Non-spectator Contributions To The Lifetime of ${\Lambda }_b$

Abstract

In this work, we evaluate the contributions of non-spectator effects to the lifetimes of ${\Lambda }_b$ and B-mesons. Based on the well-established models and within a reasonable range of the concerned parameters, the contributions can reduce the lifetime of ${\Lambda }_b$ by $7\sim 8$ compared to that of B-mesons which are not significantly affected. This might partly explain the measured ratio $\tau ({\Lambda }_b)/\tau (B^0)=0.79$ \cite{Data}, which has been a long-standing discrepancy between theory and experimental data.