Searching for a squark LSP of the first two families at the LHC

Abstract

We analyse relevant signals expected at the LHC for a squark of the first two families as the lightest supersymmetric particle (LSP). The discussion is established in the framework of the μν" role="presentation">SSM, where the presence of R-parity violating couplings involving right-handed neutrinos solves simultaneously the μ" role="presentation">-problem and the accommodation of neutrino masses and mixing angles. The squarks are pair produced and decay dominantly to a neutrino and a quark. They also have two sub-dominant three body decays to quark, Higgs and neutrino/charged lepton. The decays can be prompt or displaced, depending on the regions of the parameter space of the model. We focus the analyses on squarks of right up-type, right down-type, and left up-type; since squarks of left down-type cannot be the LSP because of D-term contributions. We compare the predictions of these scenarios with ATLAS and CMS searches for prompt and long-lived particles. To analyse the parameter space we sample the μν" role="presentation">SSM for a squark LSP, paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavour observables. Because of the contribution of squark-squark final states to the production cross section, the results depend on the squark family. In particular, for a right strange squark LSP, the lower limit on the mass is 1646 GeV, corresponding to an upper limit on the decay length of 54.7 mm, and for a right (left) scharm LSP, the limits are 1625 (1357) GeV and 13.4 (1.9) mm. However, the first family of squarks as LSP turns out to be excluded, unless the gluino is heavier than 7 TeV, which produces a limit on the squark mass of 1800 GeV.