Photon initiated single top quark production via flavor-changing neutral currents at the LHC

Abstract

Single top quark production is a powerful process to search for new physics signs. In this work we propose and investigate a search for top quark flavor changing neutral currents (FCNC) via a photon using direct single top quark production events in proton-proton collisions at the LHC at CERN. We show that the direct single top quark final state can provide constraints on the strengths of tq$\gamma$ (top-quark-$\gamma$) and tqg (top-quark-gluon) FCNC couplings simultaneously. Results of a search for direct single top quark production at the LHC at a center-of-mass energy of 8 TeV performed by the ATLAS collaboration are used to set first experimental limits on the anomalous FCNC top decay branching fractions $\mathcal{B}$(t$\to$ u$\gamma$) $<$ 0.05% and $\mathcal{B}$(t$\to$ c$\gamma$) $<$ 0.14% via direct single top quark production. Finally, the sensitivity of the proposed channel for probing the tq$\gamma$ couplings at 13 TeV is presented.

Comments: 19 pages, 6 figures, 6 tables