Electroweak Baryogenesis And The Fermi Gamma-Ray Line

TL;DR

This paper investigates whether the NMSSM can simultaneously explain the 130 GeV gamma-ray line, baryon asymmetry, and dark matter, showing it is a highly predictive and testable unified framework.

Contribution

It demonstrates that the NMSSM can produce a strongly first-order electroweak phase transition and baryogenesis while fitting the gamma-ray line and dark matter constraints.

Findings

NMSSM can accommodate a strong first-order phase transition.

Resonant CP-violation can generate the baryon asymmetry.

Model predictions are testable with future EDM and dark matter experiments.

Abstract

Many particle physics models attempt to explain the 130 GeV gamma-ray feature that the Fermi-LAT observes in the Galactic Center. Neutralino dark matter in non-minimal supersymmetric models, such as the NMSSM, is an especially well-motivated theoretical setup which 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-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 (EDM) 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 $\mu$ required to obtain a bino-like LSP consistent with the line. The wino mass is essentially a free parameter which 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 EDM and dark matter search experiments.