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Hot and Cold QCD White Paper from ALICE-USA: Input for 2023 U.S. Long
Range Plan for Nuclear Science: The ALICE-USA collaboration presents its plans for the 2023 U.S. Long Range
Plan for Nuclear Science. | nucl-ex |
Ultra-peripheral Au+Au collisions at PHENIX: Ultra-peripheral collisions (UPC) of heavy-ions involve long range
electromagnetic interactions at impact parameters twice larger than the nuclear
radius, where no nucleon-nucleon collisions occur. The first measurement of
photoproduction of $J/\psi$ and of two-photon production of high-mass $e^+ e^-$
pairs in ultra-peripheral nucleus-nucleus interactions will be presented, using
Au+Au data at $\sqrt{s_{_{NN}}}$ = 200 GeV. The measured cross sections at
midrapidity are consistent with various theoretical predictions. | nucl-ex |
Proton-proton correlations observed in two-proton decay of $^{19}$Mg and
$^{16}$Ne: Proton-proton correlations were observed for the two-proton decays of the
ground states of $^{19}$Mg and $^{16}$Ne. The trajectories of the respective
decay products, $^{17}$Ne+p+p and $^{14}$O+p+p, were measured by using a
tracking technique with microstrip detectors. These data were used to
reconstruct the angular correlations of fragments projected on planes
transverse to the precursor momenta. The measured three-particle correlations
reflect a genuine three-body decay mechanism and allowed us to obtain
spectroscopic information on the precursors with valence protons in the $sd$
shell. | nucl-ex |
Deuteron frozen spin polarized target for nd experiements at the VdG
accelerator of Charles University: A frozen spin polarized deuteron target cooled by the 3He/4He dilution
refrigerator is described. Fully deuterated 1,2-propanediol was used as a
target material. Deuteron vector polarization about 40% was obtained for the
target in the shape of a cylinder of 2 cm diameter and 6 cm length. The target
is intended for a study of 3N interactions at the polarized neutron beam
generated by the Van de Graaff accelerator at the Charles University in Prague. | nucl-ex |
Multifragmentation and the Phase Transition: A Systematic Study of the
MF of 1A GeV Au, La, and Kr: A systematic analysis of the multifragmentation (MF) in fully reconstructed
events from 1A GeV Au, La and Kr collisions with C has been performed. This
data is used to provide a definitive test of the variable volume version of the
statistical multifragmentation model (SMM). A single set of SMM parameters
directly determined by the data and the semi-empiricalmass formula are used
after the adjustable inverse level density parameter, $\epsilon_{o}$ is
determined by the fragment distributions. The results from SMM for second stage
multiplicity, size of the biggest fragment and the intermediate mass fragments
are in excellent agreement with the data. Multifragmentation thresholds have
been obtained for all three systems using SMM prior to secondary decay. The
data indicate that both thermal excitation energy $E_{th}^{*}$ and the isotope
ratio temperature $T_{He-DT}$ decrease with increase in system size at the
critical point. The breakup temperature obtained from SMM also shows the same
trend as seen in the data. The SMM model is used to study the nature of the MF
phase transition. The caloric curve for Kr exhibits back-bending (finite latent
heat) while the caloric curves for Au and La are consistent with a continuous
phase transition (nearly zero latent heat) and the values of the critical
exponents $\tau$, $\beta$ and $\gamma$, both from data and SMM, are close to
those for a 'liquid-gas' system for Au and La. We conclude that the larger
Coulomb expansion energy in Au and La reduces the latent heat required for MF
and changes the nature of the phase transition. Thus the Coulomb energy plays a
major role in nuclear MF. | nucl-ex |
Discovery of Isotopes of Elements with Z $\ge$ 100: Currently, 163 isotopes of elements with Z $\ge$ 100 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 |
Flow Phenomena at AGS Energies: In this talk some of the latest data on directed sideward, elliptic, radial,
and longitudinal flow at AGS energies will be reviewed. A method to identify
the reaction plane event by event and the measurement of its resolution will be
discussed. The distributions of global observables (transverse energy E_T and
charged particle multiplicity N_c), as well as those of identified particles
will be shown. Finally, the data will be put in context with measurements at
other beam energies. These systematics will then be discussed in terms of
possible signatures of the QCD phase transition. | nucl-ex |
Analysis of a Cyclotron Based 400 MeV/u Driver System for a Radioactive
Beam Facility: The creation of intense radioactive beams requires intense and energetic
primary beams. A task force analysis of this subject recommended an
acceleration system capable of 400 MeV/u uranium at 1 particle uA as an
appropriate driver for such a facility. The driver system should be capable of
accelerating lighter ions at higher intensity such that a constant final beam
power (~100kW) is maintained. This document is a more detailed follow on to the
previous analysis of such a system incorporating a cyclotron. The proposed
driver pre-acceleration system consists of an ion source, radio frequency
quadrupole, and linac chain capable of producing a final energy of 30 MeV/u and
a charge (Q) to mass (A) of Q/A ~1/3. This acceleration system would be
followed by a Separated Sector Cyclotron with a final output energy of 400
MeV/u. This system provides a more cost-effective solution in terms of initial
capital investment as well as of operation compared to a fully linac system
with the same primary beam output parameters. | nucl-ex |
A Honeycomb Proportional Counter for Photon Multiplicity Measurement in
the ALICE Experiment: A honeycomb detector consisting of a matrix of 96 closely packed hexagonal
cells, each working as a proportional counter with a wire readout, was
fabricated and tested at the CERN PS. The cell depth and the radial dimensions
of the cell were small, in the range of 5-10 mm. The appropriate cell design
was arrived at using GARFIELD simulations. Two geometries are described
illustrating the effect of field shaping. The charged particle detection
efficiency and the preshower characteristics have been studied using pion and
electron beams. Average charged particle detection efficiency was found to be
98%, which is almost uniform within the cell volume and also within the array.
The preshower data show that the transverse size of the shower is in close
agreement with the results of simulations for a range of energies and converter
thicknesses. | nucl-ex |
$Ω^-$ and $\barΩ^+$ production in Au+Au collisions at
$\sqrt{s_{NN}}$ = 130 and 200 GeV: Mid-rapidity Omega and anti-Omega production in Au+Au collisions at RHIC is
studied with the STAR experiment. We report preliminary results on yields and
spectra at $\sqrt{s_{NN}}$ = 130 and 200 GeV. Production relative to negatively
charged hadrons (h-) as well as thermal freeze-out and collective expansion are
discussed. | nucl-ex |
Multiplicity dependence of two-particle azimuthal correlations in pp
collisions at the LHC: We present the measurements of particle pair yields per trigger particle
obtained from di-hadron azimuthal correlations in pp collisions at $\sqrt{s} =
0.9$, $2.76$, and $7$ TeV recorded with the ALICE detector. The yields are
studied as a function of the charged particle multiplicity. Taken together with
the single particle yields the pair yields provide information about parton
fragmentation at low transverse momenta, as well as on the contribution of
multiple parton interactions to particle production. Data are compared to
calculations using the PYTHIA6, PYTHIA8, and PHOJET event generators. | nucl-ex |
High precision determination of the $Q^2$-evolution of the Bjorken Sum: We present a significantly improved determination of the Bjorken Sum for
0.6$\leq Q^{2}\leq$4.8 GeV$^{2}$ using precise new $g_{1}^{p}$ and $g_{1}^{d}$
data taken with the CLAS detector at Jefferson Lab. A higher-twist analysis of
the $Q^{2}$-dependence of the Bjorken Sum yields the twist-4 coefficient
$f_{2}^{p-n}=-0.064 \pm0.009\pm_{0.036}^{0.032}$. This leads to the color
polarizabilities $\chi_{E}^{p-n}=-0.032\pm0.024$ and
$\chi_{B}^{p-n}=0.032\pm0.013$. The strong force coupling is determined to be
$\alpha_{s}^{\overline{\mbox{ MS}}}(M_{Z}^{2})=0.1124\pm0.0061$, which has an
uncertainty a factor of 1.5 smaller than earlier estimates using polarized DIS
data. This improvement makes the comparison between $\alpha_{s}$ extracted from
polarized DIS and other techniques a valuable test of QCD. | nucl-ex |
Low-Energy $Λ-\p$ Scattering Parameters from the $pp \to
pK^+Λ$ Reaction: Constraints on the spin-averaged $\Lambda p$ scattering length and effective
range have been obtained from measurements of the $pp\to pK^+\Lambda$ reaction
close to the production threshold by comparing model phase-space Dalitz plot
occupations with experimental ones. The data fix well the position of the
virtual bound state in the $\Lambda p$ system. Combining this with information
from elastic $\Lambda p$ scattering measurements at slightly higher energies,
together with the fact that the hyperdeuteron is not bound, leads to a new
determination of the low energy $\Lambda p$ scattering parameters. | nucl-ex |
Early dissipation and viscosity: We consider dissipative phenomena due to the relaxation of an initial
anisotropic local pressure in the fireball created in relativistic heavy-ion
collisions, both for the Bjorken boost-invariant case and for the azimuthally
symmetric radial expansion with boost-invariance. The resulting increase of the
entropy can be counterbalanced by a suitable retuning of the initial
temperature. An increase of the transverse collective flow is observed. The
influence of the shear viscosity on the longitudinal expansion is also studied.
Viscosity reduces the cooling rate from the longitudinal work and counteracts
the pressure gradients that accelerate the longitudinal flow. | nucl-ex |
9Li and 8He decays in GEANT4: The decays of cosmogenic nuclei such as $^9$Li and $^8$He represent one of
the largest irreducible backgrounds for reactor antineutrino experiments. The
correct treatment of such decays are of fundamental importance in the study of
cosmogenic backgrounds and in their rejection, hence the full chain of
intermediate excited states must be accounted for. Currently the treatment in
GEANT4 of the modelling of de-excitation of $^9$Be and $^8$Li, which are the
daughter nuclei of $^9$Li and $^8$He respectively, is not correct. $^9$Be
excited states should break into a neutron and two $\alpha$'s, and $^8$Li
excited states should emit a neutron and possibly an $\alpha$ and a triton
depending on the decay chain, whereas in GEANT4 they both reach the ground
state by emitting a gamma. Based on the available nuclear measurements we
included the correct treatment of $^9$Li and $^8$He decays in GEANT4 and
compared the obtained results with the spectra published by the Double Chooz
collaboration finding an excellent agreement. | nucl-ex |
Study of the long-lived excited state in the neutron deficient nuclides
$^{195,197,199}$Po by precision mass measurement: Direct mass measurements of the low-spin $3/2^{(-)}$ and high-spin
$13/2^{(+)}$ states in the neutron-deficient isotopes $^{195}$Po, $^{197}$Po,
and high-spin $13/2^{(+)}$ state in $^{199}$Po were performed with the
Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements
allow the determination of the excitation energy of the isomeric state arising
from the $\nu$i$_{13/2}$ orbital in $^{195,197}$Po. Additionally, the
excitation energy of isomeric states of lead, radon, and radium isotopes in
this region were obtained from $\alpha$-decay chains. The new excitation
energies complete the knowledge of the energy systematics in the region and
confirm for the first time that the $13/2^{(+)}$ states remain isomeric,
independent of the number of valence neutrons. | nucl-ex |
Nuclear physics for geo-neutrino studies: Geo-neutrino studies are based on theoretical estimates of geo-neutrino
spectra. We propose a method for a direct measurement of the energy
distribution of antineutrinos from decays of long-lived radioactive isotopes.
