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Rotational Brownian motion and heavy quark polarization in QCD medium

Sourav Dey, Amaresh Jaiswal

Abstract

We consider the rotational Brownian motion of heavy quark in QCD medium and provide analytical results for polarization of open heavy-flavor hadrons. We calculate expressions for vector and tensor polarization, corresponding to baryon spin polarization and vector meson spin alignment, respectively. Assuming that heavy quarks are initially fully spin polarized along the direction of magnetic field, we compare our results with recent experimental data from ALICE collaboration for $D^{*+}$ meson and provide predictions for spin polarization of open charm baryons. We propose that the transverse momentum dependence of heavy quark polarization may serve as a distinctive signature of the intense initial magnetic field generated in off-central relativistic heavy-ion collisions.

Rotational Brownian motion and heavy quark polarization in QCD medium

Abstract

We consider the rotational Brownian motion of heavy quark in QCD medium and provide analytical results for polarization of open heavy-flavor hadrons. We calculate expressions for vector and tensor polarization, corresponding to baryon spin polarization and vector meson spin alignment, respectively. Assuming that heavy quarks are initially fully spin polarized along the direction of magnetic field, we compare our results with recent experimental data from ALICE collaboration for meson and provide predictions for spin polarization of open charm baryons. We propose that the transverse momentum dependence of heavy quark polarization may serve as a distinctive signature of the intense initial magnetic field generated in off-central relativistic heavy-ion collisions.

Paper Structure

This paper contains 6 sections, 35 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Rotational Brownian motion
  3. Heavy quark polarization
  4. Summary and outlook
  5. Fluctuations in the thermal term
  6. Averaging over heavy-quark velocity

Figures (1)

  • Figure 1: The ALICE measurements of the spin alignment parameter $\rho_{00}$ for the $D^{*+}$ meson are presented as a function of transverse momentum ALICE:2025cdf. Our best-fit result for $\rho_{00}$, obtained using Eq. \ref{['vec_ten_pol']}, is shown. We also show predictions for polarization of open-charmed baryons, expressed as $|\langle \cos\theta \rangle|$. The inset illustrates the spin-relaxation time in the lab frame as a function of $p_T$. The shaded regions indicates the rapidity window of the experimental measurement, $0.3 < |y| < 0.8$.