In supersymmetric (SUSY) models with Dirac neutrino masses, a weak-scale trilinear $ {A_{ilde{u }}} $ term that is not proportional to the small neutrino Yukawa couplings can induce a sizable mixing between left and right-handed sneutrinos. The lighters neutrino 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, $ {ilde{u }_1} $ , plus a charged lepton, and neutralinos decay invisibly into $ {ilde{u }_1}u $ . 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 $ {ilde{u }_1} $ mass from cascade decays involving charginos, using the m ~(T2)variable. Moreover, we address measurements of additional invisible sparticles, in our case $ {ilde{Z}_{1,2}} $ , and the question of discrimination against the MSSM.
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