We consider a leptophobic Zscenario in a flipped SU(5) grand unified theory obtained from heteroticstring theory. We show that the allowed Z mass, flavor conserving and flavor changing couplings of theZ to the down-type quarks are strongly constrained by the mass difference in Bs–Bs system and the fourbranching ratios of B →π K decays. It is shown that even under these constraints large deviations in directand/or indirect CP asymmetries of B →π K decays from the SM expectations are allowed. Especiallyit is possible to accommodate the apparent puzzling data in B →π K CP asymmetries.
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机译：我们考虑了从异质弦理论获得的翻转 SU（5） 大统一理论中的恐钩 Z场景。结果表明，Z与下型夸克的Z质量、风味守恒和风味变化耦合受到Bs-Bs体系质量差异和B→π K衰变的4个分支比的强烈制约。结果表明，即使在这些约束条件下，B→π K衰减的直接和/或间接CP不对称性也允许与SM预期有很大的偏差。特别是可以容纳 B →π K CP 不对称中明显令人费解的数据。
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