We present preliminary results for the geo-neutrinos from Bi-214 decay, a
process which accounts for about one half of the total geo-neutrino signal. The
feeding probability of the lowest state of Bi-214 - the most important for
geo-neutrino signal - is found to be p_0 = 0.177 \pm 0.004 (stat)
^{+0.003}_{-0.001} (sys), under the hypothesis of Universal Neutrino Spectrum
Shape (UNSS). This value is consistent with the (indirect) estimate of the
Table of Isotopes (ToI). We show that achievable larger statistics and
reduction of systematics should allow to test possible distortions of the
neutrino spectrum from that predicted using the UNSS hypothesis. Implications
on the geo-neutrino signal are discussed. | nucl-ex |
Ultrarelativistic heavy ion collisions: the first billion seconds: I first review the early history of the ultrarelativistic heavy ion program,
starting with the 1974 Bear Mountain Workshop, and the 1983 Aurora meeting of
the U.S. Nuclear Science Committee, just one billion seconds ago, which laid
out the initial science goals of an ultrarelativistic collider. The primary
goal, to discover the properties of nuclear matter at the highest energy
densities, included finding new states of matter -- the quark-gluon plasma
primarily -- and to use collisions to open a new window on related problems of
matter in cosmology, neutron stars, supernovae, and elsewhere. To bring out how
the study of heavy ions and hot, dense matter in QCD has been fulfilling these
goals. I concentrate on a few topics, the phase diagram of matter in QCD, and
connections of heavy ion physics to cold atoms, cosmology, and neutron stars. | nucl-ex |
Measurement of the invariant mass distributions for the pp -> ppeta'
reaction at excess energy of Q = 16.4 MeV: The proton-proton and proton-eta' invariant mass distributions have been
determined for the pp -> ppeta' reaction at an excess energy of Q = 16.4 MeV.
The measurement was carried out using the COSY-11 detector setup and the proton
beam of the cooler synchrotron COSY. The shapes of the determined invariant
mass distributions are similar to those of the pp -> ppeta reaction and reveal
an enhancement for large relative proton-proton momenta. This result, together
with the fact that the proton-eta interaction is much stronger that the
proton-eta' interaction, excludes the hypothesis that the observed enhancement
is caused by the interaction between the proton and the meson. | nucl-ex |
Participant and spectator scaling of spectator fragments in Au+Au and
Cu+Cu collisions at sqrt(sNN) = 19.6 and 22.4 GeV: Spectator fragments resulting from relativistic heavy ion collisions,
consisting of single protons and neutrons along with groups of stable nuclear
fragments up to Nitrogen (Z=7), are measured in PHOBOS. These fragments are
observed in Au+Au (sqrt(sNN)=19.6 GeV) and Cu+Cu (22.4 GeV) collisions at high
pseudorapidity ($\eta$). The dominant multiply-charged fragment is the tightly
bound Helium ($\alpha$), with Lithium, Beryllium, and Boron all clearly seen as
a function of collision centrality and pseudorapidity. We observe that in Cu+Cu
collisions, it becomes much more favorable for the $\alpha$ fragments to be
released than Lithium. The yields of fragments approximately scale with the
number of spectator nucleons, independent of the colliding ion. The shapes of
the pseudorapidity distributions of fragments indicate that the average
deflection of the fragments away from the beam direction increases for more
central collisions. A detailed comparison of the shapes for $\alpha$ and
Lithium fragments indicates that the centrality dependence of the deflections
favors a scaling with the number of participants in the collision. | nucl-ex |
Direct photon production at low transverse momentum in proton-proton
collisions at $\sqrt{s}$ = 2.76 and 8 TeV: Measurements of inclusive and direct photon production at mid-rapidity in pp
collisions at $\sqrt{s}=2.76$ and 8 TeV are presented by the ALICE experiment
at the LHC. The results are reported in transverse momentum ranges of
$0.4<p_{T}<10$ GeV/$c$ and $0.3<p_{T}<16$ GeV/$c$, respectively. Photons are
detected with the electromagnetic calorimeter~(EMCal) and via reconstruction of
e$^+$e$^-$ pairs from conversions in the ALICE detector material using the
central tracking system. For the final measurement of the inclusive photon
spectra the results are combined in the overlapping $p_{T}$ interval of both
methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted
using the direct photon excess ratio $R_{\gamma}$, which quantifies the ratio
of inclusive photons over decay photons generated with a decay-photon
simulation. An additional hybrid method, combining photons reconstructed from
conversions with those identified in the EMCal, is used for the combination of
the direct photon excess ratio $R_{\gamma}$, as well as the extraction of
direct photon spectra or their upper limits. While no significant signal of
direct photons is seen over the full $p_{T}$ range, $R_{\gamma}$ for $p_{T}>7$
GeV/$c$ is at least one $\sigma$ above unity and consistent with expectations
from next-to-leading order pQCD calculations. | nucl-ex |
Electromagnetic transition from the 4$^+$ to 2$^+$ resonance in $^8$Be
measured via the radiative capture in $^4$He+$^4$He: An earlier measurement on the 4$^+$ to 2$^+$ radiative transition in $^8$Be
provided the first electromagnetic signature of its dumbbell-like shape.
However, the large uncertainty in the measured cross section does not allow a
stringent test of nuclear structure models. The present paper reports a more
elaborate and precise measurement for this transition, via the radiative
capture in the $^4$He+$^4$He reaction, improving the accuracy by about a factor
of three. The {\it ab initio} calculations of the radiative transition strength
with improved three-nucleon forces are also presented. The experimental results
are compared with the predictions of the alpha cluster model and {\it ab
initio} calculations. | nucl-ex |
A novel approach for extracting model-independent nuclear level
densities far from stability: The level density of quantum states in statistical mesoscopic systems is a
critical input for various fields of physics, including nuclear physics,
nuclear astrophysics, atomic physics and their applications. In atomic nuclei,
the level density is a fundamental measure of their complex structure at
relatively high energies. Here we present the first model-independent
measurement of the absolute partial nuclear level density for a short-lived
unstable nucleus. For this purpose, we introduce the ``Shape method'' to
extract the shape of the $\gamma$-ray strength function. Combining the Shape
method with the existing $\beta$-Oslo technique allows the extraction of the
nuclear level density without the need for theoretical input. We benchmark the
Shape method using results for the stable $^{76}$Ge nucleus, finding an
excellent agreement to previous experimental results. We apply the Shape method
to new experimental data on the short-lived $^{88}$Kr nucleus. Our method opens
the door for measurements of the nuclear level density and $\gamma$-ray
strength function far away from stability, a pivotal input required to
understand the role of exotic nuclei in forming the cosmos. | nucl-ex |
Results on hyperon production from the NA57 experiment: Recent results on hyperon production in Pb--Pb collisions from the NA57
experiment are reported. Strangeness enhancement and the transverse mass
spectra properties at 158 GeV per nucleon are described. | nucl-ex |
Spectroscopic studies of Dy-168,170 using CLARA and PRISMA: Preliminary results from an experiment aiming at Dy-170. Submitted to the LNL
Annual Report 2008. | nucl-ex |
First-order event plane correlated directed and triangular flow from
fixed-target energies at RHIC-STAR: We report the measurement of first-order event plane correlated directed flow
$(v_1)$ and triangular flow $v_3$ for identified hadrons ($\pi^{\pm}$,
$K^{\pm}$, and $p$), net-particle (net-K, net-p), and light nuclei ($d$ and
$t$) in Au+Au collisions at $\sqrt{s_{\text{NN}}}$ = 3.2, 3.5, and 3.9 GeV in
fixed-target mode from the second phase of beam energy scan (BES-II) program at
RHIC-STAR. The $v_1$ slopes at mid-rapidity for identified hadrons and
net-particles except $\pi^{+}$ are found to be positive, implying the effect of
dominant repulsive baryonic interactions. The slope of $v_1$ for net-kaon
undergoes a sign change from negative to positive at a lower collision energy
compared to net-proton. An approximate atomic mass number scaling is observed
in the measured $v_1$ slopes of light nuclei at mid-rapidity, which favours the
nucleon coalescence mechanism for the production of light nuclei. The $v_3$
slope for all particles decreases in magnitude with increasing collision
energy, suggesting a notable integrated impact of the mean-field, baryon
stopping, and collision geometry at lower collision energies. | nucl-ex |
Direct observation of the decay of first excited Hoyle state in $^{12}$C: An excited state of $^{12}$C having excitation energy E$_x \sim$ 9.65 $\pm$
0.02 MeV and width (FWHM) $\sim607\pm$ 55 keV, which decays to three $ \alpha
$-particles via Hoyle state ($E_x \sim$ 7.65 MeV), has been directly identified
for the first time in the exclusive inelastic scattering of 60 MeV $^{4}$He on
$^{12}$C, measured in coincidence with the recoiling $^{12}$C$ ^* $ Hoyle state
(decaying mostly as $^{12}$C$ ^* $ $\rightarrow \ ^{8} $Be + $ \alpha $
$\rightarrow \ \alpha + \alpha + \alpha$) by event-by-event kinematic
reconstruction of the completely detected (4$ \alpha $) events. This state is
likely to be a candidate for 2$_2^+$ first excited Hoyle state, the existence
of which has recently been indirectly evidenced from the recent inclusive
inelastic scattering studies. | nucl-ex |
Fission Parameters Measurements for Np, Pu, Am, and Cm Isotopes Inside a
Salt Blanket Micromodel: The MAKET zero-power heavy water reactor has been used at ITEP to measure the
fission characteristics of the Np, Pu, Am, and Cm isotopes in the
0.52NaF+0.48ZrF_4 melt-filled salt blanket micromodel. The 237Np(n,f),
238Pu(n,f), 239Pu(n,f), 240Pu(n,f), 241Pu(n,f), 242m^Am(n,f), 243Cm(n,f),
245Cm(n,f), 247Cm(n,f), 238U(n,f), 238U(n,g), 235U(n,f) fission reaction rates
have been measured. The neutron spectrum in the isotope irradiation locations
was monitored by measuring the rates of the (235U(n,f), 238U(n,g), 55Mn(n,g),
63Cu(n,g), 176Lu(n,g), 197Au(n,g), 115In(n,n'), 27Al(n,4He), and 64Zn(n,p))
reactions whose cross sections have been commonly accepted. The measured
functionals are compared with the respective results of MCNP code simulation
obtained using the ENDF/B6 and JENDL3.2 neutron databases. | nucl-ex |
Possibilities of future double beta decay experiments to investigate
inverted and normal ordering region of neutrino mass: An overview of modern experiments on the search for neutrinoless double decay
is presented. The obtained limits on the effective mass of the Majorana
neutrino $\langle m_{\nu} \rangle$ are discussed taking into account the
uncertainties in the value of the nuclear matrix elements (NMEs) and the value
of the axial-vector constant $g_A$. Predictions for the values of $\langle
m_{\nu} \rangle$ from the results of oscillation experiments and modern
cosmological data are presented. The possibilities of the next generation
experiments with sensitivity to $\langle m_{\nu} \rangle$ at the level of
$\sim$ 10-50 meV (studying mainly the inverted ordering (IO) region) are
discussed. %Description of the most developed and promising projects is
presented. The prospects for studying the normal ordering (NO) region are
discussed too. It is shown that the possibilities of studying the NO depend on
the mass of the lightest neutrino m$_0$. In the limiting case of small mass
(m$_0$ $\le$ 0.1 meV), the values of $\langle m_{\nu} \rangle$ $\approx$ 1-4
meV are predicted, which makes the study of this region inaccessible by the
next generation experiments. But there is an allowed region of m$_0$ (7-30 meV)
in the framework of NO, where the predicted values for $\langle m_{\nu}
\rangle$ could be $\sim$ 10-30 meV and that is quite achievable for the next
generation experiments. The possibility to rich in the future sensitivity to
$\langle m_{\nu} \rangle$ at the level of $\sim$ 1-10 meV is also discussed. | nucl-ex |
Measurements of nuclear $γ$-ray line emission in interactions of
protons and $α$ particles with N, O, Ne and Si: $\gamma$-ray production cross sections have been measured in proton
irradiations of N, Ne and Si and $\alpha$-particle irradiations of N and Ne. In
