Beauty hadron lifetime ratios and the problem of $\tau ({\Lambda }_b)$

Abstract

We describe a theoretical approach to compute inclusive widths of heavy hadrons, based on a systematic expansion in the inverse powers of the heavy quark mass. The method reproduces quite well the experimental ratios of $B$ mesons lifetimes. As for $\tau ({\Lambda }_b)/\tau (B_d)$, we present a QCD sum rule calculation of the $O(m_b^{-3})$ contribution to $\tau ({\Lambda }_b)$; we conclude that such correction is not responsible of the small experimental value of $\tau ({\Lambda }_b)/\tau (B_d)$.

Comments: Talk presented at the Fifth Topical Seminar on The Irresistible Rise of the Standard Model, San Miniato, Italy, April 21-25, 1997. Latex, 4 pages, 1 figure