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Method for High Accuracy Multiplicity Correlation Measurements: Multiplicity correlation measurements provide insight into the dynamics of
high energy collisions. Models describing these collisions need these
correlation measurements to tune the strengths of the underlying QCD processes
which influence all observables. Detectors, however, often possess limited
coverage or reduced efficiency that influence correlation measurements in
obscure ways. In this paper, the effects of non-uniform detection acceptance
and efficiency on the measurement of multiplicity correlations between two
distinct detector regions (termed forward-backward correlations) are derived.
An analysis method with such effects built-in is developed and subsequently
verified using different event generators. The resulting method accounts for
acceptance and efficiency in a model independent manner with high accuracy
thereby shedding light on the relative contributions of the underlying
processes to particle production. | nucl-ex |
The beta-Oslo method: experimentally constrained ($n,γ$) reaction
rates relevant to the $r$-process: Unknown neutron-capture reaction rates remain a significant source of
uncertainty in state-of-the-art $r$-process nucleosynthesis reaction network
calculations. As the $r$-process involves highly neutron-rich nuclei for which
direct ($n,\gamma$) cross-section measurements are virtually impossible,
indirect methods are called for to constrain ($n,\gamma$) cross sections used
as input for the $r$-process nuclear network. Here we discuss the newly
developed beta-Oslo method, which is capable of providing experimental input
for calculating ($n,\gamma$) rates of neutron-rich nuclei. The beta-Oslo method
represents a first step towards constraining neutron-capture rates of
importance to the $r$-process. | nucl-ex |
Systematic comparison of ISOLDE-SC yields with calculated in-target
production rates: Recently, a series of dedicated inverse-kinematics experiments performed at
GSI, Darmstadt, has brought an important progress in our understanding of
proton and heavy-ion induced reactions at relativistic energies. The nuclear
reaction code ABRABLA that has been developed and benchmarked against the
results of these experiments has been used to calculate nuclide production
cross sections at different energies and with different targets and beams.
These calculations are used to estimate nuclide production rates by protons in
thick targets, taking into account the energy loss and the attenuation of the
proton beam in the target, as well as the low-energy fission induced by the
secondary neutrons. The results are compared to the yields of isotopes of
various elements obtained from different targets at CERN-ISOLDE with 600 MeV
protons, and the overall extraction efficiencies are deduced. The dependence of
these extraction efficiencies on the nuclide half-life is found to follow a
simple pattern in many different cases. A simple function is proposed to
parameterize this behavior in a way that quantifies the essential properties of
the extraction efficiency for the element and the target - ion-source system in
question. | nucl-ex |
Production of $^{4}$He and $^{4}\overline{\textrm{He}}$ in Pb-Pb
collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV at the LHC: Results on the production of $^{4}{\textrm{He}}$ and
$^{4}\overline{\textrm{He}}$ nuclei in Pb-Pb collisions at $
\sqrt{s_{\mathrm{NN}}} = 2.76 $ TeV in the rapidity range $ \mid y \mid < 1$,
using the ALICE detector, are presented in this paper. The rapidity densities
corresponding to 0-10% central events are found to be $\mathrm{d}N/\mathrm{d}y
_{^{4}\mathrm{He}} = (0.8 \pm 0.4 ~(\mathrm{stat}) \pm
0.3~(\mathrm{syst}))\times 10^{-6}$ and $\mathrm{d}N/\mathrm{d}y
_{^{4}\mathrm{\overline{He}}} = (1.1 \pm 0.4~(\mathrm{stat}) \pm
0.2~(\mathrm{syst}))\times 10^{-6}$, respectively. This is in agreement with
the statistical thermal model expectation assuming the same chemical freeze-out
temperature ($T_{\mathrm{chem}}$ = 156 MeV) as for light hadrons. The measured
ratio of $^{4}\overline{\mathrm{He}}$/$^{4}\mathrm{He}$ is $1.4 \pm
0.8~(\mathrm{stat}) \pm 0.5~(\mathrm{syst})$. | nucl-ex |
The nucleon resonance structure from exclusive $π^+π^-p$
photo-/electroproduction off protons: The results on the photo- and electroexcitation amplitudes of most nucleon
resonances in the mass range up to 2.0 GeV determined from the CLAS
experimental data on exclusive $\pi^+\pi^-p$ photo-/electroproduction off
protons in collaboration between the Jefferson Lab and Moscow State University
are presented. The first and only available results on electroexcitation
amplitudes from CLAS in a wide range of photon virtualities $Q^2$ $<$ 5.0
GeV$^2$ revealed the nucleon resonance structure as a complex interplay between
the inner core of three dressed quarks and external meson-baryon cloud. These
results shed light on the strong QCD dynamics which underlines the generation
of excited nucleon states of different structural features from confined quarks
and gluons. The future prospects of these studies in the new era of experiments
with the CLAS12 detector, which started successfully in Spring of 2018, are
outlined. | nucl-ex |
Review of Forward Physics at RHIC: The RHIC high energy collision of species ranging from p+p, p(d)+A to A+A
provide access to the {small-x} component of the hadron wave function. The RHIC
program has brought renewed interest in that subject with its ability to reach
values of the parton momentum fraction smaller than 0.01 with studies of
particle production at high rapidity. Furthermore, the use of heavy nuclei in
the p(d)+A collisions facilitates the study of saturation effects in the
gluonic component of the nuclei because the appropriate scale for that regime
grows as A^1/3. We review the experimental results of the RHIC program that
have relevance to {small-x} emphasizing the physics extracted from d+Au
collisions and their comparison to p+p collisions at the same energy. | nucl-ex |
Hadron yields and the phase diagram of strongly interacting matter: This paper presents a brief review of the interpretation of measurements of
hadron yields in hadronic interactions within the framework of thermal models,
over a broad energy range (from SIS to LHC energies, $\sqrt{s_{NN}} \simeq$ 2.5
GeV -- 5 TeV). Recent experimental results and theoretical developments are
reported, with an emphasis on topics discussed during the Quark Matter 2014
conference. | nucl-ex |
Anti-flow of K$^0_s$ Mesons in 6 AGeV Au + Au Collisions: We have measured the sideward flow of neutral strange ($K^0_s$) mesons in 6
AGeV Au + Au collisions. A prominent anti-flow signal is observed for an impact
parameter range (b $\lesssim 7$ fm) which spans central and mid-central events.
Since the $K^0_s$ scattering cross section is relatively small in nuclear
matter, this observation suggests that the in-medium kaon vector potential
plays an important role in high density nuclear matter. | nucl-ex |
Search for the Chiral Magnetic Effect in Relativistic Heavy-Ion
Collisions: Relativistic heavy-ion collisions provide an ideal environment to study the
emergent phenomena in quantum chromodynamics (QCD). The chiral magnetic effect
(CME) is one of the most interesting, arising from the topological charge
fluctuations of QCD vacua, immersed in a strong magnetic field. Since the first
measurement nearly a decade ago of the possibly CME-induced charge correlation,
extensive studies have been devoted to background contributions to those
measurements. Many new ideas and techniques have been developed to reduce or
eliminate the backgrounds. This article reviews these developments and the
overall progress in the search for the CME. | nucl-ex |
Comment on "Evidence for narrow resonant structures at $W\approx$ 1.68
GeV and $W\approx$ 1.72 GeV in real Compton scattering off the proton": We comment on the statement by Kuznetsov et al. that the structure around
W=1.72 GeV seen in the beam asymmetry in Compton scattering off the proton is
not observed in the total cross section of $\eta$ photoproduction on the
neutron. | nucl-ex |
Energy Deconvolution of Cross Section Measurements with an Application
to the 12C(α,γ)16O Reaction: A general framework for deconvoluting the effects of energy averaging on
charged-particle reaction measurements is presented. There are many potentially
correct approaches to the problem; the relative merits of some of are
discussed. These deconvolution methods are applied to recent
12C(\alpha,\gamma)16O measurements. | nucl-ex |
Exclusive proton asymmetry measurement in non-mesonic weak decay of
polarized 5_Lambda_He: The asymmetry parameter alpha_p^NM for a proton exclusively emitted in the
Lambda p -> np process was, for the first time, measured in the non-mesonic
weak decay of a polarized 5_La,bda_He hypernucleus by selecting the
proton-neutron pairs emitted in the back-to-back kinematics. The highly
polarized 5_Lambda_He was abundantly produced with the (pi+,K+) reaction at
1.05GeV/c in the scattering angular range of +-15$ degrees. The obtained value
alpha_p^NM=0.31+-0.22, as well as that for inclusive protons,
alpha_p^NM=0.11+-0.08+-0.04, largely contradicts recent theoretical values of
around -0.6, although these calculations well reproduce the branching ratios of
non-mesonic weak decay. | nucl-ex |
The neutron-gamma Feynman variance to mean approach: gamma detection and
total neutron-gamma detection (theory and practice): Two versions of the neutron-gamma variance to mean (Feynman-alpha method or
Feynman-Y function) formula for either gamma detection only or total
neutron-gamma detection, respectively, are derived and compared in this paper.
The new formulas have a particular importance for detectors of either gamma
photons or detectors sensitive to both neutron and gamma radiation. If applied
to a plastic or liquid scintillation detector, the total neutron-gamma
detection Feynman-Y expression corresponds to a situation where no
discrimination is made between neutrons and gamma particles. The gamma variance
to mean formulas are useful when a detector of only gamma radiation is used or
when working with a combined neutron-gamma detector at high count rates. The
theoretical derivation is based on the Chapman-Kolmogorov equation with
inclusion of general reactions and passage intensities for neutrons and gammas,
but with the inclusion of prompt reactions only. A one energy group
approximation is considered. The comparison of the two different theories is
made by using reaction intensities obtained in MCNPX simulations with a
simplified geometry for two scintillation detectors and a 252Cf-source enclosed
in a steel container. In addition, the variance to mean ratios, neutron, gamma
and total neutron-gamma, are evaluated experimentally for a weak 252Cf
neutron-gamma source in a steel container, a 137Cs random gamma source and a
22Na correlated gamma source. Due to the focus being on the possibility of
using neutron-gamma variance to mean theories for both reactor and safeguards
applications, we limited the present study to the general analytical
expressions for Feynman-Y formulas. | nucl-ex |
Characterisation of radiation damage in silicon photomultipliers with a
Monte Carlo model: Measured response functions and low photon yield spectra of silicon
photomultipliers (SiPM) were compared to multi-photoelectron pulse-height
distributions generated by a Monte Carlo model. Characteristic parameters for
SiPM were derived. The devices were irradiated with 14 MeV electrons at the
Mainz microtron MAMI. It is shown that the first noticeable damage consists of
an increase in the rate of dark pulses and the loss of uniformity in the pixel
gains. Higher radiation doses reduced also the photon detection efficiency. The
results are especially relevant for applications of SiPM in fibre detectors at
high luminosity experiments. | nucl-ex |
Measurement of the branching ratio for beta-delayed alpha decay of 16N: While the 12C(a,g)16O reaction plays a central role in nuclear astrophysics,
the cross section at energies relevant to hydrostatic helium burning is too
small to be directly measured in the laboratory. The beta-delayed alpha
spectrum of 16N can be used to constrain the extrapolation of the E1 component
of the S-factor; however, with this approach the resulting S-factor becomes
strongly correlated with the assumed beta-alpha branching ratio. We have
remeasured the beta-alpha branching ratio by implanting 16N ions in a segmented
Si detector and counting the number of beta-alpha decays relative to the number
of implantations. Our result, 1.49(5)e-5, represents a 24% increase compared to
the accepted value and implies an increase of 14% in the extrapolated S-factor. | nucl-ex |
The QCD Phase Diagram: Expectations and Challenges: A survey is given of recent QCD theory advances concerning the phase diagram,
in particular the indications for a critical point and adjacent first order
phase transition at high baryo-chemical potential, and the new ideas concerning
a further phase at high $\mu_{B}$, the quarkyonic matter phase. The latter
state might finally explain the hadro-chemical equilibrium freeze-out points
from A+A collisions at energies below SPS energy. We review several
event-by-event fluctuation signals that promise to shed a light on the
existence of a critical point, and we discuss its possible reflection in recent
lattice QCD calculations. | nucl-ex |
Measurement of cold nuclear matter effects for inclusive $J/ψ$ in
$p$+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV: Measurement by the STAR experiment at RHIC of the cold nuclear matter (CNM)
effects experienced by inclusive $J/\psi$ at mid-rapidity in 0-100\% $p$+Au
collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV is presented. Such effects
are quantified utilizing the nuclear modification factor, $R_{p\mathrm{Au}}$,
obtained by taking a ratio of $J/\psi$ yield in $p$+Au collisions to that in
$p$+$p$ collisions scaled by the number of binary nucleon-nucleon collisions.
The differential $J/\psi$ yield in both $p$+$p$ and $p$+Au collisions is
measured through the dimuon decay channel, taking advantage of the trigger
capability provided by the Muon Telescope Detector in the RHIC 2015 run.
Consequently, the $J/\psi$ $R_{p\mathrm{Au}}$ is derived within the transverse
momentum ($p_{\mathrm{T}}$) range of 0 to 10 GeV/$c$. A suppression of
approximately 30% is observed for $p_{\mathrm{T}}<2$ GeV/$c$, while $J/\psi$
$R_{p\mathrm{Au}}$ becomes compatible with unity for $p_{\mathrm{T}}$ greater
than 3 GeV/$c$, indicating the $J/\psi$ yield is minimally affected by the CNM
effects at high $p_{\mathrm{T}}$. Comparison to a similar measurement from
0-20% central Au+Au collisions reveals that the observed strong $J/\psi$
suppression above 3 Gev/$c$ is mostly due to the hot medium effects, providing
strong evidence for the formation of the quark-gluon plasma in these
collisions. Several model calculations show qualitative agreement with the
measured $J/\psi$ $R_{p\mathrm{Au}}$, while their agreement with the $J/\psi$
yields in $p$+$p$ and $p$+Au collisions is worse. | nucl-ex |
Measurement of the radiative neutron capture cross section of 206Pb and
its astrophysical implications: The (n, gamma) cross section of 206Pb has been measured at the CERN n_TOF
facility with high resolution in the energy range from 1 eV to 600 keV by using
two optimized C6D6 detectors. In the investigated energy interval about 130
resonances could be observed, from which 61 had enough statistics to be
reliably analyzed via the R-matrix analysis code SAMMY. Experimental
uncertainties were minimized, in particular with respect to (i) angular
distribution effects of the prompt capture gamma-rays, and to (ii) the
TOF-dependent background due to sample-scattered neutrons. Other background
components were addressed by background measurements with an enriched 208Pb
sample. The effect of the lower energy cutoff in the pulse height spectra of
the C6D6 detectors was carefully corrected via Monte Carlo simulations.
Compared to previous 206Pb values, the Maxwellian averaged capture cross
sections derived from these data are about 20% and 9% lower at thermal energies
of 5 keV and 30 keV, respectively. These new results have a direct impact on
the s-process abundance of 206Pb, which represents an important test for the
interpretation of the cosmic clock based on the decay of 238U. | nucl-ex |
Photoproduction of pi0-mesons off neutrons in the nucleon resonance
region: Precise angular distributions have been measured for the first time for the
photoproduction of $\pi^{0}$-mesons off neutrons bound in the deuteron. The
effects from nuclear Fermi motion have been eliminated by a complete kinematic
reconstruction of the final state. The influence of final-state-interaction
effects has been estimated by a comparison of the reaction cross section for
quasi-free protons bound in the deuteron to the results for free protons and
then applied as a correction to the quasi-free neutron data. The experiment was
performed at the tagged photon facility of the Mainz Microtron MAMI with the
Crystal Ball and TAPS detector setup for incident photon energies between
$0.45$~GeV and $1.4$~GeV. The results are compared to the predictions from
reaction models and partial-wave analyses based on data from other isospin
channels. The model predictions show large discrepancies among each other and
the present data will provide much tighter constraints. This is demonstrated by
the results of a new analysis in the framework of the Bonn-Gatchina
coupled-channel analysis which included the present data. | nucl-ex |
Coulomb displacement energies as a probe for nucleon pairing in the
$f_{7/2}$ shell: Coulomb displacement energies of $T=1/2$ mirror nuclei have been studied via
a series of high-precision $Q_\mathrm{EC}$-value measurements with the double
Penning trap mass spectrometer JYFLTRAP. Most recently, the $Q_\mathrm{EC}$
values of the $f_{7/2}$-shell mirror nuclei $^{45}$V
($Q_\mathrm{EC}=7123.82(22)$ keV) and $^{49}$Mn ($Q_\mathrm{EC}=7712.42(24)$
keV) have been measured with an unprecedented precision. The data reveal a
16-keV ($1.6\sigma$) offset in the adopted Atomic Mass Evaluation 2012 value of
$^{49}$Mn suggesting the need for further measurements to verify the breakdown
of the quadratic form of the isobaric multiplet mass equation. Precisely
measured $Q_\mathrm{EC}$ values confirm that the pairing effect in the Coulomb
energies is quenched when entering the $f_{7/2}$ shell and reaches a minimum in
the midshell. | nucl-ex |
Investigating nuclear structure near $N = 32$ and $N = 34$: Precision
mass measurements of neutron-rich Ca, Ti and V isotopes: Nuclear mass measurements of isotopes are key to improving our understanding
of nuclear structure across the chart of nuclides, in particular for the
determination of the appearance or disappearance of nuclear shell closures. We
present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes
performed at the TITAN and LEBIT facilities. These measurements were made using
the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and
the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were
measured, eight of which represent increases in precision over previous
measurements. These measurements refine trends in the mass surface around $N =
32$ and $N = 34$, and support the disappearance of the $N = 32$ shell closure
with increasing proton number. Additionally, our data does not support the
presence of a shell closure at $N = 34$. | nucl-ex |
14Be(p,n)14B reaction at 69 MeV in inverse kinematics: A Gamow-Teller (GT) transition from the drip-line nucleus 14Be to 14B was
studied via the (p,n) reaction in inverse kinematics using a secondary 14Be
beam at 69 MeV/nucleon. The invariant mass method is employed to reconstruct
the energy spectrum. A peak is observed at an excitation energy of 1.27(2) MeV
in 14B, together with bumps at 2.08 and 4.06(5) MeV. The observed forward
peaking of the state at 1.27 MeV and a good description for the differential
cross section, obtained with a DWBA calculation provide support for the 1+
assignment to this state. By extrapolating the cross section to zero momentum
transfer the GT-transition strength is deduced. The value is found to compare
well with that reported in a beta-delayed neutron emission study. | nucl-ex |
LENDA, a Low Energy Neutron Detector Array for experiments with
radioactive beams in inverse kinematics: The Low Energy Neutron Detector Array (LENDA) is a neutron time-of-flight
(TOF) spectrometer developed at the National Superconducting Cyclotron Lab-
oratory (NSCL) for use in inverse kinematics experiments with rare isotope
beams. Its design has been motivated by the need to study the spin-isospin
response of unstable nuclei using (p, n) charge-exchange reactions at
intermediate energies (> 100 MeV/u). It can be used, however, for any reaction
study that involves emission of low energy neutrons (150 keV - 10 MeV). The
array consists of 24 plastic scintillator bars and is capable of registering
the recoiling neutron energy and angle with high detection efficiency. The
neutron energy is determined by the time-of-flight technique, while the
position of interaction is deduced using the timing and energy information from
the two photomultipliers of each bar. A simple test setup utilizing radioactive
sources has been used to characterize the array. Results of test measurements
are compared with simulations. A neutron energy threshold of < 150 keV, an
intrinsic time (position) resolution of \sim 400 ps (\sim 6 cm) and an
efficiency > 20 % for neutrons below 4 MeV have been obtained. | nucl-ex |
Geo-neutrinos and the Radioactive Power of the Earth: Chemical and physical Earth models agree little as to the radioactive power
of the planet. Each predicts a range of radioactive powers, overlapping
slightly with the other at about 24 TW, and together spanning 14-46 TW.
Approximately 20 % of this radioactive power (3-8 TW) escapes to space in the
form of geo-neutrinos. The remaining 11-38 TW heats the planet with significant
geo-dynamical consequences, appearing as the radiogenic component of the 43-49
TW surface heat flow. The non-radiogenic component of the surface heat flow
(5-38 TW) is presumably primordial, a legacy of the formation and early
evolution of the planet. A constraining measurement of radiogenic heating
provides insights to the thermal history of the Earth and potentially
discriminates chemical and physical Earth models. Radiogenic heating in the
planet primarily springs from unstable nuclides of uranium, thorium, and
potassium. The paths to their stable daughter nuclides include nuclear beta
decays, producing geo-neutrinos. Large sub-surface detectors efficiently record
the energy but not the direction of the infrequent interactions of the highest
energy geo-neutrinos, originating only from uranium and thorium. The measured
energy spectrum of the interactions estimates the relative amounts of these
heat-producing elements, while the intensity estimates planetary radiogenic
power. Recent geo-neutrino observations in Japan and Italy find consistent
values of radiogenic heating. The combined result mildly excludes the lowest
model values of radiogenic heating and, assuming whole mantle convection,
identifies primordial heat loss. Future observations have the potential to
measure radiogenic heating with better precision, further constraining
geological models and the thermal evolution of the Earth. | nucl-ex |
Recent results from BRAHMS: The BRAHMS collaboration ended its data collection program in 2006. We are
now well advanced in the analysis of a comprehensive set of data that spans
systems ranging in mass from p+p to Au+Au and in energy from $\sqrt{s_{NN}} =
62.4$ to 200 GeV. Our analysis has taken two distinct paths: we explore the
rapidity dependence of intermediate and high-transverse-momentum,
identified-particle production, thus helping to characterize the
strongly-interacting quark-gluon plasma (sQGP) formed at RHIC; we also explore
particle yields at lower transverse momentum to develop a systematic
understanding of bulk particle production at RHIC energies. | nucl-ex |
Measurement of inclusive electrons from open heavy-flavor hadron decays
in $p$+$p$ collisions at $\sqrt{s} = 200$ GeV with the STAR detector: We report a new measurement of the production cross section for inclusive
electrons from open heavy-flavor hadron decays as a function of transverse
momentum ($p_{\rm T}$) at mid-rapidity ($|y|<$ 0.7) in $p$+$p$ collisions at
$\sqrt{s} = 200$ GeV. The result is presented for 2.5 $<p_{\rm T}<$ 10 GeV/$c$
with an improved precision above 6 GeV/$c$ with respect to the previous
measurements, providing more constraints on perturbative QCD calculations.
