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Recent results and future prospects of kaonic nuclei at J-PARC: $\bar K$-nuclear bound systems, kaonic nuclei, have been widely discussed as
products of the strongly attractive $\bar K N$ interaction in $I = 0$ channels.
Recently, we demonstrated that kaonic nuclei can be produced via in-flight
$(K^-,N)$ reactions using the low-momentum DC kaon beam at the J-PARC E15
experiment. We observed the simplest kaonic nuclei, $K^-pp$, having a much
deeper binding energy than normal nuclei. For further studies, we have proposed
a series of experimental programs for the systematic investigation of light
kaonic nuclei, from $\bar K N$ ($\Lambda(1405)$) to $\bar K NNNN$. In the new
experiment approved as J-PARC E80, we will measure the $\bar K NNN$ ($A=3$)
system as a first step toward a comprehensive study. | nucl-ex |
Statistical Exploration of Fragmentation Phase Space Source Sizes in
Nuclear Multifragmentation: The multiplicity distributions for individual fragment Z values in nuclear
multifragmentation are binomial. The extracted maximum value of the
multiplicity is found to depend on Z according to m=Z_0/Z, where Z_0 is the
source size. This is shown to be a strong indication of statistical coverage of
fragmentation phase space. The inferred source sizes coincide with those
extracted from the analysis of fixed multiplicity charge distributions. | nucl-ex |
Chiral symmetry restoration at high matter density observed in pionic
atoms: Modern theories of physics tell that the vacuum is not an empty space. Hidden
in the vacuum is a structure of anti-quarks $\bar{q}$ and quarks $q$. The
$\bar{q}$ and $q$ pair has the same quantum number as the vacuum and
condensates in it since the strong interaction of the quantum chromodynamics
(QCD) is too strong to leave it empty. The $\bar{q}q$ condensation breaks the
chiral symmetry of the vacuum. The expectation value $<\bar{q}q>$ is an order
parameter. For higher temperature or higher matter-density, $|<\bar{q}q>|$
decreases reflecting the restoration of the symmetry. In contrast to these
clear-cut arguments, experimental evidence is so far limited. First of all, the
$\bar{q}q$ is nothing but the vacuum itself. It is neither visible nor
perceptible. In this article, we unravel this invisible existence by high
precision measurement of pionic atoms, $\pi^-$-meson-nucleus bound systems.
Using the $\pi^-$ as a probe, we demonstrate that $|<\bar{q}q>|$ is reduced in
the nucleus at 58% of the normal nuclear density by a factor of 77 $\pm$ 2%
compared with that in the vacuum. This reduction indicates that the chiral
symmetry is partially restored due to the extremely high density of the
nucleus. The present experimental result clearly exhibits the existence of the
hidden structure, the chiral condensate, in the vacuum. | nucl-ex |
Performance of the ALICE VZERO system: ALICE is an LHC experiment devoted to the study of strongly interacting
matter in proton-proton, proton--nucleus and nucleus-nucleus collisions at
ultra-relativistic energies. The ALICE VZERO system, made of two scintillator
arrays at asymmetric positions, one on each side of the interaction point,
plays a central role in ALICE. In addition to its core function as a trigger,
the VZERO system is used to monitor LHC beam conditions, to reject beam-induced
backgrounds and to measure basic physics quantities such as luminosity,
particle multiplicity, centrality and event plane direction in nucleus-nucleus
collisions. After describing the VZERO system, this publication presents its
performance over more than four years of operation at the LHC. | nucl-ex |
Superdeformation in Asymmetric N$>$Z Nucleus $^{40}$Ar: A rotational band with five $\gamma$-ray transitions ranging from 2$^{+}$ to
12$^{+}$ states was identified in $^{40}$Ar. This band is linked through
$\gamma$ transitions from the excited 2$^{+}$, 4$^{+}$ and 6$^{+}$ levels to
the low-lying states; this determines the excitation energy and the spin-parity
of the band. The deduced transition quadrupole moment of 1.45$^{+0.49}_{-0.31}
eb$ indicates that the band has a superdeformed shape. The nature of the band
is revealed by cranked Hartree--Fock--Bogoliubov calculations and a
multiparticle--multihole configuration is assigned to the band. | nucl-ex |
Reference cross section measurements with ALICE in pp and Pb-Pb
collisions at LHC: Cross sections of reference trigger processes were obtained based on beam
property measurements in dedicated luminosity calibration experiments (van der
Meer scans). These cross-sections are essential for absolute cross section
determinations of physics processes. The reference cross sections are presented
for pp collisions at two center of mass energies; 2.76 TeV and 7 TeV, and for
Pb-Pb collisions at 2.76 TeV together with a discussion of the systematic
uncertainty originating from beam intensity and rate measurement uncertainties. | nucl-ex |
K*(892)^0 production in p+p interactions at 158 GeV/c from NA61/SHINE: The measurement of $K^{*}(892)^0$ resonance production via its $K^{+}\pi^{-}$
decay mode in inelastic p+p collisions at beam momentum 158~GeV/c
($\sqrt{s_{NN}}=17.3$~GeV) is presented. The data were recorded by the
NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The first
ever double differential measurements and $p_T$-integrated spectra of
$K^{*}(892)^0$ at beam momenta of 158 GeV/c was done by using the
\textit{template} fitting method. The full phase-space yields, mass and width
of $K^{*}(892)^0$ mesons are compared with Hadron Resonance Gas models as well
as with world data on p+p and nucleus-nucleus collisions. | nucl-ex |
Discovery of the astatine, radon, francium, and radium isotopes: Currently, thirty-nine astatine, thirty-nine radon, thirty-five francium, and
thirty-four radium isotopes have so far been observed; the discovery of these
isotopes is discussed. For each isotope a brief summary of the first refereed
publication, including the production and identification method, is presented. | nucl-ex |
Measurements using a prototype array of plastic scintillator bars for
reactor based electron anti-neutrino detection: We report measurement of reactor based electron anti-neutrinos from a
prototype array of plastic scintillator bars ( mini-ISMRAN ) located inside
Dhruva research reactor hall, BARC. The detector setup took data for 128 days
for reactor on (RON) and 51 days for reactor off (ROFF) condition. A detailed
analysis procedure is developed to select the anti-neutrino candidate events
based on the energy deposition, number of bars hit as well as topological event
selection criteria in position and time. Each of these selection criteria are
compared with Monte Carlo based simulations and further an embedding technique
is used to estimate the efficiencies from a data driven background study. The
obtained anti-neutrino like events in RON condition are 218 $\pm$ 50 (stat)
$\pm$ 37 (sys) after background subtraction. The obtained results are compared
with theoretical estimation which yields 214 $\pm$ 32 (sys) anti-neutrino
events for the RON condition. | nucl-ex |
Basic characterization of highly enriched uranium by gamma spectrometry: Gamma-spectrometric methods suitable for the characterization of highly
enriched uranium samples encountered in illicit trafficking of nuclear
materials are presented. In particular, procedures for determining the 234U,
235U, 238U, 232U and 236U contents and the age of highly enriched uranium are
described. Consequently, the total uranium content and isotopic composition can
be calculated. For determining the 238U and 232U contents a low background
chamber was used. In addition, age dating of uranium was also performed using
low-background spectrometry. | nucl-ex |
PHENIX photons and dileptons: Electro-magnetic probes such as dileptons and photons are strong probes to
investigate the thermodynamical state of the early stages of collisions since
they leave the system unscathed. The PHENIX experiment has measured both
photons and dileptons in p+p, d+Au and Au+Au collisions. An excess of dilepton
yield over the expected hadronic contribution is seen in 0.2-0.8\,GeV/$c^2$ in
Au+Au collisions, which is prominent in lower $p_T$ and most central. Direct
photons are measured through their internal conversion to electron pairs. We
saw a large enhancement in Au+Au collisions over p+p yield scaled by the number
of binary collisions. It turned out from the latest results on d+Au collisions
that this enhancement is not explainable by a nuclear effect. | nucl-ex |
Direct observation of the dead-cone effect in QCD: In particle collider experiments, elementary particle interactions with large
momentum transfer produce quarks and gluons (known as partons) whose evolution
is governed by the strong force, as described by the theory of quantum
chromodynamics (QCD). These partons subsequently emit further partons in a
process that can be described as a parton shower which culminates in the
formation of detectable hadrons. Studying the pattern of the parton shower is
one of the key experimental tools for testing QCD. This pattern is expected to
depend on the mass of the initiating parton, through a phenomenon known as the
dead-cone effect, which predicts a suppression of the gluon spectrum emitted by
a heavy quark of mass $m_{\rm{Q}}$ and energy $E$, within a cone of angular
size $m_{\rm{Q}}$/$E$ around the emitter. Previously, a direct observation of
the dead-cone effect in QCD had not been possible, owing to the challenge of
reconstructing the cascading quarks and gluons from the experimentally
accessible hadrons. We report the direct observation of the QCD dead cone by
using new iterative declustering techniques to reconstruct the parton shower of
charm quarks. This result confirms a fundamental feature of QCD. Furthermore,
the measurement of a dead-cone angle constitutes a direct experimental
observation of the non-zero mass of the charm quark, which is a fundamental
constant in the standard model of particle physics. | nucl-ex |
Determination of Critical Exponents in Nuclear Systems: Signatures of critical behaviour in nuclear fragmentation are often based on
arguments from percolation theory. We demonstrate with general thermodynamic
considerations and studies of the Ising model that the reliance on percolation
as a reference model bears the risk of missing parts of the essential physics. | nucl-ex |
Latest results from the PHOBOS experiment: Over the past years PHOBOS has continued to analyze the large datasets
obtained from the first five runs of the Relativistic Heavy Ion Collider (RHIC)
at Brookhaven National Laboratory. The two main analysis streams have been
pursued. The first one aims to obtain a broad and systematic survey of global
properties of particle production in heavy ion collisions. The second class
includes the study of fluctuations and correlations in particle production.
Both type of studies have been performed for a variety of the collision
systems, covering a wide range in collision energy and centrality. The uniquely
large angular coverage of the PHOBOS detector and its ability to measure
charged particles down to very low transverse momentum is exploited. The latest
physics results from PHOBOS, as presented at Quark Matter 2008 Conference, are
contained in this report. | nucl-ex |
Comments on the "Reply to 'Comment on "Piezonuclear decay of thorium"
[Phys. Lett. A 373 (2009) 1956]' [Phys. Lett. A (2009, in press]" [Phys.
