# Same-sign trilepton signal for stop quark in the presence of sneutrino dark matter

Ghosh, Dilip Kumar (Department of Theoretical Physics, Indian Association for the Cultivation of Science Jadavpur, Kolkata 700 032, India) ; Huitu, Katri (Department of Physics, and Helsinki Institute of Physics, P. O. Box 64, FI-00014 University of Helsinki, Finland) ; Mondal, Subhadeep (Department of Physics, and Helsinki Institute of Physics, P. O. Box 64, FI-00014 University of Helsinki, Finland) ; Mitra, Manimala (Institute of Physics, Sachivalaya Marg, Bhubaneswar, Odisha 751005, India, Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085, India)

15 April 2019

Abstract: We explore a minimal supersymmetric standard model scenario extended by one pair of gauge singlets per generation. In the model, light neutrino masses and their mixings are generated via the inverse seesaw mechanism. In such a scenario, a right-handed sneutrino can be the lightest supersymmetric particle and a cold dark matter (DM) candidate. If the Casas-Ibarra parametrization is imposed on the Dirac neutrino Yukawa coupling matrix (${Y}_{\nu }$) to fit the neutrino oscillation data, the resulting ${Y}_{\nu }$ is highly constrained from the lepton-flavor-violating decay constraints. The smallness of ${Y}_{\nu }$ requires the sneutrino DM to coannihilate with other sparticle(s) in order to satisfy the DM relic density constraint. We study sneutrino coannihilation with winos and observe that this sneutrino-wino compressed parameter space gives rise to a novel same-sign trilepton signal for the top squark, which is more effective than the conventional top squark search channels in the present framework. We show that the choice of neutrino mass hierarchy strongly affects the signal event rate, making it easier to probe the scenario with the inverted mass hierarchy.

Published in: Physical Review D 99 (2019)