Heavy Quark Distribution Functions from QCD

Abstract

The structure function of a heavy quark in a heavy hadron in electroproduction is calculated from QCD. Its deviation from the parton model prediction (a delta function) is shown to be governed by a shape function, similar to the one recently proposed by Neubert and Bigi {\em et al.} to describe the end-point behaviour of the lepton spectrum in semileptonic $B\to X_{u}e\bar{\nu }$ decays and the line shape in $B\to X_s\gamma$. Two new sum rules are derived which extend the Bjorken-Dunietz-Taron sum rule by including corrections suppressed by the inverse heavy quark mass.

Comments: 19 pages+1 figure LaTeX, MZ-TH/94-03