Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 6, 2013 | Published
Journal Article Open

Measurement of CP asymmetries and branching fractions in charmless two-body B-meson decays to pions and kaons


We present improved measurements of CP-violation parameters in the decays B^0→π^+π^-, B^0→K^+π^-, and B^0→π^0π^0, and of the branching fractions for B^0→π^0π^0 and B^0→K^0π^0. The results are obtained with the full data set collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, corresponding to (467±5)×10^6 BB pairs. We find the CP-violation parameter values and branching fractions: S_(π^+π^-)=-0.68±0.10±0.03, C_(π^+π^-)=-0.25±0.08±0.02, A_(K^-π^+)=-0.107±0.016_(-0.004)^(+0.006), C_(π^0π^0)=-0.43±0.26±0.05, B(B^0→π^0π^0)=(1.83±0.21±0.13)×10^(-6),  B(B^0→K^0π^0)= (10.1±0.6±0.4)×10^(-6), where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for B^0→π^+π^- and 6.1 standard deviations for B^0→K^+π^-, including systematic uncertainties. Constraints on the unitarity triangle angle α are determined from the isospin relations among the B→ππ rates and asymmetries. Considering only the solution preferred by the Standard Model, we find α to be in the range [71°,109°] at the 68% confidence level.

Additional Information

© 2013 American Physical Society. Received 19 June 2012; published 6 March 2013. 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 U.S. 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 Innovaciόn (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation (U.S.).

Attached Files

Published - PhysRevD.87.052009.pdf


Files (662.9 kB)
Name Size Download all
662.9 kB Preview Download

Additional details

August 19, 2023
October 23, 2023