Moreover, this measurement also provides a high-precision reference for
measurements of nuclear modification factors for inclusive electrons from
open-charm and -bottom hadron decays in heavy-ion collisions. | nucl-ex |
The PHENIX Potential in the Search for the QCD Critical Point: With the measurement of several observables at SPS energies that demonstrate
non-monotonic behavior as a function of centrality and $\sqrt{s_{NN}}$, there
is growing interest in pursuing a scan of relativistic heavy ion collisions at
low energies at the Relativistic Heavy Ion Collider. The capabilities of the
PHENIX experiment to take quality measurements at low RHIC energies is
described and directly demonstrated with analyses of Au+Au collisions at
$\sqrt{s_{NN}}$ = 19.6 GeV and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 22.5 GeV.
The contribution of upgrades to the PHENIX detector in the upcoming years will
also be discussed in the context of a low energy RHIC run. | nucl-ex |
Measurement of the Spin-Dependence of the pbar-p Interaction at the
AD-Ring: We propose to use an internal polarized hydrogen storage cell gas target in
the AD ring to determine for the first time the two total spin-dependent pbar-p
cross sections sigma_1 and sigma_2 at antiproton beam energies in the range
from 50 to 450 MeV. The data obtained are of interest by themselves for the
general theory of pbar-p interactions since they will provide a first
experimental constraint of the spin-spin dependence of the nucleon-antinucleon
potential in the energy range of interest. In addition, measurements of the
polarization buildup of stored antiprotons are required to define the optimum
parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to
feed a double-polarized asymmetric pbar-p collider with polarized antiprotons.
Such a machine has recently been proposed by the PAX collaboration for the new
Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, Germany.
The availability of an intense stored beam of polarized antiprotons will
provide access to a wealth of single- and double-spin observables, thereby
opening a new window on QCD spin physics. | nucl-ex |
Dissociation of C-10 Nuclei in a Track Nuclear Emulsion at an Energy of
1.2 GeV per Nucleon: The charge topology in the fragmentation of $^{10}$C nuclei in a track
nuclear emulsion at an energy of 1.2 GeV per nucleon is studied. In the
coherent dissociation of $^{10}$C nuclei, about 82% of events are associated
with the channel $^{10}$C $\rightarrow$ 2$\alpha +$ 2\emph{p}. The angular
distributions and correlations of product fragments are presented for this
channel. It is found that among $^{10}$C $\rightarrow$ 2$\alpha +$ 2\emph{p}
events, about 30% are associated with the process in which dissociation through
the ground state of the unstable $^9$Be$_{g.s.}$ nucleus is followed by
$^8$Be$_{g.s.} +$ \emph{p} decays. | nucl-ex |
Azimuthal anisotropy of K^0_S and Lambda production at mid-rapidity from
Au+Au collisions at root s_NN = 130 GeV: We report STAR results on the azimuthal anisotropy parameter v2 for strange
particles K0S and Lambda at midrapidity in Au+Au collisions at /s_NN = 130 GeV
at RHIC. The value of v2 as a function of transverse momentum pt and collision
centrality is presented for both particles and compared to model calculations.
A strong pt dependence in v2 is observed up to pt ~2.0 GeV/c where v2 begins to
saturate. | nucl-ex |
First measurement of near-threshold J/$ψ$ exclusive photoproduction
off the proton: We report on the measurement of the $\gamma p \rightarrow J/\psi p$ cross
section from $E_\gamma = 11.8$ GeV down to the threshold at $8.2$ GeV using a
tagged photon beam with the GlueX experiment. We find the total cross section
falls toward the threshold less steeply than expected from two-gluon exchange
models. The differential cross section $d\sigma /dt$ has an exponential slope
of $1.67 \pm 0.39$ GeV$^{-2}$ at $10.7$ GeV average energy. The LHCb pentaquark
candidates $P_c^+$ can be produced in the $s$-channel of this reaction. We see
no evidence for them and set model-dependent upper limits on their branching
fractions $\mathcal{B}(P_c^+ \rightarrow J/\psi p)$ and cross sections
$\sigma(\gamma p \to P_c^+)\times\mathcal{B}(P_c^+ \to J/\psi p) $. | nucl-ex |
Baryon spectroscopy with polarization observables from CLAS: The spectrum of nucleon excitations is dominated by broad and overlapping
resonances. Polarization observables in photoproduction reactions are key in
the study of these excitations. They give indispensable constraints to
partial-wave analyses and help clarify the spectrum. A series of polarized
photoproduction experiments have been performed at the Thomas Jefferson
National Accelerator Facility with the CEBAF Large Acceptance Spectrometer
(CLAS). These measurements include data with linearly and circularly polarized
tagged-photon beams, longitudinally and transversely polarized proton and
deuterium targets, and recoil polarizations through the observation of the weak
decay of hyperons. An overview of these studies and recent results will be
given. | nucl-ex |
High-spin intruder band in $^{107}$In: High-spin states in the neutron deficient nucleus $^{107}$In were studied via
the $^{58}$Ni($^{52}$Cr, 3p) reaction. In-beam $\gamma$ rays were measured
using the JUROGAM detector array. A rotational cascade consisting of ten
$\gamma$-ray transitions which decays to the 19/2$^{+}$ level at 2.002 MeV was
observed. The band exhibits the features typical for smooth terminating bands
which also appear in rotational bands of heavier nuclei in the A$\sim$100
region. The results are compared with Total Routhian Surface and Cranked
Nilsson-Strutinsky calculations. | nucl-ex |
Measurement of two-photon exchange effect by comparing elastic $e^\pm p$
cross sections: [Background] The electromagnetic form factors of the proton measured by
unpolarized and polarized electron scattering experiments show a significant
disagreement that grows with the squared four momentum transfer ($Q^{2}$).
Calculations have shown that the two measurements can be largely reconciled by
accounting for the contributions of two-photon exchange (TPE). TPE effects are
not typically included in the standard set of radiative corrections since
theoretical calculations of the TPE effects are highly model dependent, and,
until recently, no direct evidence of significant TPE effects has been
observed.
[Purpose] We measured the ratio of positron-proton to electron-proton
elastic-scattering cross sections in order to determine the TPE contribution to
elastic electron-proton scattering and thereby resolve the proton electric form
factor discrepancy.
[Methods] We produced a mixed simultaneous electron-positron beam in
Jefferson Lab's Hall B by passing the 5.6 GeV primary electron beam through a
radiator to produce a bremsstrahlung photon beam and then passing the photon
beam through a convertor to produce electron/positron pairs. The mixed
electron-positron (lepton) beam with useful energies from approximately 0.85 to
3.5 GeV then struck a 30-cm long liquid hydrogen (LH$_2$) target located within
the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered
leptons and the recoiling protons we identified and reconstructed elastic
scattering events and determined the incident lepton energy. A detailed
description of the experiment is presented. | nucl-ex |
Reinterpretation of classic proton charge form factor measurements: In 1963, a proton radius of $0.805(11)~\mathrm{fm}$ was extracted from
electron scattering data and this classic value has been used in the standard
dipole parameterization of the form factor. In trying to reproduce this classic
result, we discovered that there was a sign error in the original analysis and
that the authors should have found a value of $0.851(19)~\mathrm{fm}$. We
additionally made use of modern computing power to find a robust function for
extracting the radius using this 1963 data's spacing and uncertainty. This
optimal function, the Pad\'{e} $(0,1)$ approximant, also gives a result which
is consistent with the modern high precision proton radius extractions. | nucl-ex |
The influence of experimental setup on the spectroscopy investigation of
$^{\mathrm{14}}$Be by Coulomb breakup reaction: The two-body core+$2n$ cluster structure was implemented to describe the
two-neutron halo nucleus $^{\mathrm{14}}\mathrm{Be}$, where the
core$^{\mathrm{12}}\mathrm{Be}$ was assumed inert and at ground state and the
dineutron was assumed at pure $2S_0$ state. Based on such a structure the
three-body continuum-discretized coupled-channel (CDCC) calculation was
successfully used to deal with the $^{\mathrm{14}}\mathrm{Be}$ breakup
reactions of $^{\mathrm{14}}\mathrm{Be}+^{\mathrm{12}}\mathrm{C}$ at
68~MeV/nucleon and $^{\mathrm{14}}\mathrm{Be}+ $Pb at
35~MeV/nucleon.Consequently, we modeled the kinematically complete measurement
experiment of $^{\mathrm{14}}\mathrm{Be}$ (35~MeV/nucleon) Coulomb breakup at a
lead target with the help of Geant4. From the simulation data the relative
energy spectrum was constructed by the invariant mass method and $B(E1)$
spectrum was extracted using virtual photon model. The influence of the target
thickness and detector performance on the spectroscopy was investigated. | nucl-ex |
Pseudorapidity spectra of relativistic particles emitted in the Au and
Pb induced reactions at high energies: The structure of the pseudorapidity spectra of charged relativistic particles
with beta > 0.7 measured in Au+Em and Pb+Em collisions at AGS and SPS energies
are analyzed using Fourier transformation method and maximum entropy one. The
dependences of these spectra on the number of fast target protons (g-particles)
are studied. They show visually some plateau and "shoulder" which are at least
three selected points on the distributions. The plateau seems wider in Pb+Em
reactions. The existing of plateau is expected for the parton models. The
maximum entropy method confirms the existence of the plateau and the shoulder
of the distributions. | nucl-ex |
Measurement of the $ν_e$ and Total $^{8}$B Solar Neutrino Fluxes with
the Sudbury Neutrino Observatory Phase I Data Set: This article provides the complete description of results from the Phase I
data set of the Sudbury Neutrino Observatory (SNO). The Phase I data set is
based on a 0.65 kt-year exposure of heavy water to the solar $^8$B neutrino
flux. Included here are details of the SNO physics and detector model,
evaluations of systematic uncertainties, and estimates of backgrounds. Also
discussed are SNO's approach to statistical extraction of the signals from the
three neutrino reactions (charged current, neutral current, and elastic
scattering) and the results of a search for a day-night asymmetry in the
$\nu_e$ flux. Under the assumption that the $^8$B spectrum is undistorted, the
measurements from this phase yield a solar $\nu_e$ flux of $\phi(\nu_e) =
1.76^{+0.05}_{-0.05}{(stat.)}^{+0.09}_{-0.09} {(syst.)}
\times 10^{6}$ cm$^{-2}$ s$^{-1}$, and a non-$\nu_e$ component
$\phi(\nu_{\mu\tau}) =
3.41^{+0.45}_{-0.45}{(stat.)}^{+0.48}_{-0.45} {(syst.)}
\times 10^{6}$ cm$^{-2}$ s$^{-1}$. The sum of these components provides a
total flux in excellent agreement with the predictions of Standard Solar
Models. The day-night asymmetry in the $\nu_e$ flux is found to be $A_{e} = 7.0
\pm 4.9 \mathrm{(stat.)^{+1.3}_{-1.2}}% \mathrm{(sys.)}$, when the asymmetry in
the total flux is constrained to be zero. | nucl-ex |
Direct photons at low $p_{T}$ measured in PHENIX: Direct photon spectra measured at small $p_T$ in p+p, d+Au and Au+Au
collisions at $\sqrt{s_{NN}}=200$ GeV are presented. Several measurement
techniques including statistical subtraction, tagging, and internal and
external conversion were applied and found to produce consistent results. The
p+p and d+Au results are found to be in very good agreement with pQCD
predictions over the entire $p_T$ range. No excess of direct photons in Au+Au
collisions with respect to binary scaled d+Au data is observed within
systematic errors. | nucl-ex |
Study of high-pT charged particle suppression in PbPb compared to pp
collisions at sqrt(sNN)=2.76 TeV: The transverse momentum spectra of charged particles have been measured in pp
and PbPb collisions at sqrt(sNN) = 2.76 TeV by the CMS experiment at the LHC.
