Nuclear Theory·nucl-th

Wednesday·September 30, 2020

14 papers—5 primary·9 cross-listed

01
Bayesian inference of dense matter EOS encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars
Wen-Jie Xie🇨🇳 · Bao-An Li🇺🇸
[Purpose:] We infer the posterior probability distribution functions (PDFs) and correlations of nine parameters characterizing the EOS of dense neutron-rich matter encapsulating a first-order hadron-quark phase transition from the radius data of canonical NSs reported by LIGO/VIRGO, NICER and Chandra Collaborations. We also infer the quark matter (QM) mass fraction and its radius in a 1.4 M $_{⊙}$ NS and predict their values in more massive NSs. [Method:] Meta-modelings are used to generate both hadronic and QM EOSs in the Markov-Chain Monte Carlo sampling process within the Bayesian statistical framework. An explicitly isospin-dependent parametric EOS for the $n p e μ$ matter in NSs at $β$ equilibrium is connected through the Maxwell construction to the QM EOS described by the constant speed of sound (CSS) model of Alford, Han and Prakash. [Results:] (1) The most probable values of the hadron-quark transition density $ρ_{t} / ρ_{0}$ and the relative energy density jump there $\De \ep / \ep_{t}$ are $ρ_{t} / ρ_{0} = 1. 6_{- 0.4}^{+ 1.2}$ and $\De \ep / \ep_{t} = 0. 4_{- 0.15}^{+ 0.20}$ at 68\% confidence level, respectively. The corresponding probability distribution of QM fraction in a 1.4 M $_{⊙}$ NS peaks around 0.9 in a 10 km sphere. Strongly correlated to the PDFs of $ρ_{t}$ and $\De \ep / \ep_{t}$ , the PDF of the QM speed of sound squared $\cQMsq / c^{2}$ peaks at $0.9 5_{- 0.35}^{+ 0.05}$ , and the total probability of being less than 1/3 is very small. (2) The correlations between PDFs of hadronic and QM EOS parameters are very weak. [Conclusions:] The available astrophysical data considered together with all known EOS constraints from theories and terrestrial nuclear experiments prefer the formation of a large volume of QM even in canonical NSs.
nucl-thastro-ph.HEnucl-exPRC(2021)·74 citations
02
Novel feature of doubly bubble nuclei in 50 $\leq$ Z(N) $\leq$ 82 region along with magicity and weakly bound structure
M. Kumawat · G. Saxena · M. Kaushik · S. K. Jain · J. K. Deegwal · Mamta Aggarwal
In this work, we identify a unique and novel feature of central density depletion in both proton and neutron named as doubly bubble nuclei in 50 $\leq$ Z(N) $\leq$ 82 region. The major role of 2d-3s single-particle (s.p.) states in the existence of halo and bubble nuclei is probed. The occupancy in s.p. state 3s $_{1/2}$ leads to the extended neutron density distribution or halo while the unoccupancy results in the central density depletion. By employing the Relativistic Mean-Field (RMF) approach along with NL3* parameter, the separation energies, single-particle energies, pairing energies, proton, and neutron density profiles along with deformations of even-even nuclei are investigated. Our results are in concise with few other theories and available experimental data. Emergence on new shell closure and the magicity of conventional shell closures are explored systematically in this yet unknown region.
nucl-thIJMPE(2020)·2 citations
03
Critical temperature of deconfinement in a constrained space using a bag model at vanishing baryon density
Zonghou Han · Baoyi Chen · Yunpeng Liu
The geometry of fireballs in relativistic heavy ion collisions is approximated by a static box, which is infinite in two directions while finite in the other direction. The critical temperature of deconfinement phase transition is calculated explicitly in the MIT bag model at vanishing baryon density. It is found that the critical temperature shifts to a value higher than that in an unconstrained space.
nucl-thChin.Phys.Lett.(2020)·9 citations
04
Radial profile of heavy quarks in jets in high-energy nuclear collisions
Sa Wang🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
In high energy nuclear collisions, heavy flavor tagged jets are useful hard probes to study the properties of the quark-gluon plasma (QGP). In this talk, we present the first theoretical prediction of the $D^{0}$ meson radial distributions in jets relative to the jet axis both in p+p and Pb+Pb collisions at $5.02$ TeV, it shows a nice agreement with the available experimental data. The in-medium jet evolution in the study is described by a Monte Carlo transport model which has been incorporated with the initial events as input provided by the next-to-leading order (NLO) plus parton shower (PS) event generator SHERPA. In such evolution process, both elastic and inelastic parton energy loss in the hot and dense medium are taken into account. Within this same simulation framework, we predict different modification patterns of the radial profile of charm and bottom quarks in jets in Pb+Pb collisions: jet quenching effect will lead the charm quarks diffuse to lager radius while lead the bottom quarks distributed closer to jet axis.
