Search for the Pair-production of a Vector-like Quark in b + Z Events from pp Collisions at √s = 7 and 8 TeV

• Main Authors: Kai-Yi Kao, 高凱逸
• Other Authors: Wei-Shu Hou
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/79017688959248297280

博士 === 國立臺灣大學 === 物理研究所 === 101 === A search is presented for the pair production of a vector-like quark, B’. Data corresponding to integrated luminosity of 4.9 fb−1 p from pp collisions at √s = 7 TeV in 2011 and 19.6 fb−1 at 8 TeV in 2012 collected with the CMS detector at the LHC were used. The invariant mass spectrum of b-tagged jets and Z boson candidates, with the latter identified through e+e− or μ+μ− decays, is examined for an excess of events and found to be consistent with the standard model expectations. The expected 95% confidence level lower limit on the mass of the B’ quark with the assumption a 100% branching ratio fraction into a bottom quark and a Z boson is 510 GeV/c2, while the observed lower limit is 550 GeV/c2 in 2011; For the updates in 2012, the expected limit is 680 GeV/c2 and observed lower limit is 700 GeV/c2.