SUSY induced top quark FCNC decay $t \to c h$ after Run I of LHC

Abstract

In light of the Higgs discovery and the nonobservation of sparticles at the LHC, we revisit the SUSY induced top quark flavor changing decay into the Higgs boson. We perform a scan over the relevant SUSY parameter space by considering the constraints from the Higgs mass measurement, the LHC search for SUSY, the vacuum stability, the precision electro-weak observables as well as $B \to X_s \gamma$. We have the following observations: (1) In the MSSM, the branching ratio of $ t \to c h$ can only reach $3.0\times10^{-6}$, which is about one order smaller than previous results obtained before the advent of the LHC. Among the considered constraints, the Higgs mass and the LHC search for sparticles are found to play an important role in limiting the prediction. (2) In the singlet extension of the MSSM, since the squark sector is less constrained by the Higgs mass, the branching ratio of $t \to c h$ can reach the order of $10^{-5}$ in the allowed parameter space. (3) The chiral-conserving mixings $\delta_{LL}$ and $\delta_{RR}$ may have remanent effects on $t \to c h$ in heavy SUSY limit. In the MSSM with squarks and gluino above 3 TeV and meanwhile the CP-odd Higgs boson mass around 1 TeV, the branching ratio of $t\to c h$ can still reach the order of $10^{-8}$ under the constraints.