分类: 物理学 >> 基本粒子与场物理学 提交时间: 2017-08-03
摘要: : We perform a detailed semi-analytical analysis of the electroweak phase transition (EWPT) property in NMSSM, 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 γc 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 Rκ ≡ 4κvs/Aκ, which can replace Aκ in the parameterization and affect the light CP odd and even Higgs spectra. We find that SFOEWPT only occurs in Rκ ∼ −1 and positive Rκ . O(10), which in the non-PQ limit case would prefer either a relatively light CP odd or CP even Higgs boson ∼ (60, 100) GeV, therefore serves as a smoking gun signal and requires new search strategies at the LHC.
分类: 物理学 >> 核物理学 提交时间: 2016-09-22
摘要: Recently, an excess of events in diphoton channel with invariant mass of about 750 GeV has been reported by the ATLAS and CMS Collaborations. Considering it as a tantalizing hint for new physics beyond the Standard Model (SM), we propose a simple extension of the SM with an additional doublet Higgs H′ and a singlet s. We consider the neutral component H′0 of H′ as the 750 GeV resonance, and assume that s is lighter than 2.6 GeV. In particular, H′0 can be produced at tree level via qq¯ production, and decay into a pair of s at tree level. And then s can decay into a pair of collimated photons, which cannot be distinguished at the LHC. We show that the diphoton production cross section can be from 3 to 13 fb, the decay width of H′0 can be from 30 to 60 GeV, and all the current experimental constraints including dijet constraint can be satisfied.