the same experiment we extracted also line shapes for strong $\gamma$-ray lines
of $^{16}$O produced in proton and $\alpha$-particle irradiations of O. For the
measurements gas targets were used for N, O and Ne and a thick foil was used
for Si. All targets were of natural isotopic composition. Beams in the energy
range up to 26 MeV for protons and 39 MeV for $\alpha$-particles have been
delivered by the IPN-Orsay tandem accelerator. The $\gamma$ rays have been
detected with four HP-Ge detectors in the angular range 30$^{\circ}$ to
135$^{\circ}$. We extracted 36 cross section excitation functions for proton
reactions and 14 for $\alpha$-particle reactions. For the majority of the
excitation functions no other data exist to our knowledge. Where comparison
with existing data was possible usually a very good agreement was found. It is
shown that these data are very interesting for constraining nuclear reaction
models. In particular the agreement of cross section calculations in the
nuclear reaction code TALYS with the measured data could be improved by
adjusting the coupling schemes of collective levels in the target nuclei
$^{14}$N, $^{20,22}$Ne and $^{28}$Si. The importance of these results for the
modeling of nuclear $\gamma$-ray line emission in astrophysical sites is
discussed. | nucl-ex |
Observation of isotonic symmetry for enhanced quadrupole collectivity in
neutron-rich 62,64,66Fe isotopes at N=40: The transition rates for the 2_{1}^{+} states in 62,64,66Fe were studied
using the Recoil Distance Doppler-Shift technique applied to projectile Coulomb
excitation reactions. The deduced E2 strengths illustrate the enhanced
collectivity of the neutron-rich Fe isotopes up to N=40. The results are
interpreted by the generalized concept of valence proton symmetry which
describes the evolution of nuclear structure around N=40 as governed by the
number of valence protons with respect to Z~30. The deformation suggested by
the experimental data is reproduced by state-of-the-art shell calculations with
a new effective interaction developed for the fpgd valence space. | nucl-ex |
Tracing a phase transition with fluctuations of the largest fragment
size: Statistical multifragmentation models and the ALADIN S254 data: A phase transition signature associated with cumulants of the largest
fragment size distribution has been identified in statistical
multifragmentation models and examined in analysis of the ALADIN S254 data on
fragmentation of neutron-poor and neutron-rich projectiles. Characteristics of
the transition point indicated by this signature are weakly dependent on the
A/Z ratio of the fragmenting spectator source. In particular, chemical
freeze-out temperatures are estimated within the range 5.9 to 6.5 MeV. The
experimental results are well reproduced by the SMM model. | nucl-ex |
Study of the Fusion-Fission Process in the $^{35}Cl+^{24}Mg$ Reaction: Fusion-fission and fully energy-damped binary processes of the
$^{35}$Cl+$^{24}$Mg reaction were investigated using particle-particle
coincidence techniques at a $^{35}$Cl bombarding energy of E$_{lab}$ $\approx$
8 MeV/nucleon. Inclusive data were also taken in order to determine the partial
wave distribution of the fusion process. The fragment-fragment correlation data
show that the majority of events arises from a binary-decay process with a
relatively large multiplicity of secondary light-charged particles emitted by
the two primary excited fragments in the exit channel. No evidence is observed
for ternary-breakup processes, as expected from the systematics recently
established for incident energies below 15 MeV/nucleon and for a large number
of reactions. The binary-process results are compared with predictions of
statistical-model calculations. The calculations were performed using the
Extended Hauser-Feshbach method, based on the available phase space at the
scission point of the compound nucleus. This new method uses
temperature-dependent level densities and its predictions are in good agreement
with the presented experimental data, thus consistent with the fusion-fission
origin of the binary fully-damped yields. | nucl-ex |
Exploration of jet energy loss via direct $γ$-charged particle
azimuthal correlation measurements: The multiplicities of charged particles azimuthally associated with direct
photons and $\pi^{0}$ have been measured for Au+Au, p+p, and d+Au collisions at
$\sqrt{s_{NN}}$ = 200 GeV in the STAR experiment. Charged particles with
transverse momentum 0.5 $<$ $p_T^{h^{\pm}}$ $<$ 16 GeV/c for p+p and d+Au, and
3 $<$ $p_T^{h^{\pm}}$ $<$ 16 GeV/c for Au+Au and pseudorapidity $\mid\eta\mid$
$\leq$ 1.5 in coincidence with direct photons and $\pi^{0}$ of high transverse
momentum 8 $<$ $p_T^{\gamma,\pi^{0}}$ $<$ 16 GeV/c at $\mid\eta\mid$ $\leq$ 0.9
have been used for this analysis. Within the considered range of kinematics,
the observed suppressions of the associated yields per direct $\gamma$ in
central Au+Au relative to p+p and d+Au are similar and constant with direct
photon fractional energy $z_{T}$ ($z_{T}=p_{T}^{h^{\pm}}/p_{T}^{\gamma}$). The
measured suppressions of the associated yields with direct $\gamma$ are
comparable to those with $\pi^{0}$. The data are compared to theoretical
predictions. | nucl-ex |
Strongly Enhanced Low Energy Alpha-Particle Decay in Heavy Actinide
Nuclei and Long-Lived Superdeformed and Hyperdeformed Isomeric States: Relatively low energy and very enhanced alpha-particle groups have been
observed in various actinide fractions produced via secondary reactions in a
CERN W target which had been irradiated with 24-GeV protons. In particular,
5.14, 5.27 and 5.53 MeV alpha-particle groups with corresponding half-lives of
3.8(+ -)1.0 y, 625(+ -)84 d and 26(+ -)7 d, have been seen in Bk, Es and Lr-No
sources, respectively. The measured energies are a few MeV lower than the known
g.s. to g.s. alpha-decays in the corresponding neutron-deficient actinide
nuclei. The half-lives are 4 to 7 orders of magnitude shorter than expected
from the systematics of alpha-particle decay in this region of nuclei. The
deduced evaporation residue cross sections are in the mb region, about 4 orders
of magnitude higher than expected. A consistent interpretation of the data is
given in terms of production of long-lived isomeric states in the second and
third wells of the potential-energy surfaces of the parent nuclei, which decay
to the corresponding wells in the daughters. The possibility that the isomeric
states in the third minimum are actually the true or very near the true ground
states of the nuclei, and consequences regarding the production of the
long-lived superheavy elements, are discussed. | nucl-ex |
Nuclear multifragmentation and phase transition for hot nuclei: This review article is focused on the tremendous progress realized during the
last fifteen years in the understanding of multifragmentation and its
relationship to the liquid-gas phase diagram of nuclei and nuclear matter. The
explosion of the whole nucleus, early predicted by Bohr [N. Bohr, Nature 137
(1936) 351], is a very complex and rich subject which continues to fascinate
nuclear physicists as well as theoreticians who extend the thermodynamics of
phase transitions to finite systems. | nucl-ex |
First measurements of spin correlations in the np -> d pi^0 reaction: The transverse spin correlations Axx and Ayy in the np-> d pi^0 reaction have
been measured for the first time in quasi-free kinematics at the COSY-ANKE
facility using a polarised deuteron beam incident on a polarised hydrogen cell
target. The results obtained for neutron energies close to 353 MeV and 600 MeV
are in good agreement with the partial wave analysis of data on the
isospin-related pp-> d pi^+ reaction, though the present results cover also the
small-angle region, which was largely absent from these data. | nucl-ex |
Improved Comparison of Measurements and Calculations of $\hat{q}L$ via
transverse momentum broadening in Relativistic Heavy Ion Collisions using
di-hadron correlations: The renewed interest in analyzing RHIC data on di-hadron correlations as
probes of final state transverse momentum broadening as shown at Quark Matter
2018[1] by theoretical calculations[6] compared to experimental
measurements[4,5] led me to review the quoted theoretical calculations and
experimental measurements because the theoretical calculation[6] does not show
the PHENIX measurements[4] as published. The above references were checked and
fits were performed to the published measurements[4,7] to determine $\hat{q}L$
from the measured azimuthal broadening to compare with the theoretical
calculation[6]. The new results will be presented in addition to some
corrections to the previous work[3]. The measured values of $\hat{q}L$ show the
interesting effect of being consistent with zero for larger values of
associated $p_{Ta}\geq3$ GeV/c which is shown to be related to well known
measurements of the ratio of the Au+Au to p+p associated $p_{Ta}$ distributions
for a given trigger $p_{Tt}$ called $I_{AA}$[23,25]. Di-jets rather than
di-hadrons are proposed as an improved azimuthal broadening measurement to
determine $\hat{q}L$ and possibly $\hat{q}$. | nucl-ex |
Comprehensive evidences of octupole vibration in $^{158}$Gd: Comprehensive evidences of the SU(3) limit in the spdf interacting boson
model, a dynamical symmetry describing octupole vibration in rotational
nucleus, are found in the spectrum, E2 and E1 transition rates, and relative
intensities in $^{158}$Gd. This gives a good example of rotational nucleus with
octupole vibration in rare-earth region. | nucl-ex |
Detailed studies of $^{100}$Mo two-neutrino double beta decay in NEMO-3: The full data set of the NEMO-3 experiment has been used to measure the
half-life of the two-neutrino double beta decay of $^{100}$Mo to the ground
state of $^{100}$Ru, $T_{1/2} = \left[ 6.81 \pm 0.01\,\left(\mbox{stat}\right)
^{+0.38}_{-0.40}\,\left(\mbox{syst}\right) \right] \times10^{18}$ y. The
two-electron energy sum, single electron energy spectra and distribution of the
angle between the electrons are presented with an unprecedented statistics of
$5\times10^5$ events and a signal-to-background ratio of ~80. Clear evidence
for the Single State Dominance model is found for this nuclear transition.
Limits on Majoron emitting neutrinoless double beta decay modes with spectral
indices of n=2,3,7, as well as constraints on Lorentz invariance violation and
on the bosonic neutrino contribution to the two-neutrino double beta decay mode
are obtained. | nucl-ex |
Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering:
Determined by the OLYMPUS Experiment: The OLYMPUS collaboration reports on a precision measurement of the
positron-proton to electron-proton elastic cross section ratio, $R_{2\gamma}$,
a direct measure of the contribution of hard two-photon exchange to the elastic
cross section. In the OLYMPUS measurement, 2.01~GeV electron and positron beams
were directed through a hydrogen gas target internal to the DORIS storage ring
at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and
time-of-flight scintillators detected elastically scattered leptons in
coincidence with recoiling protons over a scattering angle range of $\approx
20\degree$ to $80\degree$. The relative luminosity between the two beam species
was monitored using tracking telescopes of interleaved GEM and MWPC detectors
at $12\degree$, as well as symmetric M{\o}ller/Bhabha calorimeters at
$1.29\degree$. A total integrated luminosity of 4.5~fb$^{-1}$ was collected. In
the extraction of $R_{2\gamma}$, radiative effects were taken into account
using a Monte Carlo generator to simulate the convolutions of internal
bremsstrahlung with experiment-specific conditions such as detector acceptance
and reconstruction efficiency. The resulting values of $R_{2\gamma}$, presented
here for a wide range of virtual photon polarization $0.456<\epsilon<0.978$,
are smaller than some hadronic two-photon exchange calculations predict, but
are in reasonable agreement with a subtracted dispersion model and a
phenomenological fit to the form factor data. | nucl-ex |
Identified Particle Elliptic Flow in Au+Au Collisions at
$\sqrt{s_{_{NN}}}=130$ GeV}: We report first results on elliptic flow of identified particles at
mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}}=130$ GeV using the STAR
TPC at RHIC. The elliptic flow as a function of transverse momentum and
centrality differs significantly for particles of different masses. This
dependence can be accounted for in hydrodynamic models, indicating that the
system created shows a behavior consistent with collective hydrodynamical flow.
