标题： 驯服B0(t)→π+π- CP不对称性中的企鹅：可观测量和最小理论输入 显示英文标题

标题： Taming the Penguin in the B0(t) -> Pi+Pi- CP-asymmetry: Observables and Minimal Theoretical Input

摘要： 企鹅贡献在一般情况下不可忽略，可能会隐藏来自B0(t)→π+π- CP不对称性测量的CKM角α的信息。 然而，我们表明，这些信息可以总结为一组简单的方程，将α表示为单个理论上未知参数的多值函数，该参数可以方便地选择为企鹅振幅与树图振幅的一个明确比值。 利用这些精确的解析表达式，在仅依赖标准模型的前提下，以及一些合理的假设来限制企鹅振幅的模，我们推导出几个新的企鹅引起的偏移|2α-2α_eff|的上界，推广了Grossman和Quinn最近的结果。 这些界限取决于某些衰变（π0π0，K0K0̄，K±π∓）的平均分支比，这些衰变对企鹅特别敏感。 另一方面，通过进一步且不太保守的近似，我们表明，仅知道B±→Kπ±的分支比就足以提取自由参数，而无需其他测量，也无需知道|V_td|或|V_ub|。 更一般地说，若能以约30%的精度知道企鹅振幅的模，可能会得到与实验上更困难的同位旋分析相竞争的α提取结果。 我们还表明，我们的框架能够以透明且简单的方式恢复大多数先前的方法，在某些情况下甚至可以改进它们。 此外，我们详细讨论了各种离散歧义的问题。 显示英文摘要

摘要： Penguin contributions, being not negligible in general, can hide the information on the CKM angle alpha coming from the measurement of the time-dependent B0(t) -> pi+pi- CP-asymmetry. Nevertheless, we show that this information can be summarized in a set of simple equations, expressing alpha as a multi-valued function of a single theoretically unknown parameter, which conveniently can be chosen as a well-defined ratio of penguin to tree amplitudes. Using these exact analytic expressions, free of any assumption besides the Standard Model, and some reasonable hypotheses to constrain the modulus of the penguin amplitude, we derive several new upper bounds on the penguin-induced shift |2alpha-2alpha_eff|, generalizing the recent result of Grossman and Quinn. These bounds depend on the averaged branching ratios of some decays (pi0pi0, K0K0bar, K+-pi-+) particularly sensitive to the penguin. On the other hand, with further and less conservative approximations, we show that the knowledge of the B+- -> Kpi+- branching ratio alone gives sufficient information to extract the free parameter without the need of other measurements, and without knowing |V_td| or |V_ub|. More generally, knowing the modulus of the penguin amplitude with an accuracy of ~30% might result in an extraction of alpha competitive with the experimentally more difficult isospin analysis. We also show that our framework allows to recover most of the previous approaches in a transparent and simple way, and in some cases to improve them. In addition we discuss in detail the problem of the various kinds of discrete ambiguities.