Search for top quark flavour changing neutral currents in same-sign top quark production

TL;DR

This paper reports a search for flavor-changing neutral currents involving top quarks through same-sign top production, setting upper limits on rare decay branching ratios using CMS data at 8 TeV.

Contribution

It provides new constraints on top quark FCNC interactions by analyzing CMS data, and discusses future search sensitivities in this channel.

Findings

Upper limits on top quark FCNC decay branching ratios are established.

Constraints on the strength of FCNC interactions are derived.

Future search sensitivities are discussed.

Abstract

The presence of the anomalous top quark flavour changing neutral current (FCNC) interactions leads to the production of same-sign top quarks in proton-proton collisions. The results of a search for events with same-sign dileptons and b-jets conducted by CMS collaboration with 10.5 $fb^{-1}$ of data collected in pp colisions at $\sqrt{s}=8$ TeV are used to obtain the constraints on the strength of top quark FCNC interactions. The 95$%$ confidence level upper limits on the branching ratios of top quark decays to a light quark $q=u,c$ and a gauge or a Higgs boson are set to be ${\cal B}R(t\rightarrow u \gamma) < 1.27%$, ${\cal B}R(t\rightarrow u Z) < 0.8% $, ${\cal B}R(t\rightarrow u g) < 1.02% $ and ${\cal B}R(t\rightarrow u H) < 4.21% $. The sensitivity of future searches in the same-sign top quark channel is also presented.