quantum statistics and Coulomb and
strong final state interactions. In this paper, results are presented from
femtoscopic analyses of $\pi^{\pm}\pi^{\pm}$, ${\rm K}^{\pm}{\rm K}^{\pm}$,
${\rm K}^{0}_S{\rm K}^{0}_S$, ${\rm pp}$, and ${\rm \overline{p}}{\rm
\overline{p}}$ correlations from Pb-Pb collisions at $\sqrt{s_{\mathrm
{NN}}}=2.76$ TeV by the ALICE experiment at the LHC. One-dimensional radii of
the system are extracted from correlation functions in terms of the invariant
momentum difference of the pair. The comparison of the measured radii with the
predictions from a hydrokinetic model is discussed. The pion and kaon source
radii display a monotonic decrease with increasing average pair transverse mass
$m_{\rm T}$ which is consistent with hydrodynamic model predictions for central
collisions. The kaon and proton source sizes can be reasonably described by
approximate $m_{\rm T}$-scaling. | nucl-ex |
Measurement of the Beam-Normal Single-Spin Asymmetry for Elastic
Electron Scattering from $^{12}$C and $^{27}$Al: We report measurements of the parity-conserving beam-normal single-spin
elastic scattering asymmetries $B_n$ on $^{12}$C and $^{27}$Al, obtained with
an electron beam polarized transverse to its momentum direction. These
measurements add an additional kinematic point to a series of previous
measurements of $B_n$ on $^{12}$C and provide a first measurement on $^{27}$Al.
The experiment utilized the Qweak apparatus at Jefferson Lab with a beam energy
of 1.158 GeV. The average lab scattering angle for both targets was 7.7
degrees, and the average $Q^2$ for both targets was 0.02437 GeV$^2$ (Q=0.1561
GeV). The asymmetries are $B_n$ = -10.68 $\pm$ 0.90 stat) $\pm$ 0.57 (syst) ppm
for $^{12}$C and $B_n$ = -12.16 $\pm$ 0.58 (stat) $\pm$ 0.62 (syst) ppm for
$^{27}$Al. The results are consistent with theoretical predictions, and are
compared to existing data. When scaled by Z/A, the Q-dependence of all the
far-forward angle (theta < 10 degrees) data from $^{1}$H to $^{27}$Al can be
described by the same slope out to $Q \approx 0.35$ GeV. Larger-angle data from
other experiments in the same Q range are consistent with a slope about twice
as steep. | nucl-ex |
Search for the Production of Element 112 in the 48Ca + 238U Reaction: We have searched for the production of element 112 in the reaction of 231 MeV
48Ca with 238U. We have not observed any events with a "one event" upper limit
cross section of 1.6 pb for EVR-fission events and 1.8 pb for EVR-alpha events. | nucl-ex |
Derivation and quantitative analysis of the differential
self-interrogation Feynman-alpha method: A stochastic theory for a branching process in a neutron population with two
energy levels is used to assess the applicability of the differential
self-interrogation Feynman-alpha method by numerically estimated reaction
intensities from Monte Carlo simulations. More specifically, the variance to
mean or Feynman-alpha formula is applied to investigate the appearing
exponentials using the numerically obtained reaction intensities. | nucl-ex |
Forward Lambda Production and Nuclear Stopping Power in d + Au
Collisions at sqrt(s_NN) = 200 GeV: We report the measurement of Lamda and Anti-Lamda yields and inverse slope
parameters in d + Au collisions at sqrt(s_NN) = 200 GeV at forward and backward
rapidities (y = +- 2.75), using data from the STAR forward time projection
chambers. The contributions of different processes to baryon transport and
particle production are probed exploiting the inherent asymmetry of the d + Au
system. Comparisons to model calculations show that the baryon transport on the
deuteron side is consistent with multiple collisions of the deuteron nucleons
with gold participants. On the gold side HIJING based models do not describe
the measured particle yields while models with initial state nuclear effects
and/or hadronic rescattering do. The multichain model can provide a good
description of the net baryon density in d + Au collisions at energies
available at the BNL Relativistic Heavy Ion Collider, and the derived
parameters of the model agree with those from nuclear collisions at lower
energies. | nucl-ex |
Limiting temperatures and the Equation of State of Nuclear Matter: From experimental observations of limiting temperatures in heavy ion
collisions we derive Tc, the critical temperature of infinite nuclear matter.
The critical temperature is 16.6 +- 0.86 MeV. Theoretical model correlations
between Tc, the compressibility modulus, K the effective mass, $m^*$ and the
saturation density, rho_s, are exploited to derive the quantity
(K/m^*)**1/2*rho_s^{-1/3}$. This quantity together with calculations employing
Skyrme and Gogny interactions indicates a nuclear matter incompressibility in
moderately excited nuclei that is in excellent agreement with the value
determined from Giant Monopole Resonance data. This technique of extraction of
K may prove particularly useful in investigations of very neutron rich systems
using radioactive beams. | nucl-ex |
Clustering in Nuclei from N/Z=1 to N/Z=2: The clustering of nucleons in nuclei is a widespread but elusive phenomenon
for study. Here, we wish to highlight the variety of theoretical approaches,
and demonstrate how they are mutually supportive and complementary. On the
experimental side, we describe recent advances in the study of the classic
cluster nucleus 24Mg. Also, recent studies of clustering in nuclei approaching
the neutron drip line are described. In the region near N/Z=2, both theory and
experiment now suggest that multi-centre cluster structure is important, in
particular for the very neutron rich beryllium isotopes. | nucl-ex |
Search for Deeply Bound Kaonic Nuclear States with AMADEUS: We briefly report on the search for Deeply Bound Kaonic Nuclear States with
AMADEUS in the Sigma0 p channel following K- absorption on 12C and outline
future perspectives for this work. | nucl-ex |
Systematics of azimuthal asymmetries in heavy ion collisions in the 1 A
GeV regime: Using the large acceptance apparatus FOPI, we study central and semi-central
collisions in the reactions (energies in A GeV are given in parentheses):
40Ca+40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni+58Ni (0.15, 0.25, 0.4),
96Ru+96Ru (0.4, 1.0, 1.5), 96Zr+96Zr (0.4, 1.0, 1.5), 129Xe+CsI (0.15, 0.25,
0.4), 197Au+197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The
observables include directed and elliptic flow. The data are compared to
earlier data where possible and to transport model simulations. A stiff nuclear
equation of state is found to be incompatible with the data. Evidence for
extra-repulsion of neutrons in compressed asymmetric matter is found. | nucl-ex |
NEUT Pion Final State Interactions: The pion final state interaction model in NEUT is described. Modifications
and tuning of the model are validated against neutrino and non-neutrino (pion
scattering and photoproduction) data. A method for evaluating the uncertainties
in the model and propagation of systematic errors in a neutrino oscillation
experiment is described, using T2K as a specific example. | nucl-ex |
Strange Particle Production at RHIC: We report STAR measurements of mid-rapidity yields for the $\Lambda$,
$\bar{\Lambda}$, $K^{0}_{S}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, and
$\bar{\Omega}^{+}$ particles in Cu+Cu and Au+Au $\sqrt{s_{NN}} = 200$ GeV
collisions. We show that at a given number of participating nucleons, bulk
strangeness production is higher in Cu+Cu collisions compared to Au+Au
collisions at the same center of mass energy, counter to predictions from the
Canonical formalism. We compare both the Cu+Cu and Au+Au yields to AMPT and
EPOS predictions, and find they reproduce key qualitative aspects of the data.
