ar X iv : h ep - p h / 93 12 25 7 v 2 2 6 D ec 1 99 3 The ACCMM Model and the Heavy Quark Expansion ∗ Csaba Csáki and

The ACCMM model predicts the lepton spectrum from B meson decay by assuming the meson disintegrates into a spectator quark of definite mass and momentum distribution and an off shell b quark whose decay leptons (boosted into the rest frame of the meson) determine the lepton spectrum. In this letter, we show that one can define a model dependent b quark mass so that the spectrum derived from the ACCMM model agrees very well with the free quark decay spectrum far from the endpoint. Near the endpoint, there is some disagreement, indicating the result is more model dependent. The integrated spectra are however very nearly identical. These results are in accordance with expectations based on the heavy quark effective theory. We conclude that for LEP experiments, free quark decay might be as general This work is supported in part by funds provided by the U.S. Department of Energy (DOE) under contract #DE-AC02-76ER03069 and in part by the Texas National Research Laboratory Commission under grant #RGFY92C6. National Science Foundation Young Investigator Award. Alfred P. Sloan Foundation Research Fellowship. Department of Energy Outstanding Junior Investigator Award. CTP#2262, hep-ph/9312257 December 1993 and more simple than the ACCMM ansatz for modeling the inclusive charged lepton spectrum from B meson decay.