Measurement of B(J/psi->eta_c gamma) at KEDR

/ Authors

V. Anashin, V. Aulchenko, E. Baldin, A. K. Barladyan, A. Barnyakov, M. Barnyakov, S. Baru, I. Basok, I. Bedny, O. Beloborodova

and 73 more authors

A. E. Blinov, V. Blinov, A. Bobrov, V. Bobrovnikov, A. Bogomyagkov, A. Bondar, A. Buzykaev, S. Eidelman, Y. Glukhovchenko, V. V. Gulevich, D. Gusev, S. Karnaev, G. Karpov, S. Karpov, T. Kharlamova, V. Kiselev, S. Kononov, K. Kotov, E. Kravchenko, V. Kulikov, G. Kurkin, E. Kuper, E. Levichev, D. Maksimov, V. Malyshev, A. Maslennikov, A. Medvedko, O. Meshkov, A. Milstein, S. Mishnev, I. Morozov, N. Muchnoi, V. V. Neufeld, S. Nikitin, I. Nikolaev, I. Okunev, A. Onuchin, S. Oreshkin, I. Orlov, A. Osipov, S. Peleganchuk, S. Pivovarov, P. Piminov, V. Petrov, A. Poluektov, D. Shatilov, G. Pospelov, V. Prisekin, A. Ruban, V. K. Sandyrev, G. A. Savinov, A. Shamov, B. Shwartz, E. Simonov, S. Sinyatkin, Y. Skovpen, A. Skrinsky, V. Smaluk, A. Sokolov, A. Sukharev, E. Starostina, A. Talyshev, V. Tayursky, V. Telnov, Y. Tikhonov, K. Todyshev, G. Tumaikin, Y. Usov, A. Vorobiov, A. Yushkov, V. Zhilich, V. V.Zhulanov, A. Zhuravlev

/ Abstract

We present a study of the inclusive photon spectrum from 6.3 million J/ψ decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of the radiative decay J/ψ → ηcγ, ηc width and mass. Taking into account an asymmetric photon line shape we obtain: Mηc = (2978.1 ± 1.4 ± 2.0) MeV/c2, Γηc = (43.5 ± 5.4 ± 15.8) MeV, $\mathcal{B}(J/\psi\to \eta_{{\rm c}}\gamma) = (2.59 \pm 0.16 \pm 0.31)\%$.

DOI: 10.1142/S2010194511000791