Finally, we investigate other scaling parameters and find bulk strangeness
production for both the measured data and theoretical predictions, scales
better with the number participants that undergo more than one collision. | nucl-ex |
Recent results on net-baryon fluctuations in ALICE: Recent results on the analysis of event-by-event net-baryon number
fluctuations in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ and $5.02$
TeV are presented. The cumulants of the net-proton distributions, proxies for
the net-baryon distributions, up to third order are discussed. The experimental
results are compared with HIJING and EPOS model calculations and the dependence
of fluctuation measurements on the phase-space coverage is addressed in the
context of calculations from Lattice QCD (LQCD) and the Hadron Resonance Gas
(HRG) model. | nucl-ex |
Saturation of azimuthal anisotropy in Au + Au collisions at sqrt(s_NN) =
62 - 200 GeV: New measurements are presented for charged hadron azimuthal correlations at
mid-rapidity in Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeV. They are
compared to earlier measurements obtained at sqrt(s_NN) = 130 GeV and in Pb+Pb
collisions at sqrt(s_NN) = 17.2 GeV. Sizeable anisotropies are observed with
centrality and transverse momentum (p_T) dependence characteristic of elliptic
flow (v_2). For a broad range of centralities, the observed magnitudes and
trends of the differential anisotropy, v_2(p_T), change very little over the
collision energy range sqrt(s_NN) = 62-200 GeV, indicating saturation of the
excitation function for v_2 at these energies. Such a saturation may be
indicative of the dominance of a very soft equation of state for sqrt(s_NN) =
62-200 GeV. | nucl-ex |
Upper Limit on the Chiral Magnetic Effect in Isobar Collisions at the
Relativistic Heavy-Ion Collider: The chiral magnetic effect (CME) is a phenomenon that arises from the QCD
anomaly in the presence of an external magnetic field. The experimental search
for its evidence has been one of the key goals of the physics program of the
Relativistic Heavy-Ion Collider. The STAR collaboration has previously
presented the results of a blind analysis of isobar collisions
(${^{96}_{44}\text{Ru}}+{^{96}_{44}\text{Ru}}$,
${^{96}_{40}\text{Zr}}+{^{96}_{40}\text{Zr}}$) in the search for the CME. The
isobar ratio ($Y$) of CME-sensitive observable, charge separation scaled by
elliptic anisotropy, is close to but systematically larger than the inverse
multiplicity ratio, the naive background baseline. This indicates the potential
existence of a CME signal and the presence of remaining nonflow background due
to two- and three-particle correlations which are different between the
isobars. In this post-blind analysis, we estimate the contributions from those
nonflow correlations as a background baseline to $Y$, utilizing the isobar data
as well as HIJING simulations. This baseline is found consistent with the
isobar ratio measurement, and an upper limit of 10% at 95% confidence level is
extracted for the CME fraction in the charge separation measurement in isobar
collisions at $\sqrt{s_{\rm NN}}=200$ GeV. | nucl-ex |
Density Dependence of the Symmetry energy and the Equation of State of
Isospin Asymmetric Nuclear Matter: The density dependence of the symmetry energy in the equation of state of
isospin asymmetric nuclear matter is studied using the isoscaling of the
fragment yields and the antisymmetrized molecular dynamic calculation. It is
observed that the experimental data at low densities are consistent with the
form of symmetry energy,E$_{sym}$ $\approx$ 31.6 ($\rho/\rho_{\circ})^{0.69}$,
in close agreement with those predicted by the results of variational many-body
calculation. A comparison of the present result with those reported recently
using the NSCL-MSU data suggests that the heavy ion studies favor a dependence
of the form, E$_{sym}$ $\approx$ 31.6 ($\rho/\rho_{\circ})^{\gamma}$, where
$\gamma$ = 0.6 - 1.05. This constraints the form of the density dependence of
the symmetry energy at higher densities, ruling out an extremely " stiff " and
" soft " dependences. | nucl-ex |
First Measurement of the Ar$(e,e^\prime)X$ Cross Section at Jefferson
Lab: The success of the ambitious programs of both long- and short-baseline
neutrino-oscillation experiments employing liquid-argon time-projection
chambers will greatly rely on the precision with which the weak response of the
argon nucleus can be estimated. In the E12-14-012 experiment at Jefferson Lab
Hall A, we have studied the properties of the argon nucleus by scattering a
high-quality electron beam off a high-pressure gaseous argon target. Here, we
present the measured $^{40}$Ar$(e,e^{\prime})$ double differential cross
section at incident electron energy $E=2.222$~GeV and scattering angle $\theta
= 15.541^\circ$. The data cover a broad range of energy transfers, where
quasielastic scattering and delta production are the dominant reaction
mechanisms. The result for argon is compared to our previously reported cross
sections for titanium and carbon, obtained in the same kinematical setup. | nucl-ex |
Decomposing transverse momentum balance contributions for quenched jets
in PbPb collisions at sqrt(s[NN]) = 2.76 TeV: Interactions between jets and the quark-gluon plasma produced in heavy ion
collisions are studied via the angular distributions of summed charged-particle
transverse momenta (pt) with respect to both the leading and subleading jet
axes in high-pt dijet events. The contributions of charged particles in
different momentum ranges to the overall event pt balance are decomposed into
short-range jet peaks and a long-range azimuthal asymmetry in charged-particle
pt. The results for PbPb collisions are compared to those in pp collisions
using data collected in 2011 and 2013, at collision energy sqrt(s[NN]) = 2.76
TeV with integrated luminosities of 166 inverse microbarns and 5.3 inverse
picobarns, respectively, by the CMS experiment at the LHC. Measurements are
presented as functions of PbPb collision centrality, charged-particle pt,
relative azimuth, and radial distance from the jet axis for balanced and
unbalanced dijets. | nucl-ex |
Search for Spontaneous Radiation from Wavefunction Collapse in the
Majorana Demonstrator: The Majorana Demonstrator neutrinoless double-beta decay experiment comprises
a 44 kg (30 kg enriched in $^{76}\mathrm{Ge}$) array of $p$-type, point-contact
germanium detectors. With its unprecedented energy resolution and ultralow
backgrounds, Majorana also searches for rare event signatures from beyond
standard model physics in the low energy region below 100 keV. In this Letter,
we test the continuous spontaneous localization (CSL) model, one of the
mathematically well-motivated wave function collapse models aimed at solving
the long-standing unresolved quantum mechanical measurement problem. While the
CSL predicts the existence of a detectable radiation signature in the x-ray
domain, we find no evidence of such radiation in the 19--100 keV range in a
37.5 kg-y enriched germanium exposure collected between December 31, 2015, and
November 27, 2019, with the Demonstrator. We explored both the
non-mass-proportional (n-m-p) and the mass-proportional (m-p) versions of the
CSL with two different assumptions: that only the quasifree electrons can emit
the x-ray radiation and that the nucleus can coherently emit an amplified
radiation. In all cases, we set the most stringent upper limit to date for the
white CSL model on the collapse rate, $\lambda$, providing a factor of 40--100
improvement in sensitivity over comparable searches. Our limit is the most
stringent for large parts of the allowed parameter space. If the result is
interpreted in terms of the Di\`osi-Penrose gravitational wave function
collapse model, the lower bound with a 95% confidence level is almost an order
of magnitude improvement over the previous best limit. | nucl-ex |
Competition of $β$-delayed protons and $β$-delayed $γ$ rays
in $^{56}$Zn and the exotic $β$-delayed $γ$-proton decay: Remarkable results have been published recently on the $\beta$ decay of
$^{56}$Zn. In particular, the rare and exotic $\beta$-delayed $\gamma$-proton
emission has been detected for the first time in the $fp$ shell. Here we focus
the discussion on this exotic decay mode and on the observed competition
between $\beta$-delayed protons and $\beta$-delayed $\gamma$ rays from the
Isobaric Analogue State. | nucl-ex |
Jet reconstruction in heavy ion collisions (emphasis on Underlying Event
background subtraction): A modification of the internal structure of jets is expected due to the
production of a dense QCD medium, the Quark Gluon Plasma, in heavy-ion
collisions. We discuss some aspects of jet reconstruction in p+p and A+A
collisions and emphasize the dramatically increased contribution of the
underlying event in nucleus-nucleus collisions as compared with the vacuum
case. We conclude with its consequences on the full jet spectrum and
fragmentation function extraction at LHC. | nucl-ex |
Elliptic flow of φ-meson a sensitive probe for onset of
de-confinement transition in high energy heavy-ion collisions: Elliptic flow (v_2) of \phi-meson is shown to be a sensitive probe of the
partonic collectivity using A Multi Phase Transport (AMPT) model. Within the
ambit of the AMPT model with partonic interactions (string melting version),
the \phi-meson v_2 at midrapidity is found to have negligible contribution from
hadronic interactions for Au+Au collisions at 200 GeV per nucleon. Changing the
hadron cascade time in the model calculations does not change the \phi-meson
v_2, while it reduces the v_2 of proton at low transverse momentum (pT). These
observations indicate that a substantial reduction in \phi-mesons v_2 as a
function of colliding beam energy would suggest the dominance of hadronic
interactions over partonic interactions. | nucl-ex |
A Large Scale Double Beta and Dark Matter Experiment: GENIUS: The recent results from the HEIDELBERG-MOSCOW experiment have demonstrated
the large potential of double beta decay to search for new physics beyond the
Standard Model. To increase by a major step the present sensitivity for double
beta decay and dark matter search much bigger source strengths and much lower
backgrounds are needed than used in experiments under operation at present or
under construction. We present here a study of a project proposed recently,
which would operate one ton of 'naked' enriched GErmanium-detectors in liquid
NItrogen as shielding in an Underground Setup (GENIUS). It improves the
sensitivity to neutrino masses to 0.01 eV. A ten ton version would probe
neutrino masses even down to 10^-3 eV. The first version would allow to test
the atmospheric neutrino problem, the second at least part of the solar
neutrino problem. Both versions would allow in addition significant
contributions to testing several classes of GUT models. These are especially
tests of R-parity breaking supersymmetry models, leptoquark masses and
mechanism and right-handed W-boson masses comparable to LHC. The second issue
of the experiment is the search for dark matter in the universe. The entire
MSSM parameter space for prediction of neutralinos as dark matter particles
could be covered already in a first step of the full experiment - with the same
purity requirements but using only 100 kg of 76Ge or even of natural Ge -
making the experiment competitive to LHC in the search for supersymmetry.
