Nuclear Theory·nucl-th

Tuesday·June 11, 2019

9 papers—4 primary·5 cross-listed

01
Sensitivity of the excitation functions of collective flow to relativistic scalar and vector meson interactions in the relativistic quantum molecular dynamics model RQMD.RMF
Yasushi Nara🇯🇵 · Horst Stoecker🇩🇪
Relativistic quantum molecular dynamics with scalar and vector interactions based on the relativistic mean meson field theory, RQMD.RMF, is developed.It is implemented into the microscopic transport code JAM.The sensitivity of the directed and of the elliptic proton flow in high energy heavy-ion collisions on the stiffness of the RMF equation of state (EoS) is examined. These new calculations are compared to experimental data at mid-central Au + Au collisions in the beam energy range $2.5 < s_{N N} < 20$ GeV. This new RQMD model with the relativistic mean field scalar and vector meson interactions does describe consistently, with one RMF parameter set,the beam energy dependence of both the directed flow and the elliptic flow,from SIS18 to AGS and RHIC BES-II energies, $s_{N N} < 10$ GeV.There are different sensitivities of these different kinds of flow to the EoS: elliptic flow is most sensitive to the nuclear incompressibility constant,at the moderate beam energies $s_{N N} < 3$ GeV,whereas the directed flow is most sensitive to the effective baryon mass at saturation density at $3 < s_{N N} < 5$ GeV. Matters abruptly change in the next higher energy range, $s_{N N} ≳ 10 - 20$ GeV:the directed flow data show a double change of sign of the slope of $v_{1}$ , inverting twice in this energy range,in sudden contradiction to the RQMD.RMF calculation for a monotonous, stiff EoS. This surprising oscillating behavior,a double change of sign of the $v_{1}$ slope, points to the appearance of a hitherto unknown first-order phase transition in excited QCD matter at high baryon densities in mid-central Au + Au collisions.
nucl-thhep-phnucl-exPRC(2019)·42 citations
02
Ab initio calculations of p-shell nuclei up to N2LO in chiral Effective Field Theory
Pieter Maris🇺🇸
Nuclear structure and reaction theory are undergoing a major renaissance with advances in many-body methods, realistic interactions with greatly improved links to Quantum Chromodynamics, the advent of high performance computing, and improved computational algorithms. State-of-the-art two- and three-nucleon interactions obtained from chiral Effective Field Theory provide a theoretical foundation for nuclear theory with controlled approximations. With highly efficient numerical codes, tuned to the current generation of supercomputers, we can perform ab-initio nuclear structure calculations for a range of nuclei to a remarkable level of numerical accuracy, with quantifiable numerical uncertainties. Here we present an overview of recent results for No-Core Configuration Interaction calculations of p-shell nuclei using these chiral interactions up to next-to-next-to-leading order, including three-body forces. We show the dependence of the ground state energies on the chiral order; we also present excitation spectra for selected nuclei and compare the results with experimental data.
nucl-thJ.Phys.Conf.Ser.(2019)·4 citations
03
Correlations in ultra-relativistic nuclear collisions with strings
Martin Rohrmoser🇵🇱 · Wojciech Broniowski🇵🇱
While string models describe initial state radiation in ultra-relativistic nuclear collisions well, they mainly differ in their end-point positions of the strings in spatial rapidity. We present a generic model where wounded constituents are amended with strings whose both end-point positions fluctuate and analyze semi-analytically various scenarios of string-end-point fluctuations. In particular we constrain the different cases to experimental data on rapidity spectra from collisions at $s_{NN} = 200$ ~GeV, and explore their respective two-body correlations, which allows to partially discriminate the possible solutions.
nucl-thActa Phys.Polon.Supp.(2020)·0 citations
04
Bayesian analysis of capture reactions $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$
Pradeepa Premarathna · Gautam Rupak
Bayesian analysis of the radiative capture reactions $^{3} He (α, γ)^{7} Be$ and $^{3} H (α, γ)^{7} Li$ are performed to draw inferences about the cross sections at threshold. We do a model comparison of two competing effective field theory power countings for the capture reactions. The two power countings differ in the contribution of two-body electromagnetic currents. In one power counting, two-body currents contribute at leading order, and in the other they contribute at higher orders. The former is favored for $^{3} He (α, γ)^{7} Be$ if elastic scattering data in the incoming channel is considered in the analysis. Without constraints from elastic scattering data, both the power countings are equally favored. For $^{3} H (α, γ)^{7} Li$ , the first power counting with two-body current contributions at leading order is favored with or without constraints from elastic scattering data.
nucl-thastro-ph.SREPJA(2020)·25 citations
05
Charge-dependent pair correlations relative to a third particle in $p$ +Au and $d$ +Au collisions at RHIC
STAR collaboration
Quark interactions with topological gluon configurations can induce chirality imbalance and local parity violation in quantum chromodynamics. This can lead to electric charge separation along the strong magnetic field in relativistic heavy-ion collisions -- the chiral magnetic effect (CME). We report measurements by the STAR collaboration of a CME-sensitive observable in $p$ +Au and $d$ +Au collisions at 200 GeV, where the CME is not expected, using charge-dependent pair correlations relative to a third particle. We observe strong charge-dependent correlations similar to those measured in heavy-ion collisions. This bears important implications for the interpretation of the heavy-ion data.