Lett. A (2009), in press] by F. Cardone et. al: In a recent article F. Cardone et al. [Phys. Lett. A 373 (2009) 1956] have
claimed that subjecting a solution of 228Th to cavitation leads to a
"transformation" of the thorium nuclei that is 104 times faster than the normal
nuclear decay for this isotope. We have criticized the evidence provided for
this claim in a "Comment" [Phys. Lett. A (2009), in press, DOI
10.1016/j.physleta.2009.08.045]. In their "Reply" [Phys. Lett. A (2009), in
press, DOI 10.1016/j.physleta.2009.08.047] Cardone et al. answer only some
minor points but avoid addressing the real issue. They even state a new
extraordinary claim, namely that the thorium "transformations" occur without
emission of gamma rays. In addition, the information provided in their Reply
displays a worrying lack of control of their experimental situation and the
data they put forward as evidence for their claims. We point out several
shortcomings and errors in the described experimental preparations, set-up and
reporting, as well as in the data analysis. We conclude that the evidence
presented by Cardone et al. is insufficient to justify their claims and that
the shortcomings of their work are so severe that the original paper and the
Reply should be withdrawn. | nucl-ex |
Transverse Single-Spin Asymmetry for Inclusive and Diffractive
Electromagnetic Jets at Forward Rapidity in $p^{\uparrow}$+p Collisions at
$\sqrt{s} = 200$ GeV and $510$ GeV at STAR: There have been numerous attempts, in the last decades, to understand the
origin of the unexpectedly large transverse single-spin asymmetry ($A_{N}$)
observed in inclusive hadron productions at forward rapidities in transversely
polarized $p^{\uparrow}$+$p$ collisions at different center-of-mass energies
($\sqrt{s}$). The current theoretical frameworks aimed at explaining this
puzzle include the twist-3 contributions in the collinear factorization
framework, as well as the transverse-momentum-dependent contributions from the
initial-state quark and gluon Sivers functions, and/or final-state Collins
fragmentation functions. Besides, there are indications that the diffractive
processes may contribute to the large $A_{N}$. We present the detailed
investigations into the $A_{N}$ for electromagnetic jets (EM-jets) produced in
inclusive processes using the Forward Meson Spectrometer with transversely
polarized $p^{\uparrow}$+ $p$ data at $\sqrt{s} =$ 200 GeV collected in 2015 at
STAR. We observe a negative value for the $A_{N}$ of EM-jets in diffractive
processes. This finding shows a different sign for $A_{N}$ in inclusive
processes and needs further theoretical input in order to be understood.
Finally, we present the statistical projections of the $A_{N}$ for inclusive
and diffractive EM-jets utilizing $p^{\uparrow}$+ $p$ data at $\sqrt{s} =$ 510
GeV collected in 2017 at STAR. This dataset allows for a substantial
enhancement in statistical precision. | nucl-ex |
Discovery of palladium, antimony, tellurium, iodine, and xenon isotopes: Currently, thirty-eight palladium, thirty-eight antimony, thirty-nine
tellurium, thirty-eight iodine, and forty xenon isotopes have been observed and
the discovery of these isotopes is discussed here. For each isotope a brief
synopsis of the first refereed publication, including the production and
identification method, is presented. | nucl-ex |
Accessing weak neutral-current coupling $g_{AA}^{eq}$ using positron and
electron beams at Jefferson Lab: Low-energy neutral-current couplings arising in the Standard Model of
electroweak interactions can be constrained in lepton scattering off hydrogen
or a nuclear fixed target. Recent polarized electron scattering experiments at
Jefferson Lab (JLab) have improved the precision in the parity-violating types
of effective couplings. On the other hand, the only known way to access the
parity-conserving counterparts is to compare scattering cross sections between
a lepton and an anti-lepton beam. We review the current knowledge of both types
of couplings and how to constrain them. We also present exploratory
calculations for a possible measurement of $g_{AA}^{eq}$ using the planned
SoLID spectrometer combined with a possible positron beam at JLab. | nucl-ex |
Photoproduction of low-$p_{\rm T}$ J/$ψ$ from peripheral to central
Pb$-$Pb collisions at 5.02 TeV: An excess of J/$\psi$ yield at very low transverse momentum ($p_{\rm T} <
0.3$ GeV/$c$), originating from coherent photoproduction, is observed in
peripheral and semicentral hadronic Pb$-$Pb collisions at a center-of-mass
energy per nucleon pair of $\sqrt{s_{\rm NN}} = 5.02$ TeV. The measurement is
performed with the ALICE detector via the dimuon decay channel at forward
rapidity ($2.5<y<4$). The nuclear modification factor at very low $p_{\rm T}$
and the coherent photoproduction cross section are measured as a function of
centrality down to the 10% most central collisions. These results extend the
previous study at $\sqrt{s_{\rm NN}} = 2.76$ TeV, confirming the clear excess
over hadronic production in the $p_{\rm T}$ range 0$-$0.3 GeV/$c$ and the
centrality range 70$-$90%, and establishing an excess with a significance
greater than 5$\sigma$ also in the 50$-$70% and 30$-$50% centrality ranges. The
results are compared with earlier measurements at $\sqrt{s_{\rm NN}} = 2.76$
TeV and with different theoretical predictions aiming at describing how
coherent photoproduction occurs in hadronic interactions with nuclear overlap. | nucl-ex |
Measurement of $γ$-ray production via the neutron-$^{16}$O reaction
using a 77 MeV quasi-monoenergetic neutron beam: Understanding of $\gamma$-ray production via neutron interactions on oxygen
is essential for the study of neutrino neutral-current quasielastic
interactions in water Cherenkov detectors. A measurement of $\gamma$-ray
production from such reactions was performed using a 77~MeV quasi-monoenergetic
neutron beam. Several $\gamma$-ray peaks, which are expected to come from
neutron-${\rm ^{16}O}$ reactions, are observed and production cross sections
are measured for nine $\gamma$-ray components of energies between 2 and 8~MeV.
These are the first measurements at this neutron energy using a nearly
monoenergetic beam. | nucl-ex |
Measurement of the production of charm jets tagged with D$^{0}$ mesons
in pp collisions at $\sqrt{s}$= 7 TeV: The production of charm jets in proton-proton collisions at a center-of-mass
energy of $\sqrt{s}=7$ TeV was measured with the ALICE detector at the CERN
Large Hadron Collider. The measurement is based on a data sample corresponding
to a total integrated luminosity of $6.23$ ${\rm nb}^{-1}$, collected using a
minimum-bias trigger. Charm jets are identified by the presence of a D$^0$
meson among their constituents. The D$^0$ mesons are reconstructed from their
hadronic decay D$^0\rightarrow$K$^{-}\pi^{+}$. The D$^0$-meson tagged jets are
reconstructed using tracks of charged particles (track-based jets) with the
anti-$k_{\mathrm{T}}$ algorithm in the jet transverse momentum range
$5<p_{\rm{T,jet}}^{\mathrm{ch}}<30$ ${\rm GeV/}c$ and pseudorapidity
$|\eta_{\rm jet}|<0.5$. The fraction of charged jets containing a D$^0$-meson
increases with $p_{\rm{T,jet}}^{\rm{ch}}$ from $0.042 \pm 0.004\,
\mathrm{(stat)} \pm 0.006\, \mathrm{(syst)}$ to $0.080 \pm 0.009\, \rm{(stat)}
\pm 0.008\, \rm{(syst)}$. The distribution of D$^0$-meson tagged jets as a
function of the jet momentum fraction carried by the D$^0$ meson in the
direction of the jet axis ($z_{||}^{\mathrm{ch}}$) is reported for two ranges
of jet transverse momenta, $5<p_{\rm{T,jet}}^{\rm{ch}}<15$ ${\rm GeV/}c$ and
$15<p_{\rm{T,jet}}^{\rm{ch}}<30$ ${\rm GeV/}c$ in the intervals
$0.2<z_{||}^{\rm{ch}}<1.0$ and $0.4<z_{||}^{\rm{ch}}<1.0$, respectively. The
data are compared with results from Monte Carlo event generators (PYTHIA 6,
PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum
Chromodynamics calculation, obtained with the POWHEG method and interfaced with
PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation
and underlying event. | nucl-ex |
In Beam Tests of Implanted Helium Targets: Targets consisting of 3,4He implanted into thin aluminum foils (approximately
100, 200 or 600 ug/cm^2) were prepared using intense (a few uA) helium beams at
low energy (approximately 20, 40 or 100 keV). Uniformity of the implantation
was achieved by a beam raster across a 12 mm diameter tantalum collimator at
the rates of 0.1 Hz in the vertical direction and 1 Hz in the horizontal
direction. Helium implantation into the very thin (approximately 80-100
ug/cm^2) aluminum foils failed to produce useful targets (with only
approximately 10% of the helium retained) due to an under estimation of the
range by the code SRIM. The range of low energy helium in aluminum predicted by
Northcliffe and Shilling and the NIST online tabulation are observed on the
other hand to over estimate the range of low energy helium ions in aluminum. An
attempt to increase the amount of helium by implanting a second deeper layer
was also carried out, but it did not significantly increase the helium content
beyond the blistering limit (approximately 6 x 10^17 helium/cm^2). The
implanted targets were bombarded with moderately intense 4He and 16O beams of
50-100 particle nA . Rutherford Back Scattering of 1.0 and 2.5 MeV proton beams
and recoil helium from 15.0 MeV oxygen beams were used to study the helium
content and profile before, during and after bombardments. We observed the
helium content and profile to be very stable even after a prolonged bombardment
(up to two days) with moderately intense beams of 16O or 4He. Helium implanted
into thin (aluminum) foils is a good choice for thin helium targets needed, for
example, for a measurement of the 3he(a,g)7Be reaction and the associated S34
astrophysical cross section factor (S-factor). | nucl-ex |
Low-lying Proton Intruder State in 13B: The neturon rich nucleus 13B was studied via the proton transfer reaction
4He(12Be,13B \gamma) at 50AMeV. The known 4.83-MeV excited state was strongly
populated and its spin and parity were assigned to 1/2+ by comparing the
angular differential cross section data with DWBA calculations. This low-lying
1/2+ state is interpreted as a proton intruder state and indicates a
deformation of the nucleus. | nucl-ex |
Nucleon charge exchange on the deuteron: A critical review: The existing experimental data on the d(n,p)nn and d(p,n)pp cross sections in
the forward direction are reviewed in terms of the Dean sum rule. It is shown
that the measurement of the ratio of the charge exchange on the deuteron to
that on the proton might, if taken together with other experimental data, allow
a direct construction of the np -> np scattering amplitude in the backward
direction with few ambiguities. | nucl-ex |
Isotopic distribution of fission fragments in collisions between 238U
beam and 9Be and 12C targets at 24 MeV/u: Inverse kinematics coupled to a high-resolution spectrometer is used to
investigate the isotopic yields of fission fragments produced in reactions
between a 238U beam at 24 MeV/u and 9Be and 12C targets. Mass, atomic number
and isotopic distributions are reported for the two reactions. These
informations give access to the neutron excess and the isotopic distribution
widths, which together with the atomic-number and mass distributions are used
to investigate the fusion-fission dynamics. | nucl-ex |
Recent results on femtoscopic correlations with the CMS experiment: The study of femtoscopic correlations in high-energy collisions is a powerful
tool to investigate the space-time structure of the particle emitting region
formed in such collisions, as well as to probe interactions that the involved
particles may undergo after being emitted. An overview of the recent results
from the CMS experiment at the LHC on the two-particle femtoscopic correlations
measurements using charged particles and identified hadrons in pp and PbPb
collisions is presented. In general, the femtoscopic parameters are obtained
assuming a Gaussian or an exponential shape to describe the emitting source
distribution. In some cases, however, the generalized Gaussian, i.e., the
symmetric alpha-stable L\'evy distribution, is favored to describe the source.