The layout of the proposed experiment is discussed and the shielding and
purity requirements are studied using GEANT Monte Carlo simulations. As a
demonstration of the feasibility of the experiment first results of operating a
'naked' Ge detector in liquid nitrogen are presented. | nucl-ex |
The elliptic flow of di-electrons in $\sqrt{s_{NN}}$=200 GeV Au+Au
collisions at STAR: In minimum bias (0-80%) Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV, the
elliptic flow ($v_{2}$) measurements for di-electrons from the low to
intermediate mass region are presented. The differential elliptic flow as a
function of transverse momentum in different mass regions are also reported.
The simulated and measured $v_{2}$ of di-electrons are compared in the mass
regions of $M_{ee}<0.14$ GeV/$c^{2}$ and $0.14<M_{ee}<0.3$ GeV/$c^{2}$. | nucl-ex |
Strange Magnetism and the Anapole Structure of the Proton: The violation of mirror symmetry in the weak force provides a powerful tool
to study the internal structure of the proton. Experimental results have been
obtained that address the role of strange quarks in generating nuclear
magnetism. The measurement reported here provides an unambiguous constraint on
strange quark contributions to the proton's magnetic moment through the
electron-proton weak interaction. We also report evidence for the existence of
a parity-violating electromagnetic effect known as the anapole moment of the
proton. The proton's anapole moment is not yet well understood theoretically,
but it could have important implications for precision weak interaction studies
in atomic systems such as cesium. | nucl-ex |
Proton-lambda correlations in central Au+Au collisions at sqrt
(s_NN)=200 GeV: We report on p-Lambda, p-Lambda bar, p bar-Lambda and p bar-Lambda bar
correlation functions constructed in central Au-Au collisions at
sqrt(s_NN)=200GeV by the STAR experiment at RHIC. The proton and lambda source
size is inferred from the p-Lambda and p bar-Lambda bar correlation functions.
They are found to be smaller than the pion source size also measured by the
STAR detector. This could be a consequence of the collision fireball's
collective expansion. The p-Lambda bar and p bar-Lambda correlations, which are
measured for the first time, exhibit a large anti-correlation. Annihilation
channels and/or a negative real part of the spin-averaged scattering length
must be included in the final-state interactions calculation to reproduce the
measured correlation function. | nucl-ex |
Recent ALICE results on quarkonium production in nuclear collisions: Quarkonium production has long been regarded as a potential signature of
deconfinement in nucleus-nucleus collisions. Recently, the production of
J/$\psi$ via regeneration within the quark-gluon plasma (QGP) or at the phase
boundary has been identified as an important ingredient for the interpretation
of quarkonium production results from lead-lead collisions at the Large Hadron
Collider (LHC). Quarkonium polarization could also be used to investigate the
properties of the hot and dense medium created at the LHC energies. In this
contribution, the latest ALICE results on quarkonium will be presented and
discussed. These include, among others, the nuclear modifications of (prompt
and non-prompt) J/$\psi$ and $\psi$(2S) production, and the J/$\psi$
polarisation, all measured with lead-lead collisions at the LHC. The results
will be compared with available theoretical model calculations. | nucl-ex |
Spectroscopy of the neutron-rich hypernucleus $^{7}_Λ$He from
electron scattering: The missing mass spectroscopy of the $^{7}_{\Lambda}$He hypernucleus was
performed, using the $^{7}$Li$(e,e^{\prime}K^{+})^{7}_{\Lambda}$He reaction at
the Thomas Jefferson National Accelerator Facility Hall C. The $\Lambda$
binding energy of the ground state (1/2$^{+}$) was determined with a smaller
error than that of the previous measurement, being $B_{\Lambda}$ = 5.55 $\pm$
0.10(stat.) $\pm$ 0.11(sys.) MeV. The experiment also provided new insight into
charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at
$B_{\Lambda}$ = 3.65 $\pm$ 0.20(stat.) $\pm$ 0.11(sys.) MeV was observed and
assigned as a mixture of 3/2$^{+}$ and 5/2$^{+}$ states, confirming the
"gluelike" behavior of $\Lambda$, which makes an unstable state in $^{6}$He
stable against neutron emission. | nucl-ex |
Astrophysical $S$ factor for the ${}^{15}{\rm N}(p,γ){}^{16}{\rm
O}$ reaction from $R$-matrix analysis and asymptotic normalization
coefficient for ${}^{16}{\rm O} \to {}^{15}{\rm N} + p$. Is any fit
acceptable?: The $^{15}{\rm N}(p,\gamma)^{16}{\rm O}$ reaction provides a path from the CN
cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor
for this reaction is dominated by resonant capture through two strong
$J^{\pi}=1^{-}$ resonances at $E_{R}= 312$ and 962 keV and direct capture to
the ground state. Recently, a new measurement of the astrophysical factor for
the $^{15}{\rm N}(p,\gamma)^{16}{\rm O}$ reaction has been published [P. J.
LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. The analysis has
been done using the $R$-matrix approach with unconstrained variation of all
parameters including the asymptotic normalization coefficient (ANC). The best
fit has been obtained for the square of the ANC $C^{2}= 539.2$ fm${}^{-1}$,
which exceeds the previously measured value by a factor of $\approx 3$. Here we
present a new $R$-matrix analysis of the Notre Dame-LUNA data with the fixed
within the experimental uncertainties square of the ANC $C^{2}=200.34$
fm${}^{-1}$. Rather than varying the ANC we add the contribution from a
background resonance that effectively takes into account contributions from
higher levels. Altogether we present 8 fits, five unconstrained and three
constrained. In all the fits the ANC is fixed at the previously determined
experimental value $C^{2}=200.34$ fm${}^{-1}$. For the unconstrained fit with
the boundary condition $B_{c}=S_{c}(E_{2})$, where $E_{2}$ is the energy of the
second level, we get $S(0)=39.0 \pm 1.1 $ keVb and normalized ${\tilde
\chi}^{2}=1.84$, i.e. the result which is similar to [P. J. LeBlanc {\it et
al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. From all our fits we get the range
$33.1 \leq S(0) \leq 40.1$ keVb which overlaps with the result of [P. J.
LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. We address also
physical interpretation of the fitting parameters. | nucl-ex |
Polarization Transfer in the ^4He(\vec e,e'\vec p)^3H Reaction up to Q^2
= 2.6 (GeV/c)^2: We have measured the proton recoil polarization in the ^4He(\vec e,e'\vec
p)^3H reaction at Q^2 = 0.5, 1.0, 1.6, and 2.6 (GeV/c)^2. The measured ratio of
polarization transfer coefficients differs from a fully relativistic
calculation, favoring the inclusion of a predicted medium modification of the
proton form factors based on a quark-meson coupling model. In contrast, the
measured induced polarizations agree reasonably well with the fully
relativistic calculation indicating that the treatment of final-state
interactions is under control. | nucl-ex |
Experimental study of the astrophysical gamma-process reaction
124Xe(alpha,gamma)128Ba: The synthesis of heavy, proton rich isotopes in the astrophysical
gamma-process proceeds through photodisintegration reactions. For the improved
understanding of the process, the rates of the involved nuclear reactions must
be known. The reaction 128Ba(g,a)124Xe was found to affect the abundance of the
p nucleus 124Xe. Since the stellar rate for this reaction cannot be determined
by a measurement directly, the aim of the present work was to measure the cross
section of the inverse 124Xe(a,g)128Ba reaction and to compare the results with
statistical model predictions. Of great importance is the fact that data below
the (a,n) threshold was obtained. Studying simultaneously the 124Xe(a,n)127Ba
reaction channel at higher energy allowed to further identify the source of a
discrepancy between data and prediction. The 124Xe + alpha cross sections were
measured with the activation method using a thin window 124Xe gas cell. The
studied energy range was between E = 11 and 15 MeV close above the
astrophysically relevant energy range. The obtained cross sections are compared
with statistical model calculations. The experimental cross sections are
smaller than standard predictions previously used in astrophysical
calculations. As dominating source of the difference, the theoretical alpha
width was identified. The experimental data suggest an alpha width lower by at
least a factor of 0.125 in the astrophysical energy range. An upper limit for
the 128Ba(g,a)124Xe stellar rate was inferred from our measurement. The impact
of this rate was studied in two different models for core-collapse supernova
explosions of 25 solar mass stars. A significant contribution to the 124Xe
abundance via this reaction path would only be possible when the rate was
increased above the previous standard value. Since the experimental data rule
this out, they also demonstrate the closure of this production path. | nucl-ex |
High-spin structures of 88Kr and 89Rb: Evolution from collective to
single-particle behaviors: The high-spin states of the two neutron-rich nuclei, 88Kr and 89R have been
studied from the 18O + 208Pb fusion-fission reaction. Their level schemes were
built from triple gamma-ray coincidence data and gamma-gamma angular
correlations were analyzed in order to assign spin and parity values to most of
the observed states. The two levels schemes evolve from collective structures
to single-particle excitations as a function of the excitation energy.
