Indirect measurements of the (τ)over-tilde-(χ)over-tilde10 mass difference and M(g)over-tilde in the co-annihilation region of mSUGRA models at the LHC

We study the prospects for the measurement of the (tau) over tilde-(chi) over tilde (0)(1) mass difference (Delta M) and the (g) over tilde mass (M-(g) over tilde) 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 Delta M (5-15 GeV). Focusing on taus from (chi) over tilde (0)(2) -> tau(tau) over tilde -> tau tau(chi) over tilde (0)(1) decays in and 4 production, we consider inclusive 3 tau + jet + is not an element of(T) production, with two tau's above a high E-T threshold and a third tau above a lower threshold. Two observables, the number of opposite-signed tau pairs minus the number of like-signed tau pairs, and the peak of the di-tau invariant mass distribution, allow for the simultaneous determination of Delta M and M-(g) over tilde for Delta M greater than or similar to 6 GeV. For example, for Delta M = 9 GeV and M-(g) over tilde = 850 GeV with 30 fb(-1) of data, we can measure Delta M to 15% and M-(g) over tilde to 6%. (c) 2007 Elsevier B.V. All rights reserved.