再论$B \to πK$之谜
The $B \to πK$ Puzzle Revisited
摘要：
多年来，在四种$B \to πK$衰变（$B^+ \to π^+ K^0$、$B^+ \to π^0 K^+$、$B^0 \to π^- K^+$、$B^0 \to π^0 K^0$）的分支比和CP不对称性的测量中存在一定的不一致。在本文中，我们重新审视这个$B \to πK$难题。我们发现，关键的未知参数是$|C'/T'|$，颜色抑制和颜色允许树振幅的比例。如果该比率较大，则SM可以解释数据，即$|C'/T'| = 0.5$。但是如果它很小，$|C'/T'| = 0.2$，SM就不能解释$B \to πK$之谜--需要新的物理学（NP）。在树的层次上，可以对$B \to πK$做出贡献的两种NP类型是$Z'$玻色子和双夸克。如果$Z'$与惯用右手的$u{\bar u}$和/或$d{\bar d}$（带有$g_R^{dd} \ne g_R^{uu}$）耦合，则$Z'$模型可以解释这个问题。有趣的是，在众多用来解释$b \to s μ^+ μ^-$衰变异常现象的$Z'$模型中，有一半的模型具有所需的$Z'$与$u{\bar u}$和/或$d{\bar d}$的耦合。这样的模型可以潜在地解释$b \to s μ^+ μ^-$异常和$B \to πK$之谜。与$ud$配对的彩色六重双夸克的加入也可以解释这个谜题。
英文摘要：
For a number of years, there has been a certain inconsistency among the measurements of the branching ratios and CP asymmetries of the four $B \to πK$ decays ($B^+ \to π^+ K^0$, $B^+ \to π^0 K^+$, $B^0 \to π^- K^+$, $B^0 \to π^0 K^0$). In this paper, we re-examine this $B \to πK$ puzzle. We find that the key unknown parameter is $|C'/T'|$, the ratio of color-suppressed and color-allowed tree amplitudes. If this ratio is large, $|C'/T'| = 0.5$, the SM can explain the data. But if it is small, $|C'/T'| = 0.2$, the SM cannot explain the $B \to πK$ puzzle -- new physics (NP) is needed. The two types of NP that can contribute to $B \to πK$ at tree level are $Z'$ bosons and diquarks. $Z'$ models can explain the puzzle if the $Z'$ couples to right-handed $u{\bar u}$ and/or $d{\bar d}$, with $g_R^{dd} \ne g_R^{uu}$. Interestingly, half of the many $Z'$ models proposed to explain the present anomalies in $b \to s μ^+ μ^-$ decays have the required $Z'$ couplings to $u{\bar u}$ and/or $d{\bar d}$. Such models could potentially explain both the $b \to s μ^+ μ^-$ anomalies and the $B \to πK$ puzzle. The addition of a color sextet diquark that couples to $ud$ can also explain the puzzle.
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。