Comparison with results of shell-model calculations gives the specific proton
and neutron configurations which are involved to generate the angular momentum
along the yrast lines. | nucl-ex |
Charm production and hadronization in pp and p-Pb collisions at the LHC
with ALICE: Studies of open-charm hadron production in pp and \pPb collisions are
performed by the ALICE Collaboration at the LHC to investigate charm-quark
hadronization mechanisms. Recent measurements of charm meson (${\rm D^0}$,
${\rm D^+}$, ${\rm D^+_{\rm s}}$, and ${\rm D^{*+}}$) and baryon
($\Lambda^+_{\rm c}$, $\Xi^{0,+}_{\rm c}$, $\Sigma^{0,++}_{\rm c}$, and
$\Omega^0_{\rm c}$) production in pp collisions at $\sqrt{s}$ = 5.02 TeV and
$\sqrt{s}$ = 13 TeV allow the determination of the charm cross section and the
fragmentation fractions at $\sqrt{s}$ = 5.02 TeV with unprecedented precision.
The measurements show that the fragmentation fractions significantly differ
from the ones measured in ${\rm e^+e^-}$ and \ep collisions. This highlights
possible differences in the hadronization process between electron induced
collisions and pp collisions at the LHC. \\ Furthermore, the first measurement
of the baryon-to-meson yield ratio $\Lambda^+_{\rm c}/{\rm D^0}$, down to
$p_{\rm T}=0$ in pp and \pPb collisions will be discussed. In p--Pb collisions
a modification of the hadronization mechanisms could be present due to cold
nuclear matter effects and collective phenomena. A systematic comparison
between data and model calculations will help to understand charm quark
hadronization in pp and p--Pb collisions. | nucl-ex |
Near threshold angular distributions of the $^2$H$(γ,Λ)$X
reaction: A study of the $^2$H$({\gamma},{\Lambda})$X reaction was performed using a
tagged photon beam at the Research Center for Electron Photon Science (ELPH),
Tohoku University. The photoproduced $\Lambda$ was measured in the $p{\pi^{-}}$
decay channel by the upgraded Neutral Kaon Spectrometer (NKS2+). The momentum
integrated differential cross section was determined as a function of the
scatting angle of ${\Lambda}$ in the laboratory frame for five energy bins. Our
results indicated a peak in the cross section at angles smaller than
cos$\theta^{LAB}_{\Lambda}$ = $0.96$. The experimentally obtained angular
distributions were compared to isobar models, Kaon-Maid (KM) and Saclay-Lyon A
(SLA), in addition to the composite Regge-plus-resonance (RPR) model. Both
SLA(r$K_{1}K_{\gamma}$ = $-1.4$) and RPR describe the data quite well in
contrast to the KM model, which substantially under predicted the cross section
at the most forward angles. With the anticipated finalized data on ${\Lambda}$
integrated and momentum dependent differential cross sections of
$^2$H$({\gamma},{\Lambda})$X~\cite{Kaneta_Beckford}, we present our findings on
the angular distributions in this report. | nucl-ex |
The role of elliptic flow correlations in the discovery of the sQGP at
RHIC: Flow measurements are reviewed with particular emphasis on the hydrodynamic
character of elliptic flow at RHIC. Hydrodynamic scaling compatible with the
production of highly thermalized matter having a high degree of collective
interactions and extremely low viscosity, is observed for a broad selection of
the data. These properties suggest the production of a new state of strongly
interacting nuclear matter at extremely high density and temperature where the
relevant degrees of freedom are those of quarks and gluons, ie. the sQGP. | nucl-ex |
ALICE status and plans: The ALICE experiment has been running successfully since 2010 and made an
impressive progress towards understanding of hot and dense QCD matter produced
in heavy ion collisions at LHC energies. Recent results on identified particle
spectra, azimuthal anisotropy, heavy flavour and quarkonium production in Pb-Pb
collisions at sqrt(s_NN) = 2.76 TeV are presented. First results on p-Pb
collisions and ALICE upgrade plans are briefly reviewed. | nucl-ex |
Nucleon-nucleon coincidence measurement in the non-mesonic weak decay of
5_Lambda-He and 12_Lambda-C hypernuclei: We have measured both yields of neutron-proton and neutron-neutron pairs
emitted from the non-mesonic weak decay process of 5_Lambda-He and 12_Lambda-C
hypernuclei produced via the (pi^+,K^+) reaction for the first time. We
observed clean back-to-back correlation of the np- and nn-pairs in the
coincidence spectra for both hypernuclei. The ratio of those back-to-back pair
yields, Nnn / Nnp, must be close to the ratio of neutron- and proton-induced
decay widths of the decay, Gn(Lambda n -> nn)/Gp(Lambda p -> np). The obtained
ratios for each hypernuclei support recent calculations based on short-range
interactions. | nucl-ex |
Measurement of Angular Distributions of Drell-Yan Dimuons in $p + p$
Interactions at 800 GeV/c: We report a measurement of the angular distributions of Drell-Yan dimuons
produced using an 800 GeV/c proton beam on a hydrogen target. The polar and
azimuthal angular distribution parameters have been extracted over the
kinematic range $4.5 < m_{\mu \mu} < 15$ GeV/c$^2$ (excluding the $\Upsilon$
resonance region), $0 < p_T < 4 $ GeV/c, and $0 < x_F < 0.8$. The $p+p$ angular
distributions are similar to those of $p+d$, and both data sets are compared
with models which attribute the $\cos 2 \phi$ distribution either to the
presence of the transverse-momentum-dependent Boer-Mulders structure function
$h_1^\perp$ or to QCD effects. The data indicate the presence of both
mechanisms. The validity of the Lam-Tung relation in $p+p$ Drell-Yan is also
tested. | nucl-ex |
Non-photonic electron-hadron correlations in Cu+Cu at sqrt(s_NN) = 200
GeV: In this paper we present the study of the azimuthal correlation function of
non-photonic electrons with low-pT hadrons produced in Cu+Cu collision at
sqrt(s_NN)=200 GeV measured by STAR experiment at RHIC. Possible modification
of the awayside peak is observed. | nucl-ex |
Worldwide Search for the Neutron EDM: Existing limits on the electric dipole moment (EDM) of the free neutron have
provided critical constraints on new sources of CP violation for more than 60
years. A new round of searches are actively underway with the goal of improving
the sensitivity to CP violation by up to two orders-of-magnitude. The status of
these new searches will be discussed, including recent progress on the nEDM
experiment to be carried out at the Fundamental Neutron Physics Beamline at the
Oak Ridge National Laboratory's Spallation Neutron Source. | nucl-ex |
Looking forward for Color Glass Condensate signatures: Forward $\pi^0$ production has been measured at STAR with the new Forward
Meson Spectrometer (FMS) from p+p and d+Au collisions during the 2008 RHIC run.
