Measuring Lepton Flavour Violation at LHC with Long-Lived Slepton in the Coannihilation Region

TL;DR

This paper explores how long-lived sleptons in supersymmetric models could enable detection of lepton flavor violation at the LHC, potentially improving bounds significantly through distinctive signatures.

Contribution

It proposes using long-lived sleptons in the MSSM to study lepton flavor violation at the LHC, highlighting a novel experimental approach.

Findings

Long-lived sleptons produce distinctive LHC signatures.

Measurement of slepton lifetime can reveal lepton flavor violation.

Potential to improve bounds on leptonic mass insertions by over five orders of magnitude.

Abstract

When the mass difference between the lightest slepton, the NLSP, and the lightest neutralino, the LSP, is smaller than the tau mass, the lifetime of the lightest slepton increases in many orders of magnitude with respect to typical lifetimes of other supersymmetric particles. These small mass differences are possible in the MSSM and, for instance, they correspond to the coannihilation region of the CMSSM for $M_{1/2} \gsim 700$ GeV. In a general gravity-mediated MSSM, where the lightest supersymmetric particle is the neutralino, the lifetime of the lightest slepton is inversely proportional to the square of the intergenerational mixing in the slepton mass matrices. Such a long-lived slepton would produce a distinctive signature at LHC and a measurement of its lifetime would be relatively simple. Therefore, the long-lived slepton scenario offers an excellent opportunity to study lepton flavour violation at ATLAS and CMS detectors in the LHC and an improvement of the leptonic mass insertion bounds by more than five orders of magnitude would be possible.