Some of the measurements allow to extract the parameters of the strong
interaction felt by hadrons using their femtoscopic correlations. The studies
are performed in a wide range of the pair average transverse momentum (or
average transverse mass) and charged particle multiplicities. In addition,
prospects for future physics results using the CMS experiment are also
discussed. | nucl-ex |
An improved method to access initial states in relativistic heavy-ion
collisions: Observables in heavy-ion collisions are generally categorized into
centralities, which reflect an average over events within a range of impact
parameter including a wide variety of initial state configurations. A multiple
binning method using spectator neutrons within each centrality has been
previously shown to provide access to events with rare initial state
conditions. This work suggests an improvement in quantifying the difference
between standard centrality and spectator neutron binning towards accessing the
initial state properties. A selection of events with higher initial state
density at fixed participating nucleon number was observed to result in larger
final state particle production and smaller elliptic flow. The relative
difference between observables in centrality and spectator binning shows
reduced sensitivity for the observables dominated by impact parameter
fluctuations in initial state such as triangular flow. This property makes the
spectator binning method a good candidate to separate geometric contributions
from random fluctuations in initial state towards final state observables. | nucl-ex |
Flow dominance and factorization of transverse momentum correlations in
Pb-Pb collisions at the LHC: We present the first measurement of the two-particle transverse momentum
differential correlation function, $P_2\equiv\langle \Delta p_{\rm T} \Delta
p_{\rm T} \rangle /\langle p_{\rm T} \rangle^2$, in Pb-Pb collisions at
$\sqrt{s_{_{\rm NN}}} =$ 2.76 TeV. Results for $P_2$ are reported as a function
of relative pseudorapidity ($\Delta \eta$) and azimuthal angle ($\Delta
\varphi$) between two particles for different collision centralities. The
$\Delta \phi$ dependence is found to be largely independent of $\Delta \eta$
for $|\Delta \eta| \geq$ 0.9. In 5% most central Pb-Pb collisions, the
two-particle transverse momentum correlation function exhibits a clear
double-hump structure around $\Delta \varphi = \pi$ (i.e., on the away side),
which is not observed in number correlations in the same centrality range, and
thus provides an indication of the dominance of triangular flow in this
collision centrality. Fourier decompositions of $P_2$, studied as a function of
collision centrality, show that correlations at $|\Delta \eta| \geq$ 0.9 can be
well reproduced by a flow ansatz based on the notion that measured momentum
correlations are strictly determined by the collective motion of the system. | nucl-ex |
Rescattering effects on resonances production in small systems with
ALICE at the LHC: Recent multiplicity-dependent analyses of pp and p--Pb collision data have
revealed that particle production shares similar features with that in
heavy-ion collisions. Studies using resonances could help to understand the
possible onset of collective-like phenomena and the presence of a hadronic
phase in small collision systems. Measurements of the differential yields of
resonances with different lifetime, mass, quark content, and quantum numbers
could enable understanding the mechanisms that influence the shape of particle
momentum spectra, lifetime of the hadronic phase, strangeness production,
parton energy loss, and collective effects. New ALICE results on various
hadronic resonances in small collision systems at Large Hadron Collider (LHC)
energies, including the multiplicity dependence measurements of $\Lambda$(1520)
and K$^*$(892)$^{\pm}$ and the production of $\phi$-meson pairs are presented
here. Results will be also compared with model calculations. | nucl-ex |
One-neutron knockout reaction of 17C on a hydrogen target at 70
MeV/nucleon: First experimental evidence of the population of the first 2- state in 16C
above the neutron threshold is obtained by neutron knockout from 17C on a
hydrogen target. The invariant mass method combined with in-beam gamma-ray
detection is used to locate the state at 5.45(1) MeV. Comparison of its
populating cross section and parallel momentum distribution with a Glauber
model calculation utilizing the shell-model spectroscopic factor confirms the
core-neutron removal nature of this state. Additionally, a previously known
unbound state at 6.11 MeV and a new state at 6.28(2) MeV are observed. The
position of the first 2- state, which belongs to a member of the lowest-lying
p-sd cross shell transition, is reasonably well described by the shell-model
calculation using the WBT interaction. | nucl-ex |
Beta decays in investigations and searches for rare effects: Current status of experimental investigations of rare single beta decays
(48Ca, 50V, 96Zr, 113Cd, 113mCd, 115In, 123Te, 180mTa, 222Rn) is reviewed.
Nuclei which decay through single beta decay very often constitute backgrounds
in studies of rare effects like double beta decay, solar neutrinos or dark
matter. Summary of correction factors used in description of forbidden beta
decays is also briefly given. | nucl-ex |
Multiplicity distribution and spectra of negatively charged hadrons in
Au+Au collisions at sqrt(s_nn) = 130 GeV: The minimum bias multiplicity distribution and the transverse momentum and
pseudorapidity distributions for central collisions have been measured for
negative hadrons (h-) in Au+Au interactions at sqrt(s_nn) = 130 GeV. The
multiplicity density at midrapidity for the 5% most central interactions is
dNh-/deta|_{eta = 0} = 280 +- 1(stat)+- 20(syst), an increase per participant
of 38% relative to ppbar collisions at the same energy. The mean transverse
momentum is 0.508 +- 0.012 GeV/c and is larger than in central Pb+Pb collisions
at lower energies. The scaling of the h- yield per participant is a strong
function of pt. The pseudorapidity distribution is almost constant within
|eta|<1. | nucl-ex |
Symmetry energy dependence of long timescale isospin transport: Isospin transport occurring within dinuclear projectile-like fragments (PLFs)
produced in heavy- ion collisions is explored as a probe of the nuclear
symmetry energy. Within the framework of the Constrained Molecular Dynamics
model (CoMD), the existence of the long-lived dinuclear PLFs, for up to 800
fm/c, is observed. It is demonstrated that changes in the <N/Z> of the two
fragments resulting from the breakup of the dinuclear PLF is due to isospin
transport. The rate of the transport between the two fragments is shown to be
dependent on the slope of the symmetry energy at saturation density. Comparison
of the CoMD calculations with experimental data establish that the evolution of
<N/Z> could be used to constrain the density dependence of the symmetry energy. | nucl-ex |
Methods for the Study of Particle Production Fluctuations: We discuss various measures of net charge (conserved quantities) fluctuations
proposed for the identification of critical phenomena in heavy ion collisions.
We show the dynamical component of fluctuations of the net charge can be
expressed simply in terms of integrals of two- and single-particle densities.
We discuss the dependence of the fluctuation observables on detector
acceptance, detection efficiency and colliding system size and collision
centrality. Finally, we present a toy model of particle production including
charge conservation and resonance production to gauge the effects of such
resonances and finite acceptance on the net charge fluctuations. | nucl-ex |
The pp -> pp pi pi pi reaction channels in the threshold region: The cross section for prompt neutral and charged three pion production in pp
interactions was measured at excess energies in the range 160 - 217 MeV. That
comprises the first measurement of the pp->pp pi0pi0pi0 reaction and the
comparison with the pp->pp pi+pi-pi0 reaction, in a very direct way. The
experiment was performed above the eta meson production threshold and the cross
section normalization was obtained from a concurrent measurement of the
reaction pp->pp eta with the eta decaying into 3 pions. Since the same final
states are selected, the measurement has a low systematical error. The measured
cross section ratio sigma(pp->pp pi+pi-pi0)/sigma(pp->pp pi0\pi0\pi0) is
compared to predictions of dominance of different isobars in the intermediate
state. | nucl-ex |
$J/ψ$ production in PHENIX: Heavy quarkonia production is expected to be sensitive to the formation of a
quark gluon plasma (QGP). The PHENIX experiment has measured $J/\psi$
production at $\sqrt{s_{NN}}=$~200 GeV in Au+Au and Cu+Cu collisions, as well
as in reference p+p and d+Au runs. $J/\psi$'s were measured both at mid
($|y|<0.35$) and forward ($1.2<|y|<2.2$) rapidity. In this letter, we present
the A+A preliminary results and compare them to normal cold nuclear matter
expectations derived from PHENIX d+Au and p+p measurements as well as to
theoretical models including various effects (color screening, recombination,
sequential melting...). | nucl-ex |
The Halo of 14Be: The two-neutron halo nucleus 14Be has been investigated in a kinematically
complete measurement of the fragments (12Be and neutrons) produced in
dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal
cross-sections, neutron angular distributions and invariant mass spectra
characteristic of a halo were observed and the electromagnetic (EMD)
contributions deduced. Comparison with three-body model predictions indicate
that the halo wavefunction contains a large 2s1/2^2 admixture. The EMD
invariant mass spectrum exhibited a relatively narrow structure near threshold
(Edecay=1.8+/-0.1 MeV, Gamma = 0.8+/-0.4 MeV) consistent with a soft-dipole
excitation. | nucl-ex |
Determination of gamma-ray widths in $^{15}$N using nuclear resonance
fluorescence: The stable nucleus $^{15}$N is the mirror of $^{15}$O, the bottleneck in the
hydrogen burning CNO cycle. Most of the $^{15}$N level widths below the proton
emission threshold are known from just one nuclear resonance fluorescence (NRF)
measurement, with limited precision in some cases. A recent experiment with the
AGATA demonstrator array determined level lifetimes using the Doppler Shift
Attenuation Method (DSAM) in $^{15}$O. As a reference and for testing the
method, level lifetimes in $^{15}$N have also been determined in the same
experiment. The latest compilation of $^{15}$N level properties dates back to
1991. The limited precision in some cases in the compilation calls for a new
measurement in order to enable a comparison to the AGATA demonstrator data. The
widths of several $^{15}$N levels have been studied with the NRF method. The
solid nitrogen compounds enriched in $^{15}$N have been irradiated with
bremsstrahlung. The $\gamma$-rays following the deexcitation of the excited
nuclear levels were detected with four HPGe detectors. Integrated
photon-scattering cross sections of ten levels below the proton emission
threshold have been measured. Partial gamma-ray widths of ground-state
transitions were deduced and compared to the literature. The photon scattering
cross sections of two levels above the proton emission threshold, but still
below other particle emission energies have also been measured, and proton
resonance strengths and proton widths were deduced. Gamma and proton widths
consistent with the literature values were obtained, but with greatly improved
precision. | nucl-ex |
Energy loss for heavy quarks in relation to light partons; is radiative
energy loss for heavy quarks anomalous?: The scaling properties of jet suppression measurements are compared for
non-photonic electrons ($e^{\pm}$) and neutral pions ($\pi^0$) in Au + Au
collisions at $\sqrt{s_{NN}}=200$ GeV. For a broad range of transverse momenta
and collision centralities, the comparison is consistent with jet quenching
dominated by radiative energy loss for both heavy and light partons. Less
quenching is indicated for heavy quarks via $e^{\pm}$; this gives an
independent estimate of the transport coefficient $\hat{q}$ that agrees with
its magnitude obtained from quenching of light partons via $\pi^0$'s. | nucl-ex |
Electromagnetic M1 transition strengths from inelastic proton
scattering: The cases of 48Ca and 208Pb: Inelastic proton scattering at energies of a few hundred MeV and extreme
forward angles selectively excites the isovector spin-flip M1 (IVSM1)
resonance. A method based on isospin symmetry is presented to extract its
electromagnetic transition strength from the (p,p') cross sections. It is
applied to 48Ca, a key case for an interpretation of the quenching phenomenon
of the spin-isospin response, and leads to a M1 strength consistent with an
older (e,e') experiment excluding the almost two times larger value from a
recent (\gamma,n) experiment. Good agreement with electromagnetic probes is
observed in 208Pb suggesting the possibility to extract systematic information
on the IVSM1 resonance in heavy nuclei. | nucl-ex |
High-spin states in and around doubly-magic nuclei: The study of high-spin states in regions of doubly-magic nuclei performed
with the use of deep-inelastic heavy ion reactions is reviewed. New and
tentative results concerning high-spin states in the 48Ca and yrast structures