We present the first FMS results of azimuthal correlation involving a forward
$\pi^0$ produced in p+p and d+Au collisions to search for the onset of gluon
density saturation, expected to occur at small momentum fractions. | nucl-ex |
Searching for Two-Neutrino and Neutrinoless Double Beta Decay of
$^{134}$Xe with the PandaX-4T Experiment: $^{134}$Xe is a candidate isotope for neutrinoless double beta
decay~($0\nu\beta\beta$) search. In addition, the two-neutrino case
($2\nu\beta\beta$) allowed by the Standard Model of particle physics has not
yet been observed. Utilizing the 10.4% of $^{134}$Xe in the natural xenon in
the PandaX-4T detector and its first 94.9-day exposure, we have established the
most stringent constraints on $2\nu\beta\beta$ and $0\nu\beta\beta$ of
$^{134}$Xe half-lives, with limits of $2.8\times10^{22}$ yr and
$3.0\times10^{23}$ yr at 90% confidence level, respectively. The
$2\nu\beta\beta$ ($0\nu\beta\beta$) limit surpasses the previously reported
best result by a factor of 32 (2.7), highlighting the potential of large
monolithic natural xenon detectors. | nucl-ex |
Complex fragment emission in low energy light-ion reactions: Inclusive energy spectra of the complex fragments (3 $\leq$ Z $\leq$ 5)
emitted in the reactions $^{12}$C (77 MeV)+ $^{28}$Si, $^{11}$B (64 MeV)+
$^{28}$Si and $^{12}$C (73 MeV)+ $^{27}$Al (all having the same excitation
energy of $ \sim$ 67 MeV), have been measured in the angular range of
10$^\circ$ $\lesssim \theta_{lab} \lesssim$ 60$^\circ$. The fully energy damped
(fusion-fission) and the partially energy damped (deep inelastic) components of
the fragment energy spectra have been extracted. It has been found that the
yields of the fully energy damped fragments for all the above reactions are in
conformity with the respective statistical model predictions. The time scales
of various deep inelastic fragment emissions have been extracted from the
angular distribution data. The angular momentum dissipation in deep inelastic
collisions has been estimated from the data and it has been found to be close
to the corresponding sticking limit value. | nucl-ex |
Searches for transverse momentum dependent flow vector fluctuations in
Pb-Pb and p-Pb collisions at the LHC: The measurement of azimuthal correlations of charged particles is presented
for Pb-Pb collisions at $\sqrt{s_{\rm NN}}=$ 2.76 TeV and p-Pb collisions at
$\sqrt{s_{\rm NN}}=$ 5.02 TeV with the ALICE detector at the CERN Large Hadron
Collider. These correlations are measured for the second, third and fourth
order flow vector in the pseudorapidity region $|\eta|<0.8$ as a function of
centrality and transverse momentum $p_{\rm T}$ using two observables, to search
for evidence of $p_{\rm T}$-dependent flow vector fluctuations. For Pb-Pb
collisions at 2.76 TeV, the measurements indicate that $p_{\rm T}$-dependent
fluctuations are only present for the second order flow vector. Similar results
have been found for p-Pb collisions at 5.02 TeV. These measurements are
compared to hydrodynamic model calculations with event-by-event geometry
fluctuations in the initial state to constrain the initial conditions and
transport properties of the matter created in Pb-Pb and p-Pb collisions. | nucl-ex |
Study of Proton Induced Reactions in a Radioactive 129-I Target at
Ep=660 MeV: Two NaI (85% 129-I and 15% 127-I) targets were exposed to a beam of 660-MeV
protons. Cross sections for formation of 76 residual nuclei were obtained by
the induced activity method. The results are compared with other experimental
data on 127-I and theoretical calculations by eleven models contained in the
codes LAHET3 (using the Bertini+Dresner, ISABEL+Dresner, INCL+Dresner, and
INCL+ABLA options), CASCADE, CEM95, CEM2K, LAQGSM+GEM2, CEM2k+GEM2,
LAQGSM+GEMINI, and CEM2k+GEMINI. Most of the models describe spallation
products with masses close to the target reasonably well while the reliability
of the codes differs greatly in the deep spallation and fission/fragmentation
regions. The difficulties in describing products with A=40-80 by all of the
codes tested here except for CEM2k+GEMINI and LAQGSM+GEMINI is related to the
neglect of fission (and fragmentation) processes for targets as light as 129-I. | nucl-ex |
Search for the Hypothetical pi -> mu x Decay: The KARMEN collaboration has reported the possible observation of a hitherto
unknown neutral and weakly interacting particle x, which is produced in the
decay pi -> mu + x with a mass m(x) = 33.9 MeV. We have searched for this
hypothetical decay branch by studying muons from pion decay in flight with the
LEPS spectrometer at the piE3 channel at PSI and find branching ratios BR(pi-
to mu- anti-x) < 4e-7 and BR(pi+ to mu+ x) < 7e-8 (95\% C.L.). Together with
the limit BR > 2e-8 derived in a recent theoretical paper our result would
leave only a narrow region for the existence of x if it is a heavy neutrino. | nucl-ex |
Probing the statistical decay and alpha-clustering effects in 12c+12c
and 14n+10b reactions: An experimental campaign has been undertaken at INFN Laboratori Nazionali di
Legnaro, Italy, in order to progress in our understanding of the statistical
properties of light nuclei at excitation energies above particle emission
threshold, by measuring exclusive data from fusion-evaporation reactions. A
first reaction 12C+12C at 7.9 AMeV beam energy has been measured, using the
GARFIELD+Ring Counter experimental setup. Fusion-evaporation events have been
exclusively selected. The comparison to a dedicated Hauser-Feshbach calculation
allows us to give constraints on the nuclear level density at high excitation
energy for light systems ranging from C up to Mg. Out-of-equilibrium emission
has been evidenced and attributed both to entrance channel effects favoured by
the cluster nature of reaction partners and, in more dissipative events, to the
persistence of cluster correlations well above the 24Mg threshold for 6 alphas
decay. The 24Mg compound nucleus has been studied with a new measurement 14N +
10B at 5.7 AMeV. The comparison between the two datasets would allow us to
further constrain the level density of light nuclei. Deviations from a
statistical behaviour can be analyzed to get information on nuclear clustering. | nucl-ex |
Liquid solution centrifugation for safe, scalable, and efficient isotope
separation: A general method of separating isotopes by centrifuging dissolved chemical
compounds in a liquid solution is introduced. This technique can be applied to
almost all elements and leads to large separation factors. The method has been
demonstrated in several isotopic systems including Ca, Mo, O, and Li with
single-stage selectivities of 1.046-1.067 per unit mass difference (e.g., 1.434
in 40Ca/48Ca, 1.134 in 16O/18O), which are beyond the capabilities of various
conventional methods of isotope enrichment. Equations are derived to model the
process and the results agree with those of the experiments. The scalability of
the technique has been demonstrated by performing a three-stage enrichment of
48Ca, and the scalability is more broadly supported through analogies to the
gas centrifuge, whereby countercurrent centrifugation can further multiply the
separation factor by 5-10 times per stage in a continuous process. Optimal
centrifuge conditions and solutions can achieve both high-throughput and highly
efficient isotope separation. | nucl-ex |
Precision Measurement of PArity Violation in Polarized Cold Neutron
Capture on the Proton: the NPDGamma Experiment: The NPDGamma experiment at the Los Alamos Neutron Science Center (LANSCE) is
dedicated to measure with high precision the parity violating asymmetry in the
$\gamma$ emission after capture of spin polarized cold neutrons in
para-hydrogen. The measurement will determine unambiguously the weak
pion-nucleon-nucleon ($\pi NN$) coupling constant {\it f$^1_{\pi}$} | nucl-ex |
First Measurement of the Ti$(e,e^\prime){\rm X}$ Cross Section at
Jefferson Lab: To probe CP violation in the leptonic sector using GeV energy neutrino beams
in current and future experiments using argon detectors, precise models of the
complex underlying neutrino and antineutrino interactions are needed. The
E12-14-012 experiment at Jefferson Lab Hall A was designed to perform a
combined analysis of inclusive and exclusive electron scatterings on both argon
($N = 22$) and titanium ($Z = 22$) nuclei using GeV energy electron beams. The
measurement on titanium nucleus provides essential information to understand
the neutrino scattering on argon, large contribution to which comes from
scattering off neutrons. Here we report the first experimental study of
electron-titanium scattering as double differential cross section at beam
energy $E=2.222$ GeV and electron scattering angle $\theta = 15.541$ deg,
measured over a broad range of energy transfer, spanning the kinematical
regions in which quasielastic scattering and delta production are the dominant
reaction mechanisms. The data provide valuable new information needed to
develop accurate theoretical models of the electromagnetic and weak cross
sections of these complex nuclei in the kinematic regime of interest to
neutrino experiments. | nucl-ex |
Test of Time Reversal Invariance in Polarized Proton-Deuteron Scattering: A novel test of time-reversal invariance in proton-deuteron scattering is
planned as an internal target transmission experiment at the cooler synchrotron
COSY. The P-even, T-odd observable is the polarization correlation $A_{y,xz}$
of the total cross section measured using a polarized internal proton beam
(polarization $p_y$) and an internal polarized deuterium target (tensor
polarization $p_{xz}$). Measuring this observable is a true null test of time
reversal invariance and therefore allows to reach a high accuracy. Sufficient
luminosity can be obtained using a window-less storage cell placed on the axis
of the proton beam. Tensor polarized atoms are produced in an atomic beam
source based on Stern-Gerlach separation in permanent sextupole magnets and
adiabatic high frequency transitions. The total cross section correlation is
measured by monitoring the beam transmission in the COSY storage ring mode of
operation. The proton beam momentum will be in the range 2-3 GeV/c. This
momentum is ideally suited to test possible short range contributions, i.e.
