Unconventional mechanisms of heavy quark fragmentation

TL;DR

This paper explores the unique mechanisms of heavy quark fragmentation, highlighting how their rapid color field regeneration and large dipole expansion influence jet shapes and meson production in high-energy collisions.

Contribution

It introduces a novel understanding of heavy quark fragmentation dynamics, emphasizing the role of the dead-cone effect and dipole expansion in dense media.

Findings

Heavy quarks radiate less energy than light quarks due to faster color field regeneration.

Heavy-light mesons carry most of the jet momentum, evidenced by fragmentation functions peaking at high z.

Large $Q\bar q$ dipoles are unlikely to survive in dense media, affecting meson production rates.

Abstract

Heavy and light quarks produced in high-$p_T$ partonic collisions radiate differently. Heavy quarks regenerate their color field, stripped-off in the hard reaction, much faster than the light ones and radiate a significantly smaller fraction of the initial quark energy. This peculiar feature of heavy-quark jets leads to a specific shape of the fragmentation functions observed in $e^+e^-$ annihilation. Differently from light flavors, the heavy quark fragmentation function strongly peaks at large fractional momentum $z$, i.e. the produced heavy-light mesons, $B$ or $D$, carry the main fraction of the jet momentum. This is a clear evidence of the dead-cone effect, and of a short production time of a heavy-light mesons. Contrary to propagation of a small $q\bar q$ dipole, which survives in the medium due to color transparency, a heavy-light $Q\bar q$ dipole promptly expands to a large size. Such a big dipole has no chance to remain intact in a dense medium produced in relativistic heavy ion collisions. On the other hand, a breakup of such a dipole does not affect much the production rate of $Q\bar q$ mesons, differently from the case of light $q\bar q$ meson production.