The Baffling Semileptonic Branching Ratio of $B$ Mesons

Abstract

The apparent gap between the measured and the expected value for the semileptonic branching ratio of $B$ mesons has become more serious over the last year. This is due to the improved quality of the data and to the increasing maturity of the theoretical treatment of non-perturbative corrections. We discuss various theoretical options to reduce the semileptonic $B$ branching ratio; among the more spectacular resolutions of the apparent puzzle is the possibility of an unorthodox enhancement in non-perturbative corrections or even of an intervention by `New Physics'. Phenomenological implications of such scenarios are pointed out.

Comments: 16 Latex pages; 4 figures to be obtained from I.Bigi; preprint CERN-TH.7082/93; some misprints in the original version have been corrected and some references added