in 47Ca, 47K, 49Ca and 49Sc isotopes are presented. The status of the high-spin
state study in the region of 132Sn and 208Pb is outlined, including discussion
of recently obtained results in the 208Pb core and the 206Hg two-proton-hole
nucleus. | nucl-ex |
Search for $^{22}$Na in novae supported by a novel method for measuring
femtosecond nuclear lifetimes: Classical novae are thermonuclear explosions in stellar binary systems, and
important sources of $^{26}$Al and $^{22}$Na. While gamma rays from the decay
of the former radioisotope have been observed throughout the Galaxy, $^{22}$Na
remains untraceable. The half-life of $^{22}$Na (2.6 yr) would allow the
observation of its 1.275 MeV gamma-ray line from a cosmic source. However, the
prediction of such an observation requires good knowledge of the nuclear
reactions involved in the production and destruction of this nucleus. The
$^{22}$Na($p,\gamma$)$^{23}$Mg reaction remains the only source of large
uncertainty about the amount of $^{22}$Na ejected. Its rate is dominated by a
single resonance on the short-lived state at 7785.0(7) keV in $^{23}$Mg. In the
present work, a combined analysis of particle-particle correlations and
velocity-difference profiles is proposed to measure femtosecond nuclear
lifetimes. The application of this novel method to the study of the $^{23}$Mg
states, combining magnetic and highly-segmented tracking gamma-ray
spectrometers, places strong limits on the amount of $^{22}$Na produced in
novae, explains its non-observation to date in gamma rays (flux < 2.5x$10^{-4}$
ph/(cm$^2$s)), and constrains its detectability with future space-borne
observatories. | nucl-ex |
Charge-changing cross sections for $^{42\textrm{--}51}$Ca and effect of
charged-particle evaporation induced by neutron removal reaction: Charge-changing cross sections $\sigma_\mathrm{CC}$ for
$^{42\textrm{--}51}$Ca on a carbon target at around 280~MeV/nucleon have been
measured. The measured $\sigma_\mathrm{CC}$ values differ significantly from
the previously developed calculations based on the Glauber model. However,
through introduction of the charged-particle evaporation effect induced by the
neutron-removal reaction in addition to the Glauber-model calculation,
experimental $\sigma_\mathrm{CC}$ values on $^{12}$C at around 300~MeV/nucleon
for nuclides from C to Fe isotopes are all reproduced with approximately 1\%
accuracy. This proposed model systematically reproduces $\sigma_\mathrm{CC}$
data without phenomenological corrections, and can also explain experimental
$\sigma_\mathrm{CC}$ values obtained in other energy regions. | nucl-ex |
Study of Two-Photon Exchange via the Beam Transverse Single Spin
Asymmetry in Electron-Proton Elastic Scattering at Forward Angles over a Wide
Energy Range: We report on a new measurement of the beam transverse single spin asymmetry
in electron-proton elastic scattering, $A^{ep}_{\perp}$, at five beam energies
from 315.1 MeV to 1508.4 MeV and at a scattering angle of $30^{\circ} < \theta
< 40^{\circ}$. The covered $Q^2$ values are 0.032, 0.057, 0.082, 0.218, 0.613
(GeV/c)$^2$. The measurement clearly indicates significant inelastic
contributions to the two-photon-exchange (TPE) amplitude in the low-$Q^2$
kinematic region. No theoretical calculation is able to reproduce our result.
Comparison with a calculation based on unitarity, which only takes into account
elastic and $\mathrm{\pi N}$ inelastic intermediate states, suggests that there
are other inelastic intermediate states such as $\mathrm{\pi \pi N}$,
$\mathrm{K \Lambda}$ and $\mathrm{\eta N}$. Covering a wide energy range, our
new high-precision data provide a benchmark to study those intermediate states. | nucl-ex |
Open heavy-flavour measurements in pp and Pb-Pb collisions with ALICE at
the LHC: We present an overview of measurements related to open heavy-flavour
production with the ALICE experiment at the LHC. Studies are performed using
single leptons (electrons at mid-rapidity and muons at forward-rapidity) and D
mesons, which are reconstructed via their hadronic decay channels. The measured
differential production cross sections in proton-proton collisions at
$\sqrt{s}$ = 2.76 and 7 TeV are in agreement with perturbative QCD
calculations. Results from Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV on
the nuclear modification factor $R_{AA}$ are shown, along with the elliptic
flow $\nu_2$. | nucl-ex |
Production and electromagnetic decay of hyperons: a feasibility study
with HADES as a Phase-0 experiment at FAIR: A feasibility study has been performed in order to investigate the
performance of the HADES detector to measure the electromagnetic decays of the
hyperon resonances $\Sigma(1385)^0$, $\Lambda(1405)$ and
$\Lambda{\Lambda}(1520)$ as well as the production of double strange baryon
systems $\Xi^-$ and $\Lambda\Lambda$ in p+p reactions at a beam kinetic energy
of 4.5 GeV. The existing HADES detector will be upgraded by a new Forward
Detector, which extends the detector acceptance into a range of polar angles
that plays a crucial role for these investigations. The analysis of each
channel is preceded by a consideration of the production cross-sections.
Afterwards the expected signal count rates using a target consisting of either
liquid hydrogen or polyethylene are summarized. | nucl-ex |
Heavy Flavour measurements in Pb$-$Pb collisions with the upgraded ALICE
Inner Tracking System: During the second LHC long shutdown (LS2) the Inner Tracking System (ITS) of
ALICE (A Large Ion Collider Experiment) will be replaced by seven layers of
CMOS Monolithic Active Pixel Sensors (MAPS). The latest innovations in silicon
imaging technology allow for the construction of large, ultra-thin silicon
wafers which can further improve the capabilities of the ALICE tracker. The
research and development studies towards the construction of a novel vertex
detector have started. The detector installation has been proposed for the
third LHC long shutdown (LS3) during which the three innermost layers shall be
replaced by three cylindrical layers of large curved CMOS wafers. This upgrade
(ITS3) will further improve the impact parameter resolution and the tracking
efficiency of low momentum particles. The innermost layer will be positioned
closer to the interaction point and the material budget will be reduced down to
0.05$\%X_0$ per layer. Monte Carlo simulations of a simplified ITS3 geometry
within the ITS2 design indicate an improvement in the impact parameter
resolution and the tracking efficiency, which are of crucial importance for
measurements of heavy-flavour hadrons. This contribution shows the improved
performance for the example of the $\Lambda_{\mathrm{b}}$, for which the
significance of its measurement is extracted based on these MC simulations. A
significant improvement by almost a factor of three in the low momentum region
compared to the ITS2 is observed. | nucl-ex |
Recent Findings from Heavy-Flavor Angular Correlation Measurements in
Hadronic Collisions: The study of angular correlations of heavy-flavor particles in hadronic
collisions can provide crucial insight into the heavy quark production,
showering, and hadronization processes. The comparison with model predictions
allows us to discriminate among different approaches for heavy quark production
and hadronization, as well as different treatments of the underlying event
employed by the models to reproduce correlation observables. In
ultra-relativistic heavy-ion collisions, where a deconfined state of matter,
the quark--gluon plasma (QGP), is created, heavy-flavor correlations can shed
light on the modification of the heavy quark fragmentation due to the
interaction between charm and beauty quarks with the QGP constituents, as well
as characterize their energy loss processes while traversing the medium.
Insight into the possible emergence of collective-like mechanisms in smaller
systems, resembling those observed in heavy-ion collisions, can also be
obtained by performing correlation studies in high-multiplicity proton--proton
and proton--nucleus collisions. In this review, the most recent and relevant
measurements of heavy-flavor correlations performed in all collision systems at
the LHC and RHIC will be presented, and the new understandings that they
provide will be discussed. | nucl-ex |
New experimental limits on the alpha decays of lead isotopes: For the first time a PbWO4 crystal was grown using ancient Roman lead and it
was run as a cryogenic detector. Thanks to the simultaneous and independent
read-out of heat and scintillation light, the detector was able to discriminate
beta/gamma interactions with respect to alpha particles down to low energies.
New more stringent limits on the alpha decays of the lead isotopes are
presented. In particular a limit of T_{1/2} > 1.4*10^20 y at a 90% C.L. was
evaluated for the alpha decay of 204Pb to 200Hg. | nucl-ex |
The reactor antineutrino spectrum calculation: New fissile isotopes antineutrino spectra ($^{235}$U, $^{238}$U, $^{239}$Pu
and $^{241}$Pu) calculation is presented. On base of summation method the toy
model was developed. It was shown that total antineutrino number is conserved
in framework of given database on individual fragments yields. The analysis of
antineutrino spectrum shape says that any presented antineutrino spectrum
should satisfy to the total antineutrino number conservation. | nucl-ex |
a0+(980)-resonance production in the reaction pp -> dpi+eta close to the
K(bar(K)) threshold: The reaction pp -> dpi+eta has been measured at a beam energy of T=2.65 GeV
(p=3.46 GeV/c) using the ANKE spectrometer at COSY-Juelich. The missing mass
distribution of the detected dpi+ pairs exhibits a peak around the eta mass on
top of a strong background of multi-pion pp -> dpi+(n(pi)) events. The
differential cross section d^4(sigma)/d(Omega_d)d(Omega_pi+)d(p_d)d(p_pi+) for
the reaction pp -> dpi+eta has been determined model independently for two
regions of phase space. Employing a dynamical model for the a0+ production
allows one then to deduce a total cross section of sigma(pp -> da0+ ->
dpi+eta)=(1.1 +/- 0.3_(stat) +/- 0.7_(syst)) microbarn for the production of
pi+eta via the scalar a0+(980) resonance and sigma(pp -> dpi+eta) = (3.5 +/-
0.3_(stat) +/- 1.0_(syst)) microbarn for the non-resonant production. Using the
same model as for the interpretation of recent results from ANKE for the
reaction pp -> dK+(bar(K0)), the ratio of the total cross sections is sigma(pp
-> d(K+(bar(K0)))_(L=0))/sigma(pp -> da0+ -> dpi+eta) = 0.029 +/- 0.008_(stat)
+/- 0.009_(syst), which is in agreement with branching ratios in the
literature. | nucl-ex |
Signals of a Critical Behavior in Peripheral Au + Au Collisions at 35
MeV/nucleon: Multifragment events resulting from peripheral Au + Au collisions at 35
MeV/nucleon are analysed in terms of critical behavior. The analysis of most of
criticality signals proposed so far (conditional moments of charge
distributions, Campi scatter plot, fluctuations of the size of the largest
fragment, intermittency analysis) is consistent with the occurrence of a
critical behavior of the system. | nucl-ex |
Identified high-$p_{T}$ spectra in Cu+Cu collisions at
$\sqrt{s_{NN}}$=200 GeV: We report new results on identified (anti)proton and charged pion spectra at
large transverse momenta (3<$p_{T}$<10 GeV/c) from Cu+Cu collisions at
$\sqrt{s_{NN}}$=200 GeV using the STAR detector at the Relativistic Heavy Ion
Collider (RHIC). This study explores the system size dependence of two novel
features observed at RHIC with heavy ions: the hadron suppression at
high-$p_{T}$ and the anomalous baryon to meson enhancement at intermediate
transverse momenta. Both phenomena could be attributed to the creation of a new
form of QCD matter. The results presented here bridge the system size gap
between the available pp and Au+Au data, and allow the detailed exploration for
the on-set of the novel features. Comparative analysis of all available 200 GeV
data indicates that the system size is a major factor determining both the
magnitude of the hadron spectra suppression at large transverse momenta and the
relative baryon to meson enhancement. | nucl-ex |
Measurements of Nuclear Level Densities and Gamma-Ray Strength Functions
and their Interpretations: A method to extract primary $\gamma$-ray spectra from particle-$\gamma$
coincidences at excitation energies up to the neutron binding energy is
described. From these spectra, the level density and $\gamma$-ray strength
function can be determined. From the level density, several thermodynamical
quantities are obtained within the microcanonical and canonical ensemble. Also
models for the $\gamma$-ray strength function are discussed. | nucl-ex |
First measurement of $^{30}$S+$α$ resonant elastic scattering for
the $^{30}$S($α$,p) reaction rate: Background: Type I x-ray bursts are the most frequent thermonuclear
explosions in the galaxy, resulting from thermonuclear runaway on the surface
of an accreting neutron star. The $^{30}$S($\alpha$,p) reaction plays a
critical role in burst models, yet insufficient experimental information is
available to calculate a reliable, precise rate for this reaction. Purpose: Our
measurement was conducted to search for states in $^{34}$Ar and determine their
quantum properties. In particular, natural-parity states with large
$\alpha$-decay partial widths should dominate the stellar reaction rate.
