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High-Precision Measurement of the 19Ne Half-Life and Implications for
Right-Handed Weak Currents: We report a precise determination of the 19Ne half-life to be $T_{1/2} =
17.262 \pm 0.007$ s. This result disagrees with the most recent precision
measurements and is important for placing bounds on predicted right-handed
interactions that are absent in the current Standard Model. We are able to
identify and disentangle two competing systematic effects that influence the
accuracy of such measurements. Our findings prompt a reassessment of results
from previous high-precision lifetime measurements that used similar equipment
and methods. | nucl-ex |
Ionoacoustic detection of swift heavy ions: The maximum energy loss (Bragg peak) located near the end of range is a
characteristic feature of ion stopping in matter, which generates an acoustic
pulse, if ions are deposited into a medium in adequately short bunches. This
so-called ionoacoustic effect has been studied for decades, mainly for
astrophysical applications, and it has recently found renewed interest in
proton therapy for precise range measurements in tissue. After detailed
preparatory studies with 20 MeV protons at the MLL tandem accelerator,
ionoacoustic range measurements were performed in water at the upgraded SIS18
synchrotron of GSI with 238U and 124Xe ion beams of energy about 300 MeV/u, and
12C ions of energy about 200 MeV/u using fast beam extraction to get 1
microsecond pulse lengths. Acoustic signals were recorded in axial geometry by
standard piezo-based transducers at a 500 kHz mean frequency and evaluated in
both the time and frequency domains. The resulting ranges for the different
ions and energies were found to agree with Geant4 simulations as well as
previous measurements to better than 1%. Given the high accuracy provided by
ionoacoustic range measurements in water and their relative simplicity, we
propose this new method for stopping power measurements for heavy ions at GeV
energies and above. Our experimental results clearly demonstrate the potential
of an ionoacoustic particle monitor especially for very intense heavy ion beams
foreseen at future accelerator facilities. | nucl-ex |
Accelerated electron thermometer: observation of 1D Planck radiation: We report on the observation of thermal photons from an accelerated electron
via examination of radiative beta decay of free neutrons measured by the RDK II
collaboration. The emitted photon spectrum is shown to corroborate a thermal
distribution consistent with the dynamical Casimir effect. Supported by a
robust chi-squared statistic, we find the photons reside in a one-dimensional
Planck spectrum with a temperature predicted by the moving mirror model. | nucl-ex |
Study of Azimuthal Correlations in the Target Fragmentation Region in p,
d, He, C+C, Ta and C+Ne, Cu Collisions at a Momentum of 4.2, 4.5 and 10
AGeV/c: Azimuthal correlations between the same type of particles (protons or pions)
in the target fragmentation region was studied in d, He, C + C, Ta (4.2
AGeV/c), C + Ne, Cu (4.5AGeV/c) and p + C, Ta (10 GeV/c) interactions. The data
were obtained from the SKM-200-GIBS streamer chamber and from Propane Bubble
Chamber (PBL-500) systems utilized at JINR. Study of multiparticle azimuthal
correlations offers unique information about space-time evolution of the
interactions. Azimuthal correlations were investigated by using correlation
function C($\Delta\phi$)=dN/d($\Delta\phi$), where $\Delta\phi$ represents the
angle between the sums of transverse momenta vectors for particles emitted in
the forward and backward hemispheres. For protons a "back-to back" ("negative")
azimuthal correlations were observed in the above mentioned interactions. The
absolute values of the correlation coefficient $|\xi|$ -- the slope parameter
of C($\Delta\phi$), strongly depend on the mass number of the target ($A_T$)
nuclei in the nucleon-nucleus and nucleus-nucleus collisions. Namely, $|\xi|$
-- decreases with increase of $A_T$ in p+C and p+Ta collisions, while $|\xi|$
decreases from d+C up to C+Ne and then almost does not change with increase of
$A_P$, $A_T$ in (d+He)Ta, C+Cu and C+Ta collisions. For pions a "back-to-back"
correlations were obtained for a light targets (C, Ne), and a "side-by-side"
("positive") correlations for a heavy targets (Cu, Ta). The $|\xi|$
insignificantly changes with increase of the momenta per nucleon and almost
does not change with increase of $A_P$ and $A_T$. Models, used for description
of the data -- the Ultra relativistic Quantum Molecular Dynamic (UrQMD) and
Quark-Gluon String Model (QGSM), satisfactorily describe the obtained
experimental results. | nucl-ex |
Level density of 2+ states in 40Ca from high energy-resolution (p,p')
experiments: The level density of 2+ states in 40Ca has been extracted in the energy
region of the isoscalar giant quadrupole resonance (ISGQR) from a fluctuation
analysis of high energy-resolution p,p') data taken at incident energies of 200
MeV at the K600 magnetic spectrometer of iThemba LABS, South Africa. Quasi-free
scattering cross sections were calculated to estimate their role as a
background contribution to the spectra and found to be small. The shape of the
background was determined from the discrete wavelet transform of the spectra
using a biorthogonal wavelet function normalized at the lowest particle
separation threshold. The experimental results are compared to widely used
phenomenological and microscopic models. | nucl-ex |
(Anti)nucleosynthesis in heavy-ion collisions and (anti)nuclei as
"baryonmeter" of the collision: The production mechanism of light (anti)nuclei in heavy-ion collisions has
been extensively studied experimentally and theoretically. Two competing
(anti)nucleosynthesis models are typically used to describe light (anti)nuclei
yields and their ratios to other hadrons in heavy-ion collisions: the
statistical hadronization model (SHM) and the nucleon coalescence model. The
possibility to distinguish these phenomenological models calls for new
experimental observables. Given their large baryon number, light (anti)nuclei
have a high sensitivity to the baryon chemical potential ($\mu_{\rm B}$) of the
system created in the collision. In this talk, the first measurement of
event-by-event antideuteron number fluctuations in heavy-ion collisions is
presented and compared with expectations of the SHM and coalescence model. In
addition, the antinuclei-to-nuclei ratios are used to obtain a measurement of
$\mu_{\rm B}$ in heavy-ion collisions with unprecedented precision. | nucl-ex |
Study of the N=50 major shell effect close to $^{78}$Ni : First evidence
of a weak coupling structure in $^{83}\_{32}$Ge$\_{51}$ and three-proton
configuration states in $^{81}\_{31}$Ga$\_{50}$: New levels were attributed to $^{81}\_{31}$Ga$\_{50}$ and
$^{83}\_{32}$Ge$\_{51}$ which were fed by the $\beta$-decay of their respective
mother nuclei $^{81}\_{30}$Zn$\_{51}$ and $^{83}\_{31}$Ga$\_{52}$ produced by
fission at the "PARRNe" ISOL set-up installed at the Tandem accelerator of the
Institut de Physique Nucl\'eaire, Orsay. We show that the low energy structure
of $^{81}\_{31}$Ga$\_{50}$ and $^{83}\_{32}$Ge$\_{51}$ can easily be explained
within the natural hypothesis of a strong energy gap at N=50 and a doubly-magic
character for $^{78}$Ni. | nucl-ex |
Coherent rho^0 Production in Ultra-Peripheral Heavy Ion Collisions: The STAR collaboration reports the first observation of exclusive rho^0
photo-production, AuAu->AuAu rho^0, and rho^0 production accompanied by mutual
nuclear Coulomb excitation, AuAu->Au*Au*rho^0, in ultra-peripheral heavy-ion
collisions. The rho^0 have low transverse momenta, consistent with coherent
coupling to both nuclei. The cross sections at sqrt(s_NN)=130GeV agree with
theoretical predictions treating rho^0 production and Coulomb excitation as
independent processes. | nucl-ex |
Strangelet Searches in High Energy Heavy Ion Collisions: In this contribution I concentrate on the recent results from experiment E864
at the BNL-AGS. E864's recent analysis have achieved sensitivities of
approximately $3\times 10^{-8}$ per 10% central interaction for the production
of charged strangelets and the first analysis for neutral strangelets is near
completion. I put the results in the context of coalescence and quark gluon
plasma strangelet production models. | nucl-ex |
Emerging collectivity from the nuclear structure of $^{132}$Xe:
Inelastic neutron scattering studies and shell-model calculations: Inelastic neutron scattering was used to study the low-lying nuclear
structure of $^{132}$Xe. A comprehensive level scheme is presented, as well as
new level lifetimes, multipole mixing ratios, branching ratios, and transition
probabilities. Comparisons of these data as well as previously measured $E2$
strengths and $g$ factors are made with new shell-model calculations for
$^{132,134,136}$Xe to explore the emergence of collectivity in the Xe isotopes
with $N$ < 82 near the closed shell. | nucl-ex |
Measurement of electrons from heavy-flavour decays in pp and Pb-Pb
collisions with ALICE at the LHC: The ALICE experiment has measured at mid-rapidity electrons from
heavy-flavour decays in pp collisions at $\sqrt{s}$ = 2.76 and 7 TeV, and in
Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV. In pp collisions, electrons
from charm-hadron and from beauty-hadron decays are identified by applying cuts
on displaced vertices. The relative yield of electrons from beauty-hadron
decays to those from heavy-flavour decays is extracted using electron-hadron
correlations. Results are compared to pQCD-based calculations. In Pb-Pb
collisions, the $p_{\rm T}$ dependence of the nuclear modification factor of
electrons from heavy-flavour decays is presented in two centrality classes. The
status on the analysis of electrons from beauty-hadron decays is reported in
Pb-Pb collisions, in view of the measurement of the corresponding nuclear
modification factor. | nucl-ex |
πN and ηp deexcitation channels of the N^* and Δbaryonic
resonances between 1470 and 1680 MeV: Two reactions, pp->ppX and pp->p\pi^+X, are used to study the 1.47<M<1.68 GeV
baryonic mass range. Three different final states are considered in the
invariant masses: N^* or \Delta^+, p\pi^0, and p\eta. The last two channels are
defined by software cuts applied to the missing mass of the first reaction.
Several narrow structures are extracted with widths \sigma(\Gamma) varying
between 3 and 9 MeV. Some structures are observed in one channel but not in
others. Such nonobservation may be due either to the spectrometer momenta
limits or to the physics (e.g. no such disintegration channel is allowed from
the narrow state considered).
