Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-06-28
Abstract： We consider the Higgs portal through which light scalars contribute both to the Higgs production and decay and Higgs effective potential at finite temperature via quantum loops. The positive Higgs portal coupling required by a strongly first order electroweak phase transition is disfavored by the current Higgs data if we consider one such scalar. We observe that by introducing a second scalar with negative Higgs portal coupling, one can not only improve the Higgs fits, but also enhance the strength of first order EWPT. We apply this mechanism to the light stop scenario for electroweak baryogenesis in the MSSM and find a light sbottom could play the role as the second scalar, which allows the stop to be relatively heavier. Non-decoupled effects on the Higgs or sbottom self-interactions from physics beyond MSSM are found to be indispensable for this scenario to work. A clear prediction from the picture is the existence of a light sbottom (below 200 GeV) and a light stop (can be as heavy as 140 GeV), which can be directly tested in the near future.
Peer Review Status:
Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-06-27
Abstract： We perform a detailed semianalytical analysis of the electroweak phase transition (EWPT) property in the Next-to-Minimal Supersymmetric standard model, which serves as a good benchmark model in which the 126 GeV Higgs mixes with a singlet. In this case, a strongly first-order electroweak phase transition (SFOEWPT) is achieved by the tree-level effects, and the phase transition strength gamma(c) is determined by the vacua energy gap at T = 0. We make an anatomy of the energy gap at both tree level and loop level and extract out a dimensionless phase transition parameter R-kappa equivalent to 4 kappa v(s)/A(kappa), which can replace A(kappa) in the parameterization and affect the light CP-odd/even Higgs spectra. We find that SFOEWPT only occurs in R-kappa similar to -1 and positive R-kappa less than or similar to O(10), which in the non-PQ limit case would prefer either a relatively light CP-odd or CP-even Higgs boson similar to(60, 100) GeV, and therefore serves as a smoking gun signal and requires new search strategies at the LHC.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-06-24
Abstract： The gamma-ray excess observed by the Fermi-LAT in the Galactic Center can be interpreted by the dark matter annihilation to b (b) over bar via a light pseudoscalar in the next-to-minimal supersymmetric standard model (NMSSM). It is interesting to note that the corresponding singlet scalar is useful to achieve a strongly first-order phase transition required by the electroweak baryogenesis. In this paper, we investigate the possibility that the NMSSM model can simultaneously accommodate these two issues. The phase transition strength can be characterized by the vacua energy gap at zero temperature and be sufficiently enhanced by the tree-level effect in the NMSSM. We find that the annihilation of singlino/Higgsino dark matter (DM) particles occurring close to the light pseudoscalar resonance is favored by the Galactic Center excess and the observed DM relic density, and some resulting regions in the parameter space with a small kappa/lambda. and a negative A. can simultaneously account for a successful strongly first-order electroweak phase transition.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2016-06-18
Abstract： With the assistance of a complex singlet, and an effective operator involving CP violations, the dark matter relic abundance and baryon asymmetry of the universe have been addressed simultaneously. We studied the electroweak baryogenesis mechanism systematically. The electroweak phase transition analysis indicates that the strong first order phase transition takes place by one-step or two-step type due to the dynamics of the energy gap between the electroweak vacuum and the vacuum of the complex singlet. The relation between the magnitude of baryon asymmetry of the universe and the phase transition type and strength has been explored in the framework of electroweak baryogenesis.
Peer Review Status:Awaiting Review
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