Measurement of the $Lambda_b$ lifetime in the exclusive decay $Lambda_b o J/psi Lambda$

Abstract

We have measured the Lambda_b lifetime using the exclusive decay Lambda_b to J/psi Lambda, based on 1.2 fb-1 of data collected with the D0 detector during 2002-2006. From 171 reconstructed Lambda_b decays, where the J/psi and Lambda are identified via the decays J/psi to mu_s16 mu- and Lambda to p pi, we measured the Lambda_b lifetime to be tau(Lambda_b) = 1.218(_s160.130,-0.115)(stat) _s16/- 0.042(syst)ps. We also measured the B0 lifetime in the decay B0 to J/psi(mu_s16 mu-)K0_S(pi_s16 pi-) to be tau(B0) = 1.501(_s160.078,-0.074)(stat) _s16/ -0.050(syst)ps, yielding a lifetime ratio of tau(Lambda_b)/tau(B0) = 0.811(_s160.096,-0.087)(stat) _s16/ -0.034(syst). These measurements are consistent with the current world averages and support the shorter lifetime of the Lambda_b with respect to B mesons, in contrast to another recent measurement of significant precision.