The fit to the data with a simple model gives information on the temperature
and flow velocities at freeze-out. | nucl-ex |
Neutron to Mirror-Neutron Oscillations in the Presence of Mirror
Magnetic Fields: We performed ultracold neutron (UCN) storage measurements to search for
additional losses due to neutron (n) to mirror-neutron (n') oscillations as a
function of an applied magnetic field B. In the presence of a mirror magnetic
field B', UCN losses would be maximal for B = B'. We did not observe any
indication for nn' oscillations and placed a lower limit on the oscillation
time of tau_{nn'} > 12.0 s at 95% C.L. for any B' between 0 and 12.5 uT. | nucl-ex |
Probing the effects of strong electromagnetic fields with
charge-dependent directed flow in Pb-Pb collisions at the LHC: The first measurement at the LHC of charge-dependent directed flow ($v_{1}$)
relative to the spectator plane is presented for Pb-Pb collisions at
$\sqrt{s_{\rm NN}}$ = 5.02 TeV. Results are reported for charged hadrons and
$\rm D^{0}$ mesons for the transverse momentum intervals $p_{\rm T}>0.2$
GeV/$c$ and $3<p_{\rm T}<$ 6 GeV/$c$ in the 5-40% and 10-40% centrality
classes, respectively. The difference between the positively and negatively
charged hadron $v_{1}$ has a positive slope as a function of pseudorapidity
$\eta$, ${\rm d}\Delta{v_1}/{\rm d}\eta=$[1.68 $\pm$ 0.49 (stat.) $\pm$ 0.41
(syst.)] $\times 10^{-4}$. The same measurement for $\rm D^{0}$ and
$\rm\bar{D}{}^0$ mesons yields a positive value ${\rm d}\Delta{v_1}/{\rm
d}\eta$= [4.9 $\pm$ 1.7 (stat.) $\pm$ 0.6 (syst.)]$\times 10^{-1}$, which is
about three orders of magnitude larger than the one of the charged hadrons.
These measurements can provide new insights into the effects of the strong
electromagnetic field and the initial tilt of matter created in non-central
heavy-ion collisions on the dynamics of light (u, d, and s) and heavy (c)
quarks. The large difference between the observed $\Delta{v_1}$ of charged
hadrons and $\rm D^{0}$ mesons may reflect different sensitivity of the charm
and light quarks to the early time dynamics of a heavy-ion collision. These
observations challenge some of the recent theoretical calculations, which
predicted a negative and an order of magnitude smaller value of ${\rm
d}\Delta{v_1}/{\rm d}\eta$ for both light-flavour and charmed hadrons. | nucl-ex |
Updated and novel limits on double beta decay and dark matter-induced
processes in platinum: A 510 day long-term measurement of a 45.3 g platinum foil acting as the
sample and high voltage contact in an ultra-low-background high purity
germanium detector was performed at Laboratori Nazionali del Gran Sasso
(Italy). The data was used for a detailed study of double beta decay modes in
natural platinum isotopes. Limits are set in the range $\mathcal{O}(10^{14} -
10^{19})$ yr (90% C.L.) for several double beta decay transitions to excited
states confirming, and partially extending existing limits. The highest
sensitivity of the measurement, greater than $10^{19}$ yr, was achieved for the
two neutrino and neutrinoless double beta decay modes of the isotope
$^{198}$Pt. Additionally, novel limits for inelastic dark matter scattering on
$^{195}$Pt are placed up to mass splittings of approximately 500 keV. We
analyze several techniques to extend the sensitivity and propose a few
approaches for future medium-scale experiments with platinum-group elements. | nucl-ex |
Study of one-proton transfer reaction for the $^{18}$O + $^{48}$Ti
system at 275 MeV: Single-nucleon transfer reactions are processes that selectively probe
single-particle components of the populated many-body nuclear states. In this
context, recent efforts have been made to build a unified description of the
rich nuclear spectroscopy accessible in heavy-ion collisions. An example of
this multichannel approach is the study of the competition between successive
nucleon transfer and charge exchange reactions, the latter being of particular
interest in the context of single and double beta decay studies. To this
extent, the one-proton pickup reaction $^{48}$Ti($^{18}$O,$^{19}$F)$^{47}$Sc at
275 MeV was measured for the first time, under the NUMEN experimental campaign.
Differential cross-section angular distribution measurements for the $^{19}$F
ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large
acceptance magnetic spectrometer. The data were analyzed within the
distorted-wave and coupled-channels Born approximation frameworks. The initial
and final-state interactions were described adopting the S\~ao Paulo potential,
whereas the spectroscopic amplitudes for the projectile and target overlaps
were derived from shell-model calculations. The theoretical cross sections are
found to be in very good agreement with the experimental data, suggesting the
validity of the optical potentials and the shell-model description of the
involved nuclear states within the adopted model space. | nucl-ex |
Measurements of azimuthal anisotropy and charged-particle multiplicity
in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=$200, 62.4, 39, and 19.6 GeV: We present measurements of the elliptic flow, $v_2$, as a function of
transverse momentum ($p_T$), pseudorapidity ($\eta$), and centrality in
$d$$+$Au collisions at $\sqrt{s_{_{NN}}}=$200, 62.4, 39, and 19.6 GeV. The
beam-energy scan of $d$$+$Au collisions provides a testing ground for the onset
of flow signatures in small collision systems. We measure a nonzero $v_2$
signal at all four collision energies, which, at midrapidity and low $p_T$, is
consistent with predictions from viscous hydrodynamic models. Comparisons with
calculations from parton transport models (based on the {\sc ampt} Monte Carlo
generator) show good agreement with the data at midrapidity to forward
($d$-going) rapidities and low $p_T$. At backward (Au-going) rapidities and
$p_T>1.5$ GeV/$c$, the data diverges from {\sc ampt} calculations of $v_2$
relative to the initial geometry, indicating the possible dominance of
nongeometry related correlations, referred to as nonflow. We also present
measurements of the charged-particle multiplicity ($dN_{\rm ch}/d\eta$) as a
function of $\eta$ in central $d$$+$Au collisions at the same energies. We find
that in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}=$200 GeV the $v_2$ scales with
$dN_{\rm ch}/d\eta$ over all $\eta$ in the PHENIX acceptance. At
$\sqrt{s_{_{NN}}}=$62.4, and 39 GeV, $v_2$ scales with $dN_{\rm ch}/d\eta$ at
midrapidity and forward rapidity, but falls off at backward rapidity. This
departure from the $dN_{\rm ch}/d\eta$ scaling may be a further indication of
nonflow effects dominating at backward rapidity. | nucl-ex |
Reaction mechanisms in the 6Li+59Co system: The reactions induced by the weakly bound 6Li projectile interacting with the
intermediate mass target 59Co were investigated. Light charged particles
singles and $\alpha$-$d$ coincidence measurements were performed at the near
barrier energies E_lab = 17.4, 21.5, 25.5 and 29.6 MeV. The main contributions
of the different competing mechanisms are discussed. A statistical model
analysis, Continuum-Discretized Coupled-Channels calculations and two-body
kinematics were used as tools to provide information to disentangle the main
components of these mechanisms. A significant contribution of the direct
breakup was observed through the difference between the experimental sequential
breakup cross section and the CDCC prediction for the non-capture breakup cross
section. | nucl-ex |
Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45
(GeV/c)2: The H(e,e'pi+)n cross section was measured at four-momentum transfers of
Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of
W=2.22 GeV. The charged pion form factor (F_pi) was extracted from the data by
comparing the separated longitudinal pion electroproduction cross section to a
Regge model prediction in which F_pi is a free parameter. The results indicate
that the pion form factor deviates from the charge-radius constrained monopole
form at these values of Q2 by one sigma, but is still far from its perturbative
Quantum Chromo-Dynamics prediction. | nucl-ex |
Bimodality and Latent Heat of Gold Nuclei: Peripheral collisions give access to a set of events where hot
quasi-projectile (QP) sources are produced exploring a large range of
excitation energy. In this range evaporation and multifragmentation are both
observed for a similar charge/size of the sources. In this work, this
experimental fact will be described in terms of coexistence of two classes of
events in the first order phase transition formalism. For this, a detailed
study of the experimental correlation between the size/charge of the biggest
cluster/fragment (Z1) and the excitation energy (E*) is made. Making the
parallel with the same correlation derived from the canonical ensemble
description, a first value of the latent heat and boundaries of spinodal and
coexistence zone are extracted. | nucl-ex |
Proton and Antiproton Distributions at Mid-Rapidity in Proton-Nucleus
and Sulphur-Nucleus Collisions: Experiment NA44 has measured proton and antiproton distributions at
mid-rapidity in sulphur and proton collisions with nuclear targets at 200 and
450 GeV/c per nucleon respectively. The inverse slopes of transverse mass
distributions increase with system size for both protons and antiprotons but
are slightly lower for antiprotons. this could happen if antiprotons are
annihilated in the nuclear medium. The antiproton yield increases with system
size and centrality and is largest at mid-rapdity. The proton yield also
increases with system size and centrality, but decreases from backward rapidity
to midrapidity. The stopping of protons at these energies lies between the full
stopping and nuclear transparency scenarios. The data are in reasonable
agreement with RQMD predictions except for the antiproton yields from
sulphur-nucleus collisions. PACS numbers 25.75.-q 13.85.-t 13.60.Rj | nucl-ex |
Pion and Kaon Structure at the Electron-Ion Collider: Understanding the origin and dynamics of hadron structure and in turn that of
atomic nuclei is a central goal of nuclear physics. This challenge entails the
questions of how does the roughly 1 GeV mass-scale that characterizes atomic
nuclei appear; why does it have the observed value; and, enigmatically, why are
the composite Nambu-Goldstone (NG) bosons in quantum chromodynamics (QCD)
abnormally light in comparison? In this perspective, we provide an analysis of
the mass budget of the pion and proton in QCD; discuss the special role of the
kaon, which lies near the boundary between dominance of strong and Higgs
mass-generation mechanisms; and explain the need for a coherent effort in QCD
phenomenology and continuum calculations, in exa-scale computing as provided by
lattice QCD, and in experiments to make progress in understanding the origins
of hadron masses and the distribution of that mass within them. We compare the
unique capabilities foreseen at the electron-ion collider (EIC) with those at
the hadron-electron ring accelerator (HERA), the only previous electron-proton
collider; and describe five key experimental measurements, enabled by the EIC
and aimed at delivering fundamental insights that will generate concrete
answers to the questions of how mass and structure arise in the pion and kaon,
the Standard Model's NG modes, whose surprisingly low mass is critical to the
evolution of our Universe. | nucl-ex |
Differential cross sections and spin density matrix elements for the
reaction gamma p -> p omega: High-statistics differential cross sections and spin density matrix elements
for the reaction gamma p -> p omega have been measured using the CLAS at
Jefferson Lab for center-of-mass (CM) energies from threshold up to 2.84 GeV.
