Phenomenology of light neutralinos in view of recent results at the CERN Large Hadron Collider

Abstract

We review the status of the phenomenology of light neutralinos in an effective Minimal Supersymmetric extension of the Standard Model (MSSM) 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 $B_s \rightarrow {\mu}^{+} + {\mu}^{-}$. Then we examine the possible implications of the excess of events found by the ATLAS and CMS Collaborations in a search for a SM--like Higgs boson around a mass of 126 GeV, with a most likely mass region (95% CL) restricted to 115.5--131 GeV (global statistical significance about 2.3 $\sigma$). 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 $m^{SM}_H$ = 126 GeV, which however needs a confirmation by further runs at the LHC, would imply a neutralino in the mass range 18 GeV $\lsim m_{\chi} \lsim$ 38 GeV, with neutralino--nucleon elastic cross sections fitting well the results of the dark matter direct search experiments DAMA/LIBRA and CRESST.