B_c和γ介子两体非轻衰变的研究

发布时间：2018-01-19 12:40

  本文关键词： QCD因子化 B_c介子 γ介子 非轻衰变　出处：《华中师范大学》2016年博士论文　论文类型：学位论文

【摘要】：重味物理是检验标准模型、探索CP破坏起源和寻找新物理的重要场所。LHC的运行,预计每年将产生5×1010 Bc事例数。同时,在Belle和BaBar已经收集了超过108 T介子的实验数据；而在LHCb上,每.f6-1积分亮度下预计会产生1011巧事例数；即将运行的SuperKEKB上也将会产生大量的T事例数。如此充足的数据量,使得B。介子和T介子成为重味物理研究的重要的场所。在本文中我们将采用QCD因子化方法来对Bc介子和T介子的一些弱衰变过程进行研究和分析。首先,我们介绍了一些基本理论,包括标准模型,CKM矩阵以及重整化群和算符乘积展开等。其次,我们介绍了几种常用的计算强子矩阵元的方法,并着重介绍了QCD因子化方法。最后,我们给出论文的主题部分,主要由以下两部分组成：首先,在QCD因子化框架下,对B→PP, PV的两体非轻无粲过程进行分析。在标准模型下,这一类衰变过程是纯湮灭过程,且只有流-流算符有贡献,使得这类衰变过程成为研究重介子湮灭衰变的一个很好的场所。在本文中,我们将采用两种方案来处理湮灭图计算中的端点发散问题：方案Ⅰ是通常的QCD因子化方法；方案Ⅱ是采用红外有限的胶子传播子和耦合常数。这两种不同的方案已经被用于处理玩,d,s的衰变过程,在这里我们用于研究Bc介子的衰变过程。在计算中,我们采用了三种不同形式的Bc介子波函数进行比较。结果表明：在方案Ⅰ下,该类衰变过程的分支比结果很小,较难在实验上被探测到。在方案Ⅱ下,当采用红外有限的胶子传播子时,湮灭图的贡献相对于方案Ⅰ来说得到了增强,但依然小于pQCD给出的计算结果。在我们的计算中,Bc-→π-ω过程有着最大的衰变分支比Br(Bc-→π-ω)=12.8×10-8,这个衰变过程很可能在LHC或即将运行的SuperKEKB上被探测到。接着,我们在QCD因子化方案下研究了T(nS)→BcM的衰变过程,并用非相对论波函数来计算T到介子的跃迁形状因子。唯象上,T(nS)→BcM的弱衰变过程仅有流-流算符的贡献,并且是被CKM矩阵元vd,增强的,因此这类衰变过程在T介子的弱衰变中有着相对较大的分支比。结果表明：在T(nS)→BcM这类衰变中(M=π,ρ,K和K*),T(nS)→Bcp的衰变过程有着相对较大的分支比结果,大约在O(10-10),应该最先在实验上被探测到。
[Abstract]:Heavy taste physics is a standard model for testing, exploring the origin of CP destruction and the operation of LHC, which is an important site for finding new physics. It is estimated that 5 脳 1010Bc cases will be produced every year. At the same time. More than 108T meson experimental data have been collected at Belle and BaBar; On LHCb, 1011 coincidences are expected to occur per f6-1 integral brightness; A large number of T cases will also be generated on the upcoming SuperKEKB. Such a large amount of data. In this paper, we will use QCD factorization method to study and analyze some weak decay processes of Bc mesons and T mesons. . We introduce some basic theories, including the canonical model CKM matrix, renormalization group and operator product expansion. Secondly, we introduce several common methods for calculating Hadron matrix elements. Finally, we give the theme part of the paper, which is composed of the following two parts: first, under the framework of QCD factorization, B. 鈫扞n the standard model, this kind of decay process is pure annihilation process, and only the current-current operator contributes. It makes this kind of decay process a good place to study the decay of heavy meson annihilation. We will adopt two schemes to deal with the endpoint divergence in annihilation graph calculation: scheme I is a common QCD factorization method; Scheme II uses infrared finite gluon propagators and coupling constants. These two different schemes have been used to deal with the decay process of playing with dcs. In this paper, we study the decay process of Bc mesons. In the calculation, we use three different forms of Bc meson wave functions to compare. The results show that: 1. The branch ratio of this kind of decay process is very small, which is difficult to detect experimentally. In scheme II, the contribution of annihilation diagram is enhanced compared with scheme I when the infrared finite gluon propagator is used. But still less than the results given by pQCD. 鈫捪，

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