Nuclear Theory·nucl-th

Wednesday·February 24, 2021

15 papers—8 primary·7 cross-listed

01
Determining the jet transport coefficient $q^$ from inclusive hadron suppression measurements using Bayesian parameter estimation
S. Cao🇺🇸 · Y. Chen🇺🇸 · J. Coleman🇺🇸 · J. Mulligan🇺🇸 · P. M. Jacobs🇺🇸 · R. A. Soltz🇺🇸 · A. Angerami🇺🇸 · R. Arora🇺🇸 · S. A. Bass🇺🇸 · L. Cunqueiro🇺🇸 · T. Dai🇺🇸 · L. Du🇺🇸 and 35 other authors
We report a new determination of $q^$ , the jet transport coefficient of the Quark-Gluon Plasma. We use the JETSCAPE framework, which incorporates a novel multi-stage theoretical approach to in-medium jet evolution and Bayesian inference for parameter extraction. The calculations, based on the MATTER and LBT jet quenching models, are compared to experimental measurements of inclusive hadron suppression in Au+Au collisions at RHIC and Pb+Pb collisions at the LHC. The correlation of experimental systematic uncertainties is accounted for in the parameter extraction. The functional dependence of $q^$ on jet energy or virtuality and medium temperature is based on a perturbative picture of in-medium scattering, with components reflecting the different regimes of applicability of MATTER and LBT. In the multi-stage approach, the switch between MATTER and LBT is governed by a virtuality scale $Q_{0}$ . Comparison of the posterior model predictions to the RHIC and LHC hadron suppression data shows reasonable agreement, with moderate tension in limited regions of phase space. The distribution of $q^/ T^{3}$ extracted from the posterior distributions exhibits weak dependence on jet momentum and medium temperature $T$ , with 90\% Credible Region (CR) depending on the specific choice of model configuration. The choice of MATTER+LBT, with switching at virtuality $Q_{0}$ , has 90\% CR of $2 < q^/ T^{3} < 4$ for $p_{T}^{jet} > 40$ GeV/c. The value of $Q_{0}$ , determined here for the first time, is in the range 2.0-2.7 GeV.
nucl-thhep-phnucl-exPRC(2021)·196 citations
02
$β$ -Delayed Neutron and Fission Calculations with Relativistic QRPA and Statistical Model
Futoshi Minato · Tomislav Marketin · Nils Paar
A role of \beta-delayed neutron emission and fission in r-process nucleosynthesis attracts a high interest. Although the number of study on them covering r-process nuclei is increasing recently, uncertainties of \beta-delayed neutron and fission are still large for r-process simulations. Our purpose is to make a new database on \beta-delayed neutron emission and fission rates. To this end, the data that are not investigated experimentally have to be predicted. Microscopic theoretical approaches based on a nuclear energy density functional and statistical models are one of the competent tools for the prediction. To obtain \beta strength function, p-n relativistic QRPA is adopted. Particle evaporations and fission from nuclear highly excited states are estimated by the Hauser-Feshbach statistical model. \beta-delayed neutron branching ratios (P_n) are calculated and compared with experimental data. \beta-delayed fission branching ratio (P_f) are also assessed by using four different fission barrier data. Calculated P_n values are in a good agreement with experimental data. It is found that energy withdrawal by \beta-delayed neutron emission sensitively varies P_n values for nuclei near the neutron drip line. P_f are sensitively dependent on fission barrier data. Newly calculated data on \beta-delayed neutron emission and fission are summarized as a table in supplement material. They are provided for studies of r-process as well as other fields such as nuclear engineering.
nucl-thnucl-ex0 citations
03
Effects of ground-state correlations on damping of giant dipole resonaces in $L S$ closed shell nuclei
Mitsuru Tohyama
The effects of ground-state correlations on the damping of isovector giant dipole resonances in $L S$ closed shell nuclei $^{16}$ O and $^{40}$ Ca are studied using extended random-phase-approximation (RPA) approaches derived from the time-dependent density-matrix theory. It is pointed out that unconventional two-body amplitudes of one particle--three hole and three particle--one hole types which are neglected in most extended RPA theories play an important role in the fragmentation of isovector dipole strength.
nucl-thPTEP(2022)·2 citations
04
$K_{1} / K^{*}$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions
Haesom Sung🇰🇷 · Sungtae Cho🇰🇷 · Juhee Hong🇰🇷 · Su Houng Lee🇰🇷 · Sanghoon Lim🇰🇷 · Taesoo Song🇩🇪
Based on the fact that the mass difference between the chiral partners is an order parameter of chiral phase transition and that the chiral order parameter reduces substantially at the chemical freeze-out point in ultra-relativistic heavy ion collisions, we argue that the production ratio of $K_{1}$ over $K^{*}$ in such collisions should be substantially larger than that predicted in the statistical hadronization model. We further show that while the enhancement effect might be contaminated by the relatively larger decrease of $K_{1}$ meson than $K^{*}$ meson during the hadronic phase, the signal will be visible through a systematic study on centrality as the kinetic freeze-out temperature is higher and the hadronic life time shorter in peripheral collisions than in central collisions.
nucl-thhep-phnucl-exPLB(2021)·13 citations
05
alpha clustering and neutron-skin thickness of carbon isotopes
Q. Zhao🇯🇵 · Y. Suzuki🇯🇵 · J. He🇯🇵 · B. Zhou🇯🇵 · M. Kimura🇯🇵
