Search for ηc (2S) →π+π-ηc and ηc (2S) →π+π- KS0 K±π∓ decays

Based on (27.12 +/- 0.14) x 10(8) psi(2S) events collected by the BESIII detector, we search for the decay eta(c)(2S) -> pi(+)pi(-)eta(c) via psi(2S) -> gamma eta(c)(2S). No significant signal is observed, and the upper limit on the product branching fraction B(psi(2S) -> gamma eta(c) (2S)) x B(eta(c) (2S) -> pi(+)pi(-)eta(c)) is determined to be 2.21 x 10(-5) at the 90% confidence level. In addition, the eta(c)(2S) -> pi(+)pi(-KSK +/-)-K-0 pi(-/+) decay is studied via psi(2S) -> gamma eta(c)(2S) and is observed with a statistical significance of 10 sigma for the first time. The branching fraction of eta(c)(2S) -> pi(+)pi(-KSK +/-)-K-0 pi(-/+) is determined to be (1.33 +/- 0.11 +/- 0.40 +/- 0.95)x10(-2), where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the quoted B(psi(2S) -> gamma eta(c)(2S)).