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arXiv 1904.01129hep-ph
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用$B^\pm\to DK^\pm$衰变测量CKM角$γ$时中性K介子的CP破坏和物质相互作用

CP violation and material interaction of neutral kaons in measurements of the CKM angle $γ$ using $B^\pm\to DK^\pm$ decays where $D\to K_\text{S}^0π^+π^-$

Mikkel Bjørn, Sneha Malde

摘要:

随着$b$ -强子衰变中CKM角$γ$的测量变得越来越精确,重要的是要考虑影响二级和三级衰变产物的过程的影响,并可能导致观察到的CP破坏。用于测量$γ$的黄金衰减模式为$B^\pm\to DK^\pm$,其中$D\to K_\text{S}^0π^+π^-$。由于$K_\text{S}^0$介子在最终状态的存在下,$γ$测量基于这种模式的中性K介子CP破坏和物质再生的影响,本研究探讨的影响的潜在大小。以前的研究确定的影响K介子CP破坏是几度的大小,但简化假设如何实验测量实施。本研究取消了这些假设,并首次考虑了物质再生效应。这些结果是在使用LHCb和Belle II II探测器进行$γ$测量的背景下给出的。结果表明,在所有实验条件下,由于忽略中性K介子中的CP破坏和物质再生效应而产生的期望偏差都很小,小于$0.5^\circ$度.

英文摘要:

As measurements of the CKM angle $γ$ in decays of $b$-hadrons become increasingly precise, it is important to consider the impact of processes that affect secondary and tertiary decay products and can contribute to the observed CP violation. The golden decay mode used to measure $γ$ is $B^\pm\to DK^\pm$, where $D\to K_\text{S}^0π^+π^-$. Due to the presence of a $K_\text{S}^0$ meson in the final state, $γ$ measurements based on this mode are affected by neutral kaon CP violation and matter regeneration, and this study examines the potential size of the impact. Previous studies determine the impact of kaon CP violation to be a few degrees in size, but make simplifying assumptions about how experimental measurements are implemented. These assumptions are lifted in the present study, and the matter regeneration effect is included for the first time. The results are presented within the context of $γ$ measurements to be made using the LHCb and Belle II II detectors. It is found that the expected biases due to ignoring the effects of CP violation and matter regeneration in neutral kaons is small and less than $0.5^\circ$ degrees in all experimental scenarios considered.

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