Measurement of the lifetime difference of Bd mesons:: possible and worthwhile?

We estimate the decay width difference DeltaGamma(d)/Gamma(d) in the B-d system including 1/m(b) contributions and part of the next-to-leading order QCD corrections, and find it to be around 0.3%. We explicitly show that the time measurements of an untagged B-d decaying to a single final state isotropically can only be sensitive to quadratic terms in DeltaGamma(d)/Gamma(d), and hence the use of at least two different final states is desired. We discuss such pairs of candidate decay channels for the final states and explore the feasibility of a DeltaGamma(d)/Gamma(d) measurement through them. The measurement of DeltaGamma(d) would be essential for an accurate measurement of sin(2beta) at the LHC. The nonzero width difference can also be used to identify new physics effects and to resolve a twofold discrete ambiguity in the B-d-(B) over bar (d) mixing phase. We also derive an upper bound on the value of DeltaGamma(d)/Gamma(d) in the presence of new physics, and point out some differences in the phenomenology of width differences in the B-s and B-d systems. (C) 2002 Published by Elsevier Science B.V.