We tentatively conclude that the broad Particle Data Group (PDG) baryonic
resonances N(1520)D13, N(1535)S11, Delta(1600)P33, and N(1675)D15 are
collective states built from several narrow and weakly excited resonances, each
having a (much) smaller width than the one reported by PDG. | nucl-ex |
Peering Into Hadronic Matter: The Electron-Ion Collider: A unique new facility, capable of colliding beams of electrons with a wide
range of nuclei as well as polarized protons and light ions, has been proposed
to study the role of gluons in matter and perform precision mapping of the
structure of nucleons and nuclei. The physics prospects of the proposed
Electron-Ion Collider (EIC) are discussed. | nucl-ex |
$D\overline{D}$ momentum correlations versus relative azimuth as a
sensitive probe for thermalization: In high-energy nuclear collisions at LHC, where a QGP might be created, the
degree of thermalization at the partonic level is a key issue. Due to their
large mass, heavy quarks are a powerful tool to probe thermalization. We
propose to measure azimuthal correlations of heavy-quark hadrons and their
decay products. Changes or even the complete absence of these initially
existing azimuthal correlations in $Pb-Pb$ collisions might indicate
thermalization at the partonic level. We present studies with PYTHIA for $p-p$
collisions at 14 TeV using the two-particle transverse momentum correlator
${<\overline{\Delta}p_{t,1}\overline{\Delta}p_{t,2}>}$ as a sensitive measure
of potential changes in these azimuthal correlations. Contributions from
transverse radial flow are estimated. | nucl-ex |
Half-life measurement of 66Ga with gamma-spectroscopy: The half-life of 66Ga, an isotope very important for high-energy efficiency
calibration of gamma-detectors, has been measured using gamma-spectroscopy. In
order to reduce systematic uncertainties, different source production methods
and gamma-counting conditions have been applied. A half-life value of 9.312 +-
0.032 h has been obtained in agreement with a recent measurement but in
contradiction with some of the earlier results. | nucl-ex |
New Constraint on the Local Relic Neutrino Background Overdensity with
the First KATRIN Data Runs: We report on the direct cosmic relic neutrino background search from the
first two science runs of the KATRIN experiment in 2019. Beta-decay electrons
from a high-purity molecular tritium gas source are analyzed by a
high-resolution MAC-E filter around the kinematic endpoint at 18.57 keV. The
analysis is sensitive to a local relic neutrino overdensity of 9.7e10 (1.1e11)
at a 90% (95%) confidence level. A fit of the integrated electron spectrum over
a narrow interval around the kinematic endpoint accounting for relic neutrino
captures in the Tritium source reveals no significant overdensity. This work
improves the results obtained by the previous kinematic neutrino mass
experiments at Los Alamos and Troitsk. We furthermore update the projected
final sensitivity of the KATRIN experiment to <1e10 at 90% confidence level, by
relying on updated operational conditions. | nucl-ex |
Final Measurement of the U235 Antineutrino Energy Spectrum with the
PROSPECT-I Detector at HFIR: This Letter reports one of the most precise measurements to date of the
antineutrino spectrum from a purely U235-fueled reactor, made with the final
dataset from the PROSPECT-I detector at the High Flux Isotope Reactor. By
extracting information from previously unused detector segments, this analysis
effectively doubles the statistics of the previous PROSPECT measurement. The
reconstructed energy spectrum is unfolded into antineutrino energy and compared
with both the Huber-Mueller model and a spectrum from a commercial reactor
burning multiple fuel isotopes. A local excess over the model is observed in
the 5MeV to 7MeV energy region. Comparison of the PROSPECT results with those
from commercial reactors provides new constraints on the origin of this excess,
disfavoring at 2.2 and 3.2 standard deviations the hypotheses that
antineutrinos from U235 are solely responsible and non-contributors to the
excess observed at commercial reactors respectively. | nucl-ex |
Azimuthal asymmetry of direct photons in intermediate energy heavy-ion
collisions: Hard photon emitted from energetic heavy ion collisions is of very
interesting since it does not experience the late-stage nuclear interaction,
therefore it is useful to explore the early-stage information of matter phase.
In this work, we have presented a first calculation of azimuthal asymmetry,
characterized by directed transverse flow parameter $F$ and elliptic asymmetry
coefficient $v_2$, for proton-neutron bremsstrahlung hard photons in
intermediate energy heavy-ion collisions. The positive $F$ and negative $v_2$
of direct photons are illustrated and they seem to be anti-correlated to the
corresponding free proton's flow. | nucl-ex |
Directed Flow in 158 A GeV Pb + Pb Collisions: The directed flow of protons and positive pions have been studied in 158 A
GeV Pb + Pb collisions. A directed flow analysis of the rapidity dependence of
the average transverse momentum projected onto the reaction plane is presented
for semi-central collisions with impact parameters of approximately 8 fm, where
the flow effect is largest. The magnitude of the directed flow is found to be
significantly smaller than observed at AGS energies and than RQMD model
predictions. | nucl-ex |
On the rearrangement time of the fission reaction: The rearrangement time \Deltat of the fission reaction can be extracted from
the full-width at half maximum (f.w.h.m.) of the isotopic distributions of
fission fragments if this width is attributed to an uncertainty \DeltaN in the
neutron-number N of the fragment; then the energy-time uncertainty relation
leads to \Deltat = 0.17 yoctosecond. | nucl-ex |
Experimental study of the $^{17}$F+ $^{12}$C fusion reaction and its
implications for fusion of proton-halo systems: The halo nature of the low-lying $1/2$+ first excited state of the exotic
weakly-bound proton drip-line nucleus $^{17}$F has long been hypothesized. The
structure of such a halo nucleus would imply special nuclear properties
including, possibly, an enhancement in its fusion cross section above the
barrier. The total fusion cross section of $^{17}$F + $^{12}$C near the Coulomb
barrier was studied using the newly developed "Encore" active-target detector
at Florida State University. Total fusion cross sections for the stable
counterpart systems $^{16}$O + $^{12}$C and $^{19}$F + $^{12}$C were also
measured to enable a systematic comparison. No influence of the halo nature of
the $^{17}$F $1/2$+ first excited state on its fusion excitation function was
observed when compared with the stable counterpart systems. | nucl-ex |
Single Spin Asymmetries of Inclusive Hadrons Produced in Electron
Scattering from a Transversely Polarized $^3$He Target: We report the first measurement of target single-spin asymmetries (A$_N$) in
the inclusive hadron production reaction,
$e~$+$~^3\text{He}^{\uparrow}\rightarrow h+X$, using a transversely polarized
$^3$He target. The experiment was conducted at Jefferson Lab in Hall A using a
5.9-GeV electron beam. Three types of hadrons ($\pi^{\pm}$, $\text{K}^{\pm}$
and proton) were detected in the transverse hadron momentum range 0.54 $<p_T<$
0.74 GeV/c. The range of $x_F$ for pions was -0.29 $<x_F<$ -0.23 and for kaons
-0.25 $<x_F<$-0.18. The observed asymmetry strongly depends on the type of
hadron. A positive asymmetry is observed for $\pi^+$ and $\text{K}^+$. A
negative asymmetry is observed for $\pi^{-}$. The magnitudes of the asymmetries
follow $|A^{\pi^-}| < |A^{\pi^+}| < |A^{K^+}|$. The K$^{-}$ and proton
asymmetries are consistent with zero within the experimental uncertainties. The
$\pi^{+}$ and $\pi^{-}$ asymmetries measured for the $^3$He target and
extracted for neutrons are opposite in sign with a small increase observed as a
function of $p_T$. | nucl-ex |
The Solenoidal Large Intensity Device (SoLID) for JLab 12 GeV: The Solenoidal Large Intensity Device (SoLID) is a new experimental apparatus
planned for Hall A at the Thomas Jefferson National Accelerator Facility
(JLab). SoLID will combine large angular and momentum acceptance with the
capability to handle very high data rates at high luminosity. With a slate of
approved high-impact physics experiments, SoLID will push JLab to a new limit
at the QCD intensity frontier that will exploit the full potential of its 12
GeV electron beam. In this paper, we present an overview of the rich physics
program that can be realized with SoLID, which encompasses the tomography of
the nucleon in 3-D momentum space from Semi-Inclusive Deep Inelastic Scattering
(SIDIS), expanding the phase space in the search for new physics and novel
hadronic effects in parity-violating DIS (PVDIS), a precision measurement of
$J/\psi$ production at threshold that probes the gluon field and its
contribution to the proton mass, tomography of the nucleon in combined
coordinate and momentum space with deep exclusive reactions, and more. To meet
the challenging requirements, the design of SoLID described here takes full
advantage of recent progress in detector, data acquisition and computing
technologies. In addition, we outline potential experiments beyond the
currently approved program and discuss the physics that could be explored
should upgrades of CEBAF become a reality in the future. | nucl-ex |
Is there a Sonic Boom in the Little Bang at RHIC?: The use of elliptic flow and correlation measurements as constraints to
establish the transport properties of hot and dense QCD matter is discussed.
Measured Two- and three-particle correlation functions give initial hints for a
"sonic boom". Elliptic flow measurements give the estimates $c_s \sim 0.35$ and
$\eta/s \sim 0.1$ for the sound speed and viscosity to entropy ratio. | nucl-ex |
Probing the Deuteron at Very Large Internal Momenta: $^{2}\mathrm{H}(e,e'p)n$ cross sections have been measured at 4-momentum
transfers of $Q^{2} = 4.5 \pm 0.5$ (GeV/c)$^{2}$ over a range of neutron recoil
momenta, $p_{\mathrm{r}}$, reaching up to $\sim1.0$ GeV/c. The data were
obtained at fixed neutron recoil angles $\theta_{nq} = 35^\circ$, $45^\circ$
and $75^{\circ}$ with respect to the 3-momentum transfer $\vec q$. The new data
agree well with previous data which reached $p_{\mathrm{r}}\sim500$ MeV/c. At
$\theta_{nq} = 35^\circ$ and $45^\circ$, final state interactions (FSI), meson
exchange currents (MEC) and isobar currents (IC) are suppressed and the plane
wave impulse approximation (PWIA) provides the dominant cross section
contribution. The new data are compared to recent theoretical calculations,
where we observe a significant discrepancy for missing momenta
$p_{\mathrm{r}}>700$ MeV/c. | nucl-ex |
Strange Particle Production from SIS to LHC: >1A review of meson emission in heavy ion collisions at incident energies
from SIS up to collider energies is presented. A statistical model assuming
chemical equilibrium and local strangeness conservation (i.e. strangeness
conservation per collision) explains most of the observed features.
