  When the mass difference between the lightest slepton and the lightest
neutralino is smaller than the tau mass, the lifetime of the lightest slepton
in the constrained Minimal Supersymmetric Standard Model (MSSM) increases in
many orders of magnitude with respect to typical lifetimes of other
supersymmetric particles. In a general MSSM, 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.
