arXiv subjects

Santosh K. Das

Publications and source records attributed to Santosh K. Das.

At least 19 recordsLinked to original sources

arXiv2026

Directed flow of D and B mesons in an electrically and chirally conductive QGP at LHC energies

We investigate the directed flow of D and B mesons in the presence of electromagnetic fields incorporating finite electrical and chiral conductivities at LHC energies. The momentum evolution of heavy quarks in the quark-gluon plasma (QGP) is studied using Langevin dynamics, with their interactions with the medium described within the extended quasiparticle model (QPMp) framework. The electromagnetic fields are obtained from analytical solutions of Maxwell equations that account for both electrical and chiral conductivities. These conductivities modify the space-time evolution of the electromagnetic fields and influence the splitting of the directed flow between mesons and anti-mesons. However, the influence of chiral conductivity remains secondary to that of electrical conductivity and its impact on the directed flow is marginal. The results show that heavy mesons containing a charm quark develop a directed flow with a sign opposite to that of heavy mesons containing a bottom quark, with a smaller magnitude for the latter. The present study indicates that a simultaneous experimental measurement of v1 for heavy mesons containing both charm and bottom quarks would provide valuable insight into the electromagnetic field origin of v1 for heavy quarks.

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arXiv2026

Diffractive Production of Heavy Quarkonia at the Electron Ion Collider

We study diffractive photo- and electroproduction of the $S$-wave heavy quarkonia $J/ψ$, $ψ(2S)$, and $Υ(nS)$ at energies relevant for the Electron-Ion Collider (EIC). The production amplitude is evaluated while retaining the full transverse-momentum ($\ell_t$) dependence of the hard two-gluon kernel, that is, without expanding the impact-parameter Bessel kernel as is done in the small-size color-dipole limit. The quarkonia light-cone wave functions are built from Cornell-potential solutions of the Schrödinger equation, normalized to the measured leptonic widths, and combined with a modern collinear gluon distribution. After benchmarking the framework against the full set of HERA charmonium cross-section ratio data, we provide a consistent set of bottomonium cross-section ratio predictions in EIC kinematics. We find that the full $\ell_t$-resolved treatment systematically improves the description of the radially excited states relative to the leading dipole limit, and we identify the kinematic windows where this difference is largest.

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arXiv2026

Probing collective behaviour of Heavy Quarks through $p_T$-differential radial flow $v_0(p_T)$

We discuss the $p_T$-differential radial flow $v_0(p_T)$ of charmed hadrons within a Langevin dynamics coupled to relativistic Boltzmann transport approach in an event-by-event basis. We propose heavy flavour $v_0(p_T)$ as a novel observable to probe the strength of the interaction of heavy quarks with the expanding Quark-Gluon Plasma. By comparing different temperature dependence for the spatial diffusion coefficient $D_s(T)$ we show that the $v_0(p_T)$ keep a strong sensitivity to the heavy-quark transport coefficients at intermediate $p_T$. At low $p_T$, the observable is also sensitive to hadronization where we observe a larger $v_0(p_T)$ for $Λ_c$ baryons than for $D$ mesons.

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arXiv2026

Non-Markovian heavy-quark equilibration and equilibrium correlation function in a thermal medium

We compute the charm-quark current-current correlation function within the Langevin framework and extract the heavy-quark diffusion coefficient using the Green--Kubo formula. The formalism is further extended to evaluate the correlation function using a generalized Langevin equation that incorporates memory effects via an exponentially decaying memory kernel. We find that while memory effects qualitatively modify the transient structure of the current correlations, the value of the transport coefficient remains unchanged in the non-relativistic limit. In addition, we investigate heavy-quark thermalization in the presence of memory and compare the non-equilibrium solution of a generalized Fokker--Planck equation with the one obtained from the generalized Langevin equation in the non-relativistic limit. We also consider the relativistic version of the correlated noise case and observe that memory effects can give rise to a damped, oscillatory equilibration of the heavy quark in a non-Markovian bath.

