Perspectives for the detection and measurement of supersymmetry in the focus point region of mSUGRA models with the ATLAS detector at LHC

This paper discusses the potential of ATLAS to study supersymmetry in the "focus point" region of the parameter space of mSUGRA models. The potential to discover a deviation from standard model expectations with the first few fb(-1) of LHC data was studied using the parametrized simulation of the ATLAS detector. Several signatures were considered, involving hard jets, large missing energy, and either b-tagged jets, opposite-sign isolated electron or muon pairs, or top quarks reconstructed exploiting their fully-hadronic decays. With only 1 fb(-1) of data each of these signatures may allow for observing an excess of events over standard model expectations with a statistical significance exceeding five standard deviations. Furthermore, each of the two invariant mass distributions of the two leptons produced by the (chi) over tilde (0)(3) --> (chi) over tilde (0)(1)l(+)l(-) and the (chi) over tilde (0)(2) --> ($) over tilde (0)(1) l(+)l(-) three-body decays has a kinematic endpoint that measures the difference between the masses of the parent and daughter neutralino. An analytical expression was derived for the shape of this distribution and was used to fit the simulated LHC data. A measurement of the (chi) over tilde (0)(2)-(chi) over tilde (0)(1) and (chi) over tilde (0)(3)-(chi) over tilde (0)(1) mass differences was obtained and this information was used to constrain the MSSM parameter space.