Observation of ηc(2S) → 3(π+π-) and measurements of χcJ → 3(π+π-) in ψ (3686) radiative transitions

The hadronic decay eta(c) (2S) -> 3 (pi(+)pi(-)) is observed with a statistical significance of 9.3 standard deviations using (448.1 +/- 2.9) x 10(6) psi(3686) events collected by the BESIII detector at the BEPCII collider. The measured mass and width of eta(c) (2S) are (3643.4 +/- 2.3 (stat) +/- 4.4 (syst)) MeV/c(2) and 19.8 +/- 3.9 (stat) +/- 3.1 (syst)) MeV, respectively, which are consistent with the world average values within two standard deviations. The product branching fraction B[psi(3686) -> gamma eta(c) (2S)] X B[eta(c)(2S) -> 3(pi(+)pi(-))] is measured to be (9.2 +/- 1.0(stat)+/- 1.2(syst)10(-6). Using B[psi(3686) -> gamma eta(c) (2S)] = (7.0(-2.5)(+3.4)) x 10(-4), we obtain B[eta(c)(2S) -> 3 (pi(+)pi(-))] = (1.31 +/- 0.15 (stat) +/- 0.17 (syst) ((+0.64)(-0.47)) (extr))x 10(-2), where the third uncertainty is from B [psi(3686)->gamma eta(c)(2S)]. We also measure the chi(cJ)-> 3(pi(+)pi(-)) (J = 0, 1, 2) decays via psi' -> gamma chi(cJ) transitions. The branching fractions are B[chi(c0) 3(pi(+)pi(-))] = (2.080 +/- 0.006(stat)+/- 0.068(syst))x10(-2), B [chi c(2) -> (pi(+)pi(-))]=1.092 x 0.004(stat)+/- 0.035(syst))x10(-2), and B[chi(C2) -> 3 (pi(+)pi(-))] = 1.565 +/- 0.005 (stat) +/- 0.048 (syst)) x 10(-2).

Automated summary

The hadronic decay eta(c) (2S) -> 3 (pi(+)pi(-)) is observed and measured, along with the mass, width, and branching fractions of eta(c) (2S). The branching fractions of chi(cJ)-> 3(pi(+)pi(-)) (J = 0, 1, 2) decays are also measured.