LIFETIMES OF HEAVY BARYONS REVISITED

The presently available experimental information on charmed-baryon lifetimes indicates that the nonrelativistic quark model (NQM) gives a more reliable estimate on various nonspectator effects than the relativistic model. The sizeable lifetime differences among charmed baryons are accounted for by large W'-exchange and constructive interference effects. Quantitative features of the total decay widths of bottom baryons are elaborated in NQM. We find that the emerged lifetime pattern is tau(XI(b)-) congruent-to tau(OMEGA(b)-) greater than or similar to tau(LAMBDA(b)0) greater than or similar to tau(XI(b)0) with much smaller lifetime differences among them. An estimate of the LAMBDA(b) lifetime based on the recent observation of the exclusive decay modes LAMBDA(b)-->J/psiLAMBDA and LAMBDA(b)-->LAMBDA(c)+l-upsilonBAR is made.