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arXiv2026

Non-perturbative heavy quark diffusion coefficients in arbitrarily magnetized quark-gluon plasma

Heavy quark (HQ) momentum ($κ$) and spatial diffusion ($D_s$) coefficients are computed in a non-perturbative thermal QCD medium in the presence of a background magnetic field of arbitrary strength. Both perturbative and non-perturbative effects are incorporated via the in-medium HQ potential, obtained from the resummed gluon propagator. We find that the momentum diffusion coefficients become anisotropic even in the static heavy quark limit, with the magnetic field direction defining the axis of anisotropy. This anisotropy originates from restrictions on longitudinal momentum diffusion in the gluon spectral function, and naturally leads to two spatial diffusion coefficients ($D_s^L$, $D_s^T$). Non-perturbative effects are found to be dominant at low temperatures. These results provide a more consistent input for Langevin based calculations of the heavy quark directed flow at RHIC and LHC energies.

hep-ph↗

arXiv2026

Charmonium suppression in fixed target proton-nucleus collisions

In this article, we perform a systematic investigation of the cold nuclear matter (CNM) effects, operative on charmonium ($J/ψ$, $ψ(2S)$) production, in fixed target proton-nucleus (p+A) collisions. Influence on charmonium production cross section due to the interplay of three different plausible CNM effects namely the initial-state parton energy loss, nuclear shadowing, and final-state absorption of the resonant states, are evaluated in detail. The available data on charmonium production in fixed target p+A collision experiments from SPS, Fermilab and HERA-B are examined for this purpose. The beam energy dependence of the observed $J/ψ$ production patterns are utilized to anticipate level of "normal" absorption in the upcoming proton induced collisions by the NA60+ experiment at CERN SPS and the CBM experiment at FAIR SIS100 accelerator facilities.

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arXiv2025

Probing the QGP through $p_T$-differential radial flow of heavy quarks

We introduce the $p_T$-differential radial flow $v_0(p_T)$ in the heavy-quark sector. Within an event-by-event Langevin framework, we show that this observable exhibits a strong sensitivity to the heavy quark-bulk interaction. It provides a powerful and novel tool to constrain the transport coefficients of heavy quarks in the QGP and, more generally, to assess the strength of the interaction of a Brownian particle in an expanding bulk medium. The results further indicate that heavy quarks exhibit collective behavior driven by the isotropic expansion of the QGP in heavy-ion collisions and, at low $p_T$, it offers a marked signature of the heavy quark hadronization mechanism.

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arXiv2025

The influence of electromagnetic fields on the generation of the directed and elliptic flows of heavy quark in relativistic heavy-ion collisions

We study the impact of self-generated electromagnetic fields (EMF) on the charm quarks momentum evolution in the partonic and hadronic medium created in heavy-ion collisions at RHIC energy within the Parton-Hadron-String Dynamics (PHSD) off-shell transport approach. In the quark-gluon plasma (QGP) phase, the charm quark interacts with the off-shell partons whose mass and widths are given by the Dynamical Quasi-Particle Model (DQPM), which can reproduce the lattice QCD thermodynamics. The background electromagnetic fields are computed dynamically within the PHSD considering both the spectators and participants protons as well as newly produced charged hadrons, quarks, and antiquarks, which reflects naturally the electric conductivity $σ_{el}$ of the medium. We study the directed and elliptic flow of the $D$ mesons in the presence of the electromagnetic fields. We find that electromagnetically induced splitting in the $D$ meson $v_1$ through $D^0$ and $\overline{D}^0$ mesons is consistent with the experimental data. Furthermore, we notice that the splitting in the heavy quark $v_1$ as a function of $p_T$ is more prominent as a probe of the produced electromagnetic fields. However, we find only a small impact of electromagnetic fields on the heavy quark elliptic flow $v_2$.

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arXiv2025

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

In this work, the perturbative and non-perturbative contributions to the heavy quark (HQ) momentum ($κ$) as well as spatial ($D_s$) 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 ($Σ$). The self-energy determines the scattering rate of HQs with light thermal partons, which is subsequently used to evaluate $κ$ and $D_s$. It is observed that non-perturbative effects play a dominant role at low temperature. The spatial diffusion coefficient $2πT D_s$, exhibits good agreement with recent LQCD 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.

hep-ph↗

arXiv2025

Charm and Bottom Hadrons in Hot Hadronic Matter

Heavy quarks, and the hadrons containing them, are excellent probes of the QCD medium formed in high-energy heavy-ion collisions, as they provide essential information on the transport properties of the medium and how quarks color-neutralize into hadrons. Large theoretical and phenomenological efforts have been dedicated thus far to assess the diffusion of charm and bottom quarks in the quark-gluon plasma and their subsequent hadronization into heavy-flavor (HF) hadrons. However, the fireball formed in heavy-ion collisions also features an extended hadronic phase, and therefore any quantitative analysis of experimental observables needs to account for the rescattering of charm and bottom hadrons. This is further reinforced by the presence of a QCD cross-over transition and the notion that the interaction strength is maximal in the vicinity of the pseudo-critical temperature. We review existing approaches for evaluating the interactions of open HF hadrons in a hadronic heat bath and the pertinent results for scattering amplitudes, spectral functions and transport coefficients. While most of the work to date has focused on $D$-mesons, we also discuss excited states as well as HF baryons and the bottom sector. Both the HF hadro-chemistry and bottom observables will play a key role in future experimental measurements. We also conduct a survey of transport calculations in heavy-ion collisions that have included effects of hadronic HF diffusion and assess its impact on various observables.

