Search for Flavor-Changing Neutral Currents in Top-Quark Decays t -> Zq in pp Collisions at root s=8 TeV


Chatrchyan S., Khachatryan V., Sirunyan A. M. , Tumasyan A., Adam W., Bergauer T., ...More

PHYSICAL REVIEW LETTERS, vol.112, no.17, 2014 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 112 Issue: 17
  • Publication Date: 2014
  • Doi Number: 10.1103/physrevlett.112.171802
  • Title of Journal : PHYSICAL REVIEW LETTERS

Abstract

A search for flavor-changing neutral currents in top-quark decays t -> Zq is performed in events produced from the decay chain (tt) over bar -> Zq + Wb, where both vector bosons decay leptonically, producing a final state with three leptons (electrons or muons). A data set collected with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 19.7 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. No excess is seen in the observed number of events relative to the standard model prediction; thus, no evidence for flavor-changing neutral currents in top-quark decays is found. A combination with a previous search at 7 TeV excludes a t. Zq branching fraction greater than 0.05% at the 95% confidence level.