分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-14
摘要： In light of the recent LHC Higgs search data, we investigate the pair production of a SM-like Higgs boson around 125 GeV in the MSSM and NMSSM. We first scan the parameter space of each model by considering various experimental constraints, and then calculate the Higgs pair production rate in the allowed parameter space. We find that in most cases the dominant contribution to the Higgs pair production comes from the gluon fusion process and the production rate can be greatly enhanced, maximally 10 times larger than the SM prediction (even for a TeV-scale stop the production rate can still be enhanced by a factor of 1.3). We also calculate the chi(2) value with the current Higgs data and find that in the most favored parameter region the production rate is enhanced by a factor of 1.45 in the MSSM, while in the NMSSM the production rate can be enhanced or suppressed (sigma(SUSY)/sigma(SM) varies from 0.7 to 2.4).
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： Recently the ATLAS collaboration reported a 3 sigma excess in the leptonic-Z + jets + E-T(miss) channel. This may be interpreted in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by gluino pair production with the decay chain (g) over tilde -> q (q) over bar(chi) over tilde (0)(2) -> q (q) over barZ (chi) over tilde (0)(1), where (chi) over tilde (0)(1) and (chi) over tilde (0)(2) denote the lightest and the next-to-lightest neutralinos with singlino and bino as their dominant components respectively. After exploring the relevant parameter space of the NMSSM by considering the constraints from the ATLAS searches for jets + E-T(miss) signals, we conclude that the NMSSM is able to explain the excess at 1 sigma level with the number of the signal events reaching its measured central value in optimal cases, and the best explanation comes from a compressed spectrum such as m((g) over tilde) similar or equal to 650 GeV, m((chi) over tilde2)(0) similar or equal to 565 GeV and m((chi) over tilde1)(0) similar or equal to 465 GeV. We also check the consistency of the ATLAS results with the null result of the CMS on-Z search. We find that under the CMS limits at 95% C.L., the event number of the ATLAS on-Z signal can still reach 11 in our scenario, which is about 1.2 sigma away from the measured central value.
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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