natural parity charged $\rho$-type and unnatural parity $a_1$-type meson
exchange contributions. The feasibility of the experiment, systematic errors
and the expected accuracy are discussed. | nucl-ex |
Precision study of the d+p->3He+eta reaction for excess energies between
20 and 60 MeV: The differential and total cross sections for the d+p->3He+eta reaction have
been measured at COSY-ANKE at excess energies of 19.5, 39.4, and 59.4 MeV over
the full angular range. The results are in line with trends apparent from the
detailed near-threshold studies and also agree with those from CELSIUS, though
the present data have higher precision. While at 19.5 MeV the results can be
described in terms of s- and p-wave production, by 59.4 MeV higher partial
waves are required. Including the 19.5 MeV point together with the
near-threshold data in a global s- and p-wave fit gives a poorer overall
description of the data though the position of the pole in the 3He scattering
amplitude, corresponding to the quasi-bound or virtual state, is hardly
changed. | nucl-ex |
Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2: We report the most precise measurement to date of a parity-violating
asymmetry in elastic electron-proton scattering. The measurement was carried
out with a beam energy of 3.03 GeV and a scattering angle <theta_lab>=6
degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per
million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor
combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/-
0.012 (FF) where the first two errors are experimental and the last error is
due to the uncertainty in the neutron electromagnetic form factor. This result
significantly improves current knowledge of G_E^s and G_M^s at Q^2 ~0.1 GeV^2.
A consistent picture emerges when several measurements at about the same Q^2
value are combined: G_E^s is consistent with zero while G_M^s prefers positive
values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L. | nucl-ex |
Strange Particles and Neutron Stars - Experiments at Gsi: Experiments on strangeness production in nucleus-nucleus collisions at SIS
energies address fundamental aspects of modern nuclear physics: the
determination of the nuclear equation-of-state at high baryon densities and the
properties of hadrons in dense nuclear matter. Experimental data and
theoretical results will be reviewed. Future experiments at the FAIR
accelerator aim at the exploration of the QCD phase diagram at highest baryon
densities. | nucl-ex |
Determination of quadrupole strengths in the gamma*p-->Delta(1232)
transition at Q2= 0.20 (GeV/c)2: We report new precise p$(\vec{e},e^\prime p)\pi^0$ measurements at the peak
of the $\Delta^{+}(1232)$ resonance at $Q^2=\unit[0.20](GeV/c)^2$ performed at
the Mainz Microtron (MAMI). The new data are sensitive to both the electric
quadrupole ($E2$) and the coulomb quadrupole ($C2$) amplitudes of the $\gamma^*
N\to\Delta$ transition. They yield precise quadrupole to dipole amplitude
ratios CMR $= (-5.09 \pm 0.28_{stat+sys}\pm 0.30_{model})%$ and EMR $= (-1.96
\pm 0.68_{stat+sys} \pm 0.41_{model})%$ for $M^{3/2}_{1+} = (39.57 \pm
0.75_{stat+sys}\pm 0.40_{model})(10^{-3}/m_{\pi^+})$. The new results are in
disagreement with Constituent Quark Model predictions and in qualitative
agreement with models that account for mesonic contributions, including recent
Lattice calculations. They thus give further credence to the conjecture of
deformation in hadronic systems favoring the attribution of the origin of
deformation to the dominance of mesonic effects. | nucl-ex |
Measurements of ${Λ_{\rm c}^+\rm /D^0}$ ratio as a function of
multiplicity at midrapidity at $ \sqrt{s_{\text{NN}}} = 5.02\; \text{TeV}$: In this contribution, the measurement of prompt ${\Lambda_{\rm c}^+\rm /D^0}$
ratio as a function of multiplicity in p--Pb collisions at mid-rapidity at $
\sqrt{s_{\text{NN}}} = 5.02 \;\text{TeV}$ is discussed. By performing this
measurement as a function of multiplicity in pp and p--Pb collisions, we can
evaluate the $p_{\rm T}$-differential baryon to meson enhancement and compare
them to results in $ \rm e^-e^+$ and $ \rm e^-p$ collisions, where lower
${\Lambda_{\rm c}^+\rm /D^0}$ ratios at low and intermediate $p_{\rm T}$ have
been observed, with the origin of this different behavior being still debated.
In these measurements, we aim to compare the p--Pb results to pp collisions to
investigate the possible effects of cold nuclear matter on charm-baryon
production, and to Pb--Pb collisions for investigating the impact of
quark--gluon plasma on charm quark hadronization. | nucl-ex |
Strangeness and bulk freeze-out properties at RHIC: Identified charged kaon, pion, and proton spectra and ratios from sqrt(s_NN)
= 200 and 62.4 GeV Cu+Cu collisions are studied with a hydro-motivated
blast-wave and a statistical model framework in order to explore the
strangeness production at RHIC and characterize the bulk freeze-out properties
of the created system. The spectra are measured at mid-rapidity |y|<0.1 over
the transverse momentum range of 0.25 < p_T < 1.2 GeV/c with particle
identification derived from the ionization energy loss in the STAR Time
Projection Chamber.
The multi-dimensional systematic study of pi(+/-), K(+/-), p and pbar
production in Cu+Cu, Au+Au, d+Au and p+p collisions is used to discuss the
energy, system size and inferred energy density dependence of freeze-out
parameters and strangeness production. The new data from Cu+Cu collisions
bridge the gap between the smaller d+Au and larger Au+Au systems, allowing a
detailed study of the onset of strangeness equilibration at RHIC. | nucl-ex |
A radium assay technique using hydrous titanium oxide adsorbent for the
Sudbury Neutrino Observatory: As photodisintegration of deuterons mimics the disintegration of deuterons by
neutrinos, the accurate measurement of the radioactivity from thorium and
uranium decay chains in the heavy water in the Sudbury Neutrino Observatory
(SNO) is essential for the determination of the total solar neutrino flux. A
radium assay technique of the required sensitivity is described that uses
hydrous titanium oxide adsorbent on a filtration membrane together with a
beta-alpha delayed coincidence counting system. For a 200 tonne assay the
detection limit for 232Th is a concentration of 3 x 10^(-16) g Th/g water and
for 238U of 3 x 10^(-16) g U/g water. Results of assays of both the heavy and
light water carried out during the first two years of data collection of SNO
are presented. | nucl-ex |
Azimuthal anisotropy measurements of strange and multistrange hadrons in
U+U collisions at $\sqrt{s_{NN}} = 193$ GeV at the BNL Relativistic Heavy Ion
Collider: We present systematic measurements of azimuthal anisotropy for strange and
multistrange hadrons ($K^{0}_{s}$, $\Lambda$, $\Xi$, and $\Omega$) and $\phi$
mesons at midrapidity ($|y| <$ 1.0) in collisions of U + U nuclei at
$\sqrt{s_{NN}} = 193$ GeV, recorded by the STAR detector at the Relativistic
Heavy Ion Collider. Transverse momentum ($p_{\text{T}}$) dependence of flow
coefficients ($v_{2}$, $v_{3}$, and $v_{4}$) is presented for minimum bias
collisions and three different centrality intervals. Number of constituent
quark scaling of the measured flow coefficients in U + U collisions is
discussed. We also present the ratio of $v_{n}$ scaled by the participant
eccentricity ($\varepsilon_{n}\left\lbrace 2 \right\rbrace$) to explore system
size dependence and collectivity in U + U collisions. The magnitude of
$v_{2}/\varepsilon_{2}$ is found to be smaller in U + U collisions than that in
central Au + Au collisions contradicting naive eccentricity scaling.