nucl-thhep-phPoS(2021)·3 citations
05
Light clusters in warm stellar matter: calibrating the cluster couplings
Tiago Custódio🇵🇹 · Alexandre Falcão🇵🇹 · Helena Pais🇵🇹 · Constança Providência🇵🇹 · Francesca Gulminelli🇫🇷 · Gerd Röpke🇩🇪
The abundances of light clusters within a formalism that considers in-medium effects are calculated using several relativistic mean-field models, with both density-dependent and density-independent couplings. Clusters are introduced as new quasiparticles, with a modified coupling to the scalar meson field. A comparison with experimental data from heavy ion collisions allows settling the model dependence of the results and the determination of the couplings of the light clusters to the meson fields. We find that extra experimental constraints at higher density are needed to convincingly pin down the density associated to the melting of clusters in the dense nuclear medium. The role of neutron rich clusters, such as $^{6}$ He, in asymmetric matter is discussed.
nucl-thastro-ph.HEastro-ph.SREPJA(2020)·12 citations
06
Modified MIT Bag Models -- part II: QCD phase diagram and hot quark stars
Luiz L. Lopes🇧🇷 · Carline Biesdorf🇧🇷 · K. D. Marquez🇧🇷 · Debora P. Menezes🇧🇷
In the present work we use the modified versions of the MIT bag model, on which both a vector field and a self-interacting term are introduced, to obtain hot quark matter and to investigate the QCD phase diagram. We first analyze two-flavored quark matter constrained to both the freeze-out and the liquid-gas phase transition at the hadronic phase. Later, three-flavored quark matter subject to $β$ equilibrium and charge neutrality is used to compute quark star macroscopic properties, which are confronted with recent observational massive and canonical star radius results. Finally, a comparison with QCD phase diagrams obtained from the Nambu-Jona-Lasinio model is performed.
↳ hep-phastro-ph.HEnucl-thPhys.Scripta(2021)·45 citations
07
Studying explicit $U (1)_{A}$ symmetry breaking in hot and magnetised two flavour non-local NJL model constrained using lattice results
Mahammad Sabir Ali🇮🇳 · Chowdhury Aminul Islam🇨🇳 · Rishi Sharma🇮🇳
We study the two flavour non-local Nambu\textemdash Jona-Lasinio (NJL) model in the presence of a magnetic field and explore the chiral crossover in presence of a non-local form of the 't Hooft determinant term. Its coupling is governed by a dimensionless parameter $c$ . This term is responsible for the explicit breaking of $U (1)_{A}$ symmetry. We have attempted a systematic analysis of the model parameters by fitting to self-consistent lattice QCD calculations. Three parameters of the model are fixed by $e B = 0$ results from published lattice QCD on the chiral condensate, the pion decay constant ( $F_{π}$ ), and the pion mass ( $m_{π}$ ). The difference of the $u$ and $d$ quark condensates in the presence of a magnetic field ( $e B$ ) is quite sensitive to $c$ and we fix $c$ using published lattice QCD results for this observable. We see no evidence that $c$ depends on $e B$ . The crossover temperature decreases with increasing $e B$ only for condensate values at the lower end of the allowed values (as already seen in~\cite{Pagura:2016pwr}) and $F_{π}$ at the upper end of the allowed values. We further check our model predictions by calculating the topological susceptibility with the fitted $c$ values and comparing it with lattice results. Since the topological susceptibility is related to the extent of the $U (1)_{A}$ symmetry breaking, we find that it is sensitive to the value of $c$ .
↳ hep-phnucl-thPRD(2021)·16 citations
08
On gauge invariance of transverse momentum dependent distributions at small-x
Renaud Boussarie🇺🇸 · Yacine Mehtar-Tani🇺🇸
Transverse momentum dependent (TMD) distributions at small x exhibit a rich infinite twist structure that encompasses the leading twist (partonic) distributions as well as the physics of gluon saturation. Progress to further the connection between the standard TMD framework at moderate x and small x has been recently made. In this context, we show that light cone Wilson line operators at small-x can be formulated in terms of transverse gauge links. This new formulation of small x operators allows a direct matching with the standard leading twist gluon TMD distributions and provides an efficient and general prescription for computing TMD distributions at small x beyond leading twist.
↳ hep-phnucl-thPoS(2021)·0 citations
09
Resolving the Bethe-Salpeter kernel
Si-Xue Qin🇨🇳 · Craig D. Roberts🇨🇳
A novel method for constructing a Bethe-Salpeter kernel for the meson bound-state problem is described. It produces a closed-form kernel that is symmetry-consistent (discrete and continuous) with the gap equation defined by any admissible gluon-quark vertex. Applicable even when the diagrammatic content of that vertex is unknown, the scheme can foster new synergies between continuum and lattice approaches to strong interactions. The framework is illustrated by demonstrating that the presence of a dressed-quark anomalous magnetic moment in the gluon-quark vertex, an emergent feature of strong interactions, can remedy many defects of widely used meson bound-state kernels, including the level ordering of pseudoscalar and vector meson radial excitations.
↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2021)·50 citations
10
Magnetic corrections to the boson self-coupling and boson-fermion coupling in the linear sigma model with quarks
Alejandro Ayala🇲🇽 · José Luis Hernández🇲🇽 · L. A. Hernández🇲🇽 · Ricardo L. S. Farias🇧🇷 · R. Zamora🇨🇱
We compute the magnetic field-induced modifications to the boson self-coupling and the boson-fermion coupling, in the static limit, using an effective model of QCD, the linear sigma model with quarks. The former is computed for arbitrary field strengths as well as using the strong field approximation. The latter is obtained in the strong field limit. The arbitrary field result for the boson self-coupling depends on the ultraviolet renormalization scale and this dependence cannot be removed by a simple vacuum subtraction. Using the strong field result as a guide, we find the appropriate choice for this scale and discuss the physical implications. The boson-fermion coupling depends on the Schwinger's phase and we show how this phase can be treated consistently in such a way that the magnetic field induced vertex modification is both gauge invariant and can be written with an explicit factor corresponding to energy-momentum conservation for the external particles. Both couplings show a modest decrease with the field strength.
↳ hep-phhep-thnucl-thPRD(2020)·26 citations
11
Cold Atom Quantum Simulator for String and Hadron Dynamics in Non-Abelian Lattice Gauge Theory
Raka Dasgupta🇮🇳 · Indrakshi Raychowdhury🇺🇸
We propose an analog quantum simulator for simulating real time dynamics of $(1 + 1)$ -d non-Abelian gauge theory well within the existing capacity of ultracold atom experiments. The scheme calls for the realization of a two-state ultracold fermionic system in a 1-dimensional bipartite lattice, and the observation of subsequent tunneling dynamics. Being based on novel loop string hadron formalism of SU(2) lattice gauge theory, this simulation technique is completely SU(2) invariant and simulates accurate dynamics of physical phenomena such as string breaking and/or pair production. The scheme is scalable, and particularly effective in simulating the theory in weak coupling regime, and also bulk limit of the theory in strong coupling regime up to certain approximations. This paper also presents a numerical benchmark comparison of exact spectrum and real time dynamics of lattice gauge theory to that of the atomic Hamiltonian with experimentally realizable range of parameters.
↳ hep-latcond-mat.quant-gasnucl-thphysics.atom-ph+1PRA(2022)·56 citations
12
Diffractive deeply inelastic scattering in future electron-ion colliders
D. Bendova🇨🇿 · J. Cepila🇨🇿 · J. G. Contreras🇨🇿 · V. P. Goncalves🇧🇷 · M. Matas🇨🇿
The impact of nonlinear effects in the diffractive observables that will be measured in future electron-ion collisions is investigated. We present, for the first time, the predictions for the diffractive structure function and reduced cross sections derived using the solution to the Balitsky--Kovchegov equation with the collinearly-improved kernel and including the impact-parameter dependence. We demonstrate that the contribution of the diffractive events is enhanced in nuclear collisions and that the study of the ratio between the nuclear and proton predictions will be useful to discriminate among different models of the dipole-target scattering amplitude and, consequently, will allow us to constrain the description of QCD dynamics in parton densities.
↳ hep-phnucl-thEPJC(2021)·22 citations
13
Deconfinement critical point of lattice QCD with $N_{f} = 2$ Wilson fermions
Francesca Cuteri🇩🇪 · Owe Philipsen🇩🇪 · Alena Schön🇩🇪 · Alessandro Sciarra🇩🇪
The $SU (3)$ pure gauge theory exhibits a first-order thermal deconfinement transition due to spontaneous breaking of its global $Z_{3}$ center symmetry. When heavy dynamical quarks are added, this symmetry is broken explicitly and the transition weakens with decreasing quark mass until it disappears at a critical point. We compute the critical hopping parameter and the associated pion mass for lattice QCD with $N_{f} = 2$ degenerate standard Wilson fermions on $N_{τ} \in {6, 8, 10}$ lattices, corresponding to lattice spacings $a = 0.12 fm$ , $a = 0.09 fm$ , $a = 0.07 fm$ , respectively. Significant cut-off effects are observed, with the first-order region growing as the lattice gets finer. While current lattices are still too coarse for a continuum extrapolation, we estimate $m_{π}^{c} \approx 4 GeV$ with a remaining systematic error of $\sim 20%$ . Our results allow to assess the accuracy of the LO and NLO hopping expanded fermion determinant used in the literature for various purposes. We also provide a detailed investigation of the statistics required for this type of calculation, which is useful for similar investigations of the chiral transition.
↳ hep-lathep-phnucl-thPRD(2021)·51 citations
14
Cone-size dependent jet spectrum in heavy-ion collisions
Yacine Mehtar-Tani🇳🇴 · Daniel Pablos🇺🇸 · Konrad Tywoniuk🇳🇴
Jets in the vacuum correspond to multi-parton configurations that form via a branching process sensitive to the soft and collinear divergences of QCD. In heavy-ion collisions, energy loss processes that are stimulated via interactions with the medium, affect jet observables in a profound way. Jet fragmentation factorizes into a three-stage process, involving vacuum-like emissions above the medium scale, induced emissions enhanced by the medium length and, finally, long-distance vacuum-like fragmentation. This formalism leads to a novel, non-linear resummation of jet energy loss. In this talk we present new results on the combined effects of small- $R$ resummation and energy loss to compute the $R$ -dependent jet spectrum in heavy-ion collisions.
↳ hep-phnucl-thPoS(2021)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE