Complementarity of gamma-ray and CERN LHC searches for neutralino dark matter in the focus point region

We study the complementarity between the indirect detection of dark matter with {gamma}-rays in H.E.S.S. and the supersymmetry searches with ATLAS at the Large Hadron Collider (LHC) in the focus point region within the mSUGRA framework. The sensitivity of the central telescope of the H.E.S.S. II experiment with an energy threshold of {approx}20 GeV is investigated. We show that the detection of {gamma}-ray fluxes of O(10{sup -12}) cm{sup -2} s{sup -1} with H.E.S.S. II covers a substantial part of the focus point region which may be more difficult for LHC experiments. Despite the presence of multi-TeV scalars, we show that LHC will be sensitive to a complementary part of this region through three-body next-to-lightest supersymmetric particle leptonic decays. This interesting complementarity between H.E.S.S. II and LHC searches is further highlighted in terms of the gluino mass and the two lightest neutralino mass difference.