Nuclear Theory·nucl-th

Wednesday·March 30, 2022

12 papers—9 primary·3 cross-listed

01
Nonextensive hydrodynamics of boost-invariant plasmas
Mubarak Alqahtani🇸🇦 · Nasser Demir🇰🇼 · Michael Strickland🇺🇸
We use quasiparticle anisotropic hydrodynamics to study the non-conformal and non-extensive dynamics of a system undergoing boost-invariant Bjorken expansion. To introduce nonextensivity, we use an underlying Tsallis distribution with a time-dependent nonextensivity parameter $q$ . By taking moments of the quasiparticle Boltzmann equation in the relaxation-time approximation, we obtain dynamical equations which allow us to determine the time evolution of all microscopic parameters including $q$ . We compare numerical solutions for bulk observables obtained using the nonextensive evolution with results obtained using quasiparticle anisotropic hydrodynamics with a Boltzmann distribution function ( $q \to 1$ ). We show that the evolution of the temperature, pressure ratio, and scaled energy density, are quite insensitive to which distribution function is assumed. However, we find significant differences in the early-time evolution of the bulk pressure which are observed for even small deviations from the Boltzmann distribution function. Finally, we discuss the existence of non-conformal hydrodynamic attractors for the longitudinal and transverse pressures, the bulk and shear viscous corrections, and the nonextensivity parameter $q$ .
nucl-thhep-phEPJC(2022)·16 citations
02
Search for the chiral magnetic effect in collisions between two isobars with deformed and neutron-rich nuclear structures
Xin-Li Zhao🇨🇳 · Guo-Liang Ma🇨🇳
Isobar collisions which were thought to have the same background and different magnetic fields provide an opportunity to verify the chiral magnetic effect (CME) in relativistic heavy-ion collisions. However, the first result from the RHIC-STAR isobar experiment did not observe the CME signal, but discovered that the backgrounds are different between $_{44}^{96} Ru +_{44}^{96} Ru$ and $_{40}^{96} Zr +_{40}^{96} Zr$ collisions. We test eighteen cases of Woods-Saxon parameter settings resulting from different nuclear deformation or nuclear structure effects using a mutiphase transport model. We find out that seven cases can reasonably reproduce three reference ratios measured by the STAR experiment. Considering both the halo-type neutron skin structure and CME-like charge separation, we demonstrate that it is difficult for the CME observables ( $Δ δ$ , $Δ δ$ ratio, $Δ γ$ and $Δ γ$ ratio) to distinguish the presence or absence of the CME, if the CME strength is weak in isobar collisions. It is because the final state interactions significantly weaken the initial CME signal, resulting in non-linear sensitivities of the CME observables to the CME strength. Therefore, more sensitive observables are required to search for the possible small CME signal in isobar collisions.
nucl-thhep-phnucl-exPRC(2022)·29 citations
03
An accurate relativistic chiral nucleon-nucleon interaction up to the next-to-next-to-leading order
Jun-Xu Lu🇨🇳 · Yang Xiao🇨🇳 · Chun-Xuan Wang🇨🇳 · Li-Sheng Geng🇨🇳
We report on the construction of an accurate relativistic chiral nucleon-nucleon interaction up to the next-to-next-to-leading (NNLO) order. We compare the so-obtained neutron-proton phaseshifts with the next-to-next-to-next-to-leading order (N $^{3}$ LO) nonrelativistic ones and we show that up to $T_{lab.} = 200$ MeV, the relativistic chiral nuclear force can describe the PWA93 phaseshifts and inelasticities as well as its N $^{3}$ LO nonrelativistic counterparts. As a result, the relativistic chiral nuclear force can be readily used for relativistic ab initio nuclear structure, reaction, as well astrophysical studies.
nucl-thhep-lathep-phnucl-exPoS(2024)·2 citations
04
Sliding Dumbbell Method to search for the CME in heavy ion collisions
Madan M. Aggarwal🇮🇳 · Anjali Attri🇮🇳 · Sonia Parmar🇮🇳 · Anjali Sharma🇮🇳 · Jagbir Singh🇮🇳
This study explores the Chiral Magnetic Effect (CME) in ultra-relativistic heavy-ion collisions. The CME, observed as back-to-back charge separation along the magnetic field axis, is investigated using the newly developed Sliding Dumbbell Method (SDM) applied to Au+Au events at a center-of-mass energy $s_{NN}$ = 200 GeV generated by the AMPT model with string melting configuration. The CME-like signal is externally injected in events by flipping charges of pairs of the particles perpendicular to the reaction plane. The study reports a significant enhancement of the CME-sensitive 3-particle $γ$ correlator in events with high back-to-back charge separation, in a given collision centrality. Additionally, a linear relationship is observed between the $∣ γ ∣$ correlator for same-sign charge pairs and positive charge asymmetry ( $⟨ A^{+} ⟩$ ) across the dumbbell in CME-enriched sub-samples. Furthermore, the fraction of CME in $Δ γ$ (difference between opposite and same sign $γ$ correlators) is presented across different collision centralities having different percentages of externally injected CME-like signal. Overall, the research aims to understand and detect the Chiral Magnetic Effect through innovative experimental method and detailed analysis of event structure.
