Observation of Two New Xi(-)(b) Baryon Resonances

Abstract

Two structures are observed close to the kinematic threshold in the \u39eb0\u3c0- mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb-1, recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity JP=(1/2)+ and JP=(3/2)+ states, denoted \u39eb\u2032- and \u39eb 17-. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(\u39eb\u2032-)-m(\u39eb0)-m(\u3c0-)=3.653\ub10.018\ub10.006MeV/c2, m(\u39eb 17-)-m(\u39eb0)-m(\u3c0-)=23.96\ub10.12\ub10.06MeV/c2, \u393(\u39eb 17-)=1.65\ub10.31\ub10.10MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of \u393(\u39eb\u2032-)<0.08MeV at 95% confidence level. Relative production rates of these states are also reported