Furthermore, the ratios between various flow harmonics ($v_{3}/v_{2}^{3/2}$,
$v_{4}/v_{2}^{4/2}$) are studied and compared with hydrodynamic and transport
model calculations. | nucl-ex |
New Experimental Limits on Exotic Spin- and Velocity-dependent
Interactions Using Rotationally Modulated Source-masses and an
Atomic-magnetometer Array: We conducted laboratory searching for the exotic spin- and velocity-dependent
new interactions according to the previously proposed experimental scheme. Two
$\sim$6Kg heavy source masses are rotationally modulated at a frequency of
20Hz. Four identical atomic magnetometers are used in an array form to increase
the statistics and cancel the common-mode noise. Data processing method based
on high precision numerical integration is applied for the four harmonic
frequencies of the signal. The rotation direction of the source masses was
reversed to flip the signal. Thus the [1,-3,3,-1] weighting method can be
applied to remove possible slow drifting further. The experiment method has
noise reduction features, and new constraints for Vector-Axial and Axial-Axial
were obtained. The new constraints on VA improved by as much as more than four
orders, on AA by as much as two orders in the corresponding force range,
respectively. | nucl-ex |
The RHIC Beam Energy Scan Phase II: Physics and Upgrades: The exploration of the QCD phase diagram has been one of the main drivers of
contemporary nuclear physics. The Relativistic Heavy Ion Collider (RHIC) at BNL
is uniquely suited for this task through its Beam Energy Scan (BES) program
which allowed for a large range in baryon chemical potential $\mu_B$ as was
successfully demonstrated after the completion of Phase 1 in 2014. Phase 2 of
the BES at RHIC is scheduled to start in 2019 and will explore with precision
measurements the intermediate-to-high $\mu_B$ region of the QCD phase diagram,
five energies $\sqrt{s_{NN}}$ from 7.7 to 19.6 GeV in collider mode and eight
energies $\sqrt{s{_{NN}}}$ from 3.0 to 7.7 GeV in fixed-target mode. Some of
the key measurements are: the net-protons kurtosis that could pinpoint the
position of a critical point, the directed flow that might prove a softening of
the EOS, and the chiral restoration in the dielectron channel. These
measurements will be possible with an order of magnitude better statistics
provided by the electron cooling upgrade of RHIC and with the detector upgrades
planned to improve STAR's acceptance. These proceedings review the BES Phase-2
program and the physics opportunities enabled by these upgrades. | nucl-ex |
Beyond the Neutron Drip-Line: The Unbound Oxygen Isotopes 25O and 26O: The very neutron-rich oxygen isotopes 25O and 26O are investigated
experimentally and theoret- ically. In this first R3B-LAND experiment, the
unbound states are populated at GSI via proton- knockout reactions from 26F and
27F at relativistic energies around 450 MeV/nucleon. From the kinematically
complete measurement of the decay into 24O plus one or two neutrons, the 25O
ground- state energy and lifetime are determined, and upper limits for the 26O
ground state are extracted. In addition, the results provide evidence for an
excited state in 26O at around 4 MeV. The ex- perimental findings are compared
to theoretical shell-model calculations based on chiral two- and three-nucleon
(3N) forces, including for the first time residual 3N forces, which are shown
to be amplified as valence neutrons are added. | nucl-ex |
Differential Elliptic Flow in 2 - 6 AGeV Au+Au Collisions: A New
Constraint for the Nuclear Equation of State: Proton elliptic flow is studied as a function of impact-parameter $b$, for
two transverse momentum cuts in 2 - 6 AGeV Au + Au collisions. The elliptic
flow shows an essentially linear dependence on b (for $1.5 < b < 8$ fm) with a
negative slope at 2 AGeV, a positive slope at 6 AGeV and a near zero slope at 4
AGeV. These dependencies serve as an important constraint for discriminating
between various equations of state (EOS) for high density nuclear matter, and
they provide important insights on the interplay between collision geometry and
the expansion dynamics. Extensive comparisons of the measured and calculated
differential flows provide further evidence for a softening of the EOS between
2 and 6 GeV/nucleon. | nucl-ex |
Radioactive Ion Beam Physics and Nuclear Astrophysics in China: Based on the intermediate energy radioactive Ion Beam Line in Lanzhou (RIBLL)
of Heavy Ion Research Facility in Lanzhou (HIRFL) and Low Energy Radioactive
Ion Beam Line (GIRAFFE) of Beijing National Tandem Accelerator Lab (HI13), the
radioactive ion beam physics and nuclear astrophysics will be researched in
detail. The key scientific problems are: the nuclear structure and reaction for
nuclear far from $\beta$-stability line; the synthesize of new nuclides near
drip lines and new super heavy nuclides; the properties of asymmetric nuclear
matter with extra large isospin and some nuclear astro- reactions. | nucl-ex |
Symmetry energy and density: The nuclear equation-of-state is a topic of highest current interest in
nuclear structure and reactions as well as in astrophysics. In particular, the
equation-of-state of asymmetric matter and the symmetry energy representing the
difference between the energy densities of neutron matter and of symmetric
nuclear matter are not sufficiently well constrained at present. The density
dependence of the symmetry energy is conventionally expressed in the form of
the slope parameter L describing the derivative with respect to density of the
symmetry energy at saturation. Results deduced from nuclear structure and
heavy-ion reaction data are distributed around a mean value L=60 MeV.
Recent studies have more thoroughly investigated the density range that a
particular observable is predominantly sensitive to. Two thirds of the
saturation density is a value typical for the information contained in
nuclear-structure data. Higher values exceeding saturation have been shown to
be probed with meson production and collective flows at incident energies in
the range of up to about 1 GeV/nucleon.
From the measurement of the elliptic-flow ratio of neutrons with respect to
light charged particles in recent experiments at the GSI laboratory, a new more
stringent constraint for the symmetry energy at suprasaturation density has
been deduced. It confirms, with a considerably smaller uncertainty, the
moderately soft to linear density dependence of the symmetry energy previously
deduced from the FOPI-LAND data. Future opportunities offered by FAIR will be
discussed. | nucl-ex |
Measurement of the azimuthal anisotropy of charged-particle production
in Xe+Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$ TeV with the ATLAS
detector: This paper describes the measurements of flow harmonics $v_2$-$v_6$ in 3
$\mu\mathrm{b}^{-1}$ of Xe+Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$ TeV
performed using the ATLAS detector at the LHC. Measurements of the centrality,
multiplicity and $p_{\mathrm{T}}$ dependence of the $v_n$ obtained using
two-particle correlations and the scalar product technique are presented. The
measurements are also performed using a template-fit procedure, which was
developed to remove non-flow correlations in small collision systems. This
non-flow removal is shown to have a significant influence on the measured $v_n$
at high $p_{\mathrm{T}}$, especially in peripheral events. Comparisons of the
measured $v_n$ with measurements in Pb+Pb collisions and $p$+Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=5.02$ TeV are also presented. The $v_n$ values in Xe+Xe
collisions are observed to be larger than those in Pb+Pb collisions for $n=2$,
3 and 4 in the most central events. However, with decreasing centrality or
increasing harmonic order $n$, the $v_n$ values in Xe+Xe collisions become
smaller than those in Pb+Pb collisions. The $v_n$ in Xe+Xe and Pb+Pb collisions
are also compared as a function of the mean number of participating nucleons,
$\langle N_\text{part} \rangle$, and the measured charged-particle multiplicity
in the detector. The $v_3$ values in Xe+Xe and Pb+Pb collisions are observed to
be similar at the same $\langle N_\text{part}\rangle$ or multiplicity, but the
other harmonics are significantly different. Comparisons of the $v_n$
measurements with theoretical calculations are also made. | nucl-ex |
Systematic study of symmetric cumulants at $\sqrt{s_{NN}}$ = 200 GeV in
Au+Au collision using transport approach: Measurement of 4-particle symmetric cumulants has been considered to be a
good tool to study the correlations between amplitudes of different orders of
anisotropic flow harmonics in the heavy-ion collision. These new observables
not yet been measured at RHIC. Using A Multi-Phase Transport model, a set of
predictions for the centrality dependence of the normalized 4-particle
symmetric cumulants in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV has been
given. In addition, the effects of shear viscosity and hadronic rescattering on
the magnitude of symmetric cumulants are discussed using AMPT model at
$\sqrt{s_{NN}}$ = 200 GeV. It is shown that $sc(2,3)$ is found to be more
sensitive to hadronic rescattering, whereas $sc(2,4)$ is more sensitive to the
shear viscosity. Rapidity dependence of symmetric cumulants is also shown. A
relation between symmetric cumulant and event plane correlation is investigated
using AMPT model. | nucl-ex |
Particle Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 9.2 GeV: In this report we present the first test run results from Au+Au collisions at
$\sqrt{s_{NN}}$ = 9.2 GeV at RHIC. The large acceptance STAR detector has
collected ~3k minimum bias collisions during this test run. The azimuthal
anisotropy, identified particle spectra, particle ratios and HBT radii are
observed to be consistent with the previous measurements from CERN SPS at
similar center of mass energies. These results from the lowest collision energy
at RHIC demonstrate the STAR detector's readiness to collect high quality data
for the proposed Critical Point Search Program which allows us to explore the
QCD phase diagram. | nucl-ex |
Dynamical kurtosis of net and total proton distributions in STAR at RHIC: We report the energy and centrality dependence of dynamical kurtosis for Au +
Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV at
RHIC. The dynamical kurtosis of net-proton is compared to that of total-proton.