hep-ph↗

arXiv2025

A systematic study of initial state quark energy loss in fixed target proton nucleus collision

In this article, we investigate parton energy loss in cold nuclear matter by studying the ratio of Drell-Yan production cross sections in fixed-target proton-nucleus (p + A) collisions. We analyze Drell-Yan production cross-section data from the Fermilab E866 and E906 experiments using two different quark energy loss parametrization models and various parton distribution functions for 800 GeV and 120 GeV proton beams incident on light and heavy nuclear targets. The sensitivity of the energy loss parameter on the employed parton distribution function has been thoroughly investigated. Our results have been used to predict the target mass dependence of Drell-Yan production in upcoming proton-induced collisions at SPS and FAIR.

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arXiv2025

Dynamics of Hot QCD Matter 2024 -- New facilities and instrumentation

This part of the conference proceeding provides a detailed overview of cutting-edge advancements in detector technologies, focusing on their optimization, characterization, and applications in particle physics experiments. Building on the insights and developments presented at the Hot QCD Matter 2022 conference, this section of the Hot QCD Matter 2024 proceedings highlights significant advancements in detector technologies. The development of Low Gain Avalanche Diodes (LGADs) into Ultra-Fast Silicon Detectors is explored, demonstrating their potential for superior timing resolution in future high-energy experiments. Simulation studies of Micropattern Gaseous Detectors (MPGDs), including MICROMEGAS and Gas Electron Multiplier (GEM) detectors, provide insights into their performance under high-radiation environments using tools like ANSYS and GARFIELD$^{++}$. A novel GEM foil geometry is proposed for improved gain and durability. Characterization of semiconductor detectors, such as Monolithic MALTA pixel detectors and CMS prototype silicon sensors, is also presented, highlighting their radiation tolerance, imaging capabilities, and structural integrity. These studies underscore the critical role of silicon sensors in ensuring detector reliability and performance. Additionally, the J-PARC muon g-2/EDM experiment is reviewed, showcasing its precision measurements to test Standard Model predictions and explore potential physics beyond. By addressing the interplay between detector development, simulation, and characterization, this proceeding showcases a collective effort toward advancing detector technologies and their pivotal role in pushing the boundaries of modern particle physics.

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arXiv2024

Dynamics of Hot QCD Matter 2024 -- Hard Probes

The hot and dense QCD matter, known as the Quark-Gluon Plasma (QGP), is explored through heavy-ion collision experiments at the LHC and RHIC. Jets and heavy flavors, produced from the initial hard scattering, are used as hard probes to study the properties of the QGP. Recent experimental observations on jet quenching and heavy-flavor suppression have strengthened our understanding, allowing for fine-tuning of theoretical models in hard probes. The second conference, HOT QCD Matter 2024, was organized to bring the community together for discussions on key topics in the field. This article comprises 15 sections, each addressing various aspects of hard probes in relativistic heavy-ion collisions, offering a snapshot of current experimental observations and theoretical advancements. The article begins with a discussion on memory effects in the quantum evolution of quarkonia in the quark-gluon plasma, followed by an experimental review, new insights on jet quenching at RHIC and LHC, and concludes with a machine learning approach to heavy flavor production at the Large Hadron Collider.

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arXiv2024

Dynamics of Hot QCD Matter 2024 -- Bulk Properties

The second Hot QCD Matter 2024 conference at IIT Mandi focused on various ongoing topics in high-energy heavy-ion collisions, encompassing theoretical and experimental perspectives. This proceedings volume includes 19 contributions that collectively explore diverse aspects of the bulk properties of hot QCD matter. The topics encompass the dynamics of electromagnetic fields, transport properties, hadronic matter, spin hydrodynamics, and the role of conserved charges in high-energy environments. These studies significantly enhance our understanding of the complex dynamics of hot QCD matter, the quark-gluon plasma (QGP) formed in high-energy nuclear collisions. Advances in theoretical frameworks, including hydrodynamics, spin dynamics, and fluctuation studies, aim to improve theoretical calculations and refine our knowledge of the thermodynamic properties of strongly interacting matter. Experimental efforts, such as those conducted by the ALICE and STAR collaborations, play a vital role in validating these theoretical predictions and deepening our insight into the QCD phase diagram, collectivity in small systems, and the early-stage behavior of strongly interacting matter. Combining theoretical models with experimental observations offers a comprehensive understanding of the extreme conditions encountered in relativistic heavy-ion and proton-proton collisions.

