Unconventional Mechanisms of Heavy Quark Fragmentation

Abstract

Heavy and light quarks produced in high-pT 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 qq¯ dipole, which survives in the medium due to color transparency, a heavy–light Qq¯ 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 Qq¯ mesons, differently from the case of light qq¯ meson production.

Keywords

• quarks
• jets
• fragmentation
• hadronization