Emphasis is put onto the study of $K^+$ and $K^-$ emission at low incident
energies. In the framework of this statistical model it is shown that the
experimentally observed equality of $K^+$ and $K^-$ rates at
``threshold-corrected'' energies $\sqrt{s} - \sqrt{s_{th}}$ is due to a
crossing of two excitation functions. Furthermore, the independence of the
$K^+$ to $K^-$ ratio on the number of participating nucleons observed between
SIS and RHIC is consistent with this model.
It is demonstrated that the $K^-$ production at SIS energies occurs
predominantly via strangeness exchange and this channel is approaching chemical
equilibrium. The observed maximum in the $K^+/\pi^+$ excitation function is
also seen in the ratio of strange to non-strange particle production. The
appearance of this maximum around 30 $A\cdot$GeV is due to the energy
dependence of the chemical freeze-out parameters $T$ and $\mu_B$. | nucl-ex |
First direct search for $2ε$ and $εβ^+$ decay of
$^{144}$Sm and $2β^-$ decay of $^{154}$Sm: The first direct search for the double electron capture ($2\epsilon$) and the
electron capture with positron emission ($\epsilon\beta^+$) in $^{144}$Sm to
the ground state and to the excited levels of $^{144}$Nd was realized by
measuring - over 1899 h - a 342 g sample of highly purified samarium oxide
(Sm$_2$O$_3$) with the ultra-low background HP-Ge $\gamma$ spectrometer GeCris
(465 cm$^3$) at the STELLA facility of the Gran Sasso National Laboratory
(LNGS). No effect was observed and half-life limits were estimated at the level
of $T_{1/2} \sim (0.1-1.3) \times 10^{20}$ yr (90% C.L.). Moreover, for the
first time half-life limits of the double beta ($2\beta^-$) decay of $^{154}$Sm
to several excited levels of $^{154}$Gd have been set; they are at the level of
$T_{1/2} \sim (0.06-8) \times 10^{20}$ yr (90% C.L.). | nucl-ex |
Experimental results on charge fluctuations in heavy-ion collisions: We present a subset of experimental results on charge fluctuation from the
heavy-ion collisions to search for phase transition and location of critical
point in the QCD phase diagram. Measurements from the heavy-ion experiments at
the SPS and RHIC energies observe that total charge fluctuations increase from
central to peripheral collisions. The net-charge fluctuations in terms of
dynamical fluctuation measure $\nu_{(+-,dyn)}$ are studied as a function of
collision energy (\sqsn) and centrality of the collisions. The product of
$\nu_{(+-,dyn)}$ and $\langle N_{ch} \rangle$ shows a monotonic decrease with
collision energies, which indicates that at LHC energy the fluctuations have
their origin in the QGP phase. The fluctuations in terms of higher moments of
net-proton, net-electric charge and net-kaon have been measured for various
\sqsn. Deviations are observed in both $S\sigma$ and $\kappa\sigma^2$ for
net-proton multiplicity distributions from the Skellam and hadron resonance gas
model for \sqsn $<$ 39 GeV. Higher moment results of the net-electric charge
and net-kaon do not observe any significant non-monotonic behavior as a
function of collision energy. We also discuss the extraction of the freeze-out
parameters using particle ratios and experimentally measured higher moments of
net-charge fluctuations. The extracted freeze-out parameters from
experimentally measured moments and lattice calculations, are found to be in
agreement with the results obtained from the fit of particle ratios to the
thermal model calculations. | nucl-ex |
Search for the critical point of strongly interacting matter in NA49: Theoretical calculations locate the QCD critical point at energies accessible
at the CERN SPS. Several observables were suggested to look for it. Here, we
present the system size dependence and the energy dependence of event-by-event
mean transverse momentum and multiplicity fluctuations, as well as the energy
dependence of anti-baryon to baryon ratios. | nucl-ex |
Could the GSI Oscillations be Observed in a Standard Electron Capture
Decay Experiment?: The electron-capture decay of 180Re has been investigated to search for
oscillations in the decay probability as reported from a recent measurement at
GSI, Darmstadt. The production period was kept short compared to the reported
oscillation period. No such oscillation was observed, indicating that the
reported oscillations would not have been observable in a conventional
experiment with radioactive atoms in a solid environment but must have to do
with the unique conditions in the GSI experiment where hydrogen-like ions are
moving independently in a storage ring and decaying directly by a true two-body
decay to a long-lived (ground-) state. Our finding could restrict possible
theoretical interpretations of the oscillations. | nucl-ex |
Centrality Dependence of Particle Production in p-A collisions measured
by ALICE: We present the centrality dependence of particle production in p-Pb
collisions at sqrt(s_NN)= 5.02 TeV measured by the ALICE experiment, including
the pseudo-rapidity and transverse momentum spectra, with a special emphasis on
the event classification in centrality classes and its implications for the
interpretation of the nuclear effects. | nucl-ex |
Nuclear deformation and neutron excess as competing effects for pygmy
dipole strength: The electromagnetic dipole strength below the neutron-separation energy has
been studied for the xenon isotopes with mass numbers A = 124, 128, 132, and
134 in nuclear resonance fluorescence experiments using the ELBE bremsstrahlung
facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIgS facility at
Triangle Universities Nuclear Laboratory Durham. The systematic study gained
new information about the influence of the neutron excess as well as of nuclear
deformation on the strength in the region of the pygmy dipole resonance. The
results are compared with those obtained for the chain of molybdenum isotopes
and with predictions of a random-phase approximation in a deformed basis. It
turned out that the effect of nuclear deformation plays a minor role compared
with the one caused by neutron excess. A global parametrization of the strength
in terms of neutron and proton numbers allowed us to derive a formula capable
of predicting the summed E1 strengths in the pygmy region for a wide mass range
of nuclides. | nucl-ex |
Proton charge radius from electron scattering: The rms-radius $R$ of the proton charge distribution is a fundamental
quantity needed for precision physics. This radius, traditionally determined
from elastic electron-proton scattering via the slope of the Sachs form factor
$G_e(q^2)$ extrapolated to momentum transfer $q^2$=0, shows a large scatter. We
discuss the approaches used to analyze the e-p data, partly redo these analyses
in order to identify the sources of the discrepancies, and explore alternative
parameterizations. The problem lies in the model dependence of the
parameterized $G(q)$ needed for the extrapolation. This shape of $G(q<q_{min})$
is closely related to the shape of the charge density $\rho (r)$ at large radii
$r$, a quantity which is ignored in most analyses. When using our {\em physics}
knowledge about this large-$r$ density together with the information contained
in the high-$q$ data, the model dependence of the extrapolation is reduced and
different parameterizations of the pre-2010 data yield a consistent value for
$R = 0.887 \pm 0.012fm$. This value disagrees with the more precise value
$0.8409 \pm 0.0004 fm$ determined from the Lamb shift in muonic hydrogen. | nucl-ex |
PHENIX Measurements of Single Electrons from Charm and Bottom Decays at
Midrapidity in Au+Au Collisions: Heavy quarks are an ideal probe of the quark gluon plasma created in heavy
ion collisions. They are produced in the initial hard scattering and therefore
experience the full evolution of the medium. PHENIX has previously measured the
modification of heavy quark production in Au+Au collisions at
$\sqrt{s_{NN}}=200$ GeV via electrons from semileptonic decays, which indicated
substantial modifications of the parent hadron momentum distribution. The
PHENIX barrel silicon vertex detector (VTX), installed in 2011, allows for the
separation of electrons from charm and bottom hadron decays through the use of
displaced vertex measurements. These proceedings present the results of the
completed analysis of the 2011 data set using the VTX. | nucl-ex |
Nuclear physics uncertainties of the astrophysical gamma-process studied
through the 64Zn(p,alpha)61Cu and 64Zn(p,gamma)65Ga reactions: In a recent work, the cross section measurement of the 64Zn(p,alpha)61Cu
reaction was used to prove that the standard alpha-nucleus optical potentials
used in astrophysical network calculation fail to reproduce the experimental
data at energies relevant for heavy element nucleosynthesis. In the present
paper the analysis of the obtained experimental data is continued by comparing
the results with the predictions using different parameters. It is shown that
the recently suggested modification of the standard optical potential leads to
a better description of the data. | nucl-ex |
The Emission Order of Hydrogen Isotopes via Correlation Functions in 30
MeV/u Ar+Au Reactions: The intensity interferometry is applied as a chronometer of the particle
emission of hydrogen isotopes from the intermediate velocity source formed in
$^{40}$Ar+$^{197}$Au reactions at 30 MeV/u. The dynamic emission order of
$\tau_{\rm p}>\tau_{\rm d}>\tau_{\rm t}$ is evidenced via the correlation
functions of nonidentical particle pairs. Assuming the similar source size, the
same emission order is inferred from the correlation functions of identical
particle pairs, where $\tau_{\rm p} \approx 100 {\rm ~fm/c}$ is extracted by
the fit of Koonin-Pratt equation to p-p correlation function. Transport model
simulations demonstrate that the dynamic emission order of light charged
particles depends on the stiffness of the nuclear symmetry energy. | nucl-ex |
Azimuthal anisotropy of charged particles at high transverse momenta in
PbPb collisions at sqrt(s[NN]) = 2.76 TeV: The azimuthal anisotropy of charged particles in PbPb collisions at
nucleon-nucleon center-of-mass energy of 2.76 TeV is measured with the CMS
detector at the LHC over an extended transverse momentum (pt) range up to
approximately 60 GeV. The data cover both the low-pt region associated with
hydrodynamic flow phenomena and the high-pt region where the anisotropies may
reflect the path-length dependence of parton energy loss in the created medium.
