Measurement of the Lambda(0)(b), Xi(-)(b), and Omega(-)(b) Baryon Masses

Bottom baryons decaying to a J/psi meson and a hyperon are reconstructed using 1.0 fb(-1) of data collected in 2011 with the LHCb detector. Significant Lambda(0)(b) -> J/psi Lambda, Xi(-)(b) -> J/psi Xi(-) and Omega(-)(b) -> J/psi Omega(-) signals are observed and the corresponding masses are measured to be M(Lambda(0)(b)) = 5619.53 +/- 0.13(stat.) +/- 0.45(syst.) MeV/c(2), M(Xi(-)(b)) = 5795.8 +/- 0.9(stat.) +/- 0.4(syst.) MeV/c(2), M(Omega(-)(b)) = 6046.0 +/- 2-2(stat.) +/- 0.5(syst.) MeV/c(2), while the differences with respect to the Lambda(0)(b) mass are M(Xi(-)(b)) - M(Lambda(0)(b)) = 176.2+/-0.9(stat.) +/- 0.1(syst.) MeV/c(2), M(Omega(-)(b)) - M(Lambda(0)(b)) = 426.4 +/- 2.2(stat.) +/-0.4(syst.) MeV/c(2). These are the most precise mass measurements of the Lambda(0)(b), Xi(-)(b) and Omega(-)(b) baryons to date. Averaging the above Lambda(0)(b) mass measurement with that published by LHCb using 35 pb(-1) of data collected in 2010 yields M(Lambda(0)(b)) = 5619.44 +/- 0.13(stat.) +/- 0.38(syst.) MeV/c(2).