Spin relaxation of heavy quarks from momentum diffusion in the quark-gluon plasma
Abstract
Heavy-quark spin dynamics in the quark-gluon plasma provides a potential probe of the interaction between heavy quarks and the medium. We develop a stochastic framework in which the random momentum kicks responsible for heavy-quark diffusion also induce spin rotation through Thomas precession. Starting from the Thomas-Bargmann-Michel-Telegdi equation and a Langevin equation for heavy-quark momentum, we derive a novel coupled spin-momentum Fokker-Planck equation. In the heavy-quark limit, where momentum equilibrates faster than spin, the momentum degrees of freedom can be integrated out, yielding a rotational Fokker-Planck equation for the spin orientation. This establishes a direct relation between the Thomas precession contribution to the spin-relaxation time τs and the heavy-quark momentum-diffusion coefficient κ. In the non-relativistic limit, we find τs=2τp(mQ/T)2, with τp being the momentum relaxation time. Using recent determinations of κ from lattice QCD, strong-coupling estimates, T-matrix calculations, and heavy-flavor phenomenology, we obtain the corresponding Thomas precession contribution to spin relaxation times for charm and bottom quarks. Relativistic kinematics modify the result by only a modest amount over the temperature range relevant for heavy-ion collisions, while the uncertainty is dominated by that of κ. We emphasize that the result represents the Thomas precession contribution to heavy-quark spin relaxation; direct coupling to the chromomagnetic field provides an additional channel.
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BibTeX
@misc{kumar2026spin,
title = {{Spin relaxation of heavy quarks from momentum diffusion in the quark-gluon plasma}},
author = {Ankit Kumar and Sourav Dey and Vinod Chandra and Amaresh Jaiswal},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01791},
eprint = {2610.01791},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01791},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Spin relaxation of heavy quarks from momentum diffusion in the quark-gluon plasma
AU - Ankit Kumar
AU - Sourav Dey
AU - Vinod Chandra
AU - Amaresh Jaiswal
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.01791
UR - https://arxiv.org/abs/2610.01791
AB - Heavy-quark spin dynamics in the quark-gluon plasma provides a potential probe of the interaction between heavy quarks and the medium. We develop a stochastic framework in which the random momentum kicks responsible for heavy-quark diffusion also induce spin rotation through Thomas precession. Starting from the Thomas-Bargmann-Michel-Telegdi equation and a Langevin equation for heavy-quark momentum, we derive a novel coupled spin-momentum Fokker-Planck equation. In the heavy-quark limit, where momentum equilibrates faster than spin, the momentum degrees of freedom can be integrated out, yielding a rotational Fokker-Planck equation for the spin orientation. This establishes a direct relation between the Thomas precession contribution to the spin-relaxation time τ_s and the heavy-quark momentum-diffusion coefficient κ. In the non-relativistic limit, we find τ_s=2τ_p(m_Q/T)^2, with τ_p being the momentum relaxation time. Using recent determinations of κ from lattice QCD, strong-coupling estimates, T-matrix calculations, and heavy-flavor phenomenology, we obtain the corresponding Thomas precession contribution to spin relaxation times for charm and bottom quarks. Relativistic kinematics modify the result by only a modest amount over the temperature range relevant for heavy-ion collisions, while the uncertainty is dominated by that of κ. We emphasize that the result represents the Thomas precession contribution to heavy-quark spin relaxation; direct coupling to the chromomagnetic field provides an additional channel.
ER -