The anisotropy parameter (v2) of the particles is extracted by correlating
charged tracks with respect to the event-plane reconstructed by using the
energy deposited in forward-angle calorimeters. For the six bins of collision
centrality studied, spanning the range of 0-60% most-central events, the
observed v2 values are found to first increase with pt, reaching a maximum
around pt = 3 GeV, and then to gradually decrease to almost zero, with the
decline persisting up to at least pt = 40 GeV over the full centrality range
measured. | nucl-ex |
Probing the QGP with charm at ALICE-LHC: The exclusive reconstruction of D^0 mesons in the ALICE experiment allows to
study the QCD energy loss of charm quarks in the deconfined quark-gluon plasma
(QGP) medium expected to be produced in central nucleus-nucleus collisions at
the Large Hadron Collider. | nucl-ex |
Review of anisotropic flow correlations in ultrarelativistic heavy-ion
collisions: Anisotropic flow phenomena is a key probe of the existence of Quark-Gluon
Plasma. Several new observable associated with correlations between anisotropic
flow harmonics are developed, which are expected to be sensitive to the initial
fluctuations and transport properties of the created matter in heavy ion
collisions. I review recent developments of correlations of anisotropic flow
harmonics. The experimental measurements, together with the comparisons to
theoretical model calculations, open up new opportunities of exploring novel
QCD dynamics in heavy-ion collisions. | nucl-ex |
New Measurement of the Scintillation Efficiency of Low-Energy Nuclear
Recoils in Liquid Xenon: Particle detectors that use liquid xenon (LXe) as detection medium are among
the leading technologies in the search for dark matter weakly interacting
massive particles (WIMPs). A key enabling element has been the low-energy
detection threshold for recoiling nuclei produced by the interaction of WIMPs
in LXe targets. In these detectors, the nuclear recoil energy scale is based on
the LXe scintillation signal and thus requires knowledge of the relative
scintillation efficiency of nuclear recoils, Leff. The uncertainty in Leff at
low energies is the largest systematic uncertainty in the reported results from
LXe WIMP searches at low masses. In the context of the XENON Dark Matter
project, a new LXe scintillation detector has been designed and built
specifically for the measurement of Leff at low energies, with an emphasis on
maximizing the scintillation light detection efficiency to obtain the lowest
possible energy threshold. We report new measurements of Leff at low energies
performed with this detector. Our results suggest a Leff which slowly decreases
with energy, from 0.144 +/- 0.009 at 15 keV down to 0.088 +0.014 -0.015 at 3
keV. | nucl-ex |
Collision-Induced Dissociation at TRIUMF's Ion Trap for Atomic and
Nuclear science: The performance of high-precision mass spectrometry of radioactive isotopes
can often be hindered by large amounts of contamination, including molecular
species, stemming from the production of the radioactive beam. In this paper,
we report on the development of Collision-Induced Dissociation (CID) as a means
of background reduction for experiments at TRIUMF's Ion Trap for Atomic and
Nuclear science (TITAN). This study was conducted to characterize the quality
and purity of radioactive ion beams and the reduction of molecular contaminants
to allow for mass measurements of radioactive isotopes to be done further from
nuclear stability. This is the first demonstration of CID at an ISOL-type
radioactive ion beam facility, and it is shown that molecular contamination can
be reduced up to an order of magnitude. | nucl-ex |
Direct virtual photon production in Au+Au collisions at $\sqrt{s_{NN}}$
= 200 GeV: We report the direct virtual photon invariant yields in the transverse
momentum ranges $1\!<\!p_{T}\!<\!3$ GeV/$c$ and $5\!<\!p_T\!<\!10$ GeV/$c$ at
mid-rapidity derived from the dielectron invariant mass continuum region
$0.10<M_{ee}<0.28$ GeV/$c^{2}$ for 0-80\% minimum-bias Au+Au collisions at
$\sqrt{s_{NN}}=200$ GeV. A clear excess in the invariant yield compared to the
number-of-binary-collisions ($N_{bin}$) scaled $p+p$ reference is observed in
the $p_T$ range $1\!<\!p_{T}\!<\!3$ GeV/$c$. For $p_T\!>6$ GeV/$c$ the
production follows $N_{bin}$ scaling. Model calculations with contributions
from thermal radiation and initial hard parton scattering are consistent within
uncertainties with the direct virtual photon invariant yield. | nucl-ex |
Fission Fragment Angular Anisotropy in Neutron-Induced Fission of
$^{235}$U Measured with a Time Projection Chamber: Fission fragment angular distributions can provide an important constraint on
fission theory, improving predictive fission codes, and are a prerequisite for
a precise ratio cross section measurement. Available anisotropy data is sparse,
especially at neutron energies above 5 MeV. For the first time, a
three-dimensional tracking detector is employed to study fragment emission
angles and provide a direct measurement of angular anisotropy. The Neutron
Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has
deployed the fission time projection chamber (fissionTPC) to measure nuclear
data with unprecedented precision. The fission fragment anisotropy of $^{235}$U
has been measured over a wide range of incident neutron energies from 180 keV
to 200 MeV; a careful study of the systematic uncertainties complement the
data. | nucl-ex |
Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au
collisions at RHIC: We present the first results of meson production in the K^+K^- decay channel
from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by
the PHENIX detector at RHIC. Precision resonance centroid and width values are
extracted as a function of collision centrality. No significant variation from
the PDG accepted values is observed. The transverse mass spectra are fitted
with a linear exponential function for which the derived inverse slope
parameter is seen to be constant as a function of centrality. These data are
also fitted by a hydrodynamic model with the result that the freeze-out
temperature and the expansion velocity values are consistent with the values
previously derived from fitting single hadron inclusive data. As a function of
transverse momentum the collisions scaled peripheral.to.central yield ratio RCP
for the is comparable to that of pions rather than that of protons. This result
lends support to theoretical models which distinguish between baryons and
mesons instead of particle mass for explaining the anomalous proton yield. | nucl-ex |
Mass measurement of 56Sc reveals a small A=56 odd-even mass staggering,
implying a cooler accreted neutron star crust: We present the mass excesses of 52-57Sc, obtained from recent time-of-flight
nuclear mass measurements at the National Superconducting Cyclotron Laboratory
at Michigan State University. The masses of 56Sc and 57Sc were determined for
the first time with atomic mass excesses of -24.85(59)(+0 -54) MeV and
-21.0(1.3) MeV, respectively, where the asymmetric uncertainty for 56Sc was
included due to possible contamination from a long-lived isomer. The 56Sc mass
indicates a small odd-even mass staggering in the A = 56 mass-chain towards the
neutron drip line, significantly deviating from trends predicted by the global
FRDM mass model and favoring trends predicted by the UNEDF0 and UNEDF1 density
functional calculations. Together with new shell-model calculations of the
electron-capture strength function of 56Sc, our results strongly reduce
uncertainties in model calculations of the heating and cooling at the 56Ti
electron-capture layer in the outer crust of accreting neutron stars. We found
that, in contrast to previous studies, neither strong neutrino cooling nor
strong heating occurs in this layer. We conclude that Urca cooling in the outer
crusts of accreting neutron stars that exhibit superbursts or high temperature
steady-state burning, which are predicted to be rich in A=56 nuclei, is
considerably weaker than predicted. Urca cooling must instead be dominated by
electron capture on the small amounts of adjacent odd-A nuclei contained in the
superburst and high temperature steady-state burning ashes. This may explain
the absence of strong crust Urca cooling inferred from the observed cooling
light curve of the transiently accreting x-ray source MAXI J0556-332. | nucl-ex |
Measurement of the Shared Momentum Fraction $z_g$ using Jet
Reconstruction in p+p and Au+Au Collisions with STAR: One key difference in current energy loss models lies in the treatment of the
Altarelli-Parisi, AP, splitting functions. It has been shown that the shared
momentum fraction, henceforth called Jet Splitting Function $z_g$ as determined
by the SoftDrop grooming process can be made a Sudakov-safe measurement of the
symmetrized AP functions in p+p collisions. The STAR collaboration presents the
first $z_g$ measurements at $\sqrt{s_{NN}}=200$ GeV in p+p and Au+Au
collisions, where in Au+Au we use the specific di-jet selection introduced in
our previous momentum imbalance measurement. For a jet resolution parameter of
$R=0.4$, these di-jet pairs were found to be significantly imbalanced with
respect to p+p, yet regained balance when all soft constituents were included.
We find that within uncertainties there are no signs of a modified Jet
Splitting Function on trigger or recoil side of this di-jet selection. | nucl-ex |
Anisotropy in the pion angular distribution of the reaction pp -> pp pi0
at 400 MeV: The reaction pp -> pp pi0 was studied with the WASA detector at the CELSIUS
storage ring. The center of mass angular distribution of the pi0 was obtained
by detection of the gamma decay products together with the two outgoing
protons, and found to be anisotropic with a negative second derivative slope,
in agreement with the theoretical predictions from a microscopic calculation. | nucl-ex |
Caloric Curves and Nuclear Expansion: Nuclear caloric curves have been analyzed using an expanding Fermi gas
hypothesis to extract average nuclear densities. In this approach the observed
flattening of the caloric curves reflects progressively increasing expansion
with increasing excitation energy. This expansion results in a corresponding
decrease in the density and Fermi energy of the excited system. For nuclei of
medium to heavy mass apparent densities ~ 0.4 rho_0 are reached at the higher
excitation energies. | nucl-ex |
HPRL -- International cooperation to identify and monitor priority
nuclear data needs for nuclear applications: The OECD-NEA High Priority Request List (HPRL) is a point of reference to
guide and stimulate the improvement of nuclear data for nuclear energy and
other applications, and a tool to bridge the gap between data users and
producers. The HPRL is application-driven and the requests are submitted by
nuclear data users or representatives of the user's communities. A panel of
international experts reviews and monitors the requests in the framework of an
Expert Group mandated by the NEA Nuclear Science Committee Working Party on
International Nuclear Data Evaluation Cooperation (WPEC). After approval,
individual requests are classified to three categories: high priority requests,
general requests, and special purpose requests (e.g., dosimetry, standards).
The HPRL is hosted by the NEA in the form of a relational database publicly
available on the web. This paper provides an overview of HPRL entries, status
and outlook. Examples of requests successfully completed are given and new
requests are described with emphasis on updated nuclear data needs in the
fields of nuclear energy, neutron standards and dosimetry. | nucl-ex |
Creation and decay of eta-mesic nuclei: First experimental results on photoproduction of eta-mesic nuclei are
analyzed. In an experiment performed at the 1 GeV electron synchrotron of the
Lebedev Physical Institute, correlated pi+n pairs arising from the reaction
gamma + 12C -> N + eta(A-1) -> N + pi+ + n + (A-2) and flying transversely to
the photon beam have been observed. When the photon energy exceeds the
eta-meson production threshold, a distribution of the pi+n pairs over their
total energy is found to have a peak in the subthreshold region of the
internal-conversion process eta p -> pi+ n which signals about formation of
eta-mesic nuclei. | nucl-ex |
High $p_T$ Measurements from PHENIX: We present recent high transverse momentum measurements by the PHENIX
experiment for Au+Au and p+p collisions at $\sqrt{s_{NN}} = 200$ GeV at the
Relativistic Heavy Ion Collider (RHIC). We show particle spectra for neutral
pions and charged hadrons, define and show the nuclear modification factor, and
discuss particle composition. By means of the nuclear modification factor, we
observe a suppression factor of 5-6 for neutral pions and 3-4 for charged
hadrons in central collisions at high $p_T$. We find that the ratio of $\pi^0$
to $(h^++h^-)/2$ remains nearly constant at $\sim 0.5$ for $p_T = 2-9$ GeV/c.
