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 — preprints:1997:ttp97-17 [2016/03/17 11:03] (current) Line 1: Line 1: + ====== TTP97-17 Constraining the CKM angle $\gamma$ and penguin contributions through combined $B \to \pi K$ branching ratios ====== + + + Motivated by recent CLEO measurements of $B\to\pi K$ modes, we investigate + their implications for the CKM angle $\gamma$ and a consistent description + of these decays within the Standard Model. Interestingly it turns out that + already the measurement of the combined branching ratios $B^\pm\to\pi^\pm K$ + and $B_d\to\pi^\mp K^\pm$ allows to derive stringent constraints on $\gamma$ + which are complementary to the presently allowed range for that angle. This + range, arising from the usual fits of the unitarity triangle, is typically + symmetric around $\gamma = 90^\circ$, while our method can in principle + {\it exclude} a range of this kind. Consistency within the Standard Model + implies furthermore bounds on the ratio $r\equiv|T'|/|\tilde P|$ of the + current-current and penguin operator contributions to $B_d\to\pi^\mp K^\pm$, + and upper limits for the CP-violating asymmetry arising in that decay. + Commonly accepted means to estimate $r$ yield values at the edge of + compatibility with the present CLEO measurements. + + + |**Robert Fleischer, Thomas Mannel**  | + |** Phys. Rev. D57 2752-2759 1998  **  | + | {{preprints:1997:ttp97-17.pdf|PDF}} {{preprints:1997:ttp97-17.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/9704423|arXiv]]   | + | |