<p>In this work, the perturbative and nonperturbative contributions to the heavy quark (HQ) momentum (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>κ</mi></math>) as well as spatial (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>D</mi><mi>s</mi></msub></math>) diffusion coefficients are computed in a weak background magnetic field. The formalism adopted here involves calculation of the in-medium potential of the HQ in a weak magnetic field, which then serves as a proxy for the resummed gluon propagator in the calculation of HQ self-energy (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi></math>). The self-energy determines the scattering rate of HQs with light thermal partons, which is subsequently used to evaluate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>κ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>D</mi><mi>s</mi></msub></math>. It is observed that nonperturbative effects play a dominant role at low temperature. The spatial diffusion coefficient, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>π</mi><mi>T</mi><msub><mi>D</mi><mi>s</mi></msub></math>, exhibits good agreement with recent lattice QCD results. These findings can be applied to calculate the heavy quark directed flow at RHIC and LHC energies. An extension of this formalism to the case of finite HQ momentum has also been attempted.</p>

India

Debarshi Dey

Romania

Aritra Bandyopadhyay

Santosh K. Das

Sadhana Dash

Vinod Chandra

Basanta K. Nandi

Nonperturbative heavy quark diffusion coefficients in a weakly magnetized thermal QCD medium

We evaluate the heavy quark momentum diffusion coefficients in a hot magnetized medium for the most general scenario of any arbitrary values of the external magnetic field. We choose to work with the systematic way of incorporating the effect of the magnetic field, by using the effective gluon and quark propagators, generalized for a hot and magnetized medium. To get gauge independent analytic form factors valid through all Landau levels, we apply the hard thermal loop technique for the resummed effective gluon propagator. The derived effective hard thermal loop gluon propagator and the generalized version of Schwinger quark propagator subsequently allow us to analytically evaluate the longitudinal and transverse momentum diffusion coefficients for charm and bottom quarks beyond the static limit. Within the static limit we also explore another way of incorporating the effect of the magnetic field, i.e. through the magnetized medium modified Debye mass and compare the results to justify the need for structural changes.

Germany

Heavy quark diffusion coefficients in magnetized quark-gluon plasma

We have estimated parallel and perpendicular components of electrical conductivity and shear viscosity of quark matter at finite magnetic field and temperature by using their one-loop Kubo expressions in the framework of Nambu–Jona-Lasinio (NJL) model. At finite magnetic field, a non-trivial medium dependence of those quantities can be found. Previously these NJL-profiles have been addressed in relaxation time approximation, where cyclotron motion of quarks with medium dependent mass plays the key role. With respect to the earlier estimations, the present work provides further enriched profiles via Kubo framework, where field theoretical descriptions of quark transport with medium dependent mass and (Landau) quantized energy have been identified as the key ingredients. Hence the present study can be considered as the complete quantum field theoretical description of the transport coefficients in the framework of NJL model at finite temperature and magnetic field.

Snigdha Ghosh

Brazil

Ricardo Farias

Sabyasachi Ghosh

Quantum version of transport coefficients in Nambu–Jona-Lasinio model at finite temperature and strong magnetic field

We use the two-flavor Linear Sigma Model with quarks to study the phase structure of isospin asymmetric matter at zero temperature. The meson degrees of freedom provide the mean field chiral and isospin condensates on top of which we compute the effective potential accounting for constituent quark fluctuations at one-loop order. Using the renormalizability of the model, we absorb the ultraviolet divergences into suitable counterterms that are added respecting the original structure of the theory. These counterterms are determined from the stability conditions which require the effective potential to have minima in the condensates directions at the classical values, as well as the transition from the noncondensed to the condensed phase to be smooth as a function of the isospin chemical potential. We use the model to study the evolution of the condensates as well as the pressure, energy and isospin densities and the sound velocity as functions of the isospin chemical potential. The approach does a good average description up to isospin chemical potentials values not too large as compared to the vacuum pion mass.

Mexico

South Africa

Alejandro Ayala

China

Ricardo L. S. Farias

L. A. Hernández

Spain

José Luis Hernández

QCD equation of state at finite isospin density from the linear sigma model with quarks: The cold case

The heavy quark momentum diffusion coefficient (κ) is one of the most essential ingredients for the Langevin description of heavy quark dynamics. In the temperature regime relevant to the heavy ion collision phenomenology, a substantial difference exists between the lattice estimations of κ and the corresponding leading order (LO) result from the hard thermal loop (HTL) perturbation theory. Moreover, the indication of poor convergence in the next-to-leading order (NLO) perturbative analysis has motivated the development of several approaches to incorporate the non-perturbative effects in the heavy quark phenomenology. In this work, we estimate the heavy quark diffusion coefficient based on the Gribov-Zwanziger prescription. In this framework, the gluon propagator depends on the temperature-dependent Gribov mass parameter, which has been obtained self-consistently from the one-loop gap equation. Incorporating this modified gluon propagator in the analysis, we find a reasonable agreement with the existing lattice estimations of κ within the model uncertainties.

