Indirect measurements of the τ˜–χ˜10 mass difference and Mg˜ in the co-annihilation region of mSUGRA models at the LHC

Abstract

Abstract We study the prospects for the measurement of the τ ˜ – χ ˜ 1 0 mass difference (ΔM) and the g ˜ mass ( M g ˜ ) in the supersymmetric co-annihilation region of mSUGRA at the LHC using tau leptons. Recent WMAP measurements of the amount of cold dark matter and previous accelerator experiments favor the co-annihilation region of mSUGRA, characterized by a small ΔM (5–15 GeV). Focusing on taus from χ ˜ 2 0 → τ τ ˜ → τ τ χ ˜ 1 0 decays in g ˜ and q ˜ production, we consider inclusive 3 τ + jet + E T production, with two τ's above a high E T threshold and a third τ above a lower threshold. Two observables, the number of opposite-signed τ pairs minus the number of like-signed τ pairs, and the peak of the di-tau invariant mass distribution, allow for the simultaneous determination of ΔM and M g ˜ for Δ M ≳ 6 GeV . For example, for Δ M = 9 GeV and M g ˜ = 850 GeV with 30 fb −1 of data, we can measure ΔM to 15% and M g ˜ to 6%.