Search

We address the problem of a search at the LHC for a neutralino whose mass is around 10 GeV, i.e. in the range of interest for present data of direct search for dark matter particles in the galactic halo. This light neutralino is here implemented in an effective Minimal Supersymmetric extension of the Standard Model at the electroweak scale without requirement of a gaugino mass unification at a grand unification scale. In this model, light neutralinos that have the right cosmological properties and are able to explain current results of direct dark matter detection naturally arise. Within this model we identify a specific benchmark which maximizes chances of detection at the LHC, and we determine its prospects of reconstructing the main features of the light neutralino framework at different stages of the LHC runs. Our main result is that the LHC will hardly properly reconstruct the mass of such a light neutralino, due to the intrinsic difficulty in reconstructing the mass of light stable particles in relativistic events. However, the associated measurement of the mass of the heavier neutralinos allows us to point toward the right pattern of gaugino nonuniversality. Other relevant parameters of this model, like slepton and squark masses, can be reconstructed to a good level of precision. [ABSTRACT FROM AUTHOR]

We review the status of the phenomenology of light neutralinos in an effective minimal supersymmetric extension of the standard model at the electroweak scale, in light of new results obtained at the CERN Large Hadron Collider. First, we consider the impact of the new data obtained by the CMS Collaboration on the search for the Higgs-boson decay into a tau pair, and by the CMS and LHCb Collaborations on the branching ratio for the decay Bs → &mgr;+ + &mgr;-. Then, we examine the possible implications of the excess of events found by the ATLAS and CMS Collaborations in a search for a standard-model (SM)-lik;e Higgs boson around a mass of 126 GeV, with a most likely mass region (95% C.L.) restricted to 115.5-131 GeV (global statistical significance about 2.3&sgr;). From the first set of data, we update the lower bound of the neutralino mass to be about 18 GeV. From the second set of measurements, we derive that the excess around mSMH = 126 GeV, which however needs a confirmation by further runs at the LHC, would imply a neutralino in the mass range 18 GeV ≲ mx ≲ 38 GeV, with neutraUno-nucleon elastic cross sections fitting well the results of the dark matter direct search experiments DAMA/LIBRA and CRESST. [ABSTRACT FROM AUTHOR]