Single top-quark production by strong and electroweak supersymmetric flavor-changing interactions at the LHC

Abstract

We report on a complete study of the single top-quark production by direct supersymmetric flavor-changing neutral-current (FCNC) processes at the LHC. The total cross section, σ(pp(gg) → + ), is computed at the 1-loop order within the unconstrained Minimal Supersymmetric Standard Model (MSSM). The present study extends the results of the supersymmetric strong effects (SUSY-QCD), which were advanced by some of us in a previous work, and includes the computation of the full supersymmetric electroweak corrections (SUSY-EW). Our analysis of σ(pp(gg) → + ) in the MSSM has been performed in correspondence with the stringent low-energy constraints from b → sγ. In the most favorable scenarios, the SUSY-QCD contribution can give rise to production rates of around 105 events per 100 fb−1 of integrated luminosity. Furthermore, we show that there exist regions of the MSSM parameter space where the SUSY-EW correction becomes sizeable. This could be important, especially if the SUSY-QCD effects would be suppressed. In the SUSY-EW favored regions, one obtains lower, but still appreciable, event production rates that can reach the 103 level for the same range of integrated luminosity. We study also the possible reduction in the maximum event rate obtained from the full MSSM contribution if we additionally include the constraints from the B0s−0s. However, we treat these restrictions at a different level from the b → sγ ones, due to the higher uncertainties inherent in the calculation of the matrix element associated to that mixing. In view of the fact that the FCNC production of heavy quark pairs of different flavors, such as or , is extremely suppressed in the SM, the detection of a significant number of these events could lead to evidence of new physics — of likely supersymmetric origin.