Finally we present strong evidence for the observation of jets in Au+Au
collisions. | nucl-ex |
Positrons at Jefferson Laboratory: We review the compelling case for establishing a capability to accelerate
positrons at Jefferson Lab. The potential appplications range from the study of
two-photon exchange and deeply-virtual Compton scattering to exploiting the
charge current weak interaction to probe the flavor structure of hadrons and
nuclei. There are also fascinating ideas for using such a capability to
discover new physics beyond the Standard Model of nuclear and particle physics. | nucl-ex |
Results from PHENIX at RHIC: Results from PHENIX at RHIC in p-p and Au+Au collisions are presented from
the perspective of measurements in p-p collisions at the CERN ISR which serve
as a basis for many of the techniques used. Notable results include the
equality of the suppression of inclusive pi0 and direct electrons (from the
decay of heavy quarks) in the range of transverse momentuum 4 < pT < 9 GeV/c in
central Au+Au collisions. This result appears to strongly disfavor the
explanation of suppression as due to radiative energy loss of partons
traversing a Quark Gluon Plasma but opens up a fundamental discussion of how
Fermions get mass, whether all six quarks are nearly massless in a QGP and how
to test this. | nucl-ex |
Inclusive jet spectra in 2.76 TeV collisions from ALICE: Measurements of high-pT particle production in heavy-ion collisions at RHIC
have shown that medium-induced energy loss affects the partons produced in the
early stage of a heavy-ion col- lision. The increased initial production cross
section for partons at LHC energies makes fully reconstructed jets available in
a wide kinematic range, which allows for a more differential in- vestigation of
parton energy loss. Partonic energy loss allows us to access key observables of
the hot deconfined nuclear matter produced in heavy-ion collisions. The
inclusive cross-section of reconstructed jets using the ALICE tracking
detectors and electromagnetic calorimeter is pre- sented from data collected
during the 2.76 TeV pp runs. The procedures used to reconstruct jets and
extract them from a fluctuating background in Pb-Pb collisions are discussed. | nucl-ex |
Estimation of CP violating EDMs from known mechanisms in the SM: New sources of CP violation, beyond the known sources in the standard model
(SM), are required to explain the baryon asymmetry of the universe. Measurement
of a non-zero permanent electric dipole moment (EDM) for fundamental particles,
such as in an electron or a neutron, or in nuclei or atoms, can help us gain a
handle on the sources of CP violation, both in SM and beyond. Multiple
mechanisms within the SM can generate CP violating EDMs, viz.\ through the CKM
matrix in the weak sector or through the QCD $\bar{\theta}$ parameter in the
strong sector. We will estimate the maximum possible EDMs of leptons, certain
baryons, select atoms and molecules in the (CKM$\bigoplus\bar{\theta}$)
framework, assuming that the EDM wholly originates from either of the two SM
mechanisms, independently. These estimates have been presented in light of the
current experimental upper limits on the EDMs, in the following systems -
leptons: $e^-$, $\mu^-$, $\tau^-$, $\nu_e^0$, $\nu^0_{\mu}$, $\nu^0_{\tau}$,
baryons: $n^0$, $p^+$, $\Lambda^0$, $\Sigma^0$, $\Xi^0$, $\Lambda^+_c$,
$\Xi^+_c$, atoms: $^{85}$Rb, $^{133}$Cs, $^{210}$Fr, $^{205}$Tl, $^{199}$Hg,
$^{129}$Xe, $^{225}$Ra, $^{223}$Rn, and molecules: HfF$^+$, PbO, YbF, ThO, RaF,
TlF. Particularly, to drive home the point that EDMs in different systems
constrain CP-violating interactions differently, we show that the same measured
constraint on the EDM in two different systems may not actually be equally
constraining on CP violating parameters, and to emphasize the need to measure a
non-zero EDM in multiple systems before understanding the origins of these
CP-violating EDMs. | nucl-ex |
Lambda production in central Pb+Pb collisions at CERN-SPS energies: In this paper we present recent results from the NA49 experiment for
$\Lambda$ and $\bar{\Lambda}$ hyperons produced in central Pb+Pb collisions at
40, 80 and 158 A$\cdot$GeV. Transverse mass spectra and rapidity distributions
for $\Lambda$ are shown for all three energies. The shape of the rapidity
distribution becomes flatter with increasing beam energy. The multiplicities at
mid-rapidity as well as the total yields are studied as a function of collision
energy including AGS measurements. The ratio $\Lambda/\pi$ at mid-rapidity and
in 4$\pi$ has a maximum around 40 A$\cdot$GeV. In addition, $\bar{\Lambda}$
rapidity distributions have been measured at 40 and 80 A$\cdot$GeV, which
allows to study the $\bar{\Lambda}$/$\Lambda$ ratio. | nucl-ex |
Mass Measurement of $^{27}$P to Constrain Type-I X-ray Burst Models and
Validate the IMME for the A=27, T=$\frac{3}{2}$ Isospin Quartet: Light curves are the primary observable of type-I x-ray bursts. Computational
x-ray burst models must match simulations to observed light curves. Most of the
error in simulated curves comes from uncertainties in $rp$ process reaction
rates, which can be reduced via precision mass measurements of
neutron-deficient isotopes in the $rp$ process path.
We perform a precise Penning trap mass measurement of $^{27}$P utilizing the
ToF-ICR technique. We use this measurement to calculate $rp$ process reaction
rates and input these rates into an x-ray burst model to reduce simulated light
curve uncertainty. We also use the mass measurement of $^{27}$P to validate the
Isobaric Multiplet Mass Equation (IMME) for the A=27 T=$\frac{3}{2}$ isospin
quartet which $^{27}$P belongs to.
The mass excess of $^{27}$P was measured to be -670.7(6) keV, a fourteen-fold
precision increase over the mass reported in the 2020 Atomic Mass Evaluation
(AME2020). X-ray burst light curves were produced with the MESA (Modules for
Experiments in Stellar Astrophysics) code using the new mass and associated
reaction rates. Changes in the mass of $^{27}$P seem to have minimal effect on
light curves, even in burster systems tailored to maximize impact.
The mass of $^{27}$P does not play a significant role in x-ray burst light
curves. It is important to understand that more advanced models do not just
provide more precise results, but often qualitatively different ones. This
result brings us a step closer to extracting stellar parameters from individual
x-ray burst observations. The IMME has been validated for the $A=27, T=3/2$
quartet. The normal quadratic form of the IMME using the latest data yields a
reduced $\chi^2$ of 2.9. The cubic term required to generate an exact fit to
the latest data matches theoretical attempts to predict this term. | nucl-ex |
Preliminary study of feasibility of an experiment looking for excited
state double beta transitions in tin: An attempt to study the feasibility of a new experiment to search for double
beta decay in $^{112}$Sn and $^{124}$Sn was carried out by using ultra-low
background HPGe detector (244 cm$^{3}$) inside the Gran Sasso National
Laboratory (LNGS) of the INFN (Italy). A small sample of natural Sn was
examined for 2367.5 h. The radioactive contamination of the sample has been
estimated. The data has also been considered to calculate the present
sensitivity for the proposed search; half-life limits $\sim$ $10^{17} -
10^{18}$ years for $\beta^{+}$EC and EC-EC processes in $^{112}$Sn and $\sim$
$10^{18}$ years for $\beta^{-}\beta^{-}$ transition in $^{124}$Sn were
measured. In the last section of the paper the enhancement of the sensitivity
for a proposed experiment with larger mass to reach theoretically estimated
values of half-lives is discussed. | nucl-ex |
Flow harmonics in heavy ion physics at CMS and ATLAS: How can we gain a detailed insight into the hydrodynamic response of the
system created in heavy ion collisions to the fluctuating initial geometry and
viscous effects? Do we create a strongly interacting medium in proton-nucleus
and proton-proton collisions, or rather a system of partons undergoing few
scatterings? To what extent can we discriminate between initial momentum
correlations and flow generated as a response to the initial geometry via
interactions in the final state? Do measurements of identified particle flow
confirm the observations from inclusive charged hadrons? An experimental
overview of anisotropic flow measurements, ranging from large down to the
smallest collision systems, is given in these proceedings. | nucl-ex |
Systematic Trends of 0$^+_2$, 1$^-_1$, 3$^-_1$ and 2$^+_1$ Excited
States in Even-Even Nuclei: The spin and parity ($J^{\pi}$) assignments in even-even nuclei were reviewed
across the nuclear chart using the Evaluated Nuclear Structure Data File
(ENSDF). The prevalence of 2$^+_1$ first or lowest excited states is confirmed.
The properties of 0$^+_2$, 1$^-_1$, and 3$^-_1$ lowest excited states were
reexamined using the ENSDF data evaluation procedures. The $J^{\pi}$ systematic
trends and correlations between level quantum numbers and nuclear physics
phenomena are discussed. | nucl-ex |
Joint Measurement of the $^{235}$U Antineutrino Spectrum by Prospect and
Stereo: The PROSPECT and STEREO collaborations present a combined measurement of the
pure $^{235}$U antineutrino spectrum, without site specific corrections or
detector-dependent effects. The spectral measurements of the two highest
precision experiments at research reactors are found to be compatible with
$\chi^2/\mathrm{ndf} = 24.1/21$, allowing a joint unfolding of the prompt
energy measurements into antineutrino energy. This $\bar{\nu}_e$ energy
spectrum is provided to the community, and an excess of events relative to the
Huber model is found in the 5-6 MeV region. When a Gaussian bump is fitted to
the excess, the data-model $\chi^2$ value is improved, corresponding to a
$2.4\sigma$ significance. | nucl-ex |
Exploiting neutron-rich radioactive ion beams to constrain the symmetry
energy: The Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet were used to measure
the free neutrons and heavy charged particles from the radioactive ion beam
induced 32Mg + 9Be reaction. The fragmentation reaction was simulated with the
Constrained Molecular Dynamics model(CoMD), which demonstrated that the <N/Z>
of the heavy fragments and free neutron multiplicities were observables
sensitive to the density dependence of the symmetry energy at sub-saturation
densities. Through comparison of these simulations with the experimental data
constraints on the density dependence of the symmetry energy were extracted.