Results are reported in 112 10-MeV wide CM energy bins, each subdivided into
cos(theta_CM) bins of width 0.1. These are the most precise and extensive omega
photoproduction measurements to date. A number of prominent structures are
clearly present in the data. Many of these have not previously been observed
due to limited statistics in earlier measurements. | nucl-ex |
Ground and excited quarkonium states as probes of MPI in small systems
with ALICE: Quarkonia represent excellent tools for understanding the role of multiparton
interactions (MPI) in small systems, i.e., pp and p-A collisions. Probing MPI
with quarkonia can be done directly by looking at quarkonium associated
production, or indirectly by studying the multiplicity dependence of quarkonium
production. In these proceedings, the results from the ALICE experiment on
direct and indirect MPI probes are discussed. The self-normalized yields of
charmonium production as a function of the charged-particle multiplicity in pp
and p--Pb collisions at \sqrt{s} = 13 TeV and \sqrt{s_{NN} = 8.16 TeV,
respectively, are discussed. Additionally, the corresponding measurements of
the charmonium self-normalized excited-to-ground state ratio as a function of
the charged-particle multiplicity are reported. The new measurement of the
double J/\psi production at forward rapidity in pp collisions at \sqrt{s} = 13
TeV TeV is presented. Finally, the multiplicity dependence of the bottomonium
production in pp collisions at \sqrt{s} = 13 TeV is discussed. The comparison
to the available theoretical calculations is reported. | nucl-ex |
Recoil-alpha-fission and recoil-alpha-alpha-fission events observed in
the reaction Ca-48 + Am-243: Products of the fusion-evaporation reaction Ca-48 + Am-243 were studied with
the TASISpec set-up at the gas-filled separator TASCA at the GSI
Helmholtzzentrum f\"ur Schwerionenforschung. Amongst the detected thirty
correlated alpha-decay chains associated with the production of element Z=115,
two recoil-alpha-fission and five recoil-alpha-alpha-fission events were
observed. The latter are similar to four such events reported from experiments
performed at the Dubna gas-filled separator. Contrary to their interpretation,
we propose an alternative view, namely to assign eight of these eleven decay
chains of recoil-alpha(-alpha)-fission type to start from the 3n-evaporation
channel 115-288. The other three decay chains remain viable candidates for the
2n-evaporation channel 115-289. | nucl-ex |
Calculation of light nucleus reaction cross sections in Geant4: Total reaction cross sections of light projectile nucleus (H-2, H-3, He-3 and
He-4) interactions with nuclei are calculated using Geant4 models, and compared
with experimental data. It is shown that the models give various predictions at
low energies, in the region of the Coulomb barrier. "Shen model" (W.-Q. Shen et
al., Nucl. Phys. {\bf A491} (1989) 130) is identified as an improvement over
other models. | nucl-ex |
Direct determination of the atomic mass difference of the pairs
$^{76}$As-$^{76}$Se and $^{155}$Tb-$^{155}$Gd rules out $^{76}$As and
$^{155}$Tb as possible candidates for electron (anti)neutrino mass
measurements: The first direct determination of the ground-state-to-ground-state $Q$ values
of the $\beta^-$ decay $^{76}$As $\rightarrow$ $^{76}$Se and the
electron-capture decay $^{155}$Tb $\rightarrow$ $^{155}$Gd was performed
utilizing the double Penning trap mass spectrometer JYFLTRAP. By measuring the
atomic mass difference of the decay pairs via the phase-imaging
ion-cyclotron-resonance (PI-ICR) technique, the $Q$ values of $^{76}$As
$\rightarrow$ $^{76}$Se and $^{155}$Tb $\rightarrow$ $^{155}$Gd were determined
to be 2959.265(74) keV and 814.94(18) keV, respectively. The precision was
increased relative to earlier measurements by factors of 12 and 57,
respectively. The new $Q$ values are 1.33 keV and 5 keV lower compared to the
values adopted in the most recent Atomic Mass Evaluation 2020. With the newly
determined ground-state-to-ground-state $Q$ values combined with the excitation
energy from $\gamma$-ray spectroscopy, the $Q$ values for
ground-state-to-excited-state transitions $^{76}$As (ground state)
$\rightarrow$ $^{76}$Se$^*$ (2968.4(7) keV) and $^{155}$Tb (ground state)
$\rightarrow$ $^{155}$Gd$^*$ (815.731(3) keV) were derived to be -9.13(70) keV
and -0.79(18) keV. Thus we have confirmed that both of the $\beta^{-}$-decay
and EC-decay candidate transitions are energetically forbidden at a level of at
least 4$\sigma$, thus definitely excluding these two cases from the list of
potential candidates for the search of low-$Q$-value $\beta^-$ or EC decays to
determine the electron-(anti)neutrino mass. | nucl-ex |
Searching for Hybrid Mesons with GlueX: Hybrid mesons consist of a quark-antiquark pair bound together by a gluonic
field that is in an excited state. Measuring the spectrum of these states will
provide valuable information on the gluonic degrees of freedom of QCD in the
quark-confinement regime.
A rich spectrum of hybrid meson states has been predicted, but only a few
experiments have reported evidence of their existence. The GlueX experiment at
Jefferson Lab is designed to search for and measure the spectrum of light-mass
hybrid mesons, and it has began its physics run in Spring 2017. For the
experiment, a 12 GeV electron beam incident on a diamond radiator is used to
produce a linearly-polarized, coherent bremsstrahlung tagged-photon beam with a
coherent peak at 9 GeV. The linearly-polarized photon beam is incident on a
proton target located within the hermetic GlueX detector, which can detect many
different final states to which the hybrid mesons are predicted to decay.
Measurements with these initial data are discussed, including beam asymmetry
measurements, the search for photoproduced $\Xi$ baryons, and near-threshold
charm production. | nucl-ex |
Recent results from the strong interactions program of NA61/SHINE: The NA61/SHINE experiment studies hadron production in hadron+hadron,
hadron+nucleus and nucleus+nucleus collisions. The strong interactions program
has two main purposes: study the properties of the onset of deconfinement and
search for the signatures of the critical point of strongly interacting matter.
This aim is pursued by performing a two-dimensional scan of the phase diagram
by varying the energy/momentum (13A-158A GeV/c) and the system size (p+p,
Be+Be, Ar+Sc, Xe+La) of the collisions. This publication reviews recent results
from p+p, Be+Be and Ar+Sc interactions. Measured particle spectra are discussed
and compared to NA49 results from Pb+Pb collisions. The results illustrate the
progress towards scanning the phase diagram of strongly interacting matter. | nucl-ex |
Linear polarization-direction correlations in $γ$-ray scattering
experiments: Scattering measurements with incident linearly polarized $\gamma$ rays
provide information on spins, parities, and $\gamma$-ray multipolarity mixing
coefficients, and, therefore, on the nuclear matrix elements involved in the
transitions. We present the general formalism for analyzing the observed
angular correlations. The expressions are used to compute three-dimensional
radiation patterns, which are important tools for optimizing experimental
setups. Frequently, $\gamma$-ray transitions can proceed via two
multipolarities that mix coherently. In such cases, the relative phases of the
nuclear matrix elements are important when comparing results from different
measurements. We discuss different phase conventions that have been used in the
literature and present their relationships. Finally, we propose a basic
experimental geometry consisting of detectors located at four different spatial
locations. For this geometry, we present the measured anisotropies of the
emitted $\gamma$ rays in graphical format as an aid in the data analysis. | nucl-ex |
Measurement of hadron suppression and study of its connection with
vanishing $v_{\mathrm{3}}$ at low $\sqrt{s_{\mathrm{NN}}}$ in Au+Au
collisions with STAR: At top RHIC and LHC energies the suppression of high transverse momentum
($p_{\mathrm{T}}$) hadrons provides evidence for partonic energy loss in QGP.
We study partonic energy loss in the RHIC Beam Energy Scan (BES) by
investigating the centrality dependence of the binary-collision-scaled
high-$p_{\mathrm{T}}$ yields. Observing a decrease of the scaled yield in more
central collisions is proposed as a possible signature for jet quenching. Even
at energies and centralities where this signature is lost a QGP may still be
formed since competing phenomena responsible for enhancements may overwhelm the
suppression from energy loss. Measurements in several ranges of
$p_{\mathrm{T}}$ from $\sqrt{s_{_{\mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27,
39, 62.4, and 200 GeV data show that relative hadron suppression persists at
least down to 14.5 GeV.
To further investigate both the possible formation of a QGP at these lower
energies and whether the observed hadron suppression coincides with the onset
of other QGP signatures, we examine the energy and centrality dependence of
$v_{3}$. Models have shown that the development of $v_{3}$ requires the
presence of a low viscosity phase early in the collision. We find that for
collisions with $N_{\mathrm{part}}$<50, $v_{3}$ disappears for energies below
14.5 GeV, suggestive of a turn-off of the QGP. But for $N_{\mathrm{part}}$>50,
$v_{3}$ persists down to the lowest energies. Together, these signatures
provide possible evidence for the formation of a QGP in the lowest energy
collisions at RHIC. | nucl-ex |
Neutrons from multifragmentation reactions: The neutron emission in the fragmentation of stable and radioactive Sn and La
projectiles of 600 MeV per nucleon has been studied with the Large Neutron
Detector LAND coupled to the ALADIN forward spectrometer at SIS. A
cluster-recognition algorithm is used to identify individual particles within
the hit distributions registered with LAND. The obtained momentum distributions
are extrapolated over the full phase space occupied by the neutrons from the
projectile-spectator source. The mean multiplicities of spectator neutrons
reach values of up to 12 and depend strongly on the isotopic composition of the
projectile. An effective source temperature of T approx. 3 - 4 MeV is deduced
from the transverse momentum distributions.
For the interpretation of the data, calculations with the Statistical
Multifragmentation Model for a properly chosen ensemble of excited sources were
performed. The possible modification of the liquid-drop parameters of the
fragment description in the hot environment is studied, and a significant
reduction of the symmetry-term coefficient is found necessary to simultaneously
reproduce the neutron multiplicities and the mean neutron-to-proton ratios
<N>/Z of Z <= 10 fragments. Because of the similarity of the freeze-out
conditions with those encountered in supernova scenarios, this is of
astrophysical interest. | nucl-ex |
D^0 measurements in Au+Au Collisions at \sqrt{s_{NN}} = 200 GeV using
the STAR Silicon Inner Tracker: We present preliminary results from D^0 meson measurements through the
hadronic decay channel in minimum bias Au+Au collisions at \sqrt{s_{NN}} = 200
GeV at STAR. The measurements are performed using a secondary vertexing
technique that exploits the resolution given by the Silicon detectors available
in STAR. | nucl-ex |
Scaling Characteristics of Azimuthal Anisotropy at RHIC: Recent differential measurements of elliptic flow are used to probe several
hydrodynamic scaling predictions. Eccentricity scaling is observed for Cu+Cu
and Au+Au collisions at $\sqrt{s_{NN}}=~200$ GeV, suggesting essentially
complete thermalization of the high energy density matter produced in these
collisions. An estimate of the speed of sound is also obtained from the
eccentricity scaled elliptic flow. The predicted mass scaling is observed for
particles with transverse kinetic energy KE$_T$ up to $\sim 1$ GeV. For KE$_T$
values above $\sim 1$ GeV, valence quark number scaling compatible with
partonic degrees of freedom is observed. | nucl-ex |
High precision probe of the fully sequential decay width of the Hoyle
state in $^{12}$C: The decay path of the Hoyle state in $^{12}$C ($E_x=7.654\textrm{MeV}$) has
been studied with the
$^{14}\textrm{N}(\textrm{d},\alpha_2)^{12}\textrm{C}(7.654)$ reaction induced
at $10.5\textrm{MeV}$. High resolution invariant mass spectroscopy techniques
have allowed to unambiguously disentangle direct and sequential decays of the
state passing through the ground state of $^{8}$Be. Thanks to the almost total
absence of background and the attained resolution, a fully sequential decay
contribution to the width of the state has been observed. The direct decay
width is negligible, with an upper limit of $0.043\%$ ($95\%$ C.L.). The
precision of this result is about a factor $5$ higher than previous studies.