In the transverse momentum range pt = 5-10 GeV/c, the charged particle yield in
the most central PbPb collisions is suppressed by up to a factor of 5 compared
to the pp yield scaled by the number of incoherent nucleon-nucleon collisions.
At higher pt, this suppression is significantly reduced, approaching roughly a
factor of 2 for particles with pt in the range pt=40-100 GeV/c. | nucl-ex |
Thermonuclear reaction rate of $^{29}$Si(p,$γ$)$^{30}$P: The thermonuclear rate of the $^{29}$Si(p,$\gamma$)$^{30}$P reaction impacts
the $^{29}$Si abundance in classical novae. A reliable reaction rate is
essential for testing the nova paternity of presolar stardust grains. At
present, the fact that no classical nova grains have been unambiguously
identified in primitive meteorites among thousands of grains studied is
puzzling, considering that classical novae are expected to be prolific
producers of dust grains. We investigated the $^{29}$Si $+$ $p$ reaction at
center-of-mass energies of $200$ $-$ $420$~keV, and present improved values for
resonance energies, level excitation energies, resonance strengths, and
branching ratios. One new resonance was found at a center-of-mass energy of
$303$ keV. For an expected resonance at $215$~keV, an experimental upper limit
could be determined for the strength. We evaluated the level structure near the
proton threshold, and present new reaction rates based on all the available
experimental information. Our new reaction rates have much reduced
uncertainties compared to previous results at temperatures of $T$ $\ge$
$140$~MK, which are most important for classical nova nucleosynthesis. Future
experiments to improve the reaction rates at lower temperatures are discussed. | nucl-ex |
Determination of integral cross sections of 3H in Al foils monitors
irradiated by protons with energies ranging from 40 to 2600 MeV: Results of t production in Al foil monitors are presented. These foils have
been irradiated by protons of different energies in a range of 0.04 - 2.6 GeV.
The irradiations were carried out at the ITEP accelerator U-10 under the ISTC
Project 3266 during 2006 - 2009. t has been extracted from Al foils using an
A307 Sample Oxidizer. The values of the Al(p,x)t cross sections obtained in
these experiments are compared with data measured at other laboratories and
with results of simulations by the MCNP6 radiation transport code using the
CEM03.03 event generator. | nucl-ex |
First results from Au+Au collisions at $\sqrt(s_{NN})$ = 9.2 GeV in STAR: One of the primary aims of heavy-ion collisions is to map the QCD phase
diagram and search for different phases and phase boundaries. RHIC Energy Scan
Program was launched to address this goal by studying heavy-ion collisions at
different center of mass energies. The first test run with Au+Au collisions at
$\sqrt{s_{NN}}$ = 9.2 GeV took place in early 2008. The large acceptance STAR
detector has collected few thousands minimum bias collisions at this beam
energy. We present the first results for identified particle yields and
particle ratios. The results for the azimuthal anisotropy parameters $v_1$ and
$v_2$ and those from pion interferometry measurements are also discussed in
this paper. These results are compared to data from the SPS at similar beam
energies. | nucl-ex |
Sensitivity and discovery potential of the proposed nEXO experiment to
neutrinoless double beta decay: The next-generation Enriched Xenon Observatory (nEXO) is a proposed
experiment to search for neutrinoless double beta ($0\nu\beta\beta$) decay in
$^{136}$Xe with a target half-life sensitivity of approximately $10^{28}$ years
using $5\times10^3$ kg of isotopically enriched liquid-xenon in a time
projection chamber. This improvement of two orders of magnitude in sensitivity
over current limits is obtained by a significant increase of the $^{136}$Xe
mass, the monolithic and homogeneous configuration of the active medium, and
the multi-parameter measurements of the interactions enabled by the time
projection chamber. The detector concept and anticipated performance are
presented based upon demonstrated realizable background rates. | nucl-ex |
Isolated photon production in $\sqrt{s_{NN}}$ = 2.76 TeV PbPb collisions
as a function of transverse energy and reaction centrality: In studies of the dense medium produced in ultra-relativistic heavy ion
collisions, photons are important hard probes, since they are not expected to
be modified by the medium. The measurement of isolated prompt photon production
in PbPb collisions provides a test of perturbative quantum chromodynamics
(pQCD) and the information to constrain the nuclear parton distribution
functions. CMS has shown photon purity measurement capabilities in pp
collisions using the shower shape templates. In PbPb co llisions at CMS, this
technique was applied for the first time in heavy ion collisions. We report the
first measurement of the transverse momentum spectra of isolated photons with
pT from 20 GeV/c to 80 GeV/c in PbPb collisions at $\sqrt{s_{NN}}$ =2.76 TeV.
The centrality dependence of the nuclear modification factor is also reported
by comparing the result to the photon spectrum of pp reference which is
computed from NLO calculations. | nucl-ex |
Chemical Analyses of Silicon Aerogel Samples: After five years of operating, two Aerogel counters: A1 and A2, taking data
in Hall A at Jefferson Lab, suffered a loss of performance. In this note
possible causes of degradation have been studied. In particular, various
chemical and physical analyses have been carried out on several Aerogel tiles
and on adhesive tape in order to reveal the presence of contaminants. | nucl-ex |
Precision Measurement of the Neutron Spin Asymmetries and Spin-dependent
Structure Functions in the Valence Quark Region: We report on measurements of the neutron spin asymmetries $A_{1,2}^n$ and
polarized structure functions $g_{1,2}^n$ at three kinematics in the deep
inelastic region, with $x=0.33$, 0.47 and 0.60 and $Q^2=2.7$, 3.5 and 4.8
(GeV/c)$^2$, respectively. These measurements were performed using a 5.7 GeV
longitudinally-polarized electron beam and a polarized $^3$He target. The
results for $A_1^n$ and $g_1^n$ at $x=0.33$ are consistent with previous world
data and, at the two higher $x$ points, have improved the precision of the
world data by about an order of magnitude. The new $A_1^n$ data show a zero
crossing around $x=0.47$ and the value at $x=0.60$ is significantly positive.
These results agree with a next-to-leading order QCD analysis of previous world
data. The trend of data at high $x$ agrees with constituent quark model
predictions but disagrees with that from leading-order perturbative QCD (pQCD)
assuming hadron helicity conservation. Results for $A_2^n$ and $g_2^n$ have a
precision comparable to the best world data in this kinematic region. Combined
with previous world data, the moment $d_2^n$ was evaluated and the new result
has improved the precision of this quantity by about a factor of two. When
combined with the world proton data, polarized quark distribution functions
were extracted from the new $g_1^n/F_1^n$ values based on the quark parton
model. While results for $\Delta u/u$ agree well with predictions from various
models, results for $\Delta d/d$ disagree with the leading-order pQCD
prediction when hadron helicity conservation is imposed. | nucl-ex |
Isospin Mixing and the Cubic Isobaric Multiplet Mass Equation in the
Lowest T = 2, A = 32 Quintet: The isobaric multiplet mass equation (IMME) is known to break down in the
first T = 2, A = 32 isospin quintet. In this work we combine high-resolution
experimental data with state-of-the-art shell-model calculations to investigate
isospin mixing as a possible cause for this violation. The experimental data
are used to validate isospin-mixing matrix elements calculated with newly
developed shell-model Hamiltonians. Our analysis shows that isospin mixing with
nonanalog T = 1 states contributes to the IMME breakdown, making the
requirement of an anomalous cubic term inevitable for the multiplet. | nucl-ex |
Open charm hadron measurement in p+p and Au+Au collisions at
$\sqrt{s_{NN}}$ = 200 GeV in STAR: We present the measurements of $D^0$ and $D^*$ in p+p and $D^0$ in Au+Au
collisions via hadronic decays $D^{0}\rightarrow K^{-}\pi^{+}$,
$D^{*+}\rightarrow D^{0}\pi^{+}\rightarrow K^{-}\pi^{+}\pi^{+}$ in mid-rapidity
$|y|<1$ at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV, covering $p_T$ from 0.2 to 6
GeV/$c$ in p+p and 0.4 to 5 GeV/$c$ in Au+Au, respectively. The charm pair
production cross section per nucleon-nucleon collision at mid rapidity is
measured to be 202 $\pm$ 56 (stat.) $\pm$ 40 (sys.) $\pm$ 20 (norm.) $\mu$b in
p+p and 186 $\pm$ 22 (stat.) $\pm$ 30 (sys.) $\pm$ 18 (norm.) $\mu$b in Au+Au
minimum bias collisions. The number of binary collisions scaling of charm cross
section indicates that charm is produced via initial hard scatterings. No
suppression of $D^0$ $R_{AA}$ in Au+Au 0-80% minbias collisions is observed at
$p_T$ below 3 GeV/$c$. Blast-wave predictions with light-quark hadron
parameters are different from data, which may indicate that $D^0$ decouples
earlier from the medium than the light-quark hadrons. | nucl-ex |
Absolute resonance strengths in the 6,7Li(alpha,gamma)10,11B reactions: The absolute strengths of the Ea=1175keV resonance in the 6Li(a,g)10B
reaction and of the Ea=814 keV resonance in the 7Li(a,g)11B reaction have been
measured to $\omega\gamma$=366+-38 meV and $\omega\gamma$=300+-32 meV,
respectively, in good agreement with previous values.
