分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-06-27
摘要： 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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： We consider the current experimental constraints on the parameter space of the MSSM and NMSSM. Then in the allowed parameter space we examine the Higgs pair production at the 14TeV LHC via b (b) over bar -> hh (h is the 125GeV SM-like Higg boson) with one-loop SUSY QCD correction and compare it with the production via gg -> hh. We obtain the following observations: (i) For the MSSM the production rate of b (b) over bar -> hh can reach 50 fb and thus can be competitive with gg -> hh, while for the NMSSM b (b) over bar -> hh has a much smaller rate than gg. hh due to the suppression of the hb (b) over bar coupling; (ii) The SUSY-QCD correction to b (b) over bar -> hh is sizable, which can reach 45% for the MSSM and 15% for the NMSSM within the 1s region of the Higgs data; (iii) In the heavy SUSY limit (all soft mass parameters become heavy), the SUSY effects decouple rather slowly from the Higgs pair production (especially the gg -> hh process), which, for M S U S Y = 5TeV and m A < 1TeV, can enhance the production rate by a factor of 1.5 and 1.3 for the MSSM and NMSSM, respectively. So, the Higgs pair production may be helpful for unraveling the effects of heavy SUSY.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： Motivated by the future precision test of the Higgs boson at an e(+)e(-) Higgs factory, we calculate the production e(+)e(-) -> ZH gamma in the Standard Model with complete next-to-leading order electroweak corrections. We find that for p s root s = 240 (350) GeV the cross section of this production is sizably reduced by the electroweak corrections, which is 1.03 (5.32) fb at leading order and 0.72 (4.79) fb at next-to-leading order. The transverse momentum distribution of the photon in the final states is also presented.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： In SUSY, a light dark matter is usually accompanied by light scalars to achieve the correct relic density, which opens new decay channels of the SM-like Higgs boson. Under current experimental constraints including the latest LHC Higgs data and the dark matter relic density, we examine the status of a light neutralino dark matter in the framework of NMSSM and confront it with the direct detection results of CoGeNT, CDMS-II and LUX. We have the following observations: (i) A dark matter as light as 8 GeV is still allowed and its scattering cross section off the nucleon can be large enough to explain the CoGeNT/CDMS-II favored region; (ii) The LUX data can exclude a sizable part of the allowed parameter space, but still leaves a light dark matter viable; (iii) The SM-like Higgs boson can decay into the light dark matter pair with an invisible branching ratio reaching 30% under the current LHC Higgs data, which may be tested at the 14 TeV LHC experiment.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： In the Next-to-Minimal Supersymmetric Standard Model (NMSSM), all singlet-dominated particles including one neutralino, one CP-odd Higgs boson and one CP-even Higgs boson can be simultaneously lighter than about 100 GeV. Consequently, dark matter (DM) in the NMSSM can annihilate into multiple final states to explain the galactic center gamma-ray excess (GCE). In this work we take into account the foreground and background uncertainties for the GCE and investigate these explanations. We carry out a sophisticated scan over the NMSSM parameter space by considering various experimental constraints such as the Higgs data, B-physics observables, DM relic density, LUX experiment and the dSphs constraints. Then for each surviving parameter point we perform a fit to the GCE spectrum by using the correlation matrix that incorporates both the statistical and systematic uncertainties of the measured excess. After examining the properties of the obtained GCE solutions, we conclude that the GCE can be well explained by the pure annihilations and with A (1) being the lighter singlet- dominated CP-odd Higgs boson and H (i) denoting the singlet-dominated CP-even Higgs boson or SM-like Higgs boson, and it can also be explained by the mixed annihilation , A (1) H (1). Among these annihilation channels, can provide the best interpretation with the corresponding p-value reaching 0.55. We also discuss to what extent the future DM direct detection experiments can explore the GCE solutions and conclude that the XENON-1T experiment is very promising in testing nearly all the solutions.
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