共查询到20条相似文献,搜索用时 0 毫秒
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The operators of b→sγ,b→sl+l-are usually regarded as being sufficient to describe b→sγγ,b→sl+l-γwith the statement that contributions from diagrams without an effective vertex b→sγ to processes b→sγγand b→sl+l-γ are negligible.In this work we present a comprehensive analysis of the transition b→sγγand find that 1)Effects due to off-shell quarks in vertex b→sγ on b→sγγ are large; 2)Contributions from diagrams without an effective vertex b→sγ to b→sγγare not negligible compared with others; 3)These effects cancel each other out exactly,so the operators of b→sγ can safely be used to describe b→sγγ. 相似文献
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《Physics letters. [Part B]》1988,202(4):591-595
Effects of charged Higgs bosons (H+) on various loop-induced processes in the B-meson system are discussed, within the framework of two Higgs doublet models (2HDMs). The H+ contribution to the magnetic moment form factor turns out to be very significant and it can distinguish between the two types of 2HDMs. Even with constraints from Bd mixing, both strong enhancements or strong suppressions (in b→sγ) of decay rates are possible. Thus, information from these modes is competitive with, and may soon surpass, restrictions on 2HDMs from Bd mixing. Since (inclusive) b→sγ and b→sg1 at current limits are not excluded, continued effort to detect them is encouraged. 相似文献
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CAI Hai-Ying ZHANG Da-Xin 《理论物理通讯》2005,44(5):887-890
The rare decay b → ssd is studied in a vector quark model by adding the contributions from exotic vector-like quarks. We find that the contribution from box diagrams amounts to 10^-9 in the branching ratio, while the Z-mediated tree level contribution is negligible. 相似文献
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在模型Ⅲ中研究了单举b→sτ+τ-过程的衰变分支比,包括领头阶QCD修正.发现由中性Higgs玻色子传播的树图贡献在一个合理的参数空间范围内是主要的,因此这个过程在将来的B介子实验中有可能被观察到. 相似文献
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Applying an effective Lagrangian method and an on-shell scheme, we analyze the electroweak corrections to the rare decay b→, s+γ from some special two loop diagrams in which a closed heavy fermion loop is attached to the virtual charged gauge bosons or Higgs. At the decoupling limit where the virtual fermions in the inner loop are much heavier than the electroweak scale, we verify the final results satisfying the decoupling theorem explicitly when the interactions among Higgs and heavy fermions do not contain the nondecoupling couplings. Adopting the universal assumptions on the relevant couplings and mass spectrum of new physics, we find that the relative corrections from those two loop diagrams to the SM theoretical prediction on the branching ratio of B → Xsγ can reach 5% as the energy scale of new physics ANp=200 GeV. 相似文献
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在模型Ⅲ中研究了单举b→sι^ ι^-过程的衰变分支比,包括领头阶QCD修正,发现由中性Higgs玻色子传播的树图贡献在一个合理的参数空间范围内是主要的,因此这个过程在将来的B介子实验中有可能被观察到。 相似文献
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Applying an effective Lagrangian method and an on-shell scheme, we analyze the electroweak corrections to the rare decay b→, s+γ from some special two loop diagrams in which a closed heavy fermion loop is attached to the virtual charged gauge bosons or Higgs. At the decoupling limit where the virtual fermions in the inner loop are much heavier than the electroweak scale, we verify the final results satisfying the decoupling theorem explicitly when the interactions among Higgs and heavy fermions do not contain the nondecoupling couplings. Adopting the universal assumptions on the relevant couplings and mass spectrum of new physics, we find that the relative corrections from those two loop diagrams to the SM theoretical prediction on the branching ratio of B → Xsγ can reach 5% as the energy scale of new physics ANp=200 GeV. 相似文献
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夸克胶子物质内的从夸克-夸克-反夸克到夸克-夸克-反夸克的散射过程会影响夸克物质和反夸克物质的热平衡化,其散射振幅是研究热平衡化的一个基础.依据微扰QCD理论,编制Fortran程序,推导了α_s~4阶的各个qq→qq散射费曼图的振幅平方和不同费曼图间的干涉项. 相似文献
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WU Lu-Sen XIAO Zhen-Jun 《理论物理通讯》2007,48(3):502-508
In this paper, we present the exact calculations for the vertex ^-sγb and ^sZb in the unitary gauge. We find that (a) the divergent- and μ-dependent terms are left in the effective vertex function Г^γμ(p, k) for b → sγ transition even after we sum up the contributions from four related Feynman diagrams; (b) for an on-shell photon, such terms do not contribute et al.; (c) for off-shell photon, these terms will be canceled when the contributions from both vertex ^sγb and ^sZb are taken into account simultaneously, and therefore the finite and gauge-independent function Zo(xt) = Co(xt) + Do(xt)/4, which governs the semi-leptonic decay b → sl^- l^+, is derived in the unitary gauge. 相似文献
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《Physics letters. [Part B]》1997,415(4):395-401
The short distance QCD corrections to b→sγγ are calculated in the leading logarithmic approximation. The equivalence of operator basis reduction for S-matrix elements by using the equations of motion or by proving a low energy theorem is discussed. We apply the above results to the exclusive Bs→γγ decay. The branching ratio of this decay is found to be 5×10−7 in the Standard Model. We also found that QCD corrections modify considerably the ratio between CP-even and CP-odd two-photon amplitudes. 相似文献
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We generalize the quark-pair creation model to a study of the radiative decays J/φ→γBB by assuming that the u.d,or s quark pairs are created with the same interaction strength,From the calculation of the ratio of the decay widths (J/φ→γpp)/Γ(J/φ→pp),we extract the quark-pari creation strength gI=15.40GeV,Based on the SU(6)spin-flavour basis and the “uds” basis,the radiative decay branching ratios cotaining strange baryons are evaluated.Measurements for these decay widths from the BESII data are suggested. 相似文献