This has significant implications on nuclear structure, as it provides
constraints to $3$-$\alpha$ cluster model calculations, where higher precision
limits are needed. | nucl-ex |
Extraction of jet topology using three particle correlations: Recent theoretical studies have indicated that the topological features of
away-side jet fragments can be significantly altered by medium-induced
modifications. The leading candidates resulting from such modifications are
Mach Cones and deflected jets. We show that three particle correlations are
able to distinguish between these different modification scenarios. Initial
results from an application of the method to Au+Au collisions at RHIC
($\sqrt{s_{NN}}=200$ GeV) are presented. | nucl-ex |
Observation of a structure in the M$_{pη}$ invariant mass
distribution near 1700 MeV/$c^2$ in the $\mathbf{γp \rightarrow p π^0
η} $ reaction: The reaction $\gamma p \rightarrow p \pi^0 \eta$ has been studied with the
CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for
incident photon energies from threshold up to 3.1 GeV. This paper has been
motivated by the recently claimed observation of a narrow structure in the
M$_{N\eta}$ invariant mass distribution at a mass of 1678 MeV/$c^2$. The
existence of this structure cannot be confirmed in the present work. Instead,
for E$_{\gamma}$ = 1400 - 1500 MeV and the cut M$_{p\pi^0} \le 1190 $ MeV/$c^2$
a statistically significant structure in the M$_{p\eta}$ invariant mass
distribution near 1700 MeV/$c^2$ is observed with a width of $\Gamma\approx 35$
MeV/$c^2$ while the mass resolution is $\sigma_{res}$ = 5 MeV/$c^2$. Increasing
the incident photon energy from 1420 to 1540 MeV this structure shifts in mass
from $\approx$ 1700MeV/c$^2$ to $\approx$ 1725 MeV/$c^2$; the width increases
to about 50 MeV/$c^2$ and decreases thereafter. The cross section associated
with this structure reaches a maximum of $\approx$ 100 nb around E$_{\gamma}
\approx$ 1490 MeV (W $\approx $ 1920 MeV), which coincides with the $p a_0$
threshold. Three scenarios are discussed which might be the origin of this
structure in the M$_{p\eta}$ invariant mass distribution. The most likely
interpretation is that it is due to a triangular singularity in the $\gamma p
\rightarrow p a_0 \rightarrow p \pi^0 \eta$ reaction | nucl-ex |
Study of elastic and inelastic scattering of $^7$Be + $^{12}$C at 35 MeV: The elastic and inelastic scattering of $^7$Be from $^{12}$C have been
measured at an incident energy of 35 MeV. The inelastic scattering leading to
the 4.439 MeV excited state of $^{12}$C has been measured for the first time.
The experimental data cover an angular range of $\theta_{cm}$ =
15$^{\circ}$-120$^{\circ}$. Optical model analyses were carried out with
Woods-Saxon and double-folding potential using the density dependent M3Y
(DDM3Y) effective interaction. The microscopic analysis of the elastic data
indicates breakup channel coupling effect. A coupled-channel analysis of the
inelastic scattering, based on collective form factors, show that mutual
excitation of both $^7$Be and $^{12}$C is significantly smaller than the single
excitation of $^{12}$C. The larger deformation length obtained from the DWBA
analysis could be explained by including the excitation of $^7$Be in a
coupled-channel analysis. The breakup cross section of $^7$Be is estimated to
be less than 10$\%$ of the reaction cross section. The intrinsic deformation
length obtained for the $^{12}$C$^*$ (4.439 MeV) state is $\delta _2$ = 1.37
fm. The total reaction cross section deduced from the analysis agrees very well
with Wong's calculations for similar weakly bound light nuclei on $^{12}$C
target. | nucl-ex |
A Hadron Blind Detector for the PHENIX Experiment: A novel Hadron Blind Detector (HBD) has been developed for an upgrade of the
PHENIX experiment at RHIC. The HBD will allow a precise measurement of
electron-positron pairs from the decay of the light vector mesons and the
low-mass pair continuum in heavy-ion collisions. The detector consists of a 50
cm long radiator filled with pure CF4 and directly coupled in a windowless
configuration to a triple Gas Electron Multiplier (GEM) detector with a CsI
photocathode evaporated on the top face of the first GEM foil. | nucl-ex |
Isotopic effects in multifragmentation and the nuclear equation of state: Isotopic effects in spectator fragmentations following heavy-ion collisions
at relativistic energies are investigated using data from recent exclusive
experiments with SIS beams at GSI. Reactions of 12C on 112,124Sn at incident
energies 300 and 600 MeV per nucleon were studied with the INDRA multidetector
while the fragmentation of stable 124Sn and radioactive 107Sn and 124La
projectiles was studied with the ALADIN spectrometer.
The global characteristics of the reactions are very similar. This includes
the rise and fall of fragment production and deduced observables as, e.g., the
breakup temperature obtained from double ratios of isotope yields. The mass
distributions depend strongly on the neutron-to-proton ratio of the decaying
system, as expected for a simultaneous statistical breakup. The ratios of
light-isotope yields from neutron-rich and neutron-poor systems follow the law
of isoscaling. The deduced scaling parameters decrease strongly with increasing
centrality to values smaller than 50% of those obtained for the peripheral
event groups. This is not compensated by an equivalent rise of the breakup
temperatures which suggests a reduction of the symmetry term required in a
liquid-drop description of the fragments at freeze-out. | nucl-ex |
A Detailed Analysis and Monte Carlo Simulation of the Neutron Lifetime
Experiment S. Arzumanov et al., Phys. Lett. B 483 (2000) 15: We performed a detailed analysis and the Monte Carlo simulation of the
neutron lifetime experiment [S. Arzumanov et al., Phys. Lett. B 483 (2000) 15]
because of the strong disagreement by 5.6 standard deviations between the
results of this experiment and our experiment [A. Serebrov et al., Phys. Lett.
B 605 (2005) 72]. We found a few effects which were not taken into account in
the experiment [S. Arzumanov et al., Phys. Lett. B 483 (2000) 15]. The possible
correction is -5.5 s with uncertainty of 2.4 s which comes from initial data
knowledge. We assume that after taking into account this correction the result
of work [S. Arzumanov et al., Phys. Lett. B 483 (2000) 15] for neutron lifetime
885.4 +/- 0.9stat +/- 0.4syst s could be corrected to 879.9 +/- 0.9stat +/-
2.4syst s. | nucl-ex |
Open heavy flavour reconstruction in the ALICE central barrel: The ALICE experiment will be able to detect open charm and beauty hadrons in
proton-proton and heavy ion collisions in the new energy regime of the CERN
Large Hadron Collider (LHC). Heavy flavours are a powerful tool to investigate
the medium created in high energy nucleus--nucleus interactions because they
are produced in the hard scatterings occurring at early times and, thanks to
their long lifetime on the collision timescale, they probe all the stages of
the system evolution. The detectors of the ALICE central barrel ($-0.9 < \eta <
0.9$) will allow to track charged particles down to low transverse momentum
($\approx$ 100 MeV/$c$) and will provide hadron and electron identification as
well as an accurate measurement of the positions of primary and secondary
vertices. It will therefore be possible to measure the production of open heavy
flavours in the central rapidity region down to low transverse momentum,
exploiting the semi-electronic and the hadronic decay channels. Here we present
a general overview of the ALICE perspectives for heavy flavour physics and some
examples from the open charm and beauty analyses which have been developed and
tested on detailed simulations of the experimental apparatus. | nucl-ex |
Recent results from the NA61/SHINE strong interaction physics programme: The main physics goals of the NA61/SHINE programme on strong interactions are
the study of the properties of the onset of deconfinement and the search for
signatures of the critical point of strongly interacting matter. For this
purpose a scan of the two dimensional phase diagram ($T$-$\mu_{B}$) is being
performed at the SPS by measurements of hadron production in nucleus-nucleus
collisions as a function of collision energy and system size.
This contribution presents intriguing results on the energy dependence of
hadron spectra and yields in inelastic p+p and centrality selected Be+Be and
Ar+Sc collisions. In particular, the energy dependence of the signals of
deconfinement, the "horn", "step" and "kink", and new results on fluctuations
and correlations are shown and compared with the corresponding data of other
experiments and model predictions. | nucl-ex |
Investigation of the $\mathbf{Σ^{0}}$ Production Mechanism in p(3.5
GeV)+p Collisions: The production of $\Sigma^0$ hyperons in proton proton collisions at a beam
kinetic energy of 3.5 GeV impinging on a liquid hydrogen target was
investigated using data collected with the HADES setup. The total production
cross section is found to be $\mathrm{\sigma (pK^{+}\Sigma^{0}) [\mu b] = 17.7
\pm 1.7 (stat) \pm 1.6 (syst)}$. Differential cross section distributions of
the exclusive channel $\mathrm{pp \rightarrow pK^{+}\Sigma^{0}}$ were analyzed
in the center-of-mass, Gottfried-Jackson and helicity reference frames for the
first time at the excess energy of 556 MeV. The data support the interplay
between pion and kaon exchange mechanisms and clearly demonstrate the
contribution of interfering nucleon resonances decaying to
$\mathrm{K^{+}\Sigma^{0}}$. The Bonn-Gatchina partial wave analysis was
employed to analyse the data. Due to the limited statistics, it was not
possible to obtain an unambiguous determination of the relative contribution of
intermediate nucleon resonances to the final state. However nucleon resonances
with masses around 1.710 $\mathrm{GeV/c^{2}}$ ($\mathrm{N^{*}(1710)}$) and
1.900 $\mathrm{GeV/c^{2}}$ ($\mathrm{N^{*}(1900)}$ or
$\mathrm{\Delta^{*}(1900)}$) are preferred by the fit. | nucl-ex |
First observation of in-medium modifications of the omega meson: The photoproduction of omega mesons on nuclei has been investigated using the
Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The
aim is to study possible in-medium modifications of the omega meson via the
reaction A(gamma, omega)X. Results obtained for Nb are compared to a reference
measurement on a liquid hydrogen target. While for recoiling, long-lived mesons
(pi, eta and etaprime), which decay outside of the nucleus, a difference in the
lineshape for the two data samples is not observed, we find a significant
enhancement towards lower masses for omega mesons with low momenta produced on
the Nb target. | nucl-ex |
The behaviour of constrained caloric curves as ultimate signature of a
phase transition for hot nuclei: Simulations based on experimental data obtained from multifragmenting
quasifused nuclei produced in central 129Xe + natSn collisions have been used
to deduce event by event freeze-out properties on the thermal excitation energy
range 4-12 AMeV. From these properties and temperatures deduced from proton
transverse momentum fluctuations constrained caloric curves have been built. At
constant average volumes caloric curves exhibit a monotonous behaviour whereas
for constrained pressures a backbending is observed. Such results support the
existence of a first order phase transition for hot nuclei. | nucl-ex |
High precision half-life measurement of $^{125}$Cs and $^{125}$Xe with
γ-spectroscopy: In order to provide data for the simulation of the astrophysical
$\gamma$-process, the cross section measurement of the
$^{124}$Xe(p,$\gamma$)$^{125}$Cs reaction is in progress at MTA Atomki using
the activation technique. Precise information on the decay characteristics of
the reaction products is of crucial importance for measurements carried out
using this method. The half-lives of the produced $^{125}$Cs and its daughter
$^{125}$Xe are published in previous works, but with large uncertainties and
ambiguous values. To make these nuclear parameters more precise, the half-lives
have been re-measured with high precision using $\gamma$-spectroscopy. The
obtained new half-life values are t$_{1/2}$ = 44.35 $\pm$ 0.29 minutes for
$^{125}$Cs and t$_{1/2}$ = 16.87 $\pm$ 0.08 hours for $^{125}$Xe. | nucl-ex |
Wanted! Nuclear Data for Dark Matter Astrophysics: Astronomical observations from small galaxies to the largest scales in the
universe can be consistently explained by the simple idea of dark matter. The
nature of dark matter is however still unknown. Empirically it cannot be any of
the known particles, and many theories postulate it as a new elementary
particle. Searches for dark matter particles are under way: production at
high-energy accelerators, direct detection through dark matter-nucleus
scattering, indirect detection through cosmic rays, gamma rays, or effects on
stars. Particle dark matter searches rely on observing an excess of events
above background, and a lot of controversies have arisen over the origin of
observed excesses. With the new high-quality cosmic ray measurements from the
AMS-02 experiment, the major uncertainty in modeling cosmic ray fluxes is in
the nuclear physics cross sections for spallation and fragmentation of cosmic
rays off interstellar hydrogen and helium. The understanding of direct
detection backgrounds is limited by poor knowledge of cosmic ray activation in
detector materials, with order of magnitude differences between simulation
codes. A scarcity of data on nucleon spin densities blurs the connection
between dark matter theory and experiments. What is needed, ideally, are more
and better measurements of spallation cross sections relevant to cosmic rays
and cosmogenic activation, and data on the nucleon spin densities in nuclei. | nucl-ex |
Inclusive J/$ψ$ and $ψ$(2S) production in pp and p-Pb collisions
at forward rapidity with ALICE at the LHC: The ALICE collaboration has studied inclusive J/$\psi$ and $\psi$(2S)
production at forward rapidities in pp collisions at $\sqrt{s} = 7$ TeV with
the ALICE Muon Spectrometer. The analysis has been carried out on a data sample
corresponding to an integrated luminosity $\mathcal{L}_{\rm int}$ = 1.35
pb$^{-1}$. The production cross-sections of J/$\psi$ and $\psi$(2S), integrated
over the transverse momentum (0 $<$ $p_{{\mathrm T}}$ $<$ 20 GeV/$c$) and
rapidity (2.5 $<$ $y$ $<$ 4), have been measured. The J/$\psi$ and $\psi$(2S)
differential cross-sections, in transverse momentum and rapidity, have also
been measured, significantly extending the $p_{{\mathrm T}}$ reach of previous
measurements performed in the same $y$-range. The results have been compared
with the previously published ALICE results ($\mathcal{L}_{\rm int}$ = 15.6
nb$^{-1}$) and also with the measurement performed by the LHCb collaboration.
