Measurement of ?c (1S), ?c (2S), and nonresonant ???+?- production via two-photon collisions

Abstract

We report the measurement of ????c(1S),?c(2S)????+?- with ?? decays to ?? and ??+?- using 941 fb-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The ?c(1S) mass and width are measured to be M=[2984.6�0.7 (stat)�2.2 (syst)�0.3 (model)] MeV/c2 and ?=[30.8-2.2+2.3 (stat)�2.5 (syst)�1.4 (model)] MeV, respectively. First observation of ?c(2S)????+?- with a significance of 5.5? including systematic error is obtained, and the ?c(2S) mass is measured to be M=[3635.1�3.7 (stat)�2.9 (syst)�0.4 (model)] MeV/c2. The products of the two-photon decay width and branching fraction (B) of decays to ???+?- are determined to be ??????B=[65.4�2.6 (stat)�7.8 (syst)] eV for ?c(1S) and [5.6-1.1+1.2 (stat)�1.1 (syst)] eV for ?c(2S). The cross sections for ??????+?- and ??f2(1270) are measured for the first time. � 2018 authors. Published by the American Physical Society.