CONSTRAINING THE CKM ANGLE-GAMMA AND PENGUIN CONTRIBUTIONS THROUGH COMBINED B-]PI-K BRANCHING RATIOS

Motivated by recent CLEO measurements of B-->pi K modes, we investigat e their implications for the CKM angle gamma and a consistent descript ion of these decays within the standard model. Interestingly it turns out that already the measurement of the combined branching ratios B+/- -->pi(+/-)K and B-d-->pi(+/-)K(+/-) allows us to derive stringent cons traints on gamma which are complementary to the presently allowed rang e for that angle. This range, arising from the usual fits of the unita rity triangle, is typically symmetric around gamma=90 degrees, while o ur method can in principle exclude a range of this kind. Consistency w ithin the standard model implies furthermore bounds on the ratio r=\T' \/\(P) over tilde\ of the current-current and penguin operator contrib utions to B-d-->pi(+/-)K(+/-), and upper limits for the CP-violating a symmetry arising in that decay. Commonly accepted means to estimate r yield values at the edge of compatibility with the present CLEO measur ements.