Measurements of the CKM Angle Phi3/gamma

Download or read book Measurements of the CKM Angle Phi3/gamma written by and published by . This book was released on 2007 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a review on the measurements of the CKM angle [gamma] ([phi]3)1 as performed by the BABAR and Belle experiments at the asymmetric-energy ee− B factories colliders PEP-II and KEKB. These measurements are using either charged or neutral B decays. For charged B decays the modes {tilde D}°K−, {tilde D}*°K−, and {tilde D}°K*− are employed, where {tilde D}° indicates either a D° or a {bar D}° meson. Direct CP violation is exploited. It is caused by interferences between V{sub ub} and V{sub cb} accessible transitions that generate asymmetries in the final states. For these decays various methods exist to enhance the sensitivity to the V{sub ub} transition, carrying the weak phase [gamma]. For neutral B decays, the modes D{sup (*){+-}}[pi]{sup {-+}} and D{sup {+-}}[rho]{sup {-+}} are used. In addition to the V{sub ub} and V{sub cb} interferences, these modes are sensitive to the B°-{bar B}° mixing, so that time dependent analyses are performed to extract sin(2[beta] + [gamma]). An alternative method would use the lower branching ratios decay modes {tilde D}{sup (*)0}{bar K}{sup (*)0} where much larger asymmetries are expected. The various available methods are mostly ''theoretically clean'' and always free of penguins diagrams. In some cases a high sensitivity to [gamma] is expected and large asymmetries may be seen. But these measurements are always experimentally difficult as one has to face with either low branching ratios, or small asymmetries, or additional technical/theoretical difficulties due to Dalitz/SU(3) and re-scattering models needed to treat/estimate nuisance parameters such as unknown strong phases and the relative magnitude of the amplitude of the interfering ''V{sub ub}'' transitions. Thus at the present time only a relatively limited precision on [gamma] can be extracted from these measurements. The current world average is [gamma] = (7826{sup +19}){sup o} [1]. For other methods and long term perspectives, as discussed in details, the reader is invited to consult the proceedings of the recent CKM workshop that was held in Nagoya (Japan) in December 2006 [2].