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arXiv 1009.4545hep-ph
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标准模型中的Charm混合

Charm mixing in the Standard Model

Markus Bobrowski, Alexander Lenz

摘要:

本文报道了中性粲介子混合的研究结果,并指出在现阶段,标准模型中不能排除千分之几量级的CP破坏弱相。它示出了如何一些,看似合理的,简化假设CKM耦合导致错误的结论,即CP破坏,这个数额是一个明确的指示新的物理。所提出的结果依赖于最近的短距离分析的三角洲C=2过渡,这证实了预期的主要贡献是由于味对称性破缺的影响出现在高阶的重夸克膨胀。我们调查介子反介子过渡与介子的海夸克背景,目前在10和12维的中间状态耦合,使用因式分解的方法来简化运营商的基础。由于GIM抑制提升了m_s/m_c的一次幂,对y=Delta Gamma/2 Gamma的贡献超过了形式上的前导维数6的近十倍。

英文摘要:

In this talk we report on a study on the mixing of neutral charmed mesons and argue that, at the present stage, a CP violating weak phase of the order of some per mille can not be excluded in the Standard Model. It is shown how some, seemingly reasonable, simplifying assumptions about CKM couplings lead to the wrong conclusion that CP violation of this amount is an unambiguous indication of new physics. The presented results rely on a recent short-distance analysis of the Delta C=2 transition, which confirms the expectation that the dominant contribution is due to effects of flavour symmetry breaking appearing in higher orders of the Heavy Quark Expansion. We investigate meson-antimeson transitions with an intermediate state coupling to the meson's sea quark background, present in dimension 10 and 12, using a factorisation approach to simplify the operator basis. On account of a lifting of GIM suppression by one power of m_s/m_c, the contribution to y=Delta Gamma/2 Gamma is found to exceed that of the formally leading dimension six by a factor close to ten.

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