LHC sensitivity to lepton flavour violating Z boson decays

Abstract

We estimate that the LHC could set bounds BR(Z → μ ±e∓) < 4.1 × 10-7 and BR(Z → τ±μ∓) < 3.5 × 10-6 (at 95% C.L.) with 20 fb-1 of data at 8TeV. A similar sensitivity can be anticipated for Z → τ± e ∓, because we consider leptonic τ decays such that Z → τ± μ∓ → e ±μ∓+ invisible. These limits can be compared to the LEP1 bounds of order 10-5 → 10-6. Such collider searches are sensitive to a flavour-changing effective Z coupling which is energy dependent, so are complementary to bounds obtained from τ → ℓℓ̄ℓ and μ → eēe.