共查询到19条相似文献,搜索用时 62 毫秒
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The branching ratio of the following three modes of K+-meaon decay K+→μ++π0+ν K+→e++π0+ν K+→μ++ν is calculated by using the theory of the universal Fermi weak interaction proposed by Feymann and others. Perturbation method with cut-off is used. The ratio obtained is 1:1.5:12, which is in fair agreement with the experimental value 1:1:15. It is shown, other conbinations of Fermi interactions can not give result in agreement with experiment. 相似文献
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本文基于最重要的"硬"产生机制,计算了Z0衰变产生Bc(或Bc)介子并伴有c(或c)和b(或b)两个重夸克喷注的产生率.指出在LEP上的下一次取数据中将产生出足够数目的Bc(或Bc)介子的性质成为可能. 相似文献
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K+离子通道及其研究进展 总被引:1,自引:0,他引:1
细胞是通过细胞膜与外界隔离的,在细胞膜上有很多离子通道,细胞通过这些通道与外界进行离子交换。离子通道在许多细胞活动中都起关键作用,它是生物电活动的基础,在细胞内和细胞间信号传递中起着重要作用。离子通道通过调控细胞内pH值和离子浓度来维持正常的细胞体积及细胞内生物分子活性所需的离子浓度范围。特别是通过改变作为第二信使的钙离子浓度,来调控各种生化过程。生命的很多过程如发育、生长、分泌、兴奋、运动,甚至于学习和记忆都与离子通道功能的正常发挥有直接联系。目前,离子通道的研究已成为分子生物学、分子药理学、生物物理学、神经生物学等多种学科的热点。 相似文献
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在顶色辅助的人工色(TC2)模型框架下, 研究了中性top介子π0t对轻子味破坏(LFV)过程li→ljγ,li→ljlkll和t→clilj的贡献. 考虑到当前μ→eγ过程的实验上限对TC2模型中自由参数的一些限制, 进一步计算了top介子对过程li→ljlkll和t→clilj分支比的量子修正.数值结果表明,在大部分参数空间内分支比的值可提高几个量级. top介子对某些过程的修正效应也许可被将来的实验观测到. 相似文献
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采用相对论平均场理论研究K凝聚对中子星物质的影响. 研究发现即使在含重子八重态和Δ共振态(n,p,Λ,Σ+,Σ0,Σ-,Ξ0,Ξ-,Δ0,Δ-)的中子星物质中,K-, K0凝聚也可以发生, 并详细研究了超子与K凝聚相互影响的行为. K0凝聚压低K-凝聚, 促进Δ共振态的出现, 在中子星的核心区域, 最终形成多种重子共存的、各重子数密度趋于均衡、且K0凝聚占最大比重的中子星物质. K凝聚使物态方程变软, 进而减小中子星的最大质量, 使之更接近于中子星正则质量. 相似文献
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在超荷-电荷表象中应用B2羣对称性讨论了基本粒子的轻子型衰变。将重子和介子分别填充在B2羣的4维表示时,在10维(正则)表示中正好包含所有|ΔS|≤1和|ΔQ|≤1的重子流或介子流。假定弱相互作用由中间玻色子作媒介,并将它们纳入B2羣的10维表示中,计算了包括ΔS=+ΔQ和ΔS=-ΔQ两类过程的各种奇异粒子轻子型衰变几率。结果与现有实验材料不矛盾。 相似文献
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D.C. Fries P. Heine H. Hirschmann A. Markou E. Seitz H.-J. Behrend W.P. Hesse W.A. McNeely T. Miyachi 《Nuclear Physics B》1978,143(3):408-416
A mass-dependent asymmetry was observed in the decay angular distribution of a photoproduced K+K? system near the K+K? threshold. The corresponding moments 〈Y10〉 have been evaluated. Interpreting the asymmetry as an S-P wave interface due to the states S9931(0+) and ø1019(1?) one can compute the moments 〈Y10〉 through an amplitude analysis. The theoretical calculation reproduces the experimental results well, if one assumes a real S-wave amplitude for the S9931. The data cannot be explained by a non-resonant real S-wave. Other possibilities have been discussed. An estimate of the photoproduction cross section of the can be given on the basis of the above hypothesis. 相似文献
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《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):333-342
The exclusive reactions γp → K
*0Σ+(1189) and γp → K
0π0Σ+(1189) , leading to the p 4π0 final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5GeV. The experiment
has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were
combined to a photon detector system of almost 4π geometrical acceptance. Differential and total cross-sections are reported.
At energies close to the threshold, a flat angular distribution has been observed for the reaction γp → K
0π0Σ+ suggesting dominant s -channel production. Σ*(1385) and higher-lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions
of the reaction γp → K
*0Σ+ indicates a t -channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical
predictions. 相似文献
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K^+—核散射研究进展 总被引:1,自引:0,他引:1
本简要回顾了K^ -核散射实验和理论方面近几年的研究进展。我们通过把介质中的K^ -核子相互作用与介质中的夸克凝联系起来,计算了K^ -核相互作用的非传统机制的贡献。结果表明核密度相关的介质内夸克凝聚可以解释K^ -核散射中的非传统介质效应。 相似文献
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We discuss various CP violation effects of neutral B mesons within the framework of the standard model.We classify 28 hadronic two-body decay channels of neutral B mesons into four classes,each of them has different CP violation effects, that is,CP violation due to phase dif- ference between mixing elements M12 and Г12; due to that between mixing elements and decay amplitudes; due to CP phase in the pure particle decay amplitudes and the interplay of these sources .Cascade decays of these channels are also discussed where copious interference is taken into account .Results are given in re- phasing invariants of the K-M matrix .It is shown that CP violation effects might be large(tHe largest,10-1,but the CP asymmetry event branching cross section is small,at the order or approximate 10-5±1/2. 相似文献
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The luminescence bands around 420 nm and 370 nm in CsI:Na and CsI:K have been studied by measuring the temperature dependence of decay times and luminescence and its excitation spectra. The bands are due to singlet+triplet localized excitons and to triplet localized excitons, respectively, at low temperature. Zero field splitting and life time amount to 0.2 meV and 3.3 μs for the 420 nm band, and to 2.1 meV and 1.7 μs for the 370 nm band. Creation processes of 420 nm excitons may not be the same below 40 K and near room temperature. 相似文献
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H. Ackermann T. Azemoon W. Gabriel D. Lüke H.D. Mertiens H.D. Reich G. Specht E. Ganssauge F. Janata D. Schmidt 《Nuclear Physics B》1978,133(3):397-407
We report measurements of kaon electroproduction from a hydrogen target carried out at DESY. The invariant cross section for the reaction ep → eK+ + anything is given as a function of the variables q2, W, x, p2⊥ and φ in the following region: . Finally we compare our data with a quark-parton model. 相似文献
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By means of ESR, two types of triplet excitons have been discovered in K+TCNQ? crystals, corresponding to the two independent rows of TCNQ? ions in the crystal structure of this compound. The orientational dependence of the dipolar splittings at ?46°C and intensity measurements as a function of temperature are presented. The zero field splitting parameters are small and therefore the excitons must be large with respect to a lattice parameter. The extended nature of the excitons indicates, that either the electron electron repulsions are relatively small with respect to the one electron bandwidth in this material or that the alternation of the interionic distances is small. 相似文献