↳ nucl-exhep-exhep-phnucl-thPLB(2019)·56 citations
06
Neutron production induced by $α$ -decay with Geant4
E. Mendoza🇪🇸 · D. Cano-Ott🇪🇸 · P. Romojaro🇪🇸 · V. Alcayne🇪🇸 · P. García Abia🇪🇸 · V. Pesudo🇪🇸 · L. Romero🇪🇸 · R. Santorelli🇪🇸
Neutron production induced by ( $α$ ,n) reactions is important in various scenarios. One of the most relevant ones is related to underground dark matter experiments, where the neutrons produced by the $α$ -decay from radioactive contaminants in the detector materials can generate an irreducible background, limiting the sensitivity of the experiment. A precise estimate of the background due to these neutrons is crucial for the experiments currently taking data and for the design of the next generation detectors. In this work, we prove that Geant4 can be used to calculate neutron yields and energy spectra induced by $α$ -decay. These neutrons are produced according to the information compiled in data libraries originally written in the ENDF-6 format. In this article we also review the different databases available, showing the differences and similarities among them. Finally, we compare several Geant4 neutron production yields and spectra with experimental data and other codes.
↳ hep-phnucl-thNucl.Instrum.Meth.A(2020)·34 citations
07
Quarkonium Phenomenology from a Generalised Gauss Law
David Lafferty🇩🇪 · Alexander Rothkopf🇳🇴
We present an improved analytic parametrisation of the complex in-medium heavy quark potential derived rigorously from the generalised Gauss law. To this end we combine in a self-consistent manner a non-perturbative vacuum potential with a weak-coupling description of the QCD medium. The resulting Gauss-law parametrisation is able to reproduce full lattice QCD data by using only a single temperature dependent parameter, the Debye mass $m_{D}$ . Using this parametrisation we model the in-medium potential at finite baryo-chemical potential, which allows us to estimate the $Ψ^{'}$ / $J /Ψ$ ratio in heavy-ion collisions at different beam energies.
↳ hep-phhep-latnucl-thUniverse(2019)·1 citation
08
A Baseline Study of the Event-shape and Multiplicity Dependence of Chemical Freeze-out Parameters in Proton-Proton Collisions at $s$ = 13 TeV Using PYTHIA8
Rutuparna Rath🇮🇳 · Arvind Khuntia🇵🇱 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳
The event-shape and multiplicity dependence of the chemical freeze-out temperature ( $T_{ch}$ ), freeze-out radius ( $R$ ), and strangeness saturation factor ( $γ_{s}$ ) are obtained by studying the particle yields from the PYTHIA8 Monte Carlo event generator in proton-proton (pp) collisions at the centre-of-mass $s$ = 13 TeV. Spherocity is one of the transverse event-shape techniques to distinguish jetty and isotropic events in high-energy collisions and helps in looking into various observables in a more differential manner. In this study, spherocity~classes are divided into three categories, namely (i) spherocity integrated, (ii) isotropic, and~(iii) jetty. The~chemical freeze-out parameters are extracted using a statistical thermal model as a function of the spherocity class and charged particle multiplicity in the canonical, strangeness canonical, and grand canonical ensembles. A clear observation of the multiplicity and spherocity class dependence of $T_{ch}$ , $R$ , and $γ_{s}$ is observed. A final state multiplicity, $N_{ch} \geq$ 30 in the forward multiplicity acceptance of the ALICE detector appears to be a thermodynamic limit, where the freeze-out parameters become almost independent of the ensembles. This~study plays an important role in understanding the particle production mechanism in high-multiplicity pp collisions at the Large Hadron Collider (LHC) energies in view of a finite hadronic phase lifetime in small systems.
↳ hep-phhep-exnucl-exnucl-thPhysics(2020)·7 citations
09
Treating quarks within neutron stars
Sophia Han🇺🇸 · M. A. A. Mamun🇺🇸 · S. Lalit🇺🇸 · C. Constantinou🇺🇸 · M. Prakash🇺🇸
Neutron star interiors provide the opportunity to probe properties of cold dense matter in the QCD phase diagram. Utilizing models of dense matter in accord with nuclear systematics at nuclear densities, we investigate the compatibility of deconfined quark cores with current observational constraints on the maximum mass and tidal deformability of neutron stars. We explore various methods of implementing the hadron-to-quark phase transition, specifically, first-order transitions with sharp (Maxwell construction) and soft (Gibbs construction) interfaces, and smooth crossover transitions. We find that within the models we apply, hadronic matter has to be stiff for a first-order phase transition and soft for a crossover transition. In both scenarios and for the equations of state we employed, quarks appear at the center of pre-merger neutron stars in the mass range $\approx 1.0 - 1.6 M_{⊙}$ , with a squared speed of sound $c_{QM}^{2} ≳ 0.4$ characteristic of strong repulsive interactions required to support the recently discovered neutron star masses $\geq 2 M_{⊙}$ . We also identify equations of state and phase transition scenarios that are consistent with the bounds placed on tidal deformations of neutron stars in the recent binary merger event GW170817. We emphasize that distinguishing hybrid stars with quark cores from normal hadronic stars is very difficult from the knowledge of masses and radii alone, unless drastic sharp transitions induce distinctive disconnected hybrid branches in the mass-radius relation.
↳ astro-ph.HEastro-ph.SRnucl-thPRD(2019)·104 citations

Affiliations

first authorsco-authorsvia INSPIRE