These resonances can be used to measure the absolute acceptance of the recoil
separator ERNA to a precision of about 10%. | nucl-ex |
Shape coexistence near the neutron number N=20: First identification of
the E0 decay from the deformed 0^+_2 state in 30Mg: The 1789 keV level in 30Mg was identified as the first excited 0^+ state by
measuring its E0 transition to the ground state. The measured small value of
rho^2(E0,0^+_2 --> 0^+_1) = 5.7(14) x 10^-3 implies a very small mixing of
competing configurations with largely different intrinsic quadrupole
deformation near N=20. Axially symmetric Beyond-Mean-Field configuration mixing
calculations identify the ground state of 30Mg to be based on neutron
configurations below the N=20 shell closure, while the excited 0^+ state mainly
consists of a two neutrons excitated into the nu1 f_{7/2} orbital. Using a
two-level model, a mixing amplitude of 0.08(4) can be derived. | nucl-ex |
Consistency of 8B neutrino spectra: We identify and quantify systematic effects not accounted for in two previous
measurements of the alpha-alpha relative-energy distribution in the beta decay
of 8B, which can explain the apparent disagreement with respect to two newer
measurements. This settles a current dispute concerning the shape of the 8B
neutrino spectrum of importance to solar-neutrino studies. | nucl-ex |
Search for Periodic Modulations of the Rate of Double-Beta Decay of
$^{100}$Mo in the NEMO-3 Detector: Double-beta decays of $^{100}$Mo from the 6.0195-year exposure of a 6.914 kg
high-purity sample were recorded by the NEMO-3 experiment that searched for
neutrinoless double-beta decays. These ultra-rare transitions to $^{100}$Ru
have a half-life of approximately $7\times10^{18}$ years, and have been used to
conduct the first ever search for periodic variations of this decay mode. The
Lomb-Scargle periodogram technique, and its error-weighted extension, were
employed to look for periodic modulations of the half-life. Monte Carlo
modeling was used to study the modulation sensitivity of the data over a broad
range of amplitudes and frequencies. Data show no evidence of modulations with
amplitude greater than 2.5% in the frequency range of $0.33225\,{\rm y^{-1}}$
to $365.25\,{\rm y^{-1}}$. | nucl-ex |
Projectile fragment emission in fragmentation of $^{56}$Fe on C, Al,and
CH$_{2}$ targets at 471 A MeV: The emission angle and the transverse momentum distributions of projectile
fragments produced in fragmentation of $^{56}$Fe on CH$_{2}$, C, and Al targets
at 471 A MeV are measured. It is found that for the same target the average
value and width of angular distribution decrease with increase of the
projectile fragment charge, and for the same projectile fragment the average
value of the distribution increases and the width of the distribution decreases
with increasing the target charge number. The transverse momentum distribution
of projectile fragment can be explained by a single Gaussian distribution and
the averaged transverse momentum per nucleon decreases with the increase of the
charge of projectile fragment. The cumulated squared transverse momentum
distribution of projectile fragment can be well explained by a single Rayleigh
distribution. The temperature parameter of emission source of projectile
fragment, calculated from the cumulated squared transverse momentum
distribution, decreases with the increase of the size of projectile fragment. | nucl-ex |
High PT Physics with the STAR Experiment at RHIC: The STAR experiment at RHIC is a TPC-based, general purpose detector designed
to obtain charged particle spectra, with an emphasis on hadrons over a large
phase space. An electromagnetic calorimeter provides measurement of electrons,
photons, pi-zeros and jets. Data-taking with Au+Au collisions at sqrt(s)= 200
GeV/c**2 begins in Fall 1999. The STAR experiment's investigation of techniques
and signals using hard probes to study the high energy-density matter at RHIC
and to search for quark-gluon plasma formation will be described. | nucl-ex |
First Online Mass Measurements of Isobar Chains via Multi-Reflection
Time-of-Flight Mass Spectrograph Coupled with GARIS-II: Using a mulit-reflection time-of-flight mass spectrograph (MRTOF-MS) located
after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the
masses of several heavy nuclei have been directly and precisely measured. The
nuclei were produced via fusion-evaporation reactions and separated from
projectile-like and target-like particles using GARIS-II before being stopped
in a helium-filled gas cell. Time-of-flight spectra for three isobar chains,
205Fr-205Rn-205At-205Po, 206Fr-206Rn-206At and 201Rn-201At-201Po-201Bi, were
observed. Precision atomic mass values were determined for 205,206Fr, 201At,
and 201Po. | nucl-ex |
Heavy Flavor Production at PHENIX at RHIC: A study of heavy flavor production in different collision systems in various
kinematic regions presents an opportunity to probe cold nuclear medium and hot
dense matter effects. Results from the PHENIX experiment on $J/\psi$ and open
charm production in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ =200 GeV are
presented. The data show strong $J/\psi$ suppression in central AA collisions,
similar to NA50 results, and strong suppression in high $p_T$ open charm
production. The $J/\psi$ production in Au+Au and d+Au collisions is compared to
understand the cold nuclear medium effects. The data show significant cold
nuclear effects in charm production in d+Au collisions at forward and backward
rapidity ranges. | nucl-ex |
Integral measurement of the $^{12}$C(n,p)$^{12}$B reaction up to 10 GeV: The integral measurement of the $^{12}$C(n,p)$^{12}$B reaction was performed
at the neutron time of flight facility n_TOF at CERN. The total number of
$^{12}$B nuclei produced per neutron pulse of the n_TOF beam was determined
using the activation technique in combination with a time of flight technique.
The cross section is integrated over the n_TOF neutron energy spectrum from
reaction threshold at 13.6 MeV to 10 GeV. Having been measured up to 1 GeV on
basis of the $^{235}$U(n,f) reaction, the neutron energy spectrum above 200 MeV
has been reevaluated due to the recent extension of the cross section reference
for this particular reaction, which is otherwise considered a standard up to
200 MeV. The results from the dedicated GEANT4 simulations have been used to
evaluate the neutron flux from 1 GeV up to 10 GeV. The experimental results
related to the $^{12}$C(n,p)$^{12}$B reaction are compared with the evaluated
cross sections from major libraries and with the predictions of different
GEANT4 models, which mostly underestimate the $^{12}$B production. On the
contrary, a good reproduction of the integral cross section derived from
measurements is obtained with TALYS-1.6 calculations, with optimized
parameters. | nucl-ex |
Differential Cross Section for $γd \rightarrow ωd$ using
CLAS at Jefferson Lab: The cross section for coherent $\omega$-meson photoproduction off the
deuteron has been measured for the first time as a function of the momentum
transfer $t = (P_{\gamma}-P_{\omega})^2$ and photon energy $E_{\gamma}$ using
the CLAS detector at the Thomas Jefferson National Accelerator Facility. The
cross sections are measured in the energy range $1.4 < E_{\gamma} < 3.4$ GeV. A
model based on $\omega-N$ rescattering is consistent with the data at low and
intermediate momentum transfer, $|t|$. For $2.8 < E_{\gamma} < 3.4$ GeV, the
total cross-section of $\omega-N$ scattering, based on fits within the
framework of the Vector Meson Dominance model, is in the range of 30-40 mb. | nucl-ex |
Measurement of the 18Ne(a,p_0)21Na reaction cross section in the burning
energy region for X-ray bursts: The 18Ne(a,p)21Na reaction provides one of the main HCNO-breakout routes into
the rp-process in X-ray bursts. The 18Ne(a,p_0)21Na reaction cross section has
been determined for the first time in the Gamow energy region for peak
temperatures T=2GK by measuring its time-reversal reaction 21Na(p,a)18Ne in
inverse kinematics. The astrophysical rate for ground-state to ground-state
transitions was found to be a factor of 2 lower than Hauser-Feshbach
theoretical predictions. Our reduced rate will affect the physical conditions
under which breakout from the HCNO cycles occurs via the 18Ne(a,p)21Na
reaction. | nucl-ex |
Centrality Dependence of Kaon Yields in Si+A and Au+Au Collisions at
Relativistic Energies: Charged kaon production has been measured in Si+Al and Si+Au collisions at
14.6 A GeV/c, and Au+Au collisions at 11.1 A GeV/c by Experiments 859 and 866
(the E--802 Collaboration) at the BNL AGS. Invariant transverse mass spectra
and rapidity distributions for both K+ and K- are presented. The centrality
dependence of rapidity-integrated kaon yields is studied. Strangeness
enhancement is observed as an increase in the slope of the kaon yield with the
total number of participants as well as the yield per participant. The
enhancement starts with peripheral Si+Al and Si+Au collisions (relative to N+N)
and appears to saturate for a moderate number of participating nucleons in
Si+Au collisions. It is also observed to increase slowly with centrality in
Au+Au collisions, to a level in the most central Au+Au collisions that is
greater than that found in central Si+A collisions. The enhancement factor for
$K^+$ production are 3.0 +-0.2(stat.) +-0.4(syst.) and 4.0 +-0.3(stat.)
+-0.5(syst.), respectively, for the most central 7% Si+Au collisions and the
most central 4% Au+Au collisions relative to N+N at the correponding beam
energy. | nucl-ex |
Single-particle shell strengths near the doubly magic nucleus $^{56}$Ni
and the $^{56}$Ni(p,$γ$)$^{57}$Cu reaction rate in explosive
astrophysical burning: Angle-integrated cross-section measurements of the $^{56}$Ni(d,n) and (d,p)
stripping reactions have been performed to determine the single-particle
strengths of low-lying excited states in the mirror nuclei pair
$^{57}$Cu-$^{57}$Ni situated adjacent to the doubly magic nucleus $^{56}$Ni.
The reactions were studied in inverse kinematics utilizing a beam of
radioactive $^{56}$Ni ions in conjunction with the GRETINA $\gamma$-array.
Spectroscopic factors are compared with new shell-model calculations using a
full $pf$ model space with the GPFX1A Hamiltonian for the isospin-conserving
strong interaction plus Coulomb and charge-dependent Hamiltonians. These
results were used to set new constraints on the $^{56}$Ni(p,$\gamma$)$^{57}$Cu
reaction rate for explosive burning conditions in x-ray bursts, where $^{56}$Ni
represents a key waiting point in the astrophysical rp-process. | nucl-ex |
Study of internal structures of 9,10Be and 10B in scattering of 4He from
9Be: A study of inelastic scattering and single-particle transfer reactions was
performed by an alpha beam at 63 MeV on a 9$Be target. Angular distributions of
the differential cross sections for the 9Be(4He,4He')9Be*, 9Be(4He,3He)10Be and
9Be(4He,t)10B reactions were measured. Experimental angular distributions of
the differential cross sections for the ground state and a few low-lying states
were analyzed in the framework of the optical model, coupled channels and
distorted-wave Born approximation. An analysis of the obtained spectroscopic
factors was performed. | nucl-ex |
Measurements of $^{160}$Dy($p,γ$) at energies relevant for
astrophysical $γ$ process: Rare information on photodisintegration reactions of nuclei with mass numbers
$A \approx 160$ at astrophysical conditions impedes our understanding of the
origin of $p$-nuclei. Experimental determination of the key ($p,\gamma$) cross
sections has been playing an important role to verify nuclear reaction models
and to provide rates of relevant ($\gamma,p$) reactions in $\gamma$-process. In
this paper we report the first cross section measurements of
$^{160}$Dy($p,\gamma$)$^{161}$Ho and $^{161}$Dy($p,n$)$^{161}$Ho in the beam
energy range of 3.4 - 7.0 MeV, partially covering the Gamow window. Such
determinations are possible by using two targets with various isotopic
fractions. The cross section data can put a strong constraint on the nuclear
level densities and gamma strength functions for $A \approx$ 160 in the
Hauser-Feshbach statistical model. Furthermore, we find the best parameters for
TALYS that reproduce the A $\thicksim$ 160 data available,
$^{160}$Dy($p,\gamma$)$^{161}$Ho and $^{162}$Er($p,\gamma$)$^{163}$Tm, and
recommend the constrained $^{161}$Ho($\gamma,p$)$^{160}$Dy reaction rates over
a wide temperature range for $\gamma$-process network calculations. Although
the determined $^{161}$Ho($\gamma$, p) stellar reaction rates at the
temperature of 1 to 2 GK can differ by up to one order of magnitude from the
NON-SMOKER predictions, it has a minor effect on the yields of $^{160}$Dy and
accordingly the $p$-nuclei, $^{156,158}$Dy. A sensitivity study confirms that
the cross section of $^{160}$Dy($p$, $\gamma$)$^{161}$Ho is measured precisely
enough to predict yields of $p$-nuclei in the $\gamma$-process. | nucl-ex |
Estimation of radiative half-life of $^{229m}$Th by half-life
measurement of other nuclear excited states in $^{229}$Th: We perform coincidence measurements between $\alpha$ particles and $\gamma$
rays from a $^{233}$U source to determine the half-lives of the excited state
in a $^{229}$Th nucleus. We first prove that the half-lives of 42.43- and
164.53-keV states are consistent with literature values, whereas that of the
97.14-keV state (93(7) ps) deviates from a previously measured value (147(12)
ps). The half-lives of 71.83- and 163.25-keV states are determined for the
first time. Based on the obtained half-lives and the Alaga rule, we estimate
the radiative half-life of the low-energy isomeric state ($^{229m}$Th) to be
$5.0(11)\times10^{3}$ s, which is one of the key parameters for the frequency
standard based on $^{229}$Th. | nucl-ex |
The measurement of non-photonic electrons in STAR: The measurements of non-photonic electrons (NPE), mainly produced by
semileptonic decays of D and B mesons, provide information on heavy quarks
production as well as properties of nuclear matter produced in heavy ion
collisons. In order to interpret the NPE measurements it is important to
determine the relative charm and bottom contribution to the NPE spectrum. In
this proceedings we present the measurements of NPE spectra and NPE-hadron
azimuthal correlations in p+p collisions at $\sqrt{s}$=200 GeV and at
$\sqrt{s}$=500 GeV. NPE-hadron correlations allow extraction of the B decay
contribution to the NPE. The B decay contribution is comparable to the
contribution from the D meson decay at $\sqrt{s}$=200 GeV at p$_T$ higher than
5 GeV/c, and is about 60% at $\sqrt{s}$=500 GeV at p$_T$ higher than 5 GeV/c.
STAR measured NPE spectrum in p+p collisions as well as relative constribution
of bottom decays to the spectrum is consistent with FONLL pQCD calculations.
The preliminary results of NPE spectra and NPE-hadron correlations in Au+Au
collisions at $\sqrt{s}$=200 GeV is shown. | nucl-ex |
Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at
CERN SPS energies: Measurements of Bose-Einstein correlations of pion pairs in central Pb+Pb
collisions were performed with the NA49 detector at the CERN SPS for beam
energies of 20A, 30A, 40A, 80A, and 158A GeV. Correlation functions were
measured in the longitudinally co-moving ``out-side-long'' reference frame as a
function of rapidity and transverse momentum in the forward hemisphere of the
reaction. Radius and correlation strength parameters were obtained from fits of
a Gaussian parametrization. The results show a decrease of the radius
parameters with increasing transverse momentum characteristic of strong radial
flow in the pion source. No striking dependence on pion-pair rapidity or beam
energy is observed. Static and dynamic properties of the pion source are
obtained from simultaneous fits with a blast-wave model to radius parameters
and midrapidity transverse momentum spectra. Predictions of hydrodynamic and
microscopic models of Pb+Pb collisions are discussed. | nucl-ex |
Excess of charged over neutral $K$ meson production in high-energy
collisions of atomic nuclei: Collisions of atomic nuclei at relativistic velocities produce new particles,
predominantly mesons containing one valence quark and one valence anti-quark.
These particles are produced in strong interactions, which preserve an
approximate symmetry between up ($u$) and down ($d$) quarks. In the case of $K$
meson production, if this symmetry were exact, it would result in equal numbers
of charged ($K^+$ and $K^-$) and neutral ($K^0$ and $\overline K^0$) mesons in
the final state. In this Letter, we report a measurement of the relative
abundance of charged over neutral $K$ meson production in collisions of argon
and scandium nuclei at a center-of-mass energy of 11.9~GeV per nucleon pair. We
find that production of $\mathit{K^+}$ and $\mathit{K^-}$ mesons at
mid-rapidity displays a significant excess of $(23.3\pm 5.5)\%$ relative to
that of the neutral $K$ mesons. The origin of this unexpected excess remains to
be elucidated. | nucl-ex |
Search for solar axions via axion-photon coupling with the Majorana
Demonstrator: Axions were originally proposed to explain the strong-CP problem in QCD.
Through the axion-photon coupling, the Sun could be a major source of axions,
which could be measured in solid state detection experiments with enhancements
due to coherent Primakoff-Bragg scattering. The Majorana Demonstrator
experiment has searched for solar axions with a set of $^{76}$Ge-enriched high
purity germanium detectors using a 33 kg-yr exposure collected between Jan.
2017 and Nov. 2019. A temporal-energy analysis gives a new limit on the
axion-photon coupling as $g_{a\gamma}<1.45\times 10^{-9}$ GeV$^{-1}$ (95% C.I.)
for axions with mass up to 100 eV/$c^2$. This improves laboratory-based limits
between about 1 eV/$c^2$ and 100 eV/$c^2$. | nucl-ex |
Probing the QCD Critical Point with Higher Moments of Net-proton
Multiplicity Distributions: Higher moments of event-by-event net-proton multiplicity distributions are
applied to search for the QCD critical point in the heavy ion collisions. It
has been demonstrated that higher moments as well as moment products are
sensitive to the correlation length and directly connected to the thermodynamic
susceptibilities computed in the Lattice QCD and Hadron Resonance Gas (HRG)
model. In this paper, we will present measurements for kurtosis ($\kappa$),
skewness ($S$) and variance ($\sigma^{2}$) of net-proton multiplicity
distributions at the mid-rapidity ($|y|<0.5$) and $0.4<p_{T}<0.8$ GeV/$c$ for
Au+Au collisions at $\sqrt{s_{NN}}$=19.6, 39, 62.4, 130 and 200 GeV, Cu+Cu
collisions at $\sqrt{s_{NN}}$=22.4, 62.4 and 200 GeV, d+Au collisions at
$\sqrt{s_{NN}}$=200 GeV and p+p collisions at $\sqrt{s_{NN}}$=62.4 and 200 GeV.
The moment products $\kappa \sigma^{2}$ and $S \sigma$ of net-proton
distributions, which are related to volume independent baryon number
susceptibility ratio, are compared to the Lattice QCD and HRG model
calculations. The $\kappa \sigma^{2}$ and $S \sigma$ of net-proton
distributions are consistent with Lattice QCD and HRG model calculations at
high energy, which support the thermalization of the colliding system.
Deviations of $\kappa \sigma^{2}$ and $S \sigma$ for the Au+Au collisions at
low energies from HRG model calculations are also observed. | nucl-ex |
Properties of Groove Chambers: Groove chambers with different pitch and gap height have been tested. Gas
amplifications of the order of a few times 10$^{3}$ have been obtained.
Combining a groove structure with a GEM pre-amplification foil a gas gain of
10$^{5}$ was reached. The device is robust and can be produced at low cost in
large sizes by a laser technique. | nucl-ex |
Energy, Rapidity and Transverse Momentum Dependence of Multiplicity
Fluctuations in Heavy Ion Collisions at CERN SPS: Multiplicity fluctuations in the forward hemisphere were studied for
positively, negatively and all charged hadrons produced in central Pb+Pb
collisions at 20A, 30A, 40A, 80A and 158A GeV. The multiplicity distributions
and their scaled variances are presented as a function of collision energy,
rapidity and transverse momentum. The distributions have a bell-like shape and
the scaled variance changes monotonously with energy in the range from 0.8 to
1.2. No indication of the critical point is observed.
The string-hadronic model UrQMD reproduces results on the scaled variance.
The predictions of the hadron-resonance gas model obtained within the
grand-canonical and canonical ensembles for the scaled variance disagree with
the data. | nucl-ex |
Activation cross-sections of longer-lived products of proton induced
nuclear reactions on dysprosium up to 36 MeV: Activation cross-sections of longer-lived products of proton induced nuclear
reactions on dysprosium were measured up to 36 MeV by using stacked foil
irradiation technique and gamma-spectrometry. We report for the first time
experimental cross-sections for the formation of the radionuclides 162mHo,
161Ho, 159Ho, 159Dy, 157Dy, 155Dy, 161Tb, 160Tb, 156Tb and 155Tb. The
experimental data were compared with the results of cross-section calculations
of the ALICE and EMPIRE nuclear model codes and of the TALYS nuclear reaction
model code as listed in the on-line libraries TENDL 2011 and TENDL 2012. | nucl-ex |
Radiative decay branching ratio of the Hoyle state: Background: The triple-alpha process is a vital reaction in nuclear
astrophysics, characterized by two consecutive reactions
[$2\alpha\leftrightarrows{^{8}\rm{Be}}(\alpha,\gamma){^{12}\rm{C}}$] that drive
carbon formation. The second reaction occurs through the Hoyle state, a 7.65
MeV excited state in ${^{12}\rm{C}}$ with $J^{\pi}=0^{+}$. The rate of the
process depends on the radiative width, which can be determined by measuring
the branching ratio for electromagnetic decay. Recent measurements by Kib\'edi
et al. conflicted with the adopted value and resulted in a significant increase
of nearly 50\% in this branching ratio, directly affecting the triple-alpha
reaction. Purpose: This work aims to utilize charged-particle spectroscopy with
magnetic selection as a means to accurately measure the total radiative
branching ratio ($\Gamma_{\rm{rad}}/\Gamma$) of the Hoyle state in $^{12}{\rm
C}$. Methods: The Hoyle state in $^{12}{\rm C}$ was populated via
$^{12}\rm{C}(\alpha, \alpha')^{12}\rm{C^{*}}$ inelastic scattering. The
scattered $\alpha$ particles were detected using a $\Delta$E-E telescope, while
the recoiled $^{12}{\rm C}$ ions were identified in a magnetic spectrometer.
Results: A radiative branching ratio value of
$\Gamma_{\rm{rad}}/\Gamma\times10^{4}=4.0\pm0.3({\rm stat.})\pm0.16({\rm
syst.})$ was obtained. Conclusions: The radiative branching ratio for the Hoyle
state obtained in this work is in agreement with the original adopted value.