The $\psi$(2S)/J/$\psi$ ratio, integrated over $p_{{\mathrm T}}$ and $y$, has
been measured. This ratio has also been evaluated as a function of transverse
momentum and rapidity and compared with the LHCb measurement. Finally, recent
results on cross-sections, $\psi$(2S)/J/$\psi$ production ratio, nuclear
modification factor ($R_{\rm pPb}$) and forward-to-backward yield ratio
($R_{\rm FB}$) in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV will be
discussed. | nucl-ex |
Acceptance effects in the hyperons global polarization measurement: The possible sources of systematic uncertainties in the hyperons global
polarization measurement are discussed. The equation with detector acceptance
effects taken into account is provided. Contribution of the hyperons directed
flow into the hyperons global polarization measurement is shown. The systematic
uncertainties of the Lambda hyperons global polarization measurement in Au+Au
collisions with the STAR detector at RHIC are calculated. | nucl-ex |
Differential studies of inclusive J/$ψ$ and $ψ$(2S) production at
forward rapidity in Pb-Pb collisions at $\mathbf{\sqrt{{\textit s}_{_{NN}}}}$
= 2.76 TeV: The production of J/$\psi$ and $\psi(2S)$ was measured with the ALICE
detector in Pb-Pb collisions at the LHC. The measurement was performed at
forward rapidity ($2.5 < y < 4 $) down to zero transverse momentum ($p_{\rm
T}$) in the dimuon decay channel. Inclusive J/$\psi$ yields were extracted in
different centrality classes and the centrality dependence of the average
$p_{\rm T}$ is presented. The J/$\psi$ suppression, quantified with the nuclear
modification factor ($R_{\rm AA}$), was studied as a function of centrality,
transverse momentum and rapidity. Comparisons with similar measurements at
lower collision energy and theoretical models indicate that the J/$\psi$
production is the result of an interplay between color screening and
recombination mechanisms in a deconfined partonic medium, or at its
hadronization. Results on the $\psi(2S)$ suppression are provided via the ratio
of $\psi(2S)$ over J/$\psi$ measured in pp and Pb-Pb collisions. | nucl-ex |
Dielectron production in proton-proton collisions at $\sqrt{s} = 7$ TeV
with ALICE: The ALICE Collaboration measured dielectron production as a function of the
invariant mass ($m_{\rm ee}$), the pair transverse momentum ($p_{\rm T,ee}$)
and the pair distance of closest approach ($\rm DCA_{ee}$) in pp collisions at
$\sqrt{s} = 7$ TeV. Prompt and non-prompt dielectron sources can be separated
with the $\rm DCA_{ee}$, which will give the opportunity in heavy-ion
collisions to identify thermal radiation from the medium in the
intermediate-mass range dominated by contributions from open-charm and beauty
hadron decays. The charm and beauty total cross sections are extracted from the
data by fitting the spectra with two different MC generators, i.e. PYTHIA a
leading order event generator and POWHEG a next-to-leading order event
generator. Significant model dependences are observed, reflecting the
sensitivity of this measurement to the heavy-flavour production mechanisms. | nucl-ex |
The beta-decay of 22Al: In an experiment performed at the LISE3 facility of GANIL, we studied the
decay of 22Al produced by the fragmentation of a 36Ar primary beam. A
beta-decay half-life of 91.1 +- 0.5 ms was measured. The beta-delayed one- and
two-proton emission as well as beta-alpha and beta-delayed gamma decays were
measured and allowed us to establish a partial decay scheme for this nucleus.
New levels were determined in the daughter nucleus 22Mg. The comparison with
model calculations strongly favours a spin-parity of 4+ for the ground state of
22Al. | nucl-ex |
Coherent photonuclear reactions for isotope transmutation: Coherent photonuclear isotope transmutation (CPIT) produces exclusively
radioactive isotopes (RIs) by coherent photonuclear reactions via E1 giant
resonances. Photons to be used are medium energy photons produced by laser
photons backscattered off GeV electrons. The cross sections are as large as 0.2
- 0.6 b, being independent of individual nuclides. A large fraction of photons
is effectively used for the photonuclear reactions, while the scattered GeV
electrons remain in the storage ring to be re-used. CPIT with medium energy
photons provides specific/desired RIs with the high rate and the high density
for nuclear science, molecular biology and for nuclear medicines. | nucl-ex |
A Future Polarized Drell-Yan Experiment at Fermilab: One of the great challenges of QCD is trying to understand the origin of the
nucleon spin. Several decades of experimental measurements have shown that our
current understanding is incomplete if only the quark and gluon spin
contribution is considered. Over the last few years it has become increasingly
clear that the contribution from the orbital angular momentum of the quarks and
gluons has to be included as well. For instance, the sea quark orbital
contribution remains largely unexplored. Measurements accessing the sea quark
Sivers distribution will provide a probe of the sea quark orbital contribution.
The upcoming E1039 experiment at Fermilab will access this distribution via the
Drell-Yan process using a 120 GeV unpolarized proton beam directed on a
polarized proton target. At E1039 kinematics the $u$-$\bar{u}$ annihilation
process dominates the Drell-Yan cross section ($x_{Target}$ = 0.1 $\sim$ 0.35).
If the $\bar{u}$ quark carries zero net angular momentum, then the measured
Drell-Yan single-spin asymmetry should be zero, and vice versa. This experiment
is a continuation of the currently running SeaQuest experiment. | nucl-ex |
Production of ${\rm K}^{0}_{\rm{S}}$, $Λ$ ($\barΛ$),
$Ξ^{\pm}$ and $Ω^{\pm}$ in jets and in the underlying event in pp and
p$-$Pb collisions: The production of strange hadrons (K$^{0}_{\rm S}$, $\Lambda$, $\Xi^{\pm}$,
and $\Omega^{\pm}$), baryon-to-meson ratios ($\Lambda/{\rm K}^0_{\rm S}$,
$\Xi/{\rm K}^0_{\rm S }$, and $\Omega/{\rm K}^0_{\rm S}$), and baryon-to-baryon
ratios ($\Xi/\Lambda$, $\Omega/\Lambda$, and $\Omega/\Xi$) associated with jets
and the underlying event were measured as a function of transverse momentum
($p_{\rm T}$) in pp collisions at $\sqrt{s} = 13$ TeV and p-Pb collisions at
$\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector at the LHC. The
inclusive production of the same particle species and the corresponding ratios
are also reported. The production of multi-strange hadrons, $\Xi^{\pm}$ and
$\Omega^{\pm}$, and their associated particle ratios in jets and in the
underlying event are measured for the first time. In both pp and p-Pb
collisions, the baryon-to-meson and baryon-to-baryon yield ratios measured in
jets differ from the inclusive particle production for low and intermediate
hadron $p_{\rm T}$ (0.6$-$6 GeV/$c$). Ratios measured in the underlying event
are in turn similar to those measured for inclusive particle production. In pp
collisions, the particle production in jets is compared with PYTHIA 8
predictions with three colour-reconnection implementation modes. None of them
fully reproduces the data in the measured hadron $p_{\rm T}$ region. The
maximum deviation is observed for $\Xi^{\pm}$ and $\Omega^{\pm}$, which reaches
a factor of about six. In p-Pb collisions, there is no significant
event-multiplicity dependence for particle production in jets, in contrast to
what is observed in the underlying event. The presented measurements provide
novel constraints on hadronisation and its Monte Carlo description. In
particular, they demonstrate that the fragmentation of jets alone is
insufficient to describe the strange and multi-strange particle production in
hadronic collisions at LHC energies. | nucl-ex |
Radioisotopes production using lasers: from basic science to
applications: Laser technologies improved after the understanding of the Chirped Pulse
Amplification (CPA) which allows energetic laser beams to be compressed to tens
of femtosecond (fs) pulse durations and focused to few $\mu$m. Protons of tens
of MeV can be accelerated using for instance the Target Normal Sheath
Acceleration (TNSA) method and focused on secondary targets. In such
conditions, nuclear reactions can occur and radioisotopes relevant for medical
purposes be produced. High repetition lasers can be used to produce enough
isotopes for medical applications. This route is competitive to conventional
methods mostly based on accelerators. In this paper we study the production of
$^{67}$Cu, $^{63}$Zn, $^{18}$F and $^{11}$C currently used in positron emission
tomography (PET) and other applications. At the same time, we study the
reaction $^{10}$B(p,$\alpha$)$^{7}$Be and $^{70}$Zn(p,4n)$^{67}$Ga to put
further constraints to the proton distributions at different angles and to the
reaction $^{11}$B(p,$\alpha$)$^{8}$Be relevant for energy production. The
experiment was performed at the 1 petawatt (PW) laser facility at Vega III
located in Salamanca-Spain. Angular distributions of radioisotopes in the
forward (with respect to the laser direction) and backward directions were
measured using a High Purity Germanium Detector (HPGE). Our results are
reasonably reproduced by the numerical estimates following the approach of
Kimura et al. (NIMA637(2011)167) | nucl-ex |
Measurement of azimuthal anisotropy of muons from charm and bottom
hadrons in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV with the
ATLAS detector: Azimuthal anisotropies of muons from charm and bottom hadron decays are
measured in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}= 5.02$ TeV. The data were
collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2018
with integrated luminosities of $0.5~\mathrm{nb}^{-1}$ and
$1.4~\mathrm{nb^{-1}}$, respectively. The kinematic selection for heavy-flavor
muons requires transverse momentum $4 < p_\mathrm{T} < 30$ GeV and
pseudorapidity $|\eta|<2.0$. The dominant sources of muons in this
$p_\mathrm{T}$ range are semi-leptonic decays of charm and bottom hadrons.