Sadaf Madni

Canada

Arghya Mukherjee

Najmul Haque

Estimation of the diffusion coefficient of heavy quarks in light of Gribov-Zwanziger action

In the present work, we have studied heavy quarkonia potential in hot and magnetized quark gluon plasma. Inverse magnetic catalysis (IMC) effect is incorporated within the system through the magnetic field modified Debye mass by modifying the effective quark masses. We have obtained the real and imaginary part of the heavy quark potential in this new scenario. After the evaluation of the binding energy and the decay width we comment about the dissociation temperatures of the heavy quarkonia in presence of magnetic field.

Indrani Nilima

Ritesh Ghosh

Heavy quark potential and LQCD based quark condensate at finite magnetic field

We investigate the effects of including strong <math><mrow><mi>C</mi><mi>P</mi></mrow></math> violating effects through axion fields in the microscopic equation of state of massive hybrid neutron stars. We assume that their cores contain deconfined quark matter and include the effects of axions via an effective ‘t Hooft determinant interaction. The hadronic crusts are described using different approaches in order to make our results more general. We find that the presence of axions stabilizes massive hybrid neutron stars against gravitational collapse by weakening the deconfinement phase transition and bringing it to lower densities. This enables to reproduce hybrid neutron stars in agreement with modern astrophysical constraints.

Bruno S. Lopes

United States

Veronica Dexheimer

Rudnei O. Ramos

Axion effects in the stability of hybrid stars

In this article, we have explored the very important quantity of lepton pair production from a hot and dense QCD medium in presence of an arbitrary external magnetic field for simultaneous nonzero values of both the parallel (along the direction of the external field) and perpendicular (lying on the transverse plane to the external field) components of the dilepton momentum. As opposed to the zero magnetic field case (the so-called Born rate) or the lowest Landau level approximated rate, where only the annihilation process contributes, here we observe contributions also arising out of the quark and antiquark decay processes. We found the encouraging result of considerable enhancement of lepton pair production in presence of an arbitrary magnetic field. We decompose the total rate into different physical processes and discuss their behaviors for both zero and nonzero baryon density. The whole analysis is then subjected to an effective model treatment, where we have incorporated the magnetic field induced novel effects of magnetic catalysis (MC) and inverse MC (IMC) through a medium dependent scalar coupling, which leads to some further interesting observations.

Aritra Das

Chowdhury Aminul Islam

Lepton pair production from a hot and dense QCD medium in the presence of an arbitrary magnetic field

In this work we have explored the imaginary part of the heavy quark potential and subsequently the dissociation of heavy quarkonia at finite temperature and in a magnetic field. With respect to earlier investigations on this topic, the present work contains three new ingredients. The first one is considering all Landau level summations, for which the present work can be applicable in the entire magnetic field domain—from weak to strong. The second one is the general structure of the gauge boson propagator in a hot magnetized medium, which is used here in the heavy quark potential problem for the first time. The third one is a rich anisotropic structure of the complex heavy quark potential, which explicitly depends on the longitudinal and transverse distance. By comparing with earlier references, we have attempted to display our new contributions by plotting heavy quark potential tomography and dissociation probability at finite temperature and in a magnetic field.

Anisotropic tomography of heavy quark dissociation by using the general propagator structure in a finite magnetic field

We present a calculation of the heavy quark momentum diffusion coefficients in a quark-gluon plasma under the presence of a strong external magnetic field, within the lowest Landau level (LLL) approximation. In particular, we apply the hard thermal loop (HTL) technique for the resummed effective gluon propagator, generalized for a hot and magnetized medium. Using the derived effective HTL gluon propagator and the LLL quark propagator we analytically derive the full results for the longitudinal and transverse momentum diffusion coefficients for charm and bottom quarks beyond the static limit. We also show numerical results for these coefficients in two special cases where the heavy quark is moving either parallel or perpendicular to the magnetic field.

Jinfeng Liao

Hongxi Xing

Heavy quark dynamics in a strongly magnetized quark-gluon plasma