The main purpose of this paper is to investigate energy bounds in the context of f(R, G) gravity. To meet this aim, we choose static spherically symmetric spacetime in f(R, G) gravity to develop the field equations. W...The main purpose of this paper is to investigate energy bounds in the context of f(R, G) gravity. To meet this aim, we choose static spherically symmetric spacetime in f(R, G) gravity to develop the field equations. We select three different models of f(R, G) gravity, which are thoroughly discussed in the literature. Firstly, the inequalities are formulated using energy bounds and then viability of the considered models are checked respectively. Graphical analysis show that specific f(R, G) gravity models are satisfied under suitable values of model parameters. It is shown that in a certain case energy bounds are satisfied expect SEC, which supports the late time acceleration expansion of unverse.展开更多
Motivated by the recently updated experimental measurement on Bd→μ^＋μ^- and B^-→π^-μ＋μ^- decays by CDF and Belle collaborations, we revisit these decays, as well as B^-→ρ^-μ^＋μ^- decay, within the Standa...Motivated by the recently updated experimental measurement on Bd→μ^＋μ^- and B^-→π^-μ＋μ^- decays by CDF and Belle collaborations, we revisit these decays, as well as B^-→ρ^-μ^＋μ^- decay, within the Standard Model, and evaluate the effects of a family non-universal Z＇ boson. Under the constraint from β（B- → π^-μ＋μ^-）, we find the ranges of the Z＇ couplings SLRμμ 〈 -5.2 × 10^-2 or Dμμ^LR 〈 -8.1 × 10^-2 are excluded. Within the allowed Z＇ parameters spaces, comparing with the SM predictions, we find that B（Bd→μ^＋μ^-）, B（B^-→π^-μ＋μ^-）, and B（B^-→ρ^-μ＋μ^-） could be enhanced by a factor about 226%, 245%, and 254%, respectively, by Z＇ contributions. However, they are hardly to be reduced. Furthermore, the zero crossing in the normalized forward-backward asymmetry spectrum of B^-→ρ^-μ＋μ^- decay at low dimuon mass always exists.展开更多
In this paper, we calculate the top quark rare decays t →cγ and v in an extension of the standard model, where baryon number and lepton number are local gauge symmetries. Adopting reasonable assumptions on the param...In this paper, we calculate the top quark rare decays t →cγ and v in an extension of the standard model, where baryon number and lepton number are local gauge symmetries. Adopting reasonable assumptions on the parameter space, we find that the branching ratios of t →cγ and t →cg can reach 10^-6 and 10^-5 respectively, which can be detected in near future.展开更多
文摘The main purpose of this paper is to investigate energy bounds in the context of f(R, G) gravity. To meet this aim, we choose static spherically symmetric spacetime in f(R, G) gravity to develop the field equations. We select three different models of f(R, G) gravity, which are thoroughly discussed in the literature. Firstly, the inequalities are formulated using energy bounds and then viability of the considered models are checked respectively. Graphical analysis show that specific f(R, G) gravity models are satisfied under suitable values of model parameters. It is shown that in a certain case energy bounds are satisfied expect SEC, which supports the late time acceleration expansion of unverse.
基金Supported by the National Natural Science Foundation under Grant Nos. 11105043 and 11075059Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20114104120002Startup Foundation for Doctor of Henan Normal University under Grant No. 1006
文摘Motivated by the recently updated experimental measurement on Bd→μ^＋μ^- and B^-→π^-μ＋μ^- decays by CDF and Belle collaborations, we revisit these decays, as well as B^-→ρ^-μ^＋μ^- decay, within the Standard Model, and evaluate the effects of a family non-universal Z＇ boson. Under the constraint from β（B- → π^-μ＋μ^-）, we find the ranges of the Z＇ couplings SLRμμ 〈 -5.2 × 10^-2 or Dμμ^LR 〈 -8.1 × 10^-2 are excluded. Within the allowed Z＇ parameters spaces, comparing with the SM predictions, we find that B（Bd→μ^＋μ^-）, B（B^-→π^-μ＋μ^-）, and B（B^-→ρ^-μ＋μ^-） could be enhanced by a factor about 226%, 245%, and 254%, respectively, by Z＇ contributions. However, they are hardly to be reduced. Furthermore, the zero crossing in the normalized forward-backward asymmetry spectrum of B^-→ρ^-μ＋μ^- decay at low dimuon mass always exists.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10975027,11275036,11047002Natural Science Fund of Hebei University under Grant Nos.2011JQ05 and 2012-242
文摘In this paper, we calculate the top quark rare decays t →cγ and v in an extension of the standard model, where baryon number and lepton number are local gauge symmetries. Adopting reasonable assumptions on the parameter space, we find that the branching ratios of t →cγ and t →cg can reach 10^-6 and 10^-5 respectively, which can be detected in near future.
