Nuclear Theory·nucl-th

Tuesday·April 16, 2024

14 papers—9 primary·5 cross-listed

10
Hard Thermal Loop -- theory and applications
Najmul Haque🇮🇳 · Munshi G. Mustafa🇮🇳
In this review, we present the key aspects of modern thermal perturbation theory based on the hard thermal loop (HTL) approximation, including its theoretical foundations and applications within quantum electrodynamics (QED) and quantum chromodynamics (QCD) plasmas. To maintain conciseness, we focus on scenarios in thermal equilibrium, examining a variety of physical quantities and settings. Specifically, we explore both bulk thermodynamic properties and real-time observables in high-temperature domains relevant to heavy-ion physics.
↳ hep-phhep-latnucl-thPPNP(2025)·28 citations
11
Study of transport properties of a hot and dense QCD matter using a novel approximation method
Anowar Shaikh🇮🇳 · Shubhalaxmi Rath🇨🇱 · Sadhana Dash🇮🇳 · Binata Panda🇮🇳
We have studied the charge and the heat transport properties of a hot and dense QCD matter by solving the relativistic Boltzmann transport equation using a novel approximation method. Following the recently developed novel relaxation time approximation (RTA) model, we have proposed a novel Bhatnagar-Gross-Krook (BGK) model with a modified collision integral to carry out the aforementioned study. We have also compared our findings with the results of the novel RTA, the standard RTA and the standard BGK models. Our observation shows that the novel collision integrals for both the RTA and BGK models decrease the charge and the heat transport phenomena in the medium, as evidenced by the reduced values of the transport coefficients, such as the electrical conductivity and the thermal conductivity, when compared to the standard RTA and standard BGK models. Furthermore, certain observables, such as the thermal diffusion constant and the Lorenz number have been explored using the novel approaches of the aforesaid models. We have found an overall decreasing trend of the thermal diffusion constant with the temperature in the novel BGK model, similar to the novel RTA model, but the magnitude remains higher throughout the temperature range. However, the magnitude of the thermal diffusion constant in the proposed novel BGK model remains lower than its value in the standard BGK model. The magnitude of the Lorenz number in the novel BGK model remains higher than that in the standard BGK model, but it is lower than that in the novel RTA model. We have also observed that the Lorenz number in all cases has an increasing trend at low temperatures, showing a violation of the Wiedemann-Franz law, whereas at high temperatures, it becomes saturated. The Lorenz number remaining above unity indicates that the thermal conductivity prevails over the electrical conductivity in the aforesaid models.
↳ hep-phhep-thnucl-thJ.Phys.G(2025)·4 citations
12
Upper Limit of Sound Speed in Nuclear Matter: A Harmonious Interplay of Transport Calculation and Perturbative Quantum Chromodynamic Constraint
Shao-Peng Tang🇨🇳 · Yong-Jia Huang🇨🇳 · Ming-Zhe Han🇨🇳 · Yi-Zhong Fan🇨🇳
Very recently, it has been shown that there is an upper bound on the squared sound speed of nuclear matter from the transport, which reads $c_{s}^{2} \leq 0.781$ . In this work, we demonstrate that this upper bound is corroborated by the reconstructed equation of state (EOS; modeled with a nonparametric method) for ultradense matter. The reconstruction integrates multimessenger observation for neutron stars, in particular, the latest radius measurements for PSR J0437-4715 ( $11.3 6_{- 0.63}^{+ 0.95}$ km), PSR J0030+0451 ( $11.7 1_{- 0.83}^{+ 0.88}$ km, in the ST+PDT model), and PSR J0740+6620 ( $12.4 9_{- 0.88}^{+ 1.28}$ km) by NICER have been adopted. The result shows in all cases, the $c_{s}^{2} \leq 0.781$ upper limit for EOS will naturally yield the properties of matter near the center of the massive neutron star consistent with the causality-driven constraint from pQCD, where, in practice, the density in implementing the pQCD likelihood ( $n_{L}$ ) is applied at $10 n_{s}$ (where $n_{s}$ is the nuclear saturation density). We also