arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1002.4794hep-phhep-ex
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在$D^0-\bar D^0$混合中,SM对CP破坏的贡献有多大?

How large can the SM contribution to CP violation in $D^0-\bar D^0$ mixing be?

M. Bobrowski, A. Lenz, J. Riedl, J. Rohrwild

摘要:

本文以重夸克展开为理论工具,研究了标准模型(SM)中$D$ -混合中CP破坏效应的最大尺寸。为此,我们确定了中性$D$介子混合振幅吸收部分的主导HQE贡献和$α_s$修正以及次主导$1/m_c$修正。结果表明,这些对$Γ_{12}$的贡献在精确的SU $(3)_\mathrm{F}$极限下不会消失。此外,虽然领先的HQE条款给出的结果为$Γ_{12}$数量级低于目前的实验值,我们发现一个相当大的阶段。在文献中,有人建议,高阶项的HQE可能会少得多的严重GIM取消的领先条款的影响,它甚至不排除这些高阶项可以重现$y$的实验值。如果这种增强在自然界中实现,则在领先的HQE项中发现的相位可以具有相当大的影响。因此,我们认为像这样的陈述:{ \it“$D$中的CP破坏效应--从$10^{-3}$到$10^{-2}$的混合是新物理学的明确标志”}--考虑到我们对SM预言的有限了解--是不成熟的。最后,我们给出了一个新的物理模型的例子,可以提高领先的HQE条款$Γ_{12}$的一到两个数量级。

英文摘要:

We investigate the maximum size of CP violating effects in $D$-mixing within the Standard Model (SM), using Heavy Quark Expansion (HQE) as theoretical working tool. For this purpose we determine the leading HQE contributions and also $α_s$ corrections as well as subleading $1/m_c$ corrections to the absorptive part of the mixing amplitude of neutral $D$ mesons. It turns out that these contributions to $Γ_{12}$ do not vanish in the exact SU$(3)_\mathrm{F}$ limit. Moreover, while the leading HQE terms give a result for $Γ_{12}$ orders of magnitude lower than the current experimental value, we do find a sizeable phase. In the literature it was suggested that higher order terms in the HQE might be much less affected by the severe GIM cancellations of the leading terms; it is even not excluded that these higher order terms can reproduce the experimental value of $y$. If such an enhancement is realized in nature, the phase discovered in the leading HQE terms can have a sizeable effect. Therefore, we think that statements like: {\it "CP violating effects in $D$-mixing of the order of $10^{-3}$ to $10^{-2}$ are an unambigous sign of new physics"}--given our limited knowlegde of the SM prediction--are premature. Finally, we give an example of a new physics model that can enhance the leading HQE terms to $Γ_{12}$ by one to two orders of magnitude.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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