Lightest Higgs boson and relic neutralino in the MSSM withCPviolation

Abstract

We discuss the lower bound to the lightest Higgs boson ${H}_{1}$ in the minimal supersymmetric extension of the standard model with explicit $CP$ violation, and the phenomenology of the lightest relic neutralino in the same scenario. In particular, adopting the CPX benchmark scenario, we find that the combination of experimental constraints coming from LEP, thallium electric dipole moment measurements, quarkonium decays, and ${B}_{s}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\mu}$ decay favors a region of the parameter space where the mass of ${H}_{1}$ is in the range $7\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}{M}_{{H}_{1}}\ensuremath{\lesssim}10\text{ }\text{ }\mathrm{GeV}$, while $3\ensuremath{\lesssim}\mathrm{tan}\ensuremath{\beta}\ensuremath{\lesssim}5$. Assuming a departure from the usual grand unified theory relation among gaugino masses ($|{M}_{1}|\ensuremath{\ll}|{M}_{2}|$), we find that through resonant annihilation to ${H}_{1}$ a neutralino as light as 2.9 GeV can be a viable dark matter candidate in this scenario. We call this the CPX light neutralino scenario and discuss its phenomenology showing that indirect dark matter searches are compatible with the present experimental constraints, as long as ${m}_{\ensuremath{\chi}}\ensuremath{\lesssim}{M}_{{H}_{1}}/2$. On the other hand, part of the range ${m}_{\ensuremath{\chi}}\ensuremath{\gtrsim}{M}_{{H}_{1}}/2$ which is allowed by cosmology is excluded by antiproton fluxes.