Method: We performed the first measurement of $^{30}$S+$\alpha$ resonant
elastic scattering up to a center-of-mass energy of 5.5 MeV using a radioactive
ion beam. The experiment utilized a thick gaseous active target system and
silicon detector array in inverse kinematics. Results: We obtained an
excitation function for $^{30}$S($\alpha$,$\alpha$) near $150^{\circ}$ in the
center-of-mass frame. The experimental data were analyzed with an $R$-Matrix
calculation, and we observed three new resonant patterns between 11.1 and 12.1
MeV, extracting their properties of resonance energy, widths, spin, and parity.
Conclusions: We calculated the resonant thermonuclear reaction rate of
$^{30}$S($\alpha$,p) based on all available experimental data of $^{34}$Ar and
found an upper limit about one order of magnitude larger than a rate determined
using a statistical model. The astrophysical impact of these two rates has been
investigated through one-zone postprocessing type I x-ray burst calculations.
We find that our new upper limit for the $^{30}$S($\alpha$,p)$^{33}$Cl rate
significantly affects the predicted nuclear energy generation rate during the
burst. | nucl-ex |
PHENIX results on Bose-Einstein correlation functions: Measurement of Bose-Einstein or HBT correlations of identified charged
particles provide insight into the space-time structure of particle emitting
sources in heavy-ion collisions. In this paper we present the latest results
from the RHIC PHENIX experiment on such measurements. | nucl-ex |
Light (anti)nuclei production in Pb-Pb collisions at
$\sqrt{s_{\mathrm{NN}}}=5.02$ TeV: The measurement of the production of deuterons, tritons and $^{3}\mathrm{He}$
and their antiparticles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$
TeV is presented in this article. The measurements are carried out at
midrapidity ($|y| < $ 0.5) as a function of collision centrality using the
ALICE detector. The $p_{\rm T}$-integrated yields, the coalescence parameters
and the ratios to protons and antiprotons are reported and compared with
nucleosynthesis models. The comparison of these results in different collision
systems at different centre-of-mass collision energies reveals a suppression of
nucleus production in small systems. In the Statistical Hadronisation Model
framework, this can be explained by a small correlation volume where the baryon
number is conserved, as already shown in previous fluctuation analyses.
However, a different size of the correlation volume is required to describe the
proton yields in the same data sets. The coalescence model can describe this
suppression by the fact that the wave functions of the nuclei are large and the
fireball size starts to become comparable and even much smaller than the actual
nucleus at low multiplicities. | nucl-ex |
Excited Baryon Structure Using Exclusive Reactions with CLAS12: Studying excited nucleon structure through exclusive electroproduction
reactions is an important avenue for exploring the nature of the
non-perturbative strong interaction. Electrocouplings for $N^*$ states in the
mass range below 1.8~GeV have been determined from analyses of CLAS $\pi N$,
$\eta N$, and $\pi \pi N$ data. This work made it clear that consistency of
independent analyses of exclusive channels with different couplings and
non-resonant backgrounds but the same $N^*$ electro-excitation amplitudes, is
essential to have confidence in the extracted results. In terms of hadronic
coupling, many high-lying $N^*$ states preferentially decay through the $\pi
\pi N$ channel instead of $\pi N$. Data from the $KY$ channels will therefore
be critical to provide an independent analysis to compare the extracted
electrocouplings for the high-lying $N^*$ states against those determined from
the $\pi N$ and $\pi \pi N$ channels. A program to study excited $N^*$ decays
to non-strange and strange exclusive final states using CLAS12 will measure
differential cross sections to be used as input to extract the $\gamma_vNN^*$
transition form factors for the most prominent $N^*$ states in the range of
invariant energy $W$ up 3~GeV in the virtually unexplored domain of momentum
transfers $Q^2$ up to 12~GeV$^2$. | nucl-ex |
Azimuthal anisotropy in U+U collisions at STAR: The azimuthal anisotropy of particle production is commonly used in
high-energy nuclear collisions to study the early evolution of the expanding
system. The prolate shape of uranium nuclei makes it possible to study how the
geometry of the colliding nuclei affects final state anisotropies. It also
provides a unique opportunity to understand how entropy is produced in heavy
ion collisions. In this paper, the two- and four- particle cumulant $v_2$
($v_{2}\{2\}$ and $v_{2}\{4\}$) from U+U collisions at $\sqrt{s_{NN}}$ = 193
GeV and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV for inclusive charged
hadrons will be presented. The STAR Zero Degree Calorimeters are used to select
very central collisions. Differences were observed between the multiplicity
dependence of $v_{2}\{2\}$ for most central Au+Au and U+U collisions. The
multiplicity dependence of $v_{2}\{2\}$ in central collisions were compared to
Monte Carlo Glauber model predictions and it was seen that this model cannot
explain the present results. | nucl-ex |
Multiplicity and transverse momentum dependence of charge-balance
functions in pPb and PbPb collisions at LHC energies: Measurements of the charge-dependent two-particle angular correlation
function in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass
energy of $\sqrt{s_\mathrm{NN}}$ = 8.16 TeV and lead-lead (PbPb) collisions
at$\sqrt{s_\mathrm{NN}}$ = 5.02 TeV are reported. The pPb and PbPb datasets
correspond to integrated luminosities of 186\nbinv and 0.607 nb$^{-1}$,
respectively, and were collected using the CMS detector at the CERN LHC. The
charge-dependent correlations are characterized by balance functions of same-
and opposite-sign particle pairs. The balance functions, which contain
information about the creation time of charged particle pairs and the
development of collectivity, are studied as functions of relative
pseudorapidity ($\Delta \eta$) and relative azimuthal angle ($\Delta \phi$),
for various multiplicity and transverse momentum ($p_\mathrm{T}$) intervals. A
multiplicity dependence of the balance function is observed in $\Delta \eta$
and $\Delta \phi$ for both systems. The width of the balance functions
decreases towards high-multiplicity collisions in the momentum region $\lt$2
GeV, for pPb and PbPb results. No multiplicity dependence is observed at higher
transverse momentum. The data are compared with HYDJET, HIJING and AMPT
generator predictions, none of which capture completely the multiplicity
dependence seen in the data. | nucl-ex |
Decomposition of flow and nonflow in relativistic heavy-ion collisions: We propose a method to separate \Delta\eta-dependent and
\Delta\eta-independent azimuthal correlations using two- and four-particle
cumulants between pseudo-rapidity (\eta) bins in symmetric heavy-ion
collisions. The \Delta\eta-independent correlation may be dominated by harmonic
flows, a global correlation to the common collision geometry. The
\Delta\eta-dependent correlation can be identified as nonflow, particle
correlations unrelated to the common geometry. Our method exploits the \eta
symmetry of the average harmonic flows and is "data-driven." We use the AMPT
and HIJING event generators to illustrate our method. We discuss the decomposed
\Delta\eta-independent and \Delta\eta-dependent correlations regarding flow and
nonflow in the models. | nucl-ex |
Formation of the intermediate baryon systems in hadron-nuclear and
nuclear-nuclear interactions: The centrality experiments indicate regime change and saturation in the
behavior of some characteristics of the secondary particles emitted in
hadron-nuclear and nuclear-nuclear interactions at high energies. The
phenomenon has a critical character. The simple models do not explain the
effect. We suppose that the responsible mechanism to explain the phenomenon
could be the formation and decay of the intermediate baryon systems. Such
systems could be formed as a result of nucleon percolation in compressed
baryonic matter. Formation of big percolation cluster may change the properties
of the medium, e.g., it could lead to the changing its transparency. This could
be used to get a signal of the intermediate baryonic system formation. We
consider two signals to identify the formation of the intermediate baryon
systems: the critical changing of transparency of the strongly interacting
matter and the enhancement of light nuclei production with increase in
centrality. | nucl-ex |
Probing small Bjorken-$x$ nuclear gluonic structure via coherent
J/$ψ$ photoproduction in ultraperipheral PbPb collisions at
$\sqrt{s_\mathrm{NN}}$ = 5.02 TeV: Quasireal photons exchanged in relativistic heavy ion interactions are
powerful probes of the gluonic structure of nuclei. The coherent J/$\psi$
photoproduction cross section in ultraperipheral lead-lead collisions is
measured as a function of photon-nucleus center-of-mass energies per nucleon
(W$^\text{Pb}_{\gamma\text{N}}$), over a wide range of 40 $\lt$
W$^\text{Pb}_{\gamma\text{N}}$ $\lt$ 400 GeV. Results are obtained using data
at the nucleon-nucleon center-of-mass energy of 5.02 TeV collected by the CMS
experiment at the CERN LHC, corresponding to an integrated luminosity of 1.52
nb$^{-1}$. The cross section is observed to rise rapidly at low
W$^\text{Pb}_{\gamma\text{N}}$, and plateau above
W$^\text{Pb}_{\gamma\text{N}}$ $\approx$ 40 GeV, up to 400 GeV, a new regime of
small Bjorken-$x$ ($\approx$ 6 $\times$ 10$^{-5}$) gluons being probed in a
heavy nucleus. The observed energy dependence is not predicted by current
quantum chromodynamic models. | nucl-ex |
Azimuthal anisotropy of neutral pion production in Au+Au collisions at
sqrt(s_NN) = 200 GeV: Path-length dependence of jet quenching and the role of
initial geometry: We have measured the azimuthal anisotropy of pi0's for 1 < pT < 18 GeV/c for
Au+Au collisions at sqrt s_NN = 200 GeV. The observed anisotropy shows a
gradual decrease in 3 < pT < 7 - 10 GeV/c, but remains positive beyond 10
GeV/c. The magnitude of this anisotropy is under-predicted, up to at least 10
GeV/c, by current perturbative QCD (pQCD) energy-loss model calculations. An
estimate of the increase in anisotropy expected from initial-geometry
modification due to gluon saturation effects and initial-geometry fluctuations
is insufficient to account for this discrepancy. Calculations which implement a
path length dependence steeper than what is implied by current pQCD energy-loss
models, show reasonable agreement with the data. | nucl-ex |
J/Psi Elliptic Flow in Pb-Pb Collisions at $\sqrt{s_{\rm NN}}$ = 2.76
TeV: We report on the first measurement of inclusive J/$\psi$ elliptic flow,
$v_2$, in heavy-ion collisions at the LHC. The measurement is performed with
the ALICE detector in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV in the
rapidity range $2.5 < y < 4.0$. The dependence of the J/$\psi$ $v_2$ on the
collision centrality and on the J/$\psi$ transverse momentum is studied in the
range $0 < p_{\rm T} < 10$ GeV/$c$. For semi-central Pb-Pb collisions at
$\sqrt{s_{\rm NN}} = 2.76$ TeV, an indication of non-zero $v_2$ is observed
with a maximum value of $v_2 = 0.116 \pm 0.046 {\rm (stat.)} \pm 0.029 {\rm
(syst.)}$ for J/$\psi$ in the transverse momentum range $2 < p_{\rm T} < 4$
GeV/$c$. The elliptic flow measurement complements the previously reported
ALICE results on the inclusive J/$\psi$ nuclear modification factor and favors
the scenario of a significant fraction of J/$\psi$ production from charm quarks
in a deconfined partonic phase. | nucl-ex |
SuperNEMO double beta decay experiment: SuperNEMO is a next-generation double beta decay experiment based on the
successful tracking plus calorimetry design approach of the recently stopped
NEMO3 experiment. SuperNEMO can study a range of isotopes, but the baseline
isotope is $^{82}$Se. The total isotope mass will be 100--200 kg. A sensitivity
to a $0\nu\beta\beta$ half-life greater than $10^{26}$ years can be reached
which gives access to Majorana neutrino masses of 50--100 meV. Having
successfully completed R&D stage the SuperNEMO Collaboration has commenced the
construction of the first module, the Demonstrator. The present status of
SuperNEMO program and plan for the nearest future are discussed. | nucl-ex |
Elastic proton-deuteron scattering at intermediate energies: Observables in elastic proton-deuteron scattering are sensitive probes of the
nucleon-nucleon interaction and three-nucleon force effects. The present
experimental data base for this reaction is large, but contains a large
