New Possibility of Solving the Problem of Lifetime Ratio τ(Λb)/τ(Bd)

We discuss the problem of the large discrepancy between the observed lifetime ratio of Λb to Bd and the theoretical prediction obtained by the heavy quark effective theory. A new possibility of solving this problem is proposed from the viewpoint of operator product expansion and the lifetime ratio of Ωb to Bd is predicted. The heavy quark effective theory (HQET) is successful in explaining various nature of the hadrons containing a heavy quark. The HQET has been extensively applied to the meson system containing a heavy quark and has brought about many remarkable results. The HQET has been also applied to the system of baryons containing a heavy quark and has led to some interesting results. However, when applying the HQET to the heavy baryon systems, two problems are encountered. One is that the experimental value of the mass difference between Σb and Σ ∗ b is quite large in comparison with the predicted value from the mass relation in the HQET as mΣb∗ −mΣb = 56± 13MeV (Exp.) [1], = 15.8± 3.3MeV (Theory) [2]. (1) [email protected] [email protected] [email protected]