These heavy-flavor muons are separated from light-hadron decay muons and
punch-through hadrons using the momentum imbalance between the measurements in
the tracking detector and in the muon spectrometers. Azimuthal anisotropies,
quantified by flow coefficients, are measured via the event-plane method for
inclusive heavy-flavor muons as a function of the muon $p_\mathrm{T}$ and in
intervals of Pb+Pb collision centrality. Heavy-flavor muons are separated into
contributions from charm and bottom hadron decays using the muon transverse
impact parameter with respect to the event primary vertex. Non-zero elliptic
($v_{2}$) and triangular ($v_{3}$) flow coefficients are extracted for charm
and bottom muons, with the charm muon coefficients larger than those for bottom
muons for all Pb+Pb collision centralities. The results indicate substantial
modification to the charm and bottom quark angular distributions through
interactions in the quark-gluon plasma produced in these Pb+Pb collisions, with
smaller modifications for the bottom quarks as expected theoretically due to
their larger mass. | nucl-ex |
Octupole strength in the neutron-rich calcium isotopes: Low-lying excited states of the neutron-rich calcium isotopes $^{48-52}$Ca
have been studied via $\gamma$-ray spectroscopy following inverse-kinematics
proton scattering on a liquid hydrogen target using the GRETINA $\gamma$-ray
tracking array. The energies and strengths of the octupole states in these
isotopes are remarkably constant, indicating that these states are dominated by
proton excitations. | nucl-ex |
Indications for a critical point in the phase diagram for hot and dense
nuclear matter: Two-pion interferometry measurements are studied for a broad range of
collision centralities in Au+Au (Root_s = 7.7 - 200 GeV) and Pb+Pb (Root_s =
2.76 TeV) collisions. They indicate non-monotonic excitation functions for the
Gaussian emission source radii difference [(R_out)^2 - (R_side)^2], suggestive
of reaction trajectories which spend a fair amount of time near a "soft point"
in the equation of state (EOS) that coincides with the critical end point
(CEP). A Finite-Size Scaling (FSS) analysis of these excitation functions,
provides further validation tests for the CEP. It also indicates a second order
phase transition at the CEP, and the values T^{cep} ~ 165 MeV and mu_B^{cep} ~
95 MeV for its location in the (T, mu_B)-plane of the phase diagram. The static
critical exponents (nu ~ 0.66 and gamma ~ 1.2) extracted via the same FSS
analysis, place this CEP in the 3D Ising model universality class. A Dynamic
Finite-Size Scaling analysis of the excitation functions, gives the estimate z
~ 0.87 for the dynamic critical exponent, suggesting that the associated
critical expansion dynamics is dominated by the hydrodynamic sound mode. | nucl-ex |
Study of the ground and excited states of Lambda and Sigma hyperon
production at COSY: COSY with a maximum beam momentum of ~3.65 GeV/c allows the production of
ground state (Lambda and Sigma) and excited hyperons (Lambda(1405), Sigma(1385)
and Lambda(1520)) in elementary NN interactions. The existing data base in this
field is rather poor. A systematic study of the hyperon production at COSY will
result in an improvement of our understanding concerning topics like
hyperon-nucleon interaction, kaon-nucleon interaction, nucleon resonances,
strangeness production mechanism and structure of the Lambda(1405). Precise
data on Lambda and Sigma production have been produced at the COSY-11 and TOF
installation. With the WASA detector at COSY these studies can be continued and
extended to channels including photons in the final state. | nucl-ex |
High-precision mass measurement of $^{56}$Cu and the redirection of the
rp-process flow: We report the mass measurement of $^{56}$Cu, using the LEBIT 9.4T Penning
trap mass spectrometer at the National Superconducting Cyclotron Laboratory at
Michigan State University. The mass of $^{56}$Cu is critical for constraining
the reaction rates of the
$^{55}$Ni(p,$\gamma$)$^{56}$Cu(p,$\gamma$)$^{57}$Zn($\beta^+$)$^{57}$Cu bypass
around the $^{56}$Ni waiting point. Previous recommended mass excess values
have disagreed by several hundred keV. Our new value, ME=$-38 626.7(6.4)$ keV,
is a factor of 30 more precise than the suggested value from the 2012 atomic
mass evaluation [Chin. Phys. C {\bf{36}}, 1603 (2012)], and more than a factor
of 12 more precise than values calculated using local mass extrapolations,
while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C
{\bf{41}}, 030003 (2017)]. The new experimental average was used to calculate
the astrophysical $^{55}$Ni(p,$\gamma$) and $^{57}$Zn($\gamma$,p) reaction
rates and perform reaction network calculations of the rp-process. These show
that the rp-process flow redirects around the $^{56}$Ni waiting point through
the $^{55}$Ni(p,$\gamma$) route, allowing it to proceed to higher masses more
quickly and resulting in a reduction in ashes around this waiting point and an
enhancement to higher-mass ashes. | nucl-ex |
Secondary nuclear fragment beams for investigations of relativistic
fragmentation of light radioactive nuclei using nuclear photoemulsion at
Nuclotron: Slowly extracted relativistic beams of light nuclei and a beam transportation
line net system constitute a good base for secondary nuclear beams forming at
the LHE accelerator facility. A recent years activity in the field at the
Laboratory is connected with a project on study light nuclei structure by means
the emulsion technique [1,2]. The paper shortly summarizes results of the work. | nucl-ex |
The i11/2 f5/2 and i11/2 p3/2 neutron particle-hole multiplets in 208Pb: Inelastic proton scattering via isobaric analog resonances allows to derive
rather complete information about neutron particle-hole states. We applied this
method to the doubly-magic nucleus 208Pb by measuring angular distributions of
208Pb(p, p') on top of the isobaric analog resonances in 209Bi with the Q3D
magnetic spectrograph at M\"unchen. We identify the six states of the i11/2
f5/2 multiplet and the four states of the i11/2 p3/2 multiplet in the energy
range 4.6 MeV < Ex < 5.3 MeV. Firm spin assignments for the ten states are
given, some of them new. Additional measurements of the reaction 207Pb(d, p)
confirm the fragmented i11/2 p1/2 multiplet. | nucl-ex |
Experimental neutron capture data of $^{58}$Ni from the CERN n_TOF
facility: The $^{58}$Ni $(n,\gamma)$ cross section has been measured at the neutron
time of flight facility n_TOF at CERN, in the energy range from 27 meV up to
400 keV. In total, 51 resonances have been analyzed up to 122 keV. Maxwellian
averaged cross sections (MACS) have been calculated for stellar temperatures of
kT$=$5-100 keV with uncertainties of less than 6%, showing fair agreement with
recent experimental and evaluated data up to kT = 50 keV. The MACS extracted in
the present work at 30 keV is 34.2$\pm$0.6$_\mathrm{stat}\pm$1.8$_\mathrm{sys}$
mb, in agreement with latest results and evaluations, but 12% lower relative to
the recent KADoNIS compilation of astrophysical cross sections. When included
in models of the s-process nucleosynthesis in massive stars, this change
results in a 60% increase of the abundance of $^{58}$Ni, with a negligible
propagation on heavier isotopes. The reason is that, using both the old or the
new MACS, 58Ni is efficiently depleted by neutron captures. | nucl-ex |
A New Measurement of the 6Li(n,α)t Cross Section at MeV Energies
Using a Fission Chamber and 6Li Scintillators: A new measurement is presented of the $^6$Li(n,$\alpha$)t cross section from
245 keV to 10 MeV using a $^{252}$Cf fission chamber with $^6$LiI(Eu) and
Cs$_2$LiYCl$_6$:Ce (CLYC) scintillators which act as both target and detector.
Neutron energies are determined from the time of flight (TOF) method using the
signals from spontaneous fission and reaction product recoil. Simulations of
neutron downscatter in the crystals and fission chamber bring
$^6$Li(n,$\alpha$)t cross section values measured with the $^6$LiI(Eu) into
agreement with previous experiments and evaluations, except for two resonances
at 4.2 and 6.5 MeV introduced by ENDF/B-VII.1. Suspected neutron transport
modeling issues cause the cross section values obtained with CLYC to be
discrepant above 2 MeV. | nucl-ex |
Freeze-out radii extracted from three-pion cumulants in pp, p-Pb and
Pb-Pb collisions at the LHC: In high-energy collisions, the spatio-temporal size of the particle
production region can be measured using the Bose-Einstein correlations of
identical bosons at low relative momentum. The source radii are typically
extracted using two-pion correlations, and characterize the system at the last
stage of interaction, called kinetic freeze-out. In low-multiplicity
collisions, unlike in high-multiplicity collisions, two-pion correlations are
substantially altered by background correlations, e.g. mini-jets. Such
correlations can be suppressed using three-pion cumulant correlations. We
present the first measurements of the size of the system at freeze-out
extracted from three-pion cumulant correlations in pp, p-Pb and Pb-Pb
collisions at the LHC with ALICE. At similar multiplicity, the invariant radii
extracted in p-Pb collisions are found to be 5-15% larger than those in pp,
while those in Pb-Pb are 35-55% larger than those in p-Pb. Our measurements
disfavor models which incorporate substantially stronger collective expansion
in p-Pb as compared to pp collisions at similar multiplicity. | nucl-ex |
Shape changes in the mirror nuclei $^{70}$Kr and $^{70}$Se: We studied the proton-rich $T_z=-1$ nucleus $^{70}$Kr through inelastic
scattering at intermediate energies in order to extract the reduced transition
probability, $B(E2;\;0^+ \rightarrow 2^+)$. Comparison with the other members
of the $A=70$ isospin triplet, $^{70}$Br and $^{70}$Se, studied in the same
experiment, shows a $3\sigma$ deviation from the expected linearity of the
electromagnetic matrix elements as a function of $T_z$.
At present, no established nuclear structure theory can describe this
observed deviation quantitatively. This is the first violation of isospin
symmetry at this level observed in the transition matrix elements. A heuristic
approach may explain the anomaly by a shape change between the mirror nuclei
$^{70}$Kr and $^{70}$Se contrary to the model predictions. | nucl-ex |
Correlations of electrons from heavy flavor decay in p+p, d+Au and Au+Au
collisions: In relativistic heavy ion collisions heavy flavor probes are crucial to
understand the interactions between partons and the produced hot nuclear
matter. Measurements in p+p collisions provide information about how the heavy
quarks are produced and fragment and in d+Au collisions are sensitive to
possible effects from cold nuclear matter. Azimuthal correlation measurements
involving heavy flavor probes are complementary to single particle spectra
measurements and provide additional information about production and
interactions of heavy quarks. Measurements of electrons with heavy flavor decay
with other hadrons from the event can provide information about how the heavy
quark interacts with the produced matter and can be compared to similar
measurements from light hadron correlations. Correlations between electrons
from heavy flavor decay with muons, also from heavy flavor decay, can provide
further information about heavy flavor production and cold nuclear matter
effects in d+Au collisions with a very clean signal. We present PHENIX results
for electron-hadron correlations in p+p and Au+Au collisions and electron-muon
correlations in p+p and d+Au collisions and discuss the implications of these
measurements. | nucl-ex |
Proton induced reactions on naturalU at 62.9 MeV: Double differential cross sections (DDCS) for light charged particles
(proton, deuteron, triton, 3He, alpha) and neutrons produced by a proton beam
impinging on a 238U target at 62.9 MeV were measured at the CYCLONE facility in
Louvain-la-Neuve (Belgium). These measurements have been performed using two
independent experimental set-ups ensuring neutron (DeMoN counters) and light
charged particles (Si-Si-CsI telescopes) detection. The charged particle data
were measured at 11 different angular positions from 25 degrees to 140 degrees
allowing the determination of angle differential, energy differential and total
production cross sections. | nucl-ex |
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