Measurement of the γγ^*→η_c transition form factor
We study the reaction e^+e^-→e^+e^-η_c, η_c→K_SK^±π^∓ and obtain η_c mass and width values 2982.2±0.4±1.6 MeV/c^2 and 31.7±1.2±0.8 MeV, respectively. We find Γ(η_c→γγ)B(ηc→KK π)=0.374±0.009±0.031 keV, and measure the γγ^*→η_c transition form factor in the momentum transfer range from 2 to 50 GeV^2. The analysis is based on 469 fb^(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e^+e^- center-of-mass energies near 10.6 GeV.
Additional Information© 2010 The American Physical Society. Received 16 February 2010; revised 7 March 2010; published 30 March 2010. We thank V. L. Chernyak for useful discussions. 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 Science and Technology of the Russian Federation, Ministerio de Educaciόn y Ciencia (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
Published - Lees2010p9860Phys_Rev_D.pdf