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： 2016-09-14
摘要： The candidate of minimal dark matter (MDM) is limited if one demands perturbativity up to a very high scale, and it was believed that the MDM model with a real scalar septuplet could keep perturbative up to the Planck or GUT scale. In this work we point out that it is not true after taking into account the running of the quartic self-couplings of the scalar septuplet. For the septuplet mass around 10 TeV, which is suggested by the observed dark matter relic abundance, these couplings would hit the Landau pole at a scale ∼108−109 GeV, much lower than the Planck scale. We attempt to push up the Landau pole scale as high as possible by proposing an extension with extra Yukawa interactions of the septuplet. We find that in principle the Landau pole could be deferred to a scale of ∼1014 GeV if one could tolerate a serious fine-tuning of the initial condition of the Yukawa coupling. Moreover, if the MDM particle mass could be relaxed to ∼108 GeV, which would need some nonthermal production mechanisms to give a correct relic abundance, the Landau pole scale could be pushed up above the Planck scale.
分类： 物理学 >> 核物理学 提交时间： 2016-08-31
摘要： We propose a novel framework for asymmetric scalar dark matter (ADM), which has interesting collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local U(1)d symmetry which is broken at a low scale and provides a light gauge boson X. The dark gauge coupling is strong and then ADM can annihilate away into X-pair effectively. Therefore, the ADM can form bound state due to its large self-interaction via X mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with bb¯. Of particular interest, our setup nicely explains the recent di-photon anomaly at 750 GeV via the events from ${\rm ADMonium}\ra 2X(\ra e^+e^-)$, where the electrons are identified as (un)converted photons. The remarkable prediction of an ADM near 375 GeV can be tested at the direct detection experiments in the near future.
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