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

A search is reported for the pair production of a new quark b0 with at least one b0 decaying to a Z boson and a bottom quark. The data, corresponding to 2:0 fb1 of integrated luminosity, were collected from pp collisions at pffisffiffi ¼ 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 b0 candidates is tested for an enhancement. No evidence for a b0 signal is detected in the observed mass distribution, resulting in the exclusion at a 95% confidence level of b0 quarks with masses mb0 < 400 GeV that decay entirely via b0 ! Z þ b. In the case of a vectorlike singlet b0 mixing solely with the third standard model generation, masses mb0 < 358 GeV are excluded.