Our result suggests that the proton-$\gamma$-$\gamma$ spectroscopy result
reported by Kib\'edi et al. may be excluded. | nucl-ex |
Rapidity and transverse-momentum dependence of the inclusive
J/$\mathbfψ$ nuclear modification factor in p-Pb collisions at
$\mathbf{\sqrt{\textit{s}_{NN}}}=5.02$ TeV: We have studied the transverse-momentum ($p_{\rm T}$) dependence of the
inclusive J/$\psi$ production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$
TeV, in three center-of-mass rapidity ($y_{\rm cms}$) regions, down to zero
$p_{\rm T}$. Results in the forward and backward rapidity ranges ($2.03 <
y_{\rm cms} < 3.53$ and $-4.46 <y_{\rm cms}< -2.96$) are obtained by studying
the J/$\psi$ decay to $\mu^+\mu^-$, while the mid-rapidity region ($-1.37 <
y_{\rm cms} < 0.43$) is investigated by measuring the ${\rm e}^+{\rm e}^-$
decay channel. The $p_{\rm T}$ dependence of the J/$\psi$ production cross
section and nuclear modification factor are presented for each of the rapidity
intervals, as well as the J/$\psi$ mean $p_{\rm T}$ values. Forward and
mid-rapidity results show a suppression of the J/$\psi$ yield, with respect to
pp collisions, which decreases with increasing $p_{\rm T}$. At backward
rapidity no significant J/$\psi$ suppression is observed. Theoretical models
including a combination of cold nuclear matter effects such as shadowing and
partonic energy loss, are in fair agreement with the data, except at forward
rapidity and low transverse momentum. The implications of the p-Pb results for
the evaluation of cold nuclear matter effects on J/$\psi$ production in Pb-Pb
collisions are also discussed. | nucl-ex |
Quantum Information Science and Technology for Nuclear Physics. Input
into U.S. Long-Range Planning, 2023: In preparation for the 2023 NSAC Long Range Plan (LRP), members of the
Nuclear Science community gathered to discuss the current state of, and plans
for further leveraging opportunities in, QIST in NP research at the Quantum
Information Science for U.S. Nuclear Physics Long Range Planning workshop, held
in Santa Fe, New Mexico on January 31 - February 1, 2023. The workshop included
45 in-person participants and 53 remote attendees. The outcome of the workshop
identified strategic plans and requirements for the next 5-10 years to advance
quantum sensing and quantum simulations within NP, and to develop a diverse
quantum-ready workforce. The plans include resolutions endorsed by the
participants to address the compelling scientific opportunities at the
intersections of NP and QIST. These endorsements are aligned with similar
affirmations by the LRP Computational Nuclear Physics and AI/ML Workshop, the
Nuclear Structure, Reactions, and Astrophysics LRP Town Hall, and the
Fundamental Symmetries, Neutrons, and Neutrinos LRP Town Hall communities. | nucl-ex |
First $β$-decay spectroscopy of $^{135}$In and new $β$-decay
branches of $^{134}$In: The $\beta$ decay of the neutron-rich $^{134}$In and $^{135}$In was
investigated experimentally in order to provide new insights into the nuclear
structure of the tin isotopes with magic proton number $Z=50$ above the $N=82$
shell. The $\beta$-delayed $\gamma$-ray spectroscopy measurement was performed
at the ISOLDE facility at CERN, where indium isotopes were selectively
laser-ionized and on-line mass separated. Three $\beta$-decay branches of
$^{134}$In were established, two of which were observed for the first time.
Population of neutron-unbound states decaying via $\gamma$ rays was identified
in the two daughter nuclei of $^{134}$In, $^{134}$Sn and $^{133}$Sn, at
excitation energies exceeding the neutron separation energy by 1 MeV. The
$\beta$-delayed one- and two-neutron emission branching ratios of $^{134}$In
were determined and compared with theoretical calculations. The $\beta$-delayed
one-neutron decay was observed to be dominant $\beta$-decay branch of
$^{134}$In even though the Gamow-Teller resonance is located substantially
above the two-neutron separation energy of $^{134}$Sn. Transitions following
the $\beta$ decay of $^{135}$In are reported for the first time, including
$\gamma$ rays tentatively attributed to $^{135}$Sn. In total, six new levels
were identified in $^{134}$Sn on the basis of the $\beta \gamma \gamma$
coincidences observed in the $^{134}$In and $^{135}$In $\beta$ decays. A
transition that might be a candidate for deexciting the missing neutron
single-particle $13/2^+$ state in $^{133}$Sn was observed in both $\beta$
decays and its assignment is discussed. Experimental level schemes of
$^{134}$Sn and $^{135}$Sn are compared with shell-model predictions. Using the
fast timing technique, half-lives of the $2^+$, $4^+$ and $6^+$ levels in
$^{134}$Sn were determined. | nucl-ex |
High transverse momentum eta meson production in p+p, d+Au and Au+Au
collisions at sqrt(s_NN) = 200 GeV: Inclusive transverse momentum spectra of eta mesons in the range p_T~2-12
GeV/c have been measured at mid-rapidity (|\eta| < 0,35) by the PHENIX
experiment at RHIC in p+p, d+Au and Au+Au collisions at sqrt(s_NN) = 200 GeV.
The eta mesons are reconstructed through their eta--> \gamma\gamma channel for
the three colliding systems as well as through the eta-->pi^0 pi+ pi- decay
mode in p+p and d+Au collisions. The nuclear modification factor in d+Au
collisions, R_dAu(p_T~1.0-1.1, suggests at most only modest p_T broadening
("Cronin enhancement"). In central Au+Au reactions, the eta yields are
significantly suppressed, with R_AuAu(pT)~0.2. The ratio of eta to pi^0 yields
is approximately constant as a function of p_T for the three colliding systems
in agreement with the high-p_T world average of R_eta/pi^0 \approx 0.5 in
hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range
of center-of-mass energies [sqrt(s_NN)~3-1800 GeV] as well as, for high scaled
momentum x_p, in e+e- annihilations at sqrt(s)=91.2 GeV. These results are
consistent with a scenario where high-p_T eta production in nuclear collisions
at RHIC is largely unaffected by initial-state effects, but where light-quark
mesons (pi^0;eta) are equally suppressed due to final-state interactions of the
parent partons in the dense medium produced in Au+Au reactions. | nucl-ex |
Forward-Backward Multiplicity Correlations in sqrt(s_NN)=200 GeV Au+Au
Collisions: Forward-backward correlations of charged-particle multiplicities in symmetric
bins in pseudorapidity (eta) are studied in order to gain insight into the
underlying correlation structure of particle production in Au+Au collisions.
The PHOBOS detector is used to measure integrated multiplicities in bins
defined within eta<3, centered at eta and covering an interval Delta-eta. The
variance (sigma^2_C) of a suitably defined forward-backward asymmetry variable
is calculated as a function of eta, Delta-eta, and centrality. It is found to
be sensitive to short range correlations, and the concept of ``clustering'' is
used to interpret comparisons to phenomenological models. | nucl-ex |
Isospin transport in 84Kr + 112,124Sn collisions at Fermi energies: Isotopically resolved fragments with Z<=20 have been studied with high
resolution telescopes in a test run for the FAZIA collaboration. The fragments
were produced by the collision of a 84Kr beam at 35 MeV/nucleon with a n-rich
(124Sn) and a n-poor (112Sn) target. The fragments, detected close to the
grazing angle, are mainly emitted from the phase-space region of the
projectile. The fragment isotopic content clearly depends on the n-richness of
the target and it is a direct evidence of isospin diffusion between projectile
and target. The observed enhanced neutron richness of light fragments emitted
from the phase-space region close to the center of mass of the system can be
interpreted as an effect of isospin drift in the diluted neck region. | nucl-ex |
Measuring the Neutron Lifetime Using Magnetically Trapped Neutrons: The neutron beta-decay lifetime plays an important role both in understanding
weak interactions within the framework of the Standard Model and in theoretical
predictions of the primordial abundance of 4He in Big Bang Nucleosynthesis. In
previous work, we successfully demonstrated the trapping of ultracold neutrons
(UCN) in a conservative potential magnetic trap. A major upgrade of the
apparatus is nearing completion at the National Institute of Standards and
Technology Center for Neutron Research (NCNR). In our approach, a beam of 0.89
nm neutrons is incident on a superfluid 4He target within the minimum field
region of an Ioffe-type magnetic trap. A fraction of the neutrons is
downscattered in the helium to energies <200 neV, and those in the appropriate
spin state become trapped. The inverse process is suppressed by the low phonon
density of helium at temperatures less than 200 mK, allowing the neutron to
travel undisturbed. When the neutron decays the energetic electron ionizes the
helium, producing scintillation light that is detected using photomultiplier
tubes. Statistical limitations of the previous apparatus will be alleviated by
significant increases in field strength and trap volume resulting in twenty
times more trapped neutrons. | nucl-ex |
A walk along the proton drip-line by $β$-decay spectroscopy: During the last decade we have carried out a systematic study of the $\beta$
decay of neutron-deficient nuclei, providing rich spectroscopic information of
importance for both nuclear structure and nuclear astrophysics. We present an
overview of the most relevant achievements, including the discovery of a new
exotic decay mode in the fp-shell, the $\beta$-delayed $\gamma$-proton decay in
$^{56}$Zn, the first observation of the 2$^+$ isomer in $^{52}$Co and the
latest results on the heavier systems $^{60}$Ge and $^{62}$Ge. We also report
on our deduced mass excesses in comparison with systematics and a recent
measurement. Finally, we summarise our results on the half-lives of $T_z=$
-1/2, -1 and -2 neutron-deficient nuclides, and analyse their trend. | nucl-ex |
Experimental constraints on non-linearities induced by two-photon
effects in elastic and inelastic Rosenbluth separations: The effects of two-photon exchange corrections, suggested to explain the
difference between measurements of the proton elastic electromagnetic form
factors using the polarization transfer and Rosenbluth techniques, have been
studied in elastic and inelastic scattering data. Such corrections could
introduce epsilon-dependent non-linearities in inelastic Rosenbluth
separations, where epsilon is the virtual photon polarization parameter. It is
concluded that such non-linear effects are consistent with zero for elastic,
resonance, and deep-inelastic scattering for all Q^2 and W^2 values measured. | nucl-ex |
Energy dependence of femtoscopy properties of pion source in nuclear
collisions: In the paper energy dependence of femtoscopy characteristics of pion emission
region at freeze-out is investigated for collisions of various ions and for all
experimentally available energies. For the first time the normalized values of
radii and volume of source are used for energy dependence. This approach allows
us to expand the set of interaction types, in particular, on non-symmetrical
nucleus-nucleus collisions which can be studied in the framework of common
approach. There are no the sharp changing of femtoscopic parameter values, in
particular, $R_{o}/R_{s}$ with increasing of $\sqrt{s_{NN}}$ which were
predicted by some phenomenological models as signature of first order phase
transition in strongly interacting matter. The generalized parameterization for
femtoscopic correlation function is suggested. | nucl-ex |
Radio Frequency Phototube, Optical Clock and Precise Measurements in
Nuclear Physics: Recently a new experimental program of novel systematic studies of light
hypernuclei using pionic decay was established at JLab (Study of Light
Hypernuclei by Pionic Decay at JLab, JLab Experiment PR-08-012). The highlights
of the proposed program include high precision measurements of binding energies
of hypernuclei by using a high resolution pion spectrometer, HpiS. The average
values of binding energies will be determined within an accuracy of ~10 keV or
better. Therefore, the crucial point of this program is an absolute calibration
of the HpiS with accuracy 10E-4 or better. The merging of continuous wave
laser-based precision optical-frequency metrology with mode-locked ultrafast
lasers has led to precision control of the visible frequency spectrum produced
by mode-locked lasers. Such a phase-controlled mode-locked laser forms the
foundation of an optical clock or femtosecond optical frequency comb (OFC)
generator, with a regular comb of sharp lines with well defined frequencies.