nucl-thhep-phPramana(2024)·3 citations
05
Systematics of E2 strength in the sd-shell with the valence-space in-medium similarity renormalization group
S. R. Stroberg · J. Henderson · G. Hackman · P. Ruotsalainen · G. Hagen · J. D. Holt
Background: Recent developments in {\it ab initio} nuclear theory demonstrate promising results in medium- to heavy-mass nuclei. A particular challenge for many of the many-body methodologies, however, is an accurate treatment of the electric-quadrupole, $E 2$ , strength associated with collectivity. Purpose: The valence-space in-medium similarity renormalization group (VS-IMSRG) is a particularly powerful method for accessing medium- and high-mass nuclei but has been found to underpredict $E 2$ strengths. The purpose of this work is to evaluate the isospin dependence of this underprediction. Methods: We perform a systematic comparison of valence-space in-medium similarity renormalization group (VS-IMSRG) calculations with available literature. We make use of isoscalar and isovector contributions to the $E 2$ matrix elements to assess isoscalar and isovector contributions to the missing strength. Results: It is found that the $E 2$ strength is consistent throughout $T_{z} = \frac{1}{2}$ , $T_{z} = ∣ 1 ∣$ , $T_{z} = \frac{3}{2}$ and $T_{z} = 2$ pairs within the $s d$ -shell. Furthermore, no isovector contribution to the deficiency is identified. Conclusions: A comparison with toy-models and coupled-cluster calculations is used to discuss potential origins of the missing strength, which arises from missing many-particle, many-hole excitations out of the model space. The absence of any significant isovector contribution to the missing $E 2$ strength indicates that the $E 2$ strength discrepancy, and therefore any correction, is largely independent of the isospin of the nuclei in question.
nucl-thPRC(2022)·62 citations
06
Harmonic flow correlations in Au+Au reactions at 1.23 AGeV: A new testing ground for the Equation-of-State and expansion geometry
Tom Reichert🇩🇪 · Jan Steinheimer🇩🇪 · Christoph Herold🇹🇭 · Ayut Limphirat🇹🇭 · Marcus Bleicher🇩🇪
Correlations between the harmonic flow coefficients $v_{1}$ , $v_{2}$ , $v_{3}$ and $v_{4}$ of nucleons in semi-peripheral Au+Au collisions at a beam energy of 1.23~AGeV are investigated within the hadronic transport approach Ultra-relativistic Quantum Molecular Dynamics (UrQMD). In contrast to ultra-relativistic collision energies (where the flow coefficients are evaluated with respect to the respective event plane), we predict strong correlations between the flow harmonics with respect to the reaction plane. Based on an event-by-event selection of the midrapidity final state elliptic flow of protons we show that as a function of rapidity, I) the sign of the triangular flow changes, II) that the shape of $v_{4}$ changes from convex to concave, and III) that $v_{3} \propto v_{1} v_{2}$ and $v_{4} \propto v_{2}^{2}$ for all different event classes, indicating strong correlations between all investigated harmonic flow coefficients.
nucl-thnucl-exEPJC(2022)·11 citations
07
Transport coefficients of quasi-particle models within a new relaxation time approximation of the Boltzmann equation
Gabriel S. Rocha🇧🇷 · Maurício N. Ferreira🇧🇷 · Gabriel S. Denicol🇧🇷 · Jorge Noronha🇺🇸
We investigate the transport properties of a kinetic theory model that is tuned to describe the thermodynamic properties of QCD at zero chemical potential using a new formulation of the relaxation time approximation. In contrast to previous approaches, the latter is constructed to preserve the fundamental properties of the collision term of the Boltzmann equation for any energy-dependence of the relaxation time. A novel choice of matching conditions is implemented to ensure that the background mean-field depends only on the temperature even when the system is out of equilibrium. We provide a consistent analysis of how the transport coefficients of relativistic Navier-Stokes theory vary with the energy dependence of the relaxation time. We also show that the entropy production of this theory is consistent with the second law of thermodynamics and verify that it is independent of the matching conditions employed. We used this fact to calculate the matching independent combination of transport coefficients.
nucl-thhep-phhep-thPRD(2022)·21 citations
08
Nuclear coherent population transfer to the $^{229 m}$ Th isomer using x-ray pulses
Tobias Kirschbaum · Nikolay Minkov · Adriana Pálffy
Population of the 8 eV $^{229 m}$ Th isomer via the second nuclear excited state at 29.19 keV by means of coherent x-ray pulses is investigated theoretically. We focus on two nuclear coherent population transfer schemes using partially overlapping x-ray pulses known from quantum optics: stimulated Raman adiabatic passage (STIRAP), and successive $π$ pulses. Numerical results are presented for three possible experimental setups. Our results identify the Gamma Factory as the most promising scenario, where two ultraviolet pulses combined with relativistically accelerated ions deliver the required intensities for efficient isomer population. Our simulations require knowledge of the in-band and cross-band nuclear transition probabilities. We give theoretically predicted values for the latter and discuss them in the context of recent experiments.