discrepancy between data sets for the differential cross section taken at 135
MeV/nucleon by two experimental research groups. This paper reviews the
background of this problem and presents new data taken at KVI. Differential
cross sections and analyzing powers for the $^{2}{\rm H}(\vec p,d){p}$ and
${\rm H}(\vec d,d){p}$ reactions at 135 MeV/nucleon and 65 MeV/nucleon,
respectively, have been measured. The data differ significantly from previous
measurements and consistently follow the energy dependence as expected from an
interpolation of published data taken over a large range at intermediate
energies. | nucl-ex |
A new event generator for the elastic scattering of charged leptons on
protons: This paper describes a new multipurpose event generator, ESEPP, which has
been developed for the Monte Carlo simulation of unpolarized elastic scattering
of charged leptons on protons. The generator takes into account the
lowest-order QED radiative corrections to the Rosenbluth cross section
including first-order bremsstrahlung without using the soft-photon or
ultrarelativistic approximations. ESEPP can be useful for several significant
ongoing and planned experiments. | nucl-ex |
Measuring K$^0_{\rm S}$K$^{\rm \pm}$ interactions using Pb-Pb collisions
at ${\sqrt{s_{\rm NN}}=2.76}$ TeV: We present the first ever measurements of femtoscopic correlations between
the K$^0_{\rm S}$ and K$^{\rm \pm}$ particles. The analysis was performed on
the data from Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV measured by the
ALICE experiment. The observed femtoscopic correlations are consistent with
final-state interactions proceeding via the $a_0(980)$ resonance. The extracted
kaon source radius and correlation strength parameters for K$^0_{\rm S}$K$^{\rm
-}$ are found to be equal within the experimental uncertainties to those for
K$^0_{\rm S}$K$^{\rm +}$. Comparing the results of the present study with those
from published identical-kaon femtoscopic studies by ALICE, mass and coupling
parameters for the $a_0$ resonance are constrained. Our results are also
compatible with the interpretation of the $a_0$ having a tetraquark structure
over that of a diquark. | nucl-ex |
$^{179}$Ta(n,$γ$) cross-section measurement and the astrophysical
origin of $^{180}$Ta isotope: Tantalum-180m is nature's rarest (quasi) stable isotope and its astrophysical
origin is an open question. A possible production site of this isotope is the
slow neutron capture process in Asymptotic Giant Branch stars, where it can be
produced via neutron capture reactions on unstable $^{179}$Ta. We report a new
measurement of the $^{179}$Ta($n,\gamma$)$^{180}$Ta cross section at thermal
neutron energies via the activation technique. Our results for the thermal and
resonance-integral cross-sections are 952 $\pm$ 57 b and 2013 $\pm$ 148 b,
respectively. The thermal cross section is in good agreement with the only
previous measurement (Phys. Rev C {\bf 60} 025802, 1999), while the resonance
integral is different by a factor of $\approx$1.7. While neutron energies in
this work are smaller than the energies in a stellar environment, our results
may lead to improvements in theoretical predictions of the stellar cross
section. | nucl-ex |
Bremsstrahlung from relativistic heavy ions in a fixed target experiment
at the LHC: We calculate the emission of bremsstrahlung from lead and argon ions in A
Fixed Target ExpeRiment (AFTER) that uses the LHC beams. With nuclear charges
of $Ze$ equal $208$ and $18$ respectively, these ions are accelerated to
energies of $7$ TeV$\times Z $. The bremsstrahlung peaks around $\approx 100$
GeV and the spectrum exposes the nuclear structure of the incoming ion. The
peak structure is significantly different from the flat power spectrum
pertaining to a point charge. Photons are predominantly emitted within an angle
of $1/\gamma$ to the direction of ion propagation. Our calculations are based
on the Weizs\"{a}cker-Williams method of virtual quanta with application of
existing experimental data on photonuclear interactions. | nucl-ex |
The Structure of the Nucleon: Elastic Electromagnetic Form Factors: Precise proton and neutron form factor measurements at Jefferson Lab, using
spin observables, have recently made a significant contribution to the
unraveling of the internal structure of the nucleon. Accurate experimental
measurements of the nucleon form factors are a test-bed for understanding how
the nucleon's static properties and dynamical behavior emerge from QCD, the
theory of the strong interactions between quarks. There has been enormous
theoretical progress, since the publication of the Jefferson Lab proton form
factor ratio data, aiming at reevaluating the picture of the nucleon. We will
review the experimental and theoretical developments in this field and discuss
the outlook for the future. | nucl-ex |
Dressed Spin of Polarized 3He in a Cell: We report a measurement of the modification of the effective precession
frequency of polarized 3He atoms in response to a dressing field in a room
temperature cell. The 3He atoms were polarized using the metastability
spin-exchange method. An oscillating dressing field is then applied
perpendicular to the constant magnetic field. Modification of the 3He effective
precession frequency was observed over a broad range of the amplitude and
frequency of the dressing field. The observed effects are compared with
calculations based on quantum optics formalism. | nucl-ex |
Direct jet reconstruction in p + p and Cu + Cu at PHENIX: The Relativistic Heavy Ion Collider collides heavy nuclei at
ultrarelativistic energies, creating a strongly interacting, partonic medium
that is opaque to the passage of high energy quarks and gluons. Direct jet
reconstruction applied to these collision systems provides a crucial constraint
on the mechanism for in-medium parton energy loss and jet-medium interactions.
However, traditional jet reconstruction algorithm operating in the large soft
background at RHIC give rise to fake jets well above the intrinsic production
rate of high-pT partons, impeding the detection of the low cross section jet
signal at RHIC energies. We developed a new jet reconstruction algorithm that
uses a Gaussian filter to locate and reconstruct the jet energy. This algorithm
is combined with a fake jet rejection scheme that provides efficient jet
reconstruction with acceptable fake rate in a background environment up to the
central Au + Au collision at sqrt(s_NN) = 200 GeV. We present results of its
application in p + p and Cu + Cu collisions using data from the PHENIX
detector, namely p + p cross section, Cu + Cu jet yields, the Cu + Cu nuclear
modification factor, and Cu + Cu jet-jet azimuthal correlation. | nucl-ex |
Beam-Energy Dependence of Charge Balance Functions from Au+Au Collisions
at RHIC: Balance functions have been measured in terms of relative pseudorapidity
($\Delta \eta$) for charged particle pairs at the Relativistic Heavy-Ion
Collider (RHIC) from Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7 GeV to 200
GeV using the STAR detector. These results are compared with balance functions
measured at the Large Hadron Collider (LHC) from Pb+Pb collisions at
$\sqrt{s_{\rm NN}}$ = 2.76 TeV by the ALICE Collaboration. The width of the
balance function decreases as the collisions become more central and as the
beam energy is increased. In contrast, the widths of the balance functions
calculated using shuffled events show little dependence on centrality or beam
energy and are larger than the observed widths. Balance function widths
calculated using events generated by UrQMD are wider than the measured widths
in central collisions and show little centrality dependence. The measured
widths of the balance functions in central collisions are consistent with the
delayed hadronization of a deconfined quark gluon plasma (QGP). The narrowing
of the balance function in central collisions at $\sqrt{s_{\rm NN}}$ = 7.7 GeV
implies that a QGP is still being created at this relatively low energy. | nucl-ex |
Cross sections and Rosenbluth separations in 1H(e, e'K+)Lambda up to
Q2=2.35 GeV2: The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a
function of the virtual-photon four-momentum, Q2, total energy, W, and momentum
transfer, t, for different values of the virtual- photon polarization
parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75
GeV. The center of mass cross section was determined for 21 kinematics
corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and
transverse, sigmaT, cross sections were separated using the Rosenbluth
technique at fixed W and t. The separated cross sections reveal a flat energy
dependence at forward kaon angles not satisfactorily described by existing
electroproduction models. Influence of the kaon pole on the cross sections was
investigated by adopting an off-shell form factor in the Regge model which
better describes the observed energy dependence of sigmaT and sigmaL. | nucl-ex |
Proton Capture on ^{17}O and its astrophysical implications: The reaction $^{17}$O$(p,\gamma)^{18}$F influences hydrogen-burning
nucleosynthesis in several stellar sites, such as red giants, asymptotic giant
branch (AGB) stars, massive stars and classical novae. In the relevant
temperature range for these environments ($T_{9}=0.01-0.4), the main
contributions to the rate of this reaction are the direct capture process, two
low lying narrow resonances ($E_{r}=65.1$ and 183 keV) and the low-energy tails
of two broad resonances ($E_{r}=557$ and 677 keV). Previous measurements and
calculations give contradictory results for the direct capture contribution
which in turn increases the uncertainty of the reaction rate. In addition, very
few published cross section data exist for the high energy region that might
affect the interpretation of the direct capture and the contributions of the
broad resonances in the lower energy range. This work aims to address these
issues. The reaction cross section was measured in a wide proton energy range
($E_{c.m.}=345$ - 1700 keV) and at several angles
($\theta_{lab}=0^{\circ},45^{\circ},90^{\circ},135^{\circ}$). The observed
primary $\gamma$-transitions were used as input in an $R$-matrix code in order
to obtain the contribution of the direct capture and the two broad resonances
to the low-energy region. The extrapolated S-factor from the present data is in
good agreement with the existing literature data in the low-energy region. A
new reaction rate was calculated from the combined results of this work and
literature S-factor determinations. Resonance strengths and branchings are
reported for several $^{18}$F states. We were able to extrapolate the
astrophysical S-factor of the reaction $^{17}$O$(p,\gamma)^{18}$F at low
energies from cross section data taken at higher energies. No significant
changes in the nucleosynthesis are expected from the newly calculated reaction
rate. | nucl-ex |
Coherent J/psi photoproduction in ultra-peripheral PbPb collisions at
sqrt(s[NN]) = 2.76 TeV with the CMS experiment: The cross section for coherent J/psi photoproduction accompanied by at least
one neutron on one side of the interaction point and no neutron activity on the
other side, X[n]0[n], is measured with the CMS experiment in ultra-peripheral
PbPb collisions at sqrt(s[NN]) = 2.76 TeV. The analysis is based on a data
sample corresponding to an integrated luminosity of 159 inverse microbarns,
collected during the 2011 PbPb run. The J/psi mesons are reconstructed in the
dimuon decay channel, while neutrons are detected using zero degree
calorimeters. The measured cross section is dsigma[coh,X[n]0[n]] / dy(J/psi) =
0.36 +/- 0.04 (stat) +/- 0.04 (syst) mb in the rapidity interval 1.8 < abs(y) <
2.3. Using a model for the relative rate of coherent photoproduction processes,
this X[z,n,z] measurement gives a total coherent photoproduction cross section
of dsigma[coh] / dy(J/psi) = 1.82 +/- 0.22 (stat) +/- 0.20 (syst) +/- 0.19
(theo) mb. The data strongly disfavour the impulse approximation model
prediction, indicating that nuclear effects are needed to describe coherent
J/psi photoproduction in gamma + Pb interactions. The data are found to be
consistent with the leading twist approximation, which includes nuclear gluon
shadowing. | nucl-ex |
Measurement of the complete nuclide production and kinetic energies of
the system 136Xe + hydrogen at 1 GeV per nucleon: We present an extensive overview of production cross sections and kinetic
energies for the complete set of nuclides formed in the spallation of 136Xe by
protons at the incident energy of 1 GeV per nucleon. The measurement was
performed in inverse kinematics at the FRagment Separator (GSI, Darmstadt).
