Probing penguin coefficients with the lifetime ratio τ ( B s ) / τ ( B d

We calculate penguin contributions to the lifetime splitting between the Bs and the Bd meson. In the Standard Model the penguin effects are found to be opposite in sign, but of similar magnitude as the contributions of the current-current operators, despite of the smallness of the penguin coefficients. We predict τ(Bs) τ(Bd) − 1 = (−1.2± 10.0) · 10 · ( fBs 190MeV )2 , where the error stems from hadronic uncertainties. Since penguin coefficients are sensitive to new physics and poorly tested experimentally, we analyze the possibility to extract them from a future precision measurement of τ (Bs) /τ (Bd). Anticipating progress in the determination of the hadronic parameters ε1, ε2 and fBs/fBd we find that the coefficient C4 can be extracted with an uncertainty of order |∆C4| ≃ 0.1 from the double ratio (τ(Bs) − τ(Bd))/(τ(B)− τ(Bd)), if |ε1 − ε2| is not too small. 1e-mail:[email protected] 2e-mail:[email protected]