Observation and mass measurement of the baryon Xib-

Phys Rev Lett. 2007 Aug 3;99(5):052002. doi: 10.1103/PhysRevLett.99.052002. Epub 2007 Aug 3.

Abstract

We report the observation and measurement of the mass of the bottom, strange baryon Xi(b)- through the decay chain Xi(b)- -->J/psiXi-, where J/psi-->mu+mu-, Xi- -->Lambdapi-, and Lambda-->ppi-. A signal is observed whose probability of arising from a background fluctuation is 6.6 x 10(-15), or 7.7 Gaussian standard deviations. The Xi(b)- mass is measured to be 5792.9+/-2.5(stat) +/- 1.7(syst) MeV/c2.