Slightly below the Businaro-Gallone point, 136Xe is the stable nuclide with the
largest neutron excess. The kinematic data and cross sections collected in this
work for the full nuclide production are a general benchmark for modelling the
spallation process in a neutron-rich nuclear system, where fission is
characterised by predominantly mass-asymmetric splits. | nucl-ex |
Performance of scintillation materials at cryogenic temperatures: An increasing number of applications of scintillators at low temperatures,
particularly in cryogenic experiments searching for rare events, has motivated
the investigation of scintillation properties of materials over a wide
temperature range. This paper provides an overview of the latest results on the
study of luminescence, absorption and scintillation properties of materials
selected for rare event searches so far. These include CaWO4, ZnWO4, CdWO4,
MgWO4, CaMoO4, CdMoO4, Bi4Ge3O12, CaF2, MgF2, ZnSe and AL2O3-Ti. We discuss the
progress achieved in research and development of these scintillators, both in
material preparation and in the understanding of scintillation mechanisms, as
well as the underlying physics. To understand the origin of the performance
limitation of self-activated scintillators we employed a semi-empirical model
of conversion of high energy radiation into light and made appropriate
provision for effects of temperature and energy transfer. We conclude that the
low-temperature value of the light yield of some modern scintillators, namely
CaWO4, CdWO4 and Bi4Ge3O12, is close to the theoretical limit. Finally, we
discuss the advantages and limitations of different materials with emphasis on
their application as cryogenic phonon-scintillation detectors (CPSD) in rare
event search experiments. | nucl-ex |
Quenching of $g_{\rm A}$ deduced from the $β$-spectrum shape of
$^{113}$Cd measured with the COBRA experiment: A dedicated study of the quenching of the weak axial-vector coupling strength
$g_{\rm A}$ in nuclear processes has been performed by the COBRA collaboration.
This investigation is driven by nuclear model calculations which show that the
$\beta$-spectrum shape of the fourfold forbidden non-unique decay of $^{113}$Cd
strongly depends on the effective value of $g_{\rm A}$. Using an array of
CdZnTe semiconductor detectors, 45 independent $^{113}$Cd spectra were obtained
and interpreted in the context of three nuclear models. The resulting effective
mean values are $\bar{g}_{\rm A}(\text{ISM}) = 0.915 \pm 0.007$, $\bar{g}_{\rm
A}(\text{MQPM}) = 0.911 \pm 0.013$ and $\bar{g}_{\rm A}(\text{IBFM-2}) = 0.955
\pm 0.022$. These values agree well within the determined uncertainties and
deviate significantly from the free value of $g_{\rm A}$. This can be seen as a
first step towards answering the long-standing question regarding quenching
effects related to $g_{\rm A}$ in low-energy nuclear processes. | nucl-ex |
Low-spin particle/hole-core excitations in $^{41,47,49}$Ca isotopes
studied by cold-neutron capture reactions: We present recent results on the structure of the one-valence-particle
$^{41}$Ca and $^{49}$Ca, and one-valence-hole $^{47}$Ca, nuclei. The isotopes
of interest were populated via the cold-neutron capture reactions
$^{40}$Ca(n,$\gamma$), $^{48}$Ca(n,$\gamma$) and $^{46}$Ca(n,$\gamma$),
respectively. The experiments were performed at the Institut Laue-Langevin,
within the EXILL campaign, which employed a large array of HPGe detectors. The
$\gamma$ decay and level schemes of these nuclei were investigated by
$\gamma$-ray coincidence relationships, leading to the identification of 41,
10, and 6 new transitions in $^{41}$Ca, $^{47}$Ca, and $^{49}$Ca, respectively.
Branching ratios and intensities were extracted for the $\gamma$ decay from
each state, and $\gamma$-ray angular correlations were performed to establish a
number of transition multipolarities and mixing ratios, thus helping in the
spin assignment of the states. The experimental findings are discussed along
with microscopic, self-consistent beyond-mean-field calculations performed with
the Hybrid Configuration Mixing model, based on a Skyrme SkX Hamiltonian. The
latter suggests that a fraction of the low-spin states of the $^{41}$Ca,
$^{49}$Ca, and $^{47}$Ca nuclei is characterized by the coexistence of either
2p-1h and 1p-2h excitations, or couplings between single-particle/hole degrees
of freedom and collective vibrations (phonons) of the doubly-magic "core". | nucl-ex |
Evidence for the pair-breaking process in 116,117Sn: The nuclear level densities of 116,117Sn below the neutron separation energy
have been determined experimentally from the (3He,alpha gamma) and (3He,3He
gamma') reactions, respectively. The level densities show a characteristic
exponential increase and a difference in magnitude due to the odd-even effect
of the nuclear systems. In addition, the level densities display pronounced
step-like structures that are interpreted as signatures of subsequent breaking
of nucleon pairs. | nucl-ex |
Analysing powers and spin correlations in deuteron-proton charge
exchange at 726 MeV: The charge exchange of vector polarised deuterons on a polarised hydrogen
target has been studied in a high statistics experiment at the COSY-ANKE
facility at a deuteron beam energy of Td = 726 MeV. By selecting two fast
protons at low relative energy E_{pp}, the measured analysing powers and spin
correlations are sensitive to interference terms between specific
neutron-proton charge-exchange amplitudes at a neutron kinetic energy of Tn ~
1/2 Td =363 MeV. An impulse approximation calculation, which takes into account
corrections due to the angular distribution in the diproton, describes
reasonably the dependence of the data on both E_{pp} and the momentum transfer.
This lends broad support to the current neutron-proton partial-wave solution
that was used in the estimation. | nucl-ex |
Measurement of the nuclear modification factor for muons from charm and
bottom hadrons in Pb+Pb collisions at 5.02 TeV with the ATLAS detector: Heavy-flavour hadron production provides information about the transport
properties and microscopic structure of the quark-gluon plasma created in
ultra-relativistic heavy-ion collisions. A measurement of the muons from
semileptonic decays of charm and bottom hadrons produced in Pb+Pb and $pp$
collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV with the
ATLAS detector at the Large Hadron Collider is presented. The Pb+Pb data were
collected in 2015 and 2018 with sampled integrated luminosities of
$208~\mathrm{\mu b}^{-1}$ and $38~\mathrm{\mu b^{-1}}$, respectively, and $pp$
data with a sampled integrated luminosity of $1.17~\mathrm{pb}^{-1}$ were
collected in 2017. Muons from heavy-flavour semileptonic decays are separated
from the light-flavour hadronic background using the momentum imbalance between
the inner detector and muon spectrometer measurements, and muons originating
from charm and bottom decays are further separated via the muon track's
transverse impact parameter. Differential yields in Pb+Pb collisions and
differential cross sections in $pp$ collisions for such muons are measured as a
function of muon transverse momentum from 4 GeV to 30 GeV in the absolute
pseudorapidity interval $|\eta| < 2$. Nuclear modification factors for charm
and bottom muons are presented as a function of muon transverse momentum in
intervals of Pb+Pb collision centrality. The measured nuclear modification
factors quantify a significant suppression of the yields of muons from decays
of charm and bottom hadrons, with stronger effects for muons from charm hadron
decays. | nucl-ex |
Plans for a Neutron EDM Experiment at SNS: The electric dipole moment of the neutron, leptons, and atoms provide a
unique window to Physics Beyond the Standard Model. We are currently developing
a new neutron EDM experiment (the nEDM Experiment). This experiment, which will
be run at the 8.9 A Neutron Line at the Fundamental Neutron Physics Beamline
(FNPB) at the Spallation Neutron Source (SNS) at the Oak Ridge National
Laboratory, will search for the neutron EDM with a sensitivity two orders of
magnitude better than the present limit. In this paper, the motivation for the
experiment, the experimental method, and the present status of the experiment
are discussed. | nucl-ex |
$J/ψ$ and $Υ$ measurements in STAR: Heavy-quarkonium states are expected to evidenciate the deconfinement of the
nuclear matter into a Quark-Gluon Plasma in heavy-ion collisions. To strive
conclusive information from quarkonium production modification in A+A
collisions, systematic measurements of the $J/\psi$ and $\Upsilon$ states in
p+p, d+Au and Au+Au collisions are necessary. To accomplish this mission the
STAR experiment has a Quarkonium program based on the development of specific
trigger setups that take advantage of the large STAR acceptance. In this work
we present the preliminary results of the $J/\psi$ and $\Upsilon$ measurement
in 200 GeV p+p and the first measurements of $\Upsilon$ in 200 GeV heavy ion
collisions. | nucl-ex |
New developments in the experimental data for charged particle
production of medical radioisotopes: The goal of the present work is to give a review of developments achieved
experimentally in the field of nuclear data for medically important
radioisotopes in the last three years. The availability and precision of
production related nuclear data is continuously improved mainly experimentally.
