PROBING PENGUIN COEFFICIENTS WITH THE LIFETIME RATIO TAU(B-S) TAU(B-D)/

We calculate penguin contributions to the lifetime splitting between t he B-s and the B-d meson. In the standard model the penguin effects ar e found to be opposite in sign, but of similar magnitude as the contri butions of the current-current operators, despite the smallness of the penguin coefficients. We predict tau(B-s)/tau(B-d)-1=(-1.2+/-10.0)X10 (-3)(f(Bs)/190 MeV)(2), where the error stems from hadronic uncertaint ies. Since penguin coefficients are sensitive to new physics and poorl y tested experimentally, we analyze the possibility to extract them fr om a future precision measurement of tau(B-s)/tau(B-d). Anticipating p rogress in the determination of the hadronic parameters epsilon(1), ep silon(2), and f(Bs)/f(Bd) we find that the coefficient C-4 can be extr acted with an uncertainty of order \Delta C-4\congruent to 0.1 from th e double ratio [tau(B-s)-tau(B-d)], if \epsilon(1)-epsilon(2)\ is not too small. [S0556-2821(98)04707-9].