Combination of this technique with a recently developed radio frequency (RF)
phototube results in a new tool for precision time measurement. We are
proposing a new time-of-flight (TOF) system based on an RF phototube and OFC
technique. The proposed TOF system achieves 10 fs instability level and opens
new possibilities for precise measurements in nuclear physics such as an
absolute calibration of magnetic spectrometers within accuracy 10E-4 - 10E-5. | nucl-ex |
A New Approach to Determine Radiative Capture Reaction Rates at
Astrophysical Energies: Radiative capture reactions play a crucial role in stellar nucleosynthesis
but have proved challenging to determine experimentally. In particular, the
large uncertainty ($\sim$100%) in the measured rate of the
$^{12}$C$(\alpha,\gamma)^{16}$O reaction is the largest source of uncertainty
in any stellar evolution model. With development of new high current
energy-recovery linear accelerators (ERLs) and high density gas targets,
measurement of the $^{16}$O$(e,e^\prime \alpha)^{12}$C reaction close to
threshold using detailed balance opens up a new approach to determine the
$^{12}$C$(\alpha,\gamma)^{16}$O reaction rate with significantly increased
precision ($<$20%). We present the formalism to relate photo- and
electro-disintegration reactions and consider the design of an optimal
experiment to deliver increased precision. Once the new ERLs come online, an
experiment to validate the new approach we propose should be carried out. This
new approach has broad applicability to radiative capture reactions in
astrophysics. | nucl-ex |
Global Observables at RHIC: Main characteristics of the charged particle dN_ch/deta and transverse energy
dE_T/deta production measured in Heavy Ion collisions at RHIC energies are
presented in this article. Transformation of the pseudo-rapidity shape,
relation to the incident energy and centrality profile are described in a
systematic way. Centrality profile is shown to be closely bound to the number
of nucleons participating in the collisions, at the same time an alternative
approach to study the centrality behavior is also discussed. | nucl-ex |
Evidence for a long-range component in the pion emission source in Au+Au
collisions at sqrt(s_NN) = 200 GeV: Emission source functions are extracted from correlation functions
constructed from charged pions produced at mid-rapidity in Au+Au collisions at
sqrt(s_NN)=200 GeV. The source parameters extracted from these functions at low
k_T, give first indications of a long tail for the pion emission source. The
source extension cannot be explained solely by simple kinematic considerations.
The possible role of a halo of secondary pions from resonance emissions is
explored. | nucl-ex |
Silicon Vertex Tracker for PHENIX Upgrade at RHIC: Capabilities and
Detector Technology: From the wealth of data obtained from the first three years of RHIC
operation, the four RHIC experiments, BRAHMS, PHENIX, PHOBOS and STAR, have
concluded that a high density partonic matter is formed at central Au+Au
collisions at 200 GeV. The research focus now shifts from initial discovery to
a detailed exploration of partonic matter. Particles carrying heavy flavor,
i.e. charm or beauty quarks, are powerful tool for study the properties of the
hot and dense medium created in high-energy nuclear collisions at RHIC. At the
relatively low transverse momentum region, the collective motion of the heavy
flavor will be a sensitive signal for the thermalization of light flavors. An
upgrade of RHIC (RHIC-II) is intended for the second half of the decade, with a
luminosity increase to about 20-40 times the design value of 8x1026 cm-2 s-1
for Au+Au, and 2x1032 cm-2 s-1 for polarized proton beams. The PHENIX
collaboration plans to upgrade its experiment to exploit with an enhanced
detector new physics then in reach. For this purpose, we are constructing the
Silicon Vertex Tracker (VTX). The VTX detector will provide us the tool to
measure new physics observables that are not accessible at the present RHIC or
available only with very limited accuracy. The VTX detector consists of four
layers of barrel detectors located in the region of pseudorapidity |eta| < 1.2
and covers almost 2 azimuthal angle. The pseudorapidity is defined as eta =
-ln[tan(/2)], where is the emission angle relative to the beam axis. In this
paper, we will provide details of the physics capability added to PHENIX by the
new central silicon vertex tracker, the status of the project, including
technology choices used in the design, performance of individual silicon sensor
and silicon detector prototype. | nucl-ex |
Centrality Dependence of Neutral Pion Production in 158 A GeV Pb + Pb
Collisions: The production of neutral pions in 158AGeV Pb+Pb collisions has been studied
in the WA98 experiment at the CERN SPS. Transverse momentum spectra are studied
for the range 0.3 GeV/c < mT-m0 < 4.0 GeV/c. The results for central collisions
are compared to various models. The centrality dependence of the neutral pion
spectral shape and yield is investigated. An invariance of the spectral shape
and a simple scaling of the yield with the number of participating nucleons is
observed for centralities with greater than about 30 participating nucleons
which is most naturally explained by assuming an equilibrated system. | nucl-ex |
Percolation of Color Sources and the Shear Viscosity of the QGP in
Central A-A Collisions at RHIC and LHC Energies: The Color String Percolation Model (CSPM) is used to determine the shear
viscosity to entropy ratio ($\eta/s$) of the Quark-Gluon Plasma (QGP) produced
in Au-Au collisions at $\sqrt{s_{NN}}$ = 200 GeV at RHIC and Pb-Pb at
$\sqrt{s_{NN}}$ = 2.76 TeV at LHC. The relativistic kinetic theory relation for
$\eta/s$ is evaluated using CSPM values for the temperature and the mean free
path of the QGP constituents. The experimental charged hadron transverse
momentum spectrum is used to determine the percolation density parameter $\xi$
in Au-Au collisions (STAR). For Pb-Pb at $\sqrt{s_{NN}}$ = 2.76 TeV $\xi$
values are obtained from the extrapolation at RHIC energy. The value of
$\eta/s$ is 0.204$\pm$0.020 and 0.262$\pm$0.026 at the CSPM initial
temperatures of 193.6$\pm$3 MeV (RHIC) and 262.2 $\pm$13 MeV (LHC)
respectively. These values are 2.5 and 3.3 times the AdS/CFT conjectured lower
bound $1/4\pi$. We compare the CSPM $\eta/s$ analytic expression with weak
coupling (wQGP) and strong coupling (sQGP) calculations. This indicates that
the QGP is a strongly coupled fluid in the phase transition region. | nucl-ex |
Neutron Interactions as Seen by A Segmented Germanium Detector: The GERmanium Detector Array, GERDA, is designed for the search for
``neutrinoless double beta decay'' (0-nu-2-beta) with germanium detectors
enriched in Ge76. An 18-fold segmented prototype detector for GERDA Phase II
was exposed to an AmBe neutron source to improve the understanding of neutron
induced backgrounds. Neutron interactions with the germanium isotopes
themselves and in the surrounding materials were studied. Segment information
is used to identify neutron induced peaks in the recorded energy spectra. The
Geant4 based simulation package MaGe is used to simulate the experiment. Though
many photon peaks from germanium isotopes excited by neutrons are correctly
described by Geant4, some physics processes were identified as being
incorrectly treated or even missing. | nucl-ex |
Final State Interaction Effects in pol 3He(pol e,e'p): Asymmetries in quasi-elastic pol 3He(pol e,e'p) have been measured at a
momentum transfer of 0.67 (GeV/c)^2 and are compared to a calculation which
takes into account relativistic kinematics in the final state and a
relativistic one-body current operator. With an exact solution of the Faddeev
equation for the 3He-ground state and an approximate treatment of final state
interactions in the continuum good agreement is found with the experimental
data. | nucl-ex |
Anisotropic flow of charged hadrons, pions and (anti-)protons measured
at high transverse momentum in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$
TeV: The elliptic, $v_2$, triangular, $v_3$, and quadrangular, $v_4$, azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range $|\eta|<0.8$ at different collision centralities and as a
function of transverse momentum, $p_{\rm T}$, out to $p_{\rm T}=20$ GeV/$c$.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for $p_{\rm T}>8$ GeV/$c$. The small $p_{\rm T}$ dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to $p_{\rm T}=8$ GeV/$c$. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
$p_{\rm T}=8$ GeV/$c$ indicating that the particle type dependence persists out
to high $p_{\rm T}$. | nucl-ex |
Photoproduction in Ultra-Peripheral Relativistic Heavy Ion Collisions
with STAR: We present a summary of recent photoproduction results in ultra peripheral
relativistic heavy ions collisions with STAR. These collisions have impact
parameters larger then twice the nuclear radius; the nuclei do not physically
collide, but interact via long-range electromagnetic fields. We observe
exclusive $\rho^0$ production as well as $AuAu\to Au^*Au^* \rho^0$ with
accompanying mutual nuclear excitation at $\sqrt{s_{NN}}=200$ GeV. We report
the $\rho^0$ production cross section for both coherent and incoherent coupling
accompanied by mutual nuclear excitation. We have studied the cross section as
a function of $p_T$, $y_{\rho^0}$ and $M_{\pi\pi}$ and compared it to
theoretical models. In addition, we measured the $\rho^0$ helicity matrix
elements. They are found to be consistent with s-channel helicity conservation.
The ratio of coherent $\rho^0$ and direct $\pi^+\pi^-$ pair photoproduction has
been measured and found to be consistent with earlier measurements. The 4-pion
final state $AuAu \to \pi^+\pi^-\pi^+\pi^-$ state has also been observed. | nucl-ex |
STAR Overview of Hard Probe Observables: Parton energy loss, quarkonium sequential melting and particle production
from electromagnetic interactions are tools to study Quark Gluon Plasma
properties. The STAR detector, with large acceptance at mid-rapidity, excellent
particle identification and wide transverse momentum coverage, is able to study
these probes in details. In Hard Probes 2015, the STAR collaboration reported
measurements of reconstructed jets, heavy-flavor physics, di-lepton production
and the performance of new detectors in seven presentations and one poster.
Given the rich results from STAR, this overview report will focus on a few
selected results on jets and $\Upsilon$ measurements in Au+Au collisions at
$\sqrt{s_{\rm NN}}=200\,$GeV, $J/\psi$ production in $p$+$p$ collisions at
$\sqrt{s_{\rm NN}}=500\,$GeV, and the di-electron spectrum in the low mass
region from the Beam Energy Scan - Phase I. | nucl-ex |
High precision measurement of the $^6$He half-life: The half-life of $^{6}$He has been measured using a low energy radioactive
beam implanted in a YAP scintillator and recording decay events in a 4$\pi$
geometry. Events were time-stamped with a digital data acquisition system
enabling a reliable control of dead-time effects and detector gain variations.
The result, $T_{1/2} = (807.25 \pm 0.16_{\rm stat} \pm 0.11_{\rm sys}$)~ms,
provides the most precise value obtained so far and is consistent with the only
previous measurement having a precision smaller than 0.1%. This resolves the
longstanding discrepancy previously observed between two sets of measurements. | nucl-ex |
IUPAP Report 41 Introduction: IUPAP Report 41 is a document that gives summary information about the major
nuclear physics facilities around the world. It is updated approximately every
five years by Working Group 9 of the International Union of Pure and Applied
Physics. The introduction to the report gives an overview of the field of
nuclear physics and outlines the major questions facing the field. This most
recent version of Report 41 has been updated to reflect the state of the field
in 2018. The full report can be found at
http://www.triumf.info/hosted/iupap/icnp/report41.html | nucl-ex |
Experimental Results on p(d)+A Collisions at RHIC and the LHC: Recent experimental results at both the LHC and RHIC show evidence for
hydrodynamic behavior in proton-nucleus and deuteron- nucleus collisions (p+A).
This unexpected finding has prompted new measurements in p+A collisions in
order to understand whether similar matter is created in A+A and p+A collisions
or whether some another explanation is needed. In this proceedings, we will
discuss the new experimental data and its interpretation within the context of
heavy ion collisions. | nucl-ex |
Final Results of the GEp-III Experiment and the Status of the Proton
Form Factors: The recently published final results of experiment E04-108 in Jefferson Lab
Hall C extend the recoil polarization measurements of the ratio of the proton
electric and magnetic form factors to $Q^2 = 8.5$ GeV$^2$, an increase in $Q^2$
coverage of more than 50\%. A global fit of $G_E^p$ and $G_M^p$ to selected
data for electron-proton elastic scattering cross sections and polarization
observables is presented, illustrating the statistical impact of the new
results. | nucl-ex |
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