The advantage of radioactive ion beams as a probe of the symmetry energy is
demonstrated through examination of CoMD calculations for stable and
radioactive beam induced reactions. | nucl-ex |
Elastic Positron-Proton Scattering at Low Q$^2$: Systematic differences in the the proton's charge radius, as determined by
ordinary atoms and muonic atoms, have caused a resurgence of interest in
elastic lepton scattering measurements. The proton's charge radius, defined as
the slope of the charge form factor at Q$^2$=0, does not depend on the probe.
Any difference in the apparent size of the proton, when determined from
ordinary versus muonic hydrogen, could point to new physics or need for the
higher order corrections. While recent measurements seem to now be in
agreement, there is to date no high precision elastic scattering data with both
electrons and positrons. A high precision proton radius measurement could be
performed in Hall B at Jefferson Lab with a positron beam and the calorimeter
based setup of the PRad experiment. This measurement could also be extended to
deuterons where a similar discrepancy has been observed between the muonic and
electronic determination of deuteron charge radius. A new, high precision
measurement with positrons, when viewed alongside electron scattering
measurements and the forthcoming MUSE muon scattering measurement, could help
provide new insights into the origins of the proton radius puzzle, and also
provide new experimental constraints on radiative correction calculations. | nucl-ex |
Double beta decay searches of Xe-134, Xe-126 and Xe-124 with large scale
Xe detectors: The sensitivity for double beta decay studies of Xe-134 and Xe-124 is
investigated assuming a potential large scale Xe experiment developed for dark
matter searches depleted in Xe-136. The opportunity for an observation of the
2nu double beta decay of Xe-134 is explored for various scenarios. A positive
observation should be possible for all calculated nuclear matrix elements. The
detection of 2$\nu$ ECEC of Xe-124 can be probed in all scenarios covering the
theoretical predicted half-life uncertainties and a potential search for Xe-126
is discussed. The sensitivity to beta+/EC decay of Xe-124 is discussed and a
positive observation might be possible, while beta+/beta+ decay still remains
unobservable. The performed studies take into account solar pp-neutrino
interactions, $^{85}$Kr beta decay and remaining Xe-136 double beta decay as
background components in the depleted detector. | nucl-ex |
The $(π^-,γγ)$ program at TRIUMF: We report the first observation of the doubly-radiative decay mode of pionic
hydrogen (pi- p --> gamma gamma n) and and deuterium (pi- d --> gamma gamma X)
using the RMC pair spectrometer at TRIUMF. The process is interesting in the
context of the pi-Compton scattering and the chiPT predictions of the pion
polarizability We present our preliminary values for the B.R.(pi- p --> gamma
gamma n)=3.8x10^-5 and B.R.(pi- d --> gamma gamma X)=1.6x10^-5. Our pi- p data
indicates the dominance of pi pi --> gamma gamma mechanism. The pi- d data
shows no evidence for the d1* dibaryon. | nucl-ex |
Study of the light nuclei cluster structures in three-body
photodisintegration reactions. Application for the excited states of 6He
nucleus: An experimental program for the study of the cluster structures of excited
states for the light nuclei of He, Li and Be in three-body photodisintegration
processes is proposed. The investigations will be realized with 6Li, 7Li and
9Be targets in seven photodisintegration reactions. As an application, the
photodisintegration of 7Li nuclei into the (t+t+p) final state with excitation
and decay of neutron-rich 6He nucleus into the (t+t) channel is considered. The
full Monte-Carlo simulation of the experiment is done with a special impact on
the study of experimental setup performance, concerning the photon and excited
states energy resolutions. The experiment will be performed on the
bremsstrahlung photon beam of the Yerevan Electron Synchrotron. | nucl-ex |
Measurement of the 33S(α,p)36Cl cross section: Implications for
production of 36Cl in the early Solar System: Short-lived radionuclides (SLRs) with lifetimes \tau < 100 Ma are known to
have been extant when the Solar System formed over 4.5 billion years ago.
Identifying the sources of SLRs is important for understanding the timescales
of Solar System formation and processes that occurred early in its history.
Extinct 36Cl (t_1/2 = 0.301 Ma) is thought to have been produced by interaction
of solar energetic particles (SEPs), emitted by the young Sun, with gas and
dust in the nascent Solar System. However, models that calculate SLR production
in the early Solar System (ESS) lack experimental data for the 36Cl production
reactions. We present here the first measurement of the cross section of one of
the main 36Cl production reactions, 33S(\alpha,p)36Cl, in the energy range 0.70
- 2.42 MeV/A. The cross section measurement was performed by bombarding a
target and collecting the recoiled 36Cl atoms produced in the reaction,
chemically processing the samples, and measuring the 36Cl/Cl ratio of the
activated samples with accelerator mass spectrometry (AMS). The experimental
results were found to be systematically higher than the cross sections used in
previous local irradiation models and other Hauser-Feshbach calculated
predictions. However, the effects of the experimentally measured cross sections
on the modeled production of 36Cl in the early Solar System were found to be
minimal. Reactions channels involving S targets dominate 36Cl production, but
the astrophysical event parameters can dramatically change each reactions'
relative contribution. | nucl-ex |
Quenching of Single-Particle Strength in A=15 Nuclei: Absolute cross sections for the addition of $s$- and $d$-wave neutrons to
$^{14}$C and $^{14}$N have been determined simultaneously via the ($d$,$p$)
reaction at 10 MeV/u. The difference between the neutron and proton separation
energies, $\Delta S$, is around $-20$ MeV for the $^{14}$C$+$$n$ system and
$+8$ MeV for $^{14}$N$+$$n$. The population of the $1s_{1/2}$ and $0d_{5/2}$
orbitals for both systems is reduced by a factor of approximately 0.5 compared
to the independent single-particle model, or about 0.6 when compared to the
shell model. This finding strongly contrasts with results deduced from
intermediate-energy knockout reactions between similar nuclei on targets of
$^{9}$Be and $^{12}$C. The simultaneous technique used removes many systematic
uncertainties. | nucl-ex |
Measurement of longitudinal flow de-correlations in Pb+Pb collisions at
$\sqrt{s_\mathrm{NN}} = 2.76$ and 5.02 TeV with the ATLAS detector: Measurements of longitudinal flow decorrelations are presented for charged
particles in the pseudorapidity range $|\eta|<2.4$ using 7 $\mu$b$^{-1}$ and
470 $\mu$b$^{-1}$ of Pb+Pb collisions at $\sqrt{s_{\textrm{NN}}}=2.76$ and 5.02
TeV, respectively, recorded by the ATLAS detector at the LHC. It is found that
the correlation between the harmonic flow coefficients $v_n$ measured in two
separated $\eta$ intervals does not factorise into the product of
single-particle coefficients, and this breaking of factorisation, or flow
decorrelation, increases linearly with the $\eta$ separation between the
intervals. The slopes for this flow decorrelation are found to be larger at
2.76 TeV than 5.02 TeV. Higher-order moments of the correlations are also
measured, and the corresponding linear coefficients for the
$k^{\textrm{th}}$-moment of the $v_n$ are found to be proportional to $k$ for
$v_3$, but not for $v_2$. The decorrelation effect is separated into
contributions from the magnitude of $v_n$ and the event-plane orientation
changing with $\eta$. These two contributions are found to be comparable. The
longitudinal flow correlations are also measured between $v_n$ of different
order in $n$. The longitudinal fluctuations of $v_2$ and $v_3$ are found to be
independent of each other, while the longitudinal fluctuations of $v_4$ and
$v_5$ are found to be driven by the nonlinear contribution from $v_2^2$ and
$v_2v_3$, respectively. | nucl-ex |
Measurements of the nuclear modification factor and elliptic flow of
leptons from heavy-flavour hadron decays in Pb--Pb collisions at
$\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV with ALICE: We present the ALICE results on the nuclear modification factor and elliptic
flow of electrons and muons from open heavy-flavour hadron decays at
mid-rapidity and forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ =
2.76 and 5.02 TeV for different centrality intervals. The results are compared
to model calculations that include interactions of heavy quarks with the
medium. | nucl-ex |
Strong interaction studies with kaonic atoms: The strong interaction of antikaons (K-) with nucleons and nuclei in the low
energy regime represents an active research field connected intrinsically with
few-body physics. There are important open questions like the question of
antikaon nuclear bound states - the prototype system being K-pp. A unique and
rather direct experimental access to the antikaon-nucleon scattering lengths is
provided by precision X-ray spectroscopy of transitions in low-lying states of
light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment
at the electron-positron collider DA?NE of LNF-INFN we measured the most
precise values of the strong interaction observables, i.e. the strong
interaction on the 1s ground state of the electromagnetically bound K-p atom
leading to a hadronic shift and a hadronic broadening of the 1s state. The
SIDDHARTA result triggered new theoretical work which achieved major progress
in the understanding of the low-energy strong interaction with strangeness.
