On specific QCD properties of heavy quark fragmentation ('dead cone')

It is the restriction on the phase space of emitting gluons connected with the kinematics of a heavy quark Q=c, b, . . . which determines the difference of the QCD jet produced by Q from that of ordinary light (practically massless) quarks q=u, d, s. The authors consider the Q-quark as relativistic (EQ>>MQ, Theta 0 identical to MQ/EQ<<1) and taking care of logarithmic effects ignoring small (power) corrections of the order of Theta 0.

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