Observation of the heavy baryons Σb and Σb*

Abstract

We report an observation of new bottom baryons produced in pp̄ collisions at the Tevatron. Using 1.1fb-1 of data collected by the CDF II detector, we observe four Λb0π± resonances in the fully reconstructed decay mode Λb0→Λc+π-, where Λc+→pK-π+. We interpret these states as the Σb(*) ± baryons and measure the following masses: mΣb+=5807.8-2.2+2. 0(stat.)±1.7(syst.)MeV/c2, mΣb-=5815.2±1.0(stat.)±1. 7(syst.)MeV/c2, and m(Σb*)-m(Σb)=21.2-1.9+2.0(stat.)-0.3+0. 4(syst.)MeV/c2. © 2007 The American Physical Society.