The results are also compared with AMPT model calculations. | nucl-ex |
Studies of the equation-of-state of nuclear matter by heavy-ion
collisions at intermediate energy in the multi-messenger era: The study of the equation-of-state (EoS) describing the properties of nuclear
matter away from the normal conditions is a relevant and intriguing topic of
modern nuclear physics. The last decades have witnessed a substantial
experimental progress in derivation of the symmetric matter term of the EoS and
of the so-called symmetry energy for the asymmetric matter, especially at
densities below the saturation point. But it is only in recent years that the
opening of the multi-messenger astronomy era, triggered by detection of
gravitational waves due to the neutron star mergers, has renewed and enlarged
the interest in high-density EoS, being the main ingredient for determining the
structure and properties of neutron stars. In this paper we review our
knowledge obtained from heavy-ion collisions up to the 1 GeV/nucleon regime, on
the EoS above nuclear saturation density. Special emphasis is given on the
still few results on symmetry energy at high densities and their
interconnections with multi-messenger astronomy findings. | nucl-ex |
Global polarization of $Λ$ hyperons in Au+Au collisions at
$\sqrt{s_{_{NN}}}$ = 200 GeV: Global polarization of $\Lambda$ hyperons has been measured to be of the
order of a few tenths of a percent in Au+Au collisions at $\sqrt{s_{_{NN}}}$ =
200 GeV, with no significant difference between $\Lambda$ and $\bar{\Lambda}$.
These new results reveal the collision energy dependence of the global
polarization together with the results previously observed at
$\sqrt{s_{_{NN}}}$ = 7.7 -- 62.4 GeV and indicate noticeable vorticity of the
medium created in non-central heavy-ion collisions at the highest RHIC
collision energy. The signal is in rough quantitative agreement with the
theoretical predictions from a hydrodynamic model and from the AMPT (A
Multi-Phase Transport) model. The polarization is larger in more peripheral
collisions, and depends weakly on the hyperon's transverse momentum and
pseudorapidity $\eta^H$ within $|\eta^H|<1$. An indication of the polarization
dependence on the event-by-event charge asymmetry is observed at the $2\sigma$
level, suggesting a possible contribution to the polarization from the axial
current induced by the initial magnetic field. | nucl-ex |
Flow-plane decorrelations in heavy-ion collisions with multiple-plane
cumulants: The azimuthal correlations between local flow planes at different
(pseudo)rapidities ($\eta$) may reveal important details of the initial nuclear
matter density distributions in heavy-ion collisions. Extensive experimental
measurements of a factorization ratio ($r_2$) and its derivative ($F_2$) have
shown evidence of the longitudinal flow-plane decorrelation. However, nonflow
effects also affect this observable and prevent a quantitative understanding of
the phenomenon. In this paper, to distinguish decorrelation and nonflow
effects, we propose a new cumulant observable, $T_2$, which largely suppresses
nonflow. The technique sensitivity to different initial-state scenarios and
nonflow effects are tested with a simple Monte Carlo model, and in the end, the
method is applied to events simulated by a multiphase transport model (AMPT)
for Au+Au collisions at $\sqrt{s_{\rm NN}} =200$ GeV. We also emphasize that a
distinct decorrelation signal requires not only the right sign of an
observable, but also its proper dependence on the $\eta$-window of the
reference flow plane, to be consistent with the pertinent decorrelation
picture. | nucl-ex |
Study of $^{26}$Mg through 1p pick up reaction $^{27}$Al(d,$^{3}$He): The even-even nucleus $^{26}$Mg has been studied through the reaction
$^{27}$Al(d,$^{3}$He) at 25 MeV beam energy. The spectroscopic factors have
been extracted upto 7.50 MeV excitation energy using local, zero range
distorted wave Born approximation. The comparison of the spectroscopic factors
have been done with previously reported values using the same reaction probe.
The extracted spectroscopic factors for different excited states were found to
be in good agreement with the previously reported values for the same. The
present results were also compared with the predictions from shell model as
well as rotational model. The analog states of $^{26}$Al and $^{26}$Mg were
found to be in good agreement. | nucl-ex |
Survival Mediated Heavy Element Capture Cross Sections: Formally, the cross section for producing a heavy evaporation residue,
{\sigma}EVR, in a fusion reaction can be written as. \begin{equation}
\sigma_{\rm EVR}(E)=\frac{\pi h^2}{2\mu E}\sum\limits_{\ell=0}^\infty
(2\ell+1)T(E,\ell)P_{\rm CN}(E,\ell)W_{\rm sur}(E,\ell), \end{equation} where E
is the center of mass energy, and T is the probability of the colliding nuclei
to overcome the potential barrier in the entrance channel and reach the contact
point. PCN is the probability that the projectile-target system will evolve
from the contact point to the compound nucleus. Wsur is the probability that
the compound nucleus will decay to produce an evaporation residue rather than
fissioning. However, one must remember that the Wsur term effectively sets the
allowed values of the spin, which in turn, restricts the values of the capture
and fusion cross sections. We point out the implications of this fact for
capture cross sections for heavy element formation reactions. | nucl-ex |
Half-Life of $^{14}$O: We have measured the half-life of $^{14}$O, a superallowed $(0^{+} \to
0^{+})$ $\beta$ decay isotope. The $^{14}$O was produced by the
$^{12}$C($^{3}$He,n)$^{14}$O reaction using a carbon aerogel target. A
low-energy ion beam of $^{14}$O was mass separated and implanted in a thin
beryllium foil. The beta particles were counted with plastic scintillator
detectors. We find $t_{1/2} = 70.696\pm 0.052$ s. This result is $1.5\sigma$
higher than an average value from six earlier experiments, but agrees more
closely with the most recent previous measurement. | nucl-ex |
Discovery of Long-Lived Shape Isomeric States which Decay by Strongly
Retarded High-Energy Particle Radioactivity: The reaction 28Si + 181Ta has been studied at E(Lab) = 125 and 135 MeV.
Coincidences between high energy particles and various X- and gamma-rays from
abnormally long-lived states were observed. e.g. 7.8 - 8.6 MeV alpha-particles
with gamma-rays of a superdeformed band, 5.1 - 5.5 MeV alpha-particles with X-
and gamma-rays of W, Re, and Pt, and 3.88 MeV particles (interpreted as
protons) with 185.8 keV gamma-rays. The data are interpreted in terms of the
production of long-lived (t(1/2) of several months) high spin isomeric states
in the second well of the potential in the parent nuclei, which decay to the
normal states in the daughters, and in the third well of the potential, which
decay to the second well. | nucl-ex |
J/$ψ$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV in STAR: In this paper, J/$\psi$ polarization at mid-rapidity in $p+p$ collisions at
$\sqrt{s}$ = 200 GeV measured in the STAR experiment at RHIC is reported.
J/$\psi$ production is analyzed via the dielectron decay channel. J/$\psi$
polarization is extracted from the decay angular distribution in the helicity
frame. The J/$\psi$ polarization is measured at transverse momentum range (2 -
6) GeV/c and is found to be consistent with $NLO^+$ Color Singlet Model
($NLO^+$ CSM), Color Octet Model (COM) predictions and with no polarization
within current uncertainties. | nucl-ex |
Masses of ground and isomeric states of $^{101}$In and
configuration-dependent shell evolution in odd-$A$ indium isotopes: We report first precision mass measurements of the $1/2^-$ isomeric and
$9/2^+$ ground states of $^{101}$In. The determined isomeric excitation energy
continues a smooth trend of odd-$A$ indium isotopes up to the immediate
vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell
model calculations only if the neutron configuration mixing is considered. We
find that the single particle energies are different for different states of
the same isotope. The presented configuration-dependent shell evolution, type
II shell evolution, in odd-$A$ nuclei is discussed for the first time. Our
results will facilitate future studies of single-particle neutron states. | nucl-ex |
Estimation of double differential angle-dependent neutron production
cross sections from tritons on 197Au at energies from 5.97 to 19.14 MeV: Estimated cross sections for neutron production from triton bombardment of
gold are deduced from measurements of triton interactions with gas targets that
used gold as a triton beam stop material. Differential cross sections for
production of neutrons from 5.97-, 7.47-, 10.45-, 16.41- and 19.14-MeV tritons
on 197Au were evaluated. Corrections for the neutron interaction in gold, in
the target structure and in the air of the flight path were obtained by means
of a Monte Carlo technique. Uncorrelated scale uncertainties range from 24 to
41% whereas those of double differential cross sections range from 0.2 to 5%.
Based on these cross section data, calculation of neutron yield at 0o from
fully stopped tritons at 20.22 MeV agree with an independent measurement.
Least-squares fits with a gamma distribution model indicate an anisotropy in
the high energy portion of the neutron spectra. Legendre polynomial fits of
differential cross sections are reported. All neutron cross section data are
made available through the Experimental Nuclear Reaction Data (EXFOR) library
at international data centers. | nucl-ex |
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