Light Sneutrino Dark Matter at the LHC

TL;DR

This paper explores the possibility of light sneutrino particles as dark matter candidates in supersymmetric models, analyzing their signatures at the LHC and methods to distinguish them from other particles.

Contribution

It introduces a scenario where light sneutrinos are the LSP and dark matter, and studies their detection prospects and differentiation from MSSM at the LHC.

Findings

Light sneutrino LSPs can be viable dark matter candidates below 10 GeV.

Charginos predominantly decay into sneutrinos and charged leptons in this scenario.

Methods to measure sneutrino mass and distinguish it from other neutral particles at the LHC are proposed.

Abstract

In supersymmetric (SUSY) models with Dirac neutrino masses, a weak-scale trilinear A-term that is not proportional to the small neutrino Yukawa couplings can induce a sizable mixing between left and right-handed sneutrinos. The lighter sneutrino mass eigenstate can hence become the lightest SUSY particle (LSP) and a viable dark matter candidate. In particular, it can be an excellent candidate for light dark matter with mass below ~10 GeV. Such a light mixed sneutrino LSP has a dramatic effect on SUSY signatures at the LHC, as charginos decay dominantly into the light sneutrino plus a charged lepton, and neutralinos decay invisibly to a neutrino plus a sneutrino. We perform a detailed study of the LHC potential to resolve the light sneutrino dark matter scenario by means of three representative benchmark points with different gluino and squark mass hierarchies. We study in particular the determination of the LSP (sneutrino) mass from cascade decays involving charginos, using the mT2 variable. Moreover, we address measurements of additional invisible sparticles, in our case the lightest neutralino, and the question of discrimination against the MSSM.