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Published October 1, 2010 | Published
Journal Article Open

Search for b→u transitions in B^-→DK^- and D^*K^- decays


We report results from an updated study of the suppressed decays B^-→DK^- and B^-→D^*K^- followed by D→K^+π^-, where D^(*) indicates a D^((*)0) or a D^((*)0) meson, and D^*→Dπ^0 or D^*→Dγ. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity triangle angle γ due to interference between the b→c transition B^-→D^((*))0K^- followed by the doubly Cabibbo-suppressed decay D^0→K^+π^-, and the b→u transition B^-→D^((*)0)K^- followed by the Cabibbo-favored decay D^0→K^+π^-. We also report an analysis of the decay B^-→D^(*)π^- with the D decaying into the doubly Cabibbo-suppressed mode D→K^+π^-. Our results are based on 467× 10^6 Υ(4S)→BB decays collected with the BABAR detector at SLAC. We measure the ratios R^(*) of the suppressed ([K^+π^-]_DK^-/π^-) to favored ([K^-π^+]_DK^-/π^-) branching fractions as well as the CP asymmetries A^(*) of those modes. We see indications of signals for the B^-→DK^- and B^-→D_(Dπ0)^*K^- suppressed modes, with statistical significances of 2.1 and 2.2σ, respectively, and we measure: RDK=(1.1±0.6±0.2)×10^(-2), ADK=-0.86±0.47_(-0.16)^(+0.12), R_((Dπ0))K^*=(1.8±0.9± 0.4)×10^-2, A_((Dπ0))K^*=+0.77±0.35±0.12, R_((Dγ))K^*=(1.3±1.4±0.8)×10^-2,A_((Dγ))K^*=+0.36 ±0.94-_(0.41)^(+0.25), where the first uncertainty is statistical and the second is systematic. We use a frequentist approach to obtain the magnitude of the ratio r_B≡|A(B^-→D ^0K^-)/A(B^-→D^0K^-)|=(9.5_(-4.1)^(+5.1))%, with r_B<16.7% at 90% confidence level. In the case of B^-→D^*K^- we find r_B^*≡|A(B^-→D ^*0K^-)/A(B^-→D^*0K^-)|=(9.6_(-5.1)^(+3.5))%, with rB*<15.0% at 90% confidence level.

Additional Information

© 2010 The American Physical Society. Received 23 June 2010; published 11 October 2010. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relies critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and the kind hospitality extended to them. This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat à l'Energie Atomique and Institut National de Physique Nucléaire et de Physique des Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e Innovacio´n (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union), the A. P. Sloan Foundation (USA), and the Binational Science Foundation (USA-Israel).

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