Evidence for the eta(c)(2S) -> pi(+)pi(-)eta decay

The decay eta(c)(2S) -> pi(+)pi(-)eta is searched for through the radiative transition psi(3686) -> gamma eta(c)(2S) using 448 million psi(3686) events accumulated at the BESIII detector. The first evidence of eta(c)(2S) -> pi(+)pi(-)eta is found with a statistical significance of 3.5 sigma. The product of the branching fractions of psi(3686) -> gamma eta(c)(2S) and eta(c)(2S) -> pi(+)pi(-)eta is measured to be Br(psi(3686) -> gamma eta(c)(2S)) x Br(eta(c)(2S) -> pi(+)pi(-)eta) = (2.97 +/- 0.81 +/- 0.26) x 10(-6), where the first uncertainty is statistical and the second one is systematic. The branching fraction of the decay eta(c)(2S) -> pi(+)pi(-)eta is determined to be Br(eta(c)(2S) -> pi(+)pi(-)eta) = (42.4 +/- 11.6 +/- 3.8 +/- 30.3) x 10(-4), where the third uncertainty is transferred from the uncertainty of the branching fraction of psi(3686) -> gamma eta(c)(2S).
For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.107.052007