note that there is a strong correlation for the maximum $c_{s}^{2}$ with $n_{L}$ , and $c_{s}^{2} \leq 0.781$ is somehow violated when $n_{L} = n_{c, TOV}$ . The result indicates that a higher $n_{L}$ , even considering the uncertainties from statistics, is more natural. Moreover, the remarkable agreement between the outcomes derived from these two distinct and independent constraints (i.e., the transport calculation and pQCD boundary) lends strong support to their validity. In addition, the latest joint constraint for $R_{1.4}$ , $R_{2.0}$ , $R_{1.4} - R_{2.0}$ , and $M_{TOV}$ are $11.9 4_{- 0.68}^{+ 0.77}$ km, $11.9 9_{- 0.67}^{+ 0.88}$ km, $- 0. 1_{- 0.27}^{+ 0.42}$ km, and $2.2 4_{- 0.10}^{+ 0.13} M_{⊙}$ (at $90%$ credible level), respectively.
↳ astro-ph.HEnucl-thApJ(2024)·12 citations
13
Electrical conductivity of QGP with quasiparticle quarks and Gribov gluon
Sadaf Madni🇮🇳 · Sumit🇨🇳 · Lata Thakur🇰🇷 · Najmul Haque🇮🇳
We investigate the electrical conductivity of the quark-gluon plasma (QGP) using a non-perturbative resummation scheme incorporating the Gribov-modified gluon propagator. The electrical conductivity is evaluated by solving the relativistic Boltzmann transport equation within the relaxation-time approximation, where the relaxation times are obtained from microscopic two-body scattering amplitudes. A quasiparticle description is employed for quarks, providing a unified framework for studying transport properties across both weakly and strongly coupled regimes. Above the deconfinement transition temperature, we estimate the electrical conductivity of the QGP and compare our results with available lattice QCD data and various phenomenological models, finding good agreement with the lattice results.
↳ hep-phnucl-thEPJC(2026)·10 citations
14
A machine learning-based study of open-charm hadrons in proton-proton collisions at the Large Hadron Collider
Kangkan Goswami🇮🇳 · Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳 · Gagan B. Mohanty🇮🇳
n proton-proton and heavy-ion collisions, the study of charm hadrons plays a pivotal role in understanding the QCD medium and provides an undisputed testing ground for the theory of strong interaction, as they are mostly produced in the early stages of collisions via hard partonic interactions. The lightest open-charm, $D^{0}$ meson ( $c \Bar u$ ), can originate from two separate sources. The prompt $D^{0}$ originates from either direct charm production or the decay of excited open charm states, while the nonprompt stems from the decay of beauty hadrons. In this paper, using different machine learning (ML) algorithms such as XGBoost, CatBoost, and Random Forest, an attempt has been made to segregate the prompt and nonprompt production modes of $D^{0}$ meson signal from its background. The ML models are trained using the invariant mass through its hadronic decay channel, i.e., $D^{0} \to π^{+} K^{-}$ , pseudoproper time, pseudoproper decay length, and distance of closest approach of $D^{0}$ meson, using PYTHIA8 simulated $pp$ collisions at $s = 13 TeV$ . The ML models used in this analysis are found to retain the pseudorapidity, transverse momentum, and collision energy dependence. In addition, we report the ratio of nonprompt to prompt $D^{0}$ yield, the self-normalized yield of prompt and nonprompt $D^{0}$ and explore the charmonium, $J / ψ$ to open-charm, $D^{0}$ yield ratio as a function of transverse momenta and normalized multiplicity. The observables studied in this manuscript are well predicted by all the ML models compared to the simulation.
↳ hep-phhep-exhep-thnucl-ex+1PRD(2024)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE

Hard Thermal Loop -- theory and applications

Study of transport properties of a hot and dense QCD matter using a novel approximation method

Upper Limit of Sound Speed in Nuclear Matter: A Harmonious Interplay of Transport Calculation and Perturbative Quantum Chromodynamic Constraint

Electrical conductivity of QGP with quasiparticle quarks and Gribov gluon

A machine learning-based study of open-charm hadrons in proton-proton collisions at the Large Hadron Collider

Affiliations