nucl-thnucl-exphysics.acc-phPRC(2022)·16 citations
09
$Λ$ spin polarization in event-by-event relativistic heavy-ion collisions
Sahr Alzhrani🇺🇸 · Sangwook Ryu🇺🇸 · Chun Shen🇺🇸
We present a systematic study of $Λ$ hyperon's polarization observables using event-by-event (3+1)D relativistic hydrodynamics. The effects of initial hot spot size and QGP's specific shear viscosity on the polarization observables are quantified. We examine the effects of the two formulations of the thermal shear tensor on the polarization observables using the same hydrodynamic background. With event-by-event simulations, we make predictions for the Fourier coefficients of $Λ$ 's longitudinal polarization $P^{z}$ with respect to the event planes of different orders of anisotropic flow. We propose new correlations among the Fourier coefficients of $P^{z}$ and charged hadron anisotropic flow coefficients to further test the mapping from fluid velocity gradients to hyperon's polarization. Finally, we present a system size scan with Au+Au, Ru+Ru, and O+O collisions at $s_{NN} = 200$ GeV to study the system size dependence of polarization observables at the Relativistic Heavy-ion Collider.
nucl-thhep-phnucl-exPRC(2022)·77 citations
10
On the Sound Speed in Neutron Stars
Sinan Altiparmak🇩🇪 · Christian Ecker🇩🇪 · Luciano Rezzolla🇩🇪
Determining the sound speed $c_{s}$ in compact stars is an important open question with numerous implications on the behaviour of matter at large densities and hence on gravitational-wave emission from neutron stars. To this scope, we construct more than $1 0^{7}$ equations of state (EOSs) with continuous sound speed and build more than $1 0^{8}$ nonrotating stellar models consistent not only with nuclear theory and perturbative QCD, but also with astronomical observations. In this way, we find that EOSs with sub-conformal sound speeds, i.e. with $c_{s}^{2} < 1/3$ within the stars, are possible in principle but very unlikely in practice, being only $0.03%$ of our sample. Hence, it is natural to expect that $c_{s}^{2} > 1/3$ somewhere in the stellar interior. Using our large sample, we obtain estimates at $95%$ credibility of neutron-star radii for representative stars with $1.4$ and $2.0$ solar masses, $R_{1.4} = 12.4 2_{- 0.99}^{+ 0.52} km$ , $R_{2.0} = 12.1 2_{- 1.23}^{+ 1.11} km$ , and for the binary tidal deformability of the GW170817 event, $Λ ~_{1.186} = 48 5_{- 211}^{+ 225}$ . Interestingly, our lower-bounds on the radii are in very good agreement with the prediction derived from very different arguments, namely, the threshold mass. Finally, we provide simple analytic expressions to determine the minimum and maximum values of $Λ ~$ as a function of the chirp mass.
↳ astro-ph.HEgr-qchep-phnucl-thApJL(2022)·266 citations
11
Pure Quark and Gluon Observables in Collinear Drop
Iain W. Stewart🇺🇸 · Xiaojun Yao🇺🇸
We construct a class of pure quark and gluon observables by using the collinear drop grooming technique. The construction is based on linear combinations of multiple cumulative distributions of the jet mass in collinear drop, whose specific weights are fully predicted perturbatively. This yields observables which obtain their values purely from quarks (or purely from gluons) in a wide region of phase space. We demonstrate this by showing that these observables are effective in two phase space regions, one dominated by perturbative resummation and one dominated by nonperturbative effects. The nonperturbative effects are included using shape functions which only appear as a common factor in the linear combinations constructed. We test this construction using a numerical analysis with next-to-leading logarithmic resummation and various shape function models, as well as analyzing these observables with Pythia and Vincia. Choices for the collinear drop parameters are optimized for experimental use.
↳ hep-phhep-exnucl-thJHEP(2022)·15 citations
12
Semi-classical kinetic theory for massive spin-half fermions with leading-order spin effects
Arpan Das🇵🇱 · Wojciech Florkowski🇵🇱 · Avdhesh Kumar🇹🇼 · Radoslaw Ryblewski🇵🇱 · Rajeev Singh🇵🇱
We consider the quantum kinetic-theory description for interacting massive spin-half fermions using the Wigner function formalism. We derive a general kinetic theory description assuming that the spin effects appear at the classical and quantum level. To track the effect of such different contributions we use the semi-classical expansion method to obtain the generalized dynamical equations including spin, analogous to classical Boltzmann equation. This approach can be used to obtain a collision kernel involving local as well as non-local collisions among the microscopic constituent of the system and eventually, a framework of spin hydrodynamics ensuring the conservation of the energy-momentum tensor and total angular momentum tensor.
↳ hep-thhep-phnucl-thActa Phys.Polon.B(2023)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE