Electroweak baryogenesis and the Fermi gamma-ray line

Abstract

Many particle physics models attempt to explain the 130 GeV gamma-ray feature that the Fermi large area telescope observes in the Galactic center. Neutralino dark matter in nonminimal supersymmetric models, such as the next-to-minimal supersymmetric standard Model (NMSSM), is an especially well-motivated theoretical setup that can explain the line. We explore the possibility that regions of the NMSSM consistent with the 130 GeV line can also produce the observed baryon asymmetry of the universe via electroweak baryogenesis. We find that such regions can, in fact, accommodate a strongly first-order electroweak phase transition (due to the singlet contribution to the effective potential), while also avoiding a light stop and producing a Standard Model (SM)-like Higgs in the observed mass range. Simultaneously, $CP$ violation from a complex phase in the wino-Higgsino sector can account for the observed baryon asymmetry through resonant sources at the electroweak phase transition, while satisfying current constraints from dark matter, collider, and electric dipole moment experiments. This result is possible by virtue of a relatively light pseudoscalar Higgs sector with a small degree of mixing, which yields efficient $s$-channel resonant neutralino annihilation consistent with indirect detection constraints, and of the moderate values of $\ensuremath{\mu}$ required to obtain a binolike lightest supersymmetric particle consistent with the line. The wino mass is essentially a free parameter that one can tune to satisfy electroweak baryogenesis. Thus, the NMSSM framework can potentially explain the origins of both baryonic and dark matter components in the Universe. The tightness of the constraints we impose on this scenario makes it extraordinarily predictive and conclusively testable in the near future by modest improvements in electric dipole moment and dark matter search experiments.