The interplay between the formation of neutron skin and alpha cluster at the dilute surface of neutron-rich nuclei is one of the interesting subjects in the study of neutron-rich nuclei and nuclear clustering. A theoretical model has predicted that the growth of neutron skin will prevent the alpha clustering at the nuclear surface. Quite recently, this theoretical perspective; the suppression of alpha clustering by the neutron-skin formation was first confirmed experimentally in Sn isotopes as the reduction of the (p, p alpha) reaction cross-section. Motivated by the novel discovery, in this work, we have investigated the relationship between the neutron-skin thickness and alpha clustering in C isotopes. Based on the analysis by the antisymmetrized molecular dynamics, we show that the alpha spectroscopic factor at nuclear exterior decreases in neutron-rich C isotopes, and the clustering suppression looks correlated with the growth of the neutron-skin thickness.
nucl-thnucl-exEPJA(2021)·17 citations
06
Bjorken flow attractors with transverse dynamics
Victor E. Ambrus🇩🇪 · Sergiu Busuioc🇬🇧 · Jan A. Fotakis🇩🇪 · Kai Gallmeister🇩🇪 · Carsten Greiner🇩🇪
In the context of the longitudinally boost-invariant Bjorken flow with transverse expansion, we use three different numerical methods to analyze the emergence of attractor solutions in an ideal gas of massless particles exhibiting constant shear viscosity to entropy density ratio $η / s$ . The fluid energy density is initialized using a Gaussian profile in the transverse plane, while the ratio $χ = P_{L} / P_{T}$ between the longitudinal and transverse pressures is set at initial time $τ_{0}$ to a constant value $χ_{0}$ throughout the system employing the Romatschke-Strickland distribution. We introduce the hydrodynamization time $δ τ_{H} = (τ_{H} - τ_{0}) / τ_{0}$ based on the time $τ_{H}$ when the standard deviation $σ (χ)$ of a family of solutions with different $χ_{0}$ reaches a minimum value at the point of maximum convergence of the solutions. In the $0 + 1 D$ setup, $δ τ_{H}$ exhibits scale invariance, being a function only of $(η / s) / (τ_{0} T_{0})$ . With transverse expansion, we find a similar $δ τ_{H}$ computed with respect to the local initial temperature, $T_{0} (r)$ . We highlight the transition between the regimes where the longitudinal and transverse expansions dominate. We find that the hydrodynamization time required for the attractor solution to be reached increases with the distance from the origin, as expected based on the properties of the $0 + 1 D$ system defined by the local initial conditions. We argue that hydrodynamization is predominantly the effect of the longitudinal expansion, being significantly influenced by the transverse dynamics only for small systems or for large values of $η / s$ .
nucl-thhep-phphysics.flu-dynPRD(2021)·34 citations
07
Newly Evaluated Neutron Reaction Data on Chromium Isotopes
G.P.A. Nobre🇺🇸 · M.T. Pigni🇺🇸 · D.A. Brown🇺🇸 · R. Capote🇦🇹 · A. Trkov🇸🇮 · K.H. Guber🇺🇸 · R. Arcilla🇺🇸 · J. Gutierrez🇺🇸 · A. Cuadra🇺🇸 · G. Arbanas🇺🇸 · B. Kos🇸🇮 · D. Bernard🇫🇷 · P. Leconte🇫🇷
Neutron reaction data for the set of major chromium isotopes were reevaluated from the thermal energy range up to 20 MeV. In the low energy region, updates to the thermal values together with an improved $R$ -matrix analysis of the resonance parameters characterizing the cluster of large $s$ -wave resonances for $^{50, 53}$ Cr isotopes were performed. In the intermediate and high energy range up to 20 MeV, the evaluation methodology used statistical nuclear reaction models implemented in the EMPIRE code within the Hauser-Feshbach framework to evaluate the reaction cross sections and angular distributions. Exceptionally, experimental data were used to evaluate relevant cross sections above the resonance region up to 5 MeV in the major $^{52}$ Cr isotope. Evaluations were benchmarked with Monte Carlo simulations of a small suite of critical assemblies highly sensitive to Chromium data, and with the Oktavian shielding benchmark to judge deep penetration performance with a 14-MeV D-T neutron source. A significant improvement in performance is demonstrated compared to existing evaluations.
nucl-thnucl-exNucl.Data Sheets(2021)·10 citations
08
Beam-normal single-spin asymmetry in elastic scattering of electrons from a spin-0 nucleus
Oleksandr Koshchii🇩🇪 · Mikhail Gorchtein🇩🇪 · Xavier Roca-Maza🇮🇹 · Hubert Spiesberger🇩🇪
We study the beam-normal single-spin asymmetry (BNSSA) in high-energy elastic electron scattering from several spin-0 nuclei. Existing theoretical approaches work in the plane-wave formalism and predict the BNSSA to scale as $\sim A / Z$ with the atomic number $Z$ and nuclear mass number $A$ . While this prediction holds for light and intermediate nuclei, a striking disagreement in both the sign and the magnitude of BNSSA was observed by the PREX collaboration for $^{208}$ Pb, coined the "PREX puzzle". To shed light on this disagreement, we go beyond the plane-wave approach which neglects Coulomb distortions known to be significant for heavy nuclei. We explicitly investigate the dependence of BNSSA on $A$ and $Z$ by i) including inelastic intermediate states' contributions into the Coulomb problem in the form of an optical potential, ii) by accounting for the experimental information on the $A$ -dependence of the Compton slope parameter, and iii) giving a thorough account of the uncertainties of the calculation. Despite of these improvements, the PREX puzzle remains unexplained. We discuss further strategies to resolve this riddle.
nucl-thhep-phnucl-exPRC(2021)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE