Search for Pair Production of a New b Quark that Decays into a Z Boson and a Bottom Quark with the ATLAS Detector

Abstract

A search is reported for the pair production of a new quark b with at least one b decaying to a Z boson and a bottom quark. The data, corresponding to 2.0 fb(-1) of integrated luminosity, were collected from pp collisions at root s = 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. Using events with a b-tagged jet and a Z boson reconstructed from opposite-charge electrons, the mass distribution of large transverse momentum b candidates is tested for an enhancement. No evidence for a b signal is detected in the observed mass distribution, resulting in the exclusion at a 95% confidence level of b quarks with masses m(b) LT 400 GeV that decay entirely via b - GT Z + b. In the case of a vectorlike singlet b mixing solely with the third standard model generation, masses m(b) LT 358 GeV are excluded.