A Measurement of gamma from the Decays Bd(t) -> D(*)+ D(*)- and Bd ->   Ds(*)+ D(*)-
  Recently, it was proposed to use measurements of Bd(t) -> D(*)+ D(*)- and Bd -> Ds(*)+ D(*)- decays to measure the CP phase gamma. In this paper, we present the extraction of gamma using this method. We find that gamma is favored to lie in one of the ranges [19.4o - 80.6o] (+ 0o or 180o), [120o - 147o] (+ 0o or 180o), or [160o - 174o] (+ 0o or 180o) at 68% confidence level (the (+ 0o or 180o) represents an additional ambiguity for each range). These constraints come principally from the vector-vector final states; the vector-pseudoscalar decays improve the results only slightly. Although, with present data, the constraints disappear for larger confidence levels, this study does demonstrate the feasibility of the method. Strong constraints on gamma can be obtained with more data. 
Justin Albert, Alakabha Datta and David London