An exploratory lattice study of spectator effects in inclusive decays of the Lambda(b) baryon

A possible explanation of the apparent discrepancy between the theoretical prediction and experimental measurement of the ratio of lifetimes tau(Lambd a(b))/tau(B-d) is that "spectator effects", which appear at O(1/m(b)(3)) in the heavy quark expansion, contribute significantly. We investigate this p ossibility by computing the corresponding operator matrix elements in a lat tice simulation. We find that spectator effects are indeed significant, but do not appear to be sufficiently large to account for the full discrepancy . We stress, however, that this is an exploratory study, and it is importan t to check our conclusions on a larger lattice and using a larger sample of gluon configurations. (C) 1999 Published by Elsevier Science B.V. All righ ts reserved.