This review emphasizes a couple of larger fields: the Mo/Tc generator problem
and the generator isotopes in general, heavy alpha-emitters and the rare-earth
elements. Other results in the field of medical radioisotope production are
also listed. | nucl-ex |
Background Studies for the Neutral Current Detector Array in the Sudbury
Neutrino Observatory: An array of 3He-filled proportional counters will be used in the Sudbury
Neutrino Observatory to measure the neutral-current interaction of neutrinos
and deuterium. We describe the backgrounds to this detection method. | nucl-ex |
Nuclear Muon Capture in Hydrogen and its Interplay with Muon Atomic
Physics: The singlet capture rate $\Lambda_S$ for the semileptonic weak process $\mu+p
\to n+\nu_\mu$ has been measured in the MuCap experiment. The novel
experimental technique is based on stopping muons in an active target,
consisting of a time projection chamber operating with ultra-pure hydrogen.
This allows the unambiguous determination of the pseudoscalar form factor $g_P$
of the charged electroweak current of the nucleon. Our first result
$g_P(q^2=-0.88 m^2_\mu) = 7.3 \pm 1.1 $ is consistent with accurate theoretical
predictions and constitutes an important test of QCD symmetries. Additional
data are being collected with the aim of a three-fold reduction of the
experimental uncertainties. Building on the developed advanced techniques, the
new MuSun experiment is being planned to measure the muon capture rate on the
deuteron to 1.5% precision. This would provide the by far most accurate
experimental information on the axial current interacting with the two-nucleon
system and determine the low energy constant $L_{1A}$ relevant for solar
neutrino reactions.
Muon induced atomic and molecular processes represent challenges as well as
opportunities for this science program, and their interplay with the main
nuclear and weak-interaction physics aspects will be discussed. | nucl-ex |
Virtual Compton Scattering and Neutral Pion Electroproduction in the
Resonance Region up to the Deep Inelastic Region at Backward Angles: We have made the first measurements of the virtual Compton scattering (VCS)
process via the H$(e,e'p)\gamma$ exclusive reaction in the nucleon resonance
region, at backward angles. Results are presented for the $W$-dependence at
fixed $Q^2=1$ GeV$^2$, and for the $Q^2$-dependence at fixed $W$ near 1.5 GeV.
The VCS data show resonant structures in the first and second resonance
regions. The observed $Q^2$-dependence is smooth. The measured ratio of
H$(e,e'p)\gamma$ to H$(e,e'p)\pi^0$ cross sections emphasizes the different
sensitivity of these two reactions to the various nucleon resonances. Finally,
when compared to Real Compton Scattering (RCS) at high energy and large angles,
our VCS data at the highest $W$ (1.8-1.9 GeV) show a striking $Q^2$-
independence, which may suggest a transition to a perturbative scattering
mechanism at the quark level. | nucl-ex |
Investigation of $ββ$ decay in $^{150}$Nd and $^{148}$Nd to the
excited states of daughter nuclei: Double beta decay of $^{150}$Nd and $^{148}$Nd to the excited states of
daughter nuclei have been studied using a 400 cm$^3$ low-background HPGe
detector and an external source consisting of 3046 g of natural Nd$_2$O$_3$
powder. The half-life for the two-neutrino double beta decay of $^{150}$Nd to
the excited 0$^+_1$ state in $^{150}$Sm is measured to be
$T_{1/2}=[1.33^{+0.36}_{-0.23}(stat)^{+0.27}_{-0.13}(syst)]\cdot 10^{20}$ y.
For other $(0\nu + 2\nu)$ transitions to the 2$^+_1$, 2$^+_2$, 2$^+_3$, and
0$^+_2$ levels in $^{150}$Sm, limits are obtained at the level of $\sim
(2-8)\cdot 10^{20}$ y. In the case of $^{148}$Nd only limits for the $(0\nu +
2\nu)$ transitions to the 2$^+_1$, 0$^+_1$, and 2$^+_2$ excited states in
$^{148}$Sm were obtained and are at the level of \sim (4-8)\cdot 10^{20}$ y. | nucl-ex |
Energy dependence of identified hadron spectra and event-by-event
fluctuations in p+p interactions from NA61/SHINE at the CERN SPS: NA61/SHINE at the CERN SPS is a fixed-target experiment pursuing a rich
physics program including measurements for heavy ion, neutrino and cosmic ray
physics. The main goal of the ion program is to explore the most interesting
$T, mu_{B}$ region of the phase diagram of strongly interacting matter. We plan
to study the properties of the onset of deconfinement and to search for the
signatures of the critical point. The search is performed by varying collision
energy (13A-158A GeV/c) and system size (p+p, Be+Be, Ar+Ca, Xe+La).
Thanks to its large acceptance and excellent particle identification
capability NA61/SHINE is well suited for performing high-precision particle
production measurements as well as for studying event-by-event fluctuations in
p+p, p+nucleus and nucleus+nucleus collisions.
Preliminary results on p+p interactions at 20, 31, 40, 80 and 158 GeV/c are
presented. They include inclusive spectra of pi+, pi-, K- and protons as a
function of transverse momentum/mass and rapidity as well as event-by-event
fluctuations of transverse momentum, azimuthal angle and chemical composition.
The new NA61 measurements are compared with the corresponding results of NA49
on central Pb+Pb collisions and with predictions of Monte Carlo models.
Finally, the future plans of NA61/SHINE are summarised. | nucl-ex |
System size dependence of freeze-out properties at RHIC: The STAR experiment at RHIC has measured identified pi(+/-), K(+/-) and
p(pbar) spectra and ratios from sqrt(s_NN) = 62.4 and 200 GeV Cu+Cu collisions.
The new Cu+Cu results are studied with hydro-motivated blast-wave and
statistical model frameworks in order to characterize the freeze-out properties
of this system. Along with measurements from Au+Au and p+p collisions, the
obtained freeze-out parameters are discussed as a function of collision energy,
system size, centrality and inferred energy density. This multi-dimensional
systematic study reveals the importance of the collision geometry and furthers
our understanding of the QCD phases. | nucl-ex |
Multifragmentation in Collisions of 4.4gev-Deuterons with Gold Target: The relative velocity correlation function of pairs of intermediate mass
fragments has been studied for d+Au collitions at 4.4 GeV. Experimental
correlation functions are compared to that obtained by multibody Coulomb
trajectory calculations under the assumption of various decay timees of the
fragmenting system. The combined approach with the empirically modified
intranuclear cascade code followed by the statistical multifragmentation model
was used to generate the starting conditions for these calculations. The
fragment emossion time is found to be less than 40 fm/c. | nucl-ex |
Nuclear Moments of Germanium Isotopes around $N$ = 40: Collinear laser spectroscopy measurements were performed on $^{69,71,73}$Ge
isotopes ($Z = 32$) at ISOLDE-CERN. The hyperfine structure of the $4s^2 4p^2
\, ^3P_1 \rightarrow 4s^2 4p 5s \, ^3P_1^o$ transition of the germanium atom
was probed with laser light of 269 nm, produced by combining the
frequency-mixing and frequency-doubling techniques. The hyperfine fields for
both atomic levels were calculated using state-of-the-art atomic relativistic
Fock-space coupled-cluster calculations. A new $^{73}$Ge quadrupole moment was
determined from these calculations and previously measured precision hyperfine
parameters, yielding $Q_{\rm s}$ = $-$0.198(4) b, in excellent agreement with
the literature value from molecular calculations. The moments of $^{69}$Ge have
been revised: $\mu$ = +0.920(5) $\mu_{N}$ and $Q_{\rm s}$= +0.114(8) b, and
those of $^{71}$Ge have been confirmed. The experimental moments around $N =
40$ are interpreted with large-scale shell-model calculations using the JUN45
interaction, revealing rather mixed wave function configurations, although
their $g$-factors are lying close to the effective single-particle values.
Through a comparison with neighboring isotones, the structural change from the
single-particle nature of nickel to deformation in germanium is further
investigated around $N = 40$. | nucl-ex |
Study of $J/ψ$ production and cold nuclear matter effects in $p$Pb
collisions at $\sqrt{s_{NN}}=5 \mathrm{TeV}$: The production of $J/\psi$ mesons with rapidity $1.5<y<4.0$ or $-5.0<y<-2.5$
and transverse momentum $p_\mathrm{T}<14 \mathrm{GeV}/c$ is studied with the
LHCb detector in proton-lead collisions at a nucleon-nucleon centre-of-mass
energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$. The analysis is based on a data sample
corresponding to an integrated luminosity of about $1.6 \mathrm{nb}^{-1}$. For
the first time the nuclear modification factor and forward-backward production
ratio are determined separately for prompt $J/\psi$ mesons and $J/\psi$ from
$b$-hadron decays. Clear suppression of prompt $J/\psi$ production with respect
to proton-proton collisions at large rapidity is observed, while the production
of $J/\psi$ from $b$-hadron decays is less suppressed. These results show good
agreement with available theoretical predictions. The measurement shows that
cold nuclear matter effects are important for interpretations of the related
quark-gluon plasma signatures in heavy-ion collisions. | nucl-ex |
Heavy Flavor Results at RHIC - A Comparative Overview: I review the latest heavy flavor measurements at RHIC experiments.
Measurements from RHIC together with preliminary results from LHC offer us an
opportunity to systematically study the sQGP medium properties. In the end, I
will outlook a prospective future on precision heavy flavor measurements with
detector upgrades at RHIC. | nucl-ex |
Spatial Distribution of Initial Interactions in High Energy Collisions
of Heavy Nuclei: The spatial distribution of interactions in high energy collisions of heavy
nuclei is discussed using the wounded nucleon, binary collision, hard sphere,
and colliding disk parameterizations of interaction densities. The mean radius,
its dispersion, and the eccentricity of the interaction region are calculated
as a function of impact parameter. The eccentricity is of special interest for
comparison to measurements of anisotropic flow. The number of participants and
binary collisions is also tabulated as a function of impact parameter. | nucl-ex |
Neutral pion production at midrapidity in pp and Pb-Pb collisions at
$\sqrt{s_{\rm NN}}$ = 2.76 TeV: Invariant yields of neutral pions at midrapidity in the transverse momentum
range $0.6 < p_{T} < 12 GeV/c$ measured in Pb-Pb collisions at $\sqrt{s_{\rm
NN}} = 2.76$ TeV are presented for six centrality classes. The pp reference
spectrum was measured in the range $0.4 < p_{T} < 10 GeV/c$ at the same
center-of-mass energy. The nuclear modification factor, $R_{\rm AA}$, shows a
suppression of neutral pions in central Pb-Pb collisions by a factor of up to
about $8-10$ for $5 \lesssim p_{T} \lesssim 7 GeV/c$. The presented
measurements are compared with results at lower center-of-mass energies and
with theoretical calculations. | nucl-ex |
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