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Register a new userUsing the value of beta to help determine gamma from B decays
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It has been pointed out by Gronau and Rosner that the angle gamma of the unitarity triangle could be determined by combining future results on B_s and B_d decays to K pi. Here we show that it is important to include in the analysis the information on the phase beta which will be determined in the near future. Omitting this information could lead to an error as large as 8 degrees in gamma.
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Some years ago, a method was proposed for measuring the CP-violating phase gamma using pairs of two-body decays that are related by U-spin reflection (d <-> s). In this paper we adapt this method to charmless B -> PPP decays. Time-dependent Dalitz-plot analyses of these three-body decays are required for the measurement of the mixing-induced CP asymmetries. However, isobar analyses of the decay amplitudes are not necessary. A potential advantage of using three-body decays is that the effects of U-spin breaking may be reduced by averaging over the Dalitz plot. This can be tested independently using the measurements of direct CP asymmetries and branching ratios in three-body charged B decays.
We give a summary of the discussions in Working Group V of the CKM2010 workshop dealing with determinations of the angle gamma of the unitarity triangle of the Cabibbo-Kobayashi-Maskawa matrix from B-meson decays into charmed final states.
The angle $gamma$ of the Cabibbo--Kobayashi--Maskawa unitarity triangle is a benchmark parameter of the Standard Model of particle physics. A method to determine $gamma$ from $B^{pm} to D K^{pm}$ with subsequent $D to K_{rm S}^0pi^+pi^-$ or similar multibody decays has been proven to provide good sensitivity. We review the first discussions on the use of this technique, and its impact subsequently. We propose that this approach should be referred to as the BPGGSZ method.
To date, the weak-phase $gamma$ has been measured using two-body $B$-meson decays such as $Bto D K$ and $Bto Dpi$, whose amplitudes contain only tree-level diagrams. But $gamma$ can also be extracted from three-body charmless hadronic $B$ decays. Since the amplitudes for such decays contain both tree- and loop-level diagrams, $gamma$ obtained in this way is sensitive to new physics that can enter into these loops. The comparison of the values of $gamma$ extracted using tree-level and loop-level methods is therefore an excellent test for new physics. In this talk, we will show how U-spin and flavor-SU(3) symmetries can be used to develop methods for extracting $gamma$ from $Bto Kpipi$ and $Bto KK{bar K}$ decays. We describe a successful implementation of the flavor-SU(3) symmetry method applied to BaBar data.
We suggest a novel method to determine the sign of cos(2 beta) in the decays B --> psi K, by creating interference between KL and KS final states via ``regeneration, that is propagation through a matter target region to convert some KL to KS. The determination of this quantity resolves an ambiguity between beta and (90o - beta) that remains after the standard measurements of sin(2 beta) and may turn out to be important in resolving whether the result is in agreement with Standard Model predictions or indicates the presence of new physics. We find the measurement is feasible at a B-factory, but requires several years of high-luminosity running with a regeneration target affecting a significant fraction of the detector.
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