分类: 物理学 >> 核物理学 分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2023-09-12
摘要: The neutron capture cross sections (${n, upgamma}$) of Bromine was performed with the time-of-flight (TOF) technique at the Back-n facility of the China Spallation Neutron Source (CSNS). Prompt $ upgamma$-rays originating from neutron-induced capture events were detected by four C${}_6$D${}_6$ detectors. The pulse height weighting technique (PHWT) and the double-bunch unfolding method based on the Bayesian theory were used in the data analysis. To obtain reliable measurement results, background deductions, normalization, and corrections were carefully considered. The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region (RRR). The average cross sections in unresolved resonance region the was obtained from 10 to 400 keV. The experimental results were compared with the data of several evaluated libraries and previous experiments in the resolved and unresolved resonance region. The TALYS code was used to describe the average cross sections in the unresolved resonance region. Astrophysical Maxwell average cross sections (MACSs) of ${}^{79,81}$Br from $ kT $ = 5 to 100 keV was calculated over a sufficiently wide range of neutron energies. At a thermal energy of $kT=30$ keV, the MACS value for ${}^{79}$Br 638$ pm$64 mb is in good agreement with the KADoNiS recommended value. By contrast, the value of 293$ pm$29 mb for ${}^{81}$Br is substantially higher than those of the evaluated database and the KADoNiS recommended value.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-06-28
摘要: 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.
分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-06-28
摘要: We observe a generic connection between LHC Higgs data and electroweak baryogenesis: the particle that contributes to the CP-odd hgg or h gamma gamma vertex would provide the CP-violating source during a first-order phase transition. It is illustrated in the two Higgs doublet model that a common complex phase controls the lightest Higgs properties at the LHC, electric dipole moments, and the CP-violating source for electroweak baryogenesis. We perform a general parametrization of Higgs effective couplings and a global fit to the LHC Higgs data. Current LHC measurements prefer a nonzero phase for tan beta less than or similar to 1 and electric dipole moment constraints still allow an order-one phase for tan beta similar to 1, which gives sufficient room to generate the correct cosmic baryon asymmetry. We also give some prospects in the direct measurements of CP violation in the Higgs sector at the LHC.