First Observation of Heavy Baryons Sigma_b and Sigma*_b

Abstract

We report an observation of new bottom baryons produced in pp\u304 collisions at the Tevatron. Using 1.1fb-1 of data collected by the CDF II detector, we observe four \u39bb0\u3c0\ub1 resonances in the fully reconstructed decay mode \u39bb0\u2192\u39bc+\u3c0-, where \u39bc+\u2192pK-\u3c0+. We interpret these states as the \u3a3b(*) \ub1 baryons and measure the following masses: m\u3a3b+=5807.8-2.2+2. 0(stat.)\ub11.7(syst.)MeV/c2, m\u3a3b-=5815.2\ub11.0(stat.)\ub11. 7(syst.)MeV/c2, and m(\u3a3b*)-m(\u3a3b)=21.2-1.9+2.0(stat.)-0.3+0. 4(syst.)MeV/c