Antikaon-nucleon scattering lengths have been calculated constrained by the
SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent
scattering lengths a measurement of the hadronic shift and width of kaonic
deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic
deuterium are in preparation (SIDDHARTA2). Many improvements in the
experimental setup will allow to measure kaonic deuterium which is challenging
due to the anticipated low X-ray yield. Especially important are the data on
the X-ray yields of kaonic deuterium extracted from a exploratory experiment
within SIDDHARTA. | nucl-ex |
Accessing the Sign and Magnitude of $Δ$G via high $p_{T}$,
$A_{LL}^{π^{\pm}}$ in Polarized p+p Collisions at PHENIX: The double-helicity asymmetries ($A_{LL}$) of $\pi^{+}$ and $\pi^{-}$
production in polarized proton proton collisions are specially interesting
probes of the gluon's polarization. Relative differences among $A_{LL}$ of
positive, neutral, and negative pions at high transverse momentum are sensitive
to the sign and of magnitude of $\Delta$G. Quark-gluon (qg) scattering starts
to dominate mid-rapidity pion production at RHIC at transverse momenta above
5GeV/c. In this kinematic region the favored and unfavored fragmentation
functions for each pion species are sensitive to both the gluon and the quark
distributions, with different flavors having different weights for each pion
species. Charged pion asymmetry measurements will be an important component in
future global analyses, aiming to determine the gluon polarization over a wide
range in x, the most recent results using polarized longitudinal data at
$\sqrt{s}=$200GeV, are presented. | nucl-ex |
High-Intensity and High-Brightness Source of Moderated Positrons Using a
Brilliant gamma Beam: Presently large efforts are conducted towards the development of highly
brilliant gamma beams via Compton back scattering of photons from a
high-brilliance electron beam, either on the basis of a normal-conducting
electron linac or a (superconducting) Energy Recovery Linac (ERL). Particularly
ERL's provide an extremely brilliant electron beam, thus enabling to generate
highest-quality gamma beams. A 2.5 MeV gamma beam with an envisaged intensity
of 10^15 s^-1, as ultimately envisaged for an ERL-based gamma-beam facility,
narrow band width (10^-3), and extremely low emittance (10^-4 mm^2 mrad^2)
offers the possibility to produce a high-intensity bright polarized positron
beam. Pair production in a face-on irradiated W converter foil (200 micron
thick, 10 mm long) would lead to the emission of 2 x 10^13 (fast) positrons per
second, which is four orders of magnitude higher compared to strong radioactive
^22Na sources conventionally used in the laboratory.Using a stack of converter
foils and subsequent positron moderation, a high-intensity low-energy beam of
moderated positrons can be produced. Two different source setups are presented:
a high-brightness positron beam with a diameter as low as 0.2 mm, and a
high-intensity beam of 3 x 10^11 moderated positrons per second. Hence,
profiting from an improved moderation efficiency, the envisaged positron
intensity would exceed that of present high-intensity positron sources by a
factor of 100. | nucl-ex |
Neutron beta-decay, Standard Model and cosmology: The precise value of the neutron lifetime is of fundamental importance to
particle physics and cosmology. The neutron lifetime recently obtained, 878.5
+/- 0.7stat +/- 0.3sys s, is the most accurate one to date. The new result for
the neutron lifetime differs from the world average value by 6.5 standard
deviations. The impact of the new result on testing of Standard Model and on
data analysis for the primordial nucleosynthesis model is scrutinized. | nucl-ex |
Measurement of the $β^+$ and orbital electron-capture decay rates in
fully-ionized, hydrogen-like, and helium-like $^{140}$Pr ions: We report on the first measurement of the $\beta^+$- and orbital electron
capture decay rates of $^{140}$Pr nuclei with the most simple electron
configurations: bare nuclei, hydrogen-like and helium-like ions. The measured
electron capture decay constant of hydrogen-like $^{140}$Pr$^{58+}$ ions is
about 50% larger than that of helium-like $^{140}$Pr$^{57+}$ ions. Moreover,
$^{140}$Pr ions with one bound electron decay faster than neutral
$^{140}$Pr$^{0+}$ atoms with 59 electrons. To explain this peculiar observation
one has to take into account the conservation of the total angular momentum,
since only particular spin orientations of the nucleus and of the captured
electron can contribute to the allowed decay. | nucl-ex |
Inclusive photon production at forward rapidities using PMD in p-Pb
collisions at $\sqrt{\it{s}_{\rm{NN}}} = 8.16$ TeV with ALICE: We report on the performance studies of two correction methods, namely the
efficiency-purity method and the Bayesian unfolding method applied to the
pseudorapidity distribution of photons. The pseudorapidity distribution of
inclusive photons at forward rapidities in the range \mbox{\small
$(2.3<\eta<3.9)$} in p\textendash Pb collisions at $\sqrt{\it{s}_{\rm{NN}}} =
8.16$ TeV is obtained with the HIJING Monte Carlo event generator. The
simulated data samples were obtained from the Photon Multiplicity Detector
(PMD) in ALICE. | nucl-ex |
Direct photons ~basis for characterizing heavy ion collisions~: After years of experimental and theoretical efforts, direct photons become a
strong and reliable tool to establish the basic characteristics of a hot and
dense matter produced in heavy ion collisions. The recent direct photon
measurements are reviewed and a future prospect is given. | nucl-ex |
New Narrow $N(1685)$ and $N(1726)$? Remarks on the Interpretation of the
Neutron Anomaly as an Interference Phenomenon: Different interpretations of narrow structures at $W\sim 1.68$ and $W\sim
1.72$ GeV observed in several reactions are discussed. It is questionable
whether interference phenomena could explain the whole complex of experimental
findings. More probable hypotheses would be the existence of one or two narrow
resonances $N(1685)$ and $N(1726)$ and/or the sub-threshold virtual $K\Sigma$
and $\omega p$ production (cusps). | nucl-ex |
Evolution of the $γ$-ray strength function in neodymium isotopes: The experimental gamma-ray strength functions (gamma-SFs) of 142,144-151Nd
have been studied for gamma-ray energies up to the neutron separation energy.
The results represent a unique set of gamma-SFs for an isotopic chain with
increasing nuclear deformation. The data reveal how the low-energy enhancement,
the scissors mode and the pygmy dipole resonance evolve with nuclear
deformation and mass number. The data indicate that the mechanisms behind the
low-energy enhancement and the scissors mode are decoupled from each other. | nucl-ex |
A No-Go Theorem for Matter-Wave Interferometry with Application to the
Neutron's Electric-Dipole Moment: A theorem that relies only on the unitary property of the Schroedinger
equation and not upon any classical or semi-classical approximation negates
some, but not all, suggestions that have been made for measuring the neutron's
electric-dipole moment by interferometry. | nucl-ex |
The Majorana Demonstrator: A Search for Neutrinoless Double-beta Decay
of 76Ge: Neutrinoless double-beta decay is a hypothesized process where in some
even-even nuclei it might be possible for two neutrons to simultaneously decay
into two protons and two electrons without emitting neutrinos. This is possible
only if neutrinos are Majorana particles, i.e. fermions that are their own
antiparticles. Neutrinos being Majorana particles would explicitly violate
lepton number conservation, and might play a role in the matter-antimatter
asymmetry in the universe. The observation of neutrinoless double-beta decay
would also provide complementary information related to neutrino masses. The
Majorana Collaboration is constructing the Majorana Demonstrator, a 40-kg
modular germanium detector array, to search for the Neutrinoless double-beta
decay of 76Ge and to demonstrate a background rate at or below 3
counts/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039 keV
Q-value for 76Ge Neutrinoless double-beta decay. In this paper, we discuss the
physics of neutrinoless double beta decay and then focus on the Majorana
Demonstrator, including its design and approach to achieve ultra-low
backgrounds and the status of the experiment. | nucl-ex |
Half Life of the Doubly-magic r-Process Nucleus 78Ni: Nuclei with magic numbers serve as important benchmarks in nuclear theory. In
addition, neutron-rich nuclei play an important role in the astrophysical rapid
neutron-capture process (r-process). 78Ni is the only doubly-magic nucleus that
is also an important waiting point in the r-process, and serves as a major
bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been
experimentally deduced for the first time at the Coupled Cyclotron Facility of
the National Superconducting Cyclotron Laboratory at Michigan State University,
and was found to be 110 (+100 -60) ms. In the same experiment, a first
half-life was deduced for 77Ni of 128 (+27 -33) ms, and more precise half-lives
were deduced for 75Ni and 76Ni of 344 (+20 -24) ms and 238 (+15 -18) ms
respectively. | nucl-ex |
Kaon pair production in proton-nucleus collisions at 2.83 GeV kinetic
energy: The production of non-phi K+K- pairs by protons of 2.83 GeV kinetic energy on
C, Cu, Ag, and Au targets has been investigated using the COSY-ANKE magnetic
spectrometer. The K- momentum dependence of the differential cross section has
been measured at small angles over the 0.2--0.9 GeV/c range. The comparison of
the data with detailed model calculations indicates an attractive K- -nucleus
potential of about -60 MeV at normal nuclear matter density at a mean momentum
of 0.5 GeV/c. However, this approach has difficulty in reproducing the
smallness of the observed cross sections at low K- momenta. | nucl-ex |
Broken axial symmetry as essential feature to predict radiative capture
in heavy nuclei: Cross sections for neutron capture in the range of unresolved resonances are
predicted for more than 140 spin-0 target nuclei with A > 50. Allowing the
breaking of spherical and axial symmetry in nearly all these nuclei a combined
parameterization for both, level density and photon strength is obtained which
employs a surprisingly small number of parameters only. The strength functions
used are based on a global fit to IVGDR shapes by the sum of three Lorentzians.
They are based on theoretical predictions for the A-dependence of pole energies
and spreading widths and add up to the TRK sum rule. For the small spins
reached by capture resonance spacings are well described by a level density
parameter close to the nuclear matter value; a significant collective
enhancement is apparent due to the deviation from axial symmetry. Reliable
predictions for compound nuclear reactions also outside the valley of stability
(as important for nuclear astrophysics and for the transmutation of nuclear
waste) are expected to result from the global parameterization presented. | nucl-ex |
Determination of shear forces inside the proton: We report on the first determination of the shear forces quarks inside the
proton from experimental data on deeply virtual Compton scattering. The maximum
shear force of approximately 40 MeV/fm occurs near 0.6 fm from the proton
center, indicating where confinement forces may be strongest. On the
macroscopic scale of the earth surface, this force corresponds to the weight of
a mass of about 650 kg. The shear forces in the proton reverse direction at r =
0.45 fm from the center. | nucl-ex |
Measurements of Ks, Lambda and Xi from Au+Au collisions at \sqrt{s_NN} =
7.7, 11.5 and 39 GeV in STAR: We report on the measurements of Ks, Lambda and Xi spectra at mid-rapidity
(|y|<0.5) in the most central (0-5%) Au+Au collisions at \sqrt{s_NN} = 7.7,
11.5 and 39 GeV from the STAR experiment. The extracted yields and the
corresponding data from Pb+Pb collisions measured by the NA49 and CERES
experiments at SPS are consistent. The Lambda, Anti-Lambda, Xi- and Xi+ to pion
ratios agree well with the predictions from a statistical hadronization model
at all three energies. | nucl-ex |
Strong Interaction Physics at the Luminosity Frontier with 22 GeV
Electrons at Jefferson Lab: This document presents the initial scientific case for upgrading the
Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab)
to 22 GeV. It is the result of a community effort, incorporating insights from
a series of workshops conducted between March 2022 and April 2023. With a track
record of over 25 years in delivering the world's most intense and precise
multi-GeV electron beams, CEBAF's potential for a higher energy upgrade
presents a unique opportunity for an innovative nuclear physics program, which
seamlessly integrates a rich historical background with a promising future. The
proposed physics program encompass a diverse range of investigations centered
around the nonperturbative dynamics inherent in hadron structure and the
exploration of strongly interacting systems. It builds upon the exceptional
capabilities of CEBAF in high-luminosity operations, the availability of
existing or planned Hall equipment, and recent advancements in accelerator
technology. The proposed program cover various scientific topics, including
Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse
Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent
Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme
Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic
highlights the key measurements achievable at a 22 GeV CEBAF accelerator.
