CP-Violating Effects in Neutralino Scattering and Annihilation

Abstract

CP-violating effects that mix the CP-even and CP-odd Higgs bosons can have important consequences for annihilation and scattering of supersymmetric neutralino dark matter. Specifically, we study the dependence on the phase of the third generation trilinear couplings At and Ab. We find enhancements in the neutralino annihilation scattering rate which are typically factors of one to four; in the narrow regime of parameter space with neutralino mass close to half the Higgs mass, we find new (CP violating) resonances which may increase the annihilation cross section by factors up to 106. CP-violating effects can also modify the neutralino scattering rate off nucleons. For cross sections accessible to upcoming experiments, the rate can be enhanced by a factor as large as 2 or suppressed by a factor of up to 3; for lower cross sections, the suppression can be as large as seven orders of magnitude. We find cases in the region being probed by dark matter searches which are experimentally or cosmologically excluded when CP is conserved but are allowed when CP is violated. These effects are important for direct and indirect detection of neutralino dark matter in cryogenic detectors, the Earth, the Sun, the galactic halo and the galactic center.