| Summary: | Abstract Stop searches in supersymmetric frameworks with R-parity conservation usually assume the lightest neutralino to be the lightest supersymmetric particle. In this paper we consider an alternative scenario in which the left-handed tau sneutrino is lighter than neutralinos and stable at collider scales, but possibly unstable at cosmological scales. Moreover the (mostly right-handed) stop t ∼ $$ \overset{\sim }{t} $$ is lighter than all electroweakinos, and heavier than the scalars of the third generation lepton doublet, whose charged component, τ ∼ $$ \overset{\sim }{\tau } $$ , is heavier than the neutral one, ν ∼ $$ \overset{\sim }{\nu } $$ . The remaining supersymmetric particles are decoupled from the stop phenomenology. In most of the parameter space, the relevant stop decays are only into t τ ∼ τ $$ t\overset{\sim }{\tau}\tau $$ , t ν ∼ ν $$ t\overset{\sim }{\nu}\nu $$ and b ν ∼ τ $$ b\overset{\sim }{\nu}\tau $$ via off-shell electroweakinos. We constrain the branching ratios of these decays by recasting the most sensitive stop searches. Due to the “double invisible” kinematics of the t ∼ → t ν ∼ ν $$ \overset{\sim }{t}\to t\overset{\sim }{\nu}\nu $$ process, and the low efficiency in tagging the t τ ∼ τ $$ t\overset{\sim }{\tau}\tau $$ decay products, light stops are generically allowed. In the minimal supersymmetric standard model with ∼ 100 GeV sneutrinos, stops with masses as small as ∼ 350 GeV turn out to be allowed at 95% CL.
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