Abstract
We present searches for the top quark flavor-changing neutral current (FCNC) interactions by the CMS experiment. The FCNC searches have been performed in the vertices of tqZ, tqg, and tqγ in decay and production processes. The results are based on the data collected from proton proton collisions at the LHC at centre-of-mass energies of 7 and 8 TeV.
Highlights
Within the Standard Model (SM) framework, top quark decays around 100% of the time into a W boson and a bottom quark
While flavor-changing neutral currents (FCNC) decays are strongly suppressed in the SM because of the GIM (Glashow-Iliopoulos-Maiani) mechanism [1] with branching ratios of the order of 10−13,−14 [2]
We report the results of the CMS experiment [3] on searches for FCNC couplings of tqγ, tqg and tqZ based on data collected at the center-of-mass energies of 7 TeV and 8 TeV at the LHC
Summary
Within the Standard Model (SM) framework, top quark decays around 100% of the time into a W boson and a bottom quark. While flavor-changing neutral currents (FCNC) decays are strongly suppressed in the SM because of the GIM (Glashow-Iliopoulos-Maiani) mechanism [1] with branching ratios of the order of 10−13,−14 [2]. Several extensions of the SM predict much larger branching ratios for the FCNC decays of the top quark. The FCNC branching ratios of top quark decays in these models are typically greater than the SM branching ratios by several orders of magnitude. The effective Lagrangian approach has been used as a model independent way to search for the FCNC couplings. The most general Lagrangian describing the FCNC couplings has the following form [4],[5]: Le f f. New The physics scales coefficients of is denoted by the projection operators are in general complex and normalized to one
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