Mixed Sneutrinos, Dark Matter and the LHC

TL;DR

This paper investigates the phenomenology of mixed sneutrino dark matter within supersymmetric models, analyzing constraints from cosmology and direct detection, and exploring unique collider signatures at the LHC to distinguish these models from the MSSM.

Contribution

It introduces the concept of mixed sneutrinos as dark matter candidates and studies their collider signatures, providing methods to differentiate them from MSSM predictions.

Findings

Mixed sneutrino LSP can produce distinctive dilepton signatures at the LHC.

Cascade decays involving sneutrinos can lead to unique jet-lepton invariant-mass distributions.

Mass estimation techniques can help distinguish mixed sneutrino signals from MSSM scenarios.

Abstract

We study the phenomenology of supersymmetric models in which gauge-singlet scalars mix with the MSSM sneutrinos through weak-scale $A$ terms. After reviewing the constraints on mixed-sneutrino dark matter from measurements of $\Omega_{CDM}$ and from direct-detection experiments, we explore mixed-sneutrino signatures relevant to the LHC. For a mixed-sneutrino LSP and a right-handed slepton NLSP, decays of the lightest neturalino can produce opposite-sign, same-flavor (OSSF) dileptons with an invariant-mass distribution shifted away from the kinematic endpoint. In different parameter regions, the charginos and neutralinos produced in cascades all decay dominantly to the lighter sneutrinos, leading to a kinematic edge in the jet-lepton invariant-mass distribution from the decay chain $\tilde{q} \to \chi^- q \to \snu^* l q$, without an OSSF dilepton signature. We explore the possibility of using mass estimation methods to distinguish this mixed-sneutrino jet-lepton signature from an MSSM one. Finally, we consider signatures associated with Higgs-lepton or $Z$-lepton production in cascades involving the heavier sneutrinos.