Evidence for the bottom baryon resonance state Lambda_b* with the CDF II detector

Abstract

Using data from proton-antiproton collisions at Ecms=1.96 TeV recorded by the CDF II detector at the Fermilab Tevatron, we present evidence for the excited resonance state Lambda_b* in its fully reconstructed decay mode to Lambda_b0 pi+ pi- where Lambda_b0 -->Lambda_c+ (-->proton K- pi+) pi-. The analysis is based on a data sample corresponding to an integrated luminosity of 9.6/fb collected by an online event selection based on tracks displaced from the proton-antiproton interaction point. The local significance of the observed signal is 4.6 Gaussian sigmas. while the significance of the signal for the search region is 3.5 Gaussian sigmas. The mass of the observed state is found to be 5919.5+-0.35+-1.72 MeV .