Light dark matter from the U(1)_<i>X</i>sector in the NMSSM with gauge mediation

Abstract

Cosmic ray anomalies observed by PAMELA and Fermi-LAT experiments may be\ninterpreted by heavy (TeV-scale) dark matter annihilation enhanced by\nSommerfeld effects mediated by a very light (sub-GeV) U(1)_X gauge boson, while\nthe recent direct searches from CoGeNT and DAMA/LIBRA experiments may indicate\na rather light (\\sim 7 GeV) dark matter with weak interaction. Motivated by\nthese apparently different scales, we consider a gauge mediated next-to-the\nminimal supersymmetric standard model (NMSSM) entended with a light U(1)_X\nsector plus a heavy sector (\\bar H_h,H_h), which can provide both a light (\\sim\n7 GeV) and a heavy (TeV-scale) dark matter without introducing any ad hoc new\nscale. Through the Yukawa coupling between H_h and the messager fields, the\nU(1)_X gauge symmetry is broken around the GeV scale radiatively and a large\nnegative m_S^2 is generated for the NMSSM singlet S. Furthermore, the small\nkinetic mixing parameter between U(1)_X and U(1)_Y is predicted to be\n\\theta\\sim 10^{-5}-10^{-6} after integrating out the messengers. Such a light\ndark matter, which can have a normal relic density from the late decay of the\nright-handed sneutrino (assumed to be the ordinary next-to-the lightest\nsupersymmetric particle and thermally produced in the early universe), can\nserve a good candidate to explain the recent CoGeNT and DAMA/LIBRA results.\n