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arXiv2024

$c {\bar c}$ and $b {\bar b}$ suppression in Glasma

This study investigates the evolution and dissociation dynamics of $c\bar{c}$ and $b\bar{b}$ pairs within the pre-equilibrium, gluon-dominated stage of high energy nuclear collisions. An attractive potential made of a perturbative Coulomb-like term and of a confining term is used to simulate the attractive strong force in the pairs. Besides, we implement the interaction of the pairs with the evolving Glasma fields by virtue of the Wong equations. The interaction with the classical color fields dominates the dynamics, causing an increase in pair separation and subsequent dissociation. The observed finite probability of dissociation for these states reveals the intricate interplay between QCD dynamics and the suppression of $c\bar{c}$ and $b\bar{b}$ states during the pre-equilibrium stage. The research highlights differences between $c\bar{c}$ and $b\bar{b}$ pairs, revealing the role of quark flavor in the dissociation process. Dissociation spectra analysis indicates a peak shift towards higher momentum, reflecting a slight energy gain by the pairs. This investigation provides valuable insights into the complex dynamics of $c\bar{c}$ and $b\bar{b}$ pairs in the Glasma, which may help in better interpretation of experimental results on further integration with subsequent phases of the created matter.

hep-ph↗

arXiv2024

B-mesons as essential probes of hot QCD matter

This article elucidates the pivotal role of b-mesons and bottomonium states in exploring the existence and properties of hot QCD matter (commonly known as quark-gluon-plasma (QGP) produced within the crucible heavy-ion collision experiments). Owing to the complex and confounding nature of strong interaction force the direct detection of probing the hot QCD matter is not feasible. In light of this, investigating the dynamics of b-quarks and anti-quarks within the hot QCD medium emerges as an invaluable indirect probe. The impact of b-quarks and the mesons spans a spectrum of interesting domains regarding the physics of QCD at finite temperature, encompassing the QCD phase transition, color screening, quarkonia dissociation, heavy quark energy loss and collective flow, anisotropic aspects, and strongly coupled nature of hot QCD medium. These aspects underscore the indispensable nature of B-mesons in the quest to create and explore the complex nature of strong interaction force through the QGP/hot QCD matter. In this context, we mainly focus on works related to transport studies of b-mesons in hot QCD medium, lattice QCD, and effective field theory studies on bottomonium states, and finally, open quantum system frameworks to quarkonia to explore the properties of hot QCD medium in relativistic heavy-ion collision experiments.

hep-ph↗

arXiv2023

Heavy quark radiation in an anisotropic hot QCD medium

The impact of momentum anisotropy on the heavy quarks (HQs) dynamics has been investigated in a hot QCD medium while considering both collisional and radiative processes within the ambit of the Fokker-Planck approach. The relative orientation of the HQs motion (momentum vector) with respect to the direction of anisotropy is responsible for the character of transport coefficients. Therefore, the drag and diffusion coefficients of the HQs are decomposed, respectively, into two and four components by considering a general tensor basis. Each component of the drag and diffusion coefficient of the HQs has been analyzed in detail. It is observed that the anisotropy has a significant impact on the transport coefficients of the HQ for both the collisional and the radiational processes. The nuclear suppression factor, $R_{AA}$, has been computed considering the anisotropic medium. It is observed that the momentum anisotropy affects the $R_{AA}$ of the HQs significantly in both elastic and inelastic cases.

hep-ph↗

arXiv2023

Open heavy flavors: Theory

A brief overview of the theory of open heavy flavor dynamics in QCD matter produced in high energy heavy-ion collisions is presented. First, we will summarise the phenomenological efforts to estimate the heavy quark diffusion coefficients obtained within different models. Then, the recent theoretical developments from different groups to probe the medium properties using heavy quarks will be presented. Heavy quarks are also considered as an ideal probe for the initial stage of heavy-ion collisions. In the end, we present the recent theoretical progress made to probe the early-stage effects, pre-equilibrium phase, and electromagnetic fields.

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