Furthermore, this document outlines the significant physics outcomes and unique
aspects of these programs that distinguish them from other existing or planned
facilities. In summary, this document provides an exciting rationale for the
energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific
potential that lies within reach, and the remarkable opportunities it offers
for advancing our understanding of hadron physics and related fundamental
phenomena. | nucl-ex |
CNN-based event classification for alpha-decay events in nuclear
emulsion: We developed an efficient classifier that sorts alpha-decay events from
various vertex-like objects in nuclear emulsion using a convolutional neural
network (CNN). Alpha-decay events in the emulsion are standard calibration
sources for the relation between the track length and kinetic energy in each
emulsion sheet. We trained the CNN using 15,885 images of vertex-like objects
including 906 alpha-decay events and tested it using a dataset of 46,948 images
including 255 alpha-decay events. By tuning the hyperparameters of the CNN, the
trained models achieved an Average Precision Score of 0.740 +/- 0.009 for the
test dataset. For the model obtained, a discrimination threshold of the
classification can be arbitrarily adjusted according to the balance between the
precision and recall. The precision and recall of the classification using
previous method without a CNN were 0.081 +/- 0.006 and 0.788 +/- 0.056,
respectively, for the same dataset. By contrast, the developed classifier
obtained a precision of 0.547 +/- 0.025 when a similar recall value of 0.788
was set. The developed CNN method reduced the human load for further visual
inspection after the classification by approximately 1/7 compared to the
estimated load of the former method without a CNN. | nucl-ex |
First observation of excited states in 173Hg: The neutron-deficient nucleus 173Hg has been studied following
fusion-evaporation reactions. The observation of gamma rays decaying from
excited states are reported for the first time and a tentative level scheme is
proposed. The proposed level scheme is discussed within the context of the
systematics of neighbouring neutron-deficient Hg nuclei. In addition to the
gamma-ray spectroscopy, the alpha decay of this nucleus has been measured
yielding superior precision to earlier measurements. | nucl-ex |
Structure of 23Al from one-proton breakup reaction and astrophysical
implications: The ground state of the proton-rich nucleus 23Al has been studied by
one-proton removal on a carbon target at about 50 MeV/nucleon using the EXOGAM
+ SPEG experimental setup at GANIL. Longitudinal momentum distributions of the
22Mg breakup fragments, inclusive and in coincidence with gamma rays
de-exciting the residues, were measured. The ground-state structure of 23Al is
found to be a configuration mixing of a d-orbital valence proton coupled to
four core states - 0$^{+}_{gs}$, 2$^{+}_{1}$, 4$^{+}_{1}$, 4$^{+}_{2}$. We
confirm the ground state spin and parity of 23Al as $J^{\pi} = 5/2^{+}$. The
measured exclusive momentum distributions are compared with extended Glauber
model calculations to extract spectroscopic factors and asymptotic
normalization coefficients (ANCs). The spectroscopic factors are presented in
comparison with those obtained from large-scale shell model calculations. We
determined the asymptotic normalization coefficient of the nuclear system
$^{23}$Al$_{gs}$ $\rightarrow$ $^{22}$Mg(0$^{+}$) + p to be
$C^{2}_{d_{5/2}}$($^{23}Al_{gs}$) = (3.90 $\pm$ 0.44) $\times$ 10$^{3}$
fm$^{-1}$, and used it to infer the stellar reaction rate of the direct
radiative proton capture $^{22}$Mg(p,$\gamma$)$^{23}$Al. Astrophysical
implications related to $^{22}$Na nucleosynthesis in ONe novae and the use of
one-nucleon breakup at intermediate energies as an indirect method in nuclear
astrophysics are discussed. | nucl-ex |
Quadrupole Moments of Collective Structures up to Spin $\sim$ $65\hbar$
in $^{157}$Er and $^{158}$Er: A Challenge for Understanding Triaxiality in
Nuclei: The transition quadrupole moments, $Q_{\rm t}$, of four weakly populated
collective bands up to spin $\sim$ $65\hbar$ in $^{157,158}$Er have been
measured to be ${\sim}11 {\rm eb}$ demonstrating that these sequences are
associated with large deformations. However, the data are inconsistent with
calculated values from cranked Nilsson-Strutinsky calculations that predict the
lowest energy triaxial shape to be associated with rotation about the short
principal axis. The data appear to favor either a stable triaxial shape
rotating about the intermediate axis or, alternatively, a triaxial shape with
larger deformation rotating about the short axis. These new results challenge
the present understanding of triaxiality in nuclei. | nucl-ex |
Measurement of single electrons and implications for charm production in
Au+Au collisions at sqrt(s_NN)= 130 GeV: Transverse momentum spectra of electrons from Au+Au collisions at sqrt(s_NN)
= 130 GeV have been measured by the PHENIX experiment at RHIC. The spectra show
an excess above the background from photon conversions and light hadron decays.
The electron signal is consistent with that expected from semi-leptonic decays
of charm. The yield of the electron signal dN_e/dy for p_T > 0.8 GeV/c is 0.025
+/- 0.004 (stat.) +/- 0.010 (sys.) in central collisions, and the corresponding
charm cross section is 380 +/- 60 (stat.) +/- 200 (sys.) micro barns per binary
nucleon-nucleon collision. | nucl-ex |
First measurements of the ^16O(e,e'pn)^14N reaction: This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction.
Data were measured in kinematics centred on a super-parallel geometry at energy
and momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution
was sufficient to distinguish groups of states in the residual nucleus but not
good enough to separate individual states. The data show a strong dependence on
missing momentum and this dependence appears to be different for two groups of
states in the residual nucleus. Theoretical calculations of the reaction using
the Pavia code do not reproduce the shape or the magnitude of the data. | nucl-ex |
Spectroscopy of $^{26}$F: The structure of the weakly-bound $^{26}_{\;\;9}$F$_{17}$ odd-odd nucleus,
produced from $^{27,28}$Na nuclei, has been investigated at GANIL by means of
the in-beam $\gamma$-ray spectroscopy technique. A single $\gamma$-line is
observed at 657(7) keV in $^{26}_{9}$F which has been ascribed to the decay of
the excited J=$2^+$ state to the J=1$^+$ ground state. The possible presence of
intruder negative parity states in $^{26}$F is also discussed. | nucl-ex |
Probing dense and hot matter with low-mass dileptons and photons: Results on low-mass dileptons, covering the very broad energy range from the
BEVALAC up to SPS are reviewed. The emphasis is on the open questions raised by
the intriguing results obtained so far and the prospects for addressing them in
the near future with the second generation of experiments, in particular HADES,
NA60 and PHENIX. | nucl-ex |
New neutron-deficient isotopes from $^{78}$Kr fragmentation: In an experiment with the BigRIPS separator at the RIKEN Nishina Center, the
fragmentation of a $^{78}$Kr beam allowed the observation of new
neutron-deficient isotopes at the proton drip-line. Clean identification
spectra could be produced and $^{63}$Se, $^{67}$Kr, and $^{68}$Kr were
identified for the first time. In addition, $^{59}$Ge was also observed. Three
of these isotopes, $^{59}$Ge, $^{63}$Se, and $^{67}$Kr, are potential
candidates for ground-state two-proton radioactivity. In addition, the isotopes
$^{58}$Ge, $^{62}$Se, and $^{66}$Kr were also sought but without success. The
present experiment also allowed the determination of production cross sections
for some of the most exotic isotopes. These measurements confirm the trend
already observed that the empirical parameterization of fragmentation cross
sections, EPAX, significantly overestimates experimental cross sections in this
mass region. | nucl-ex |
Identical pion intensity interferometry in central Au+Au collisions at
1.23A GeV: We investigate identical pion HBT intensity interferometry for central Au+Au
collisions at 1.23A GeV. High-statistics $\pi^-\pi^-$ and $\pi^+\pi^+$ data are
measured with HADES at SIS18/GSI. The radius parameters, derived from the
correlation function depending on relative momenta in the longitudinal-comoving
system and parametrized as three-dimensional Gaussian distribution, are studied
as function of transverse momentum. A substantial charge-sign difference of the
source radii is found, particularly pronounced at low transverse momentum. The
extracted Coulomb-corrected source parameters agree well with a smooth
extrapolation of the center-of-mass energy dependence established at higher
energies, extending the corresponding excitation functions down towards a very
low energy. Our data would thus rather disfavour any strong energy dependence
of the radius parameters in the low energy region. | nucl-ex |
Hadronization and chirality in strongly interacting partonic matter -
the future of the RHIC program: New physics and detector concepts for a future pp and heavy ion program at
the RHIC-II accelerator facility will be discussed. I will focus on hadronic
observables which enable us to gain a better understanding on the hadronization
from a sQGP and the chiral symmetry restoration in a sQGP. The ultimate
question of how matter acquires mass can be addressed by this program in a
complementary way to the Higgs search in high energy physics. The contributions
of the RHIC program to the study of QCD will be discussed in detail. | nucl-ex |
Neutron inelastic scattering in natural Cu as a background in
neutrinoless double-beta decay experiments: Experiments designed to study rare processes, such as neutrinoless double
beta decay ($0\nu\beta\beta$), are crucial tests for physics beyond the
standard model. These experiments rely on reducing the intrinsic radioactive
background to unprecedented levels, while adequately shielding the detectors
from external sources of radioactivity. An understanding of the potential for
neutron excitation of the shielding and detector materials is important for
obtaining this level of sensitivity. Using the broad-spectrum neutron beam at
LANSCE, we have measured inelastic neutron scattering on $^{nat}$Cu. The goal
of this work is focused on understanding the background rates from neutrons
interacting in these materials in regions around the Q-values of many candidate
$0\nu\beta\beta$ decay isotopes, as well as providing data for benchmarking
Monte Carlo simulations of background events. Results: We extracted the level
cross sections from the $\gamma$ production cross section for 46 energy levels
in $^{nat}$Cu . These level cross sections were compared with the available
experimental data, as well as the ENDF/B-VII evaluation for discrete levels. We
also examined the potential implications of our measurements on
$0\nu\beta\beta$ measurements and found that many of the commonly studied
$0\nu\beta\beta$ isotopes had Q-values below the cutoff for ENDF/B-VII
evaluated discrete levels in either Cu nucleus. | nucl-ex |
Single-particle isomeric states in 121Pd and 117Ru: Neutron-rich nuclei were populated in a relativistic fission of 238U.
Gamma-rays with energies of 135 keV and 184 keV were associated with two
isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and
2.0(3) micrisecondss were deduced and the isomeric states were interpreted in
terms of deformed single-particle states. | nucl-ex |
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