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

Abstract

The hadronic decay ηc(2S)→3(π+π−) is observed with a statistical significance of 9.3 standard deviations using (448.1±2.9)×106 ψ(3686) events collected by the BESIII detector at the BEPCII collider. The measured mass and width of ηc(2S) are (3643.4±2.3 (stat)±4.4 (syst)) MeV/c2 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[ψ(3686)→γηc(2S)]×B[ηc(2S)→3(π+π−)] is measured to be (9.2±1.0 (stat)±1.2 (syst))×10−6. Using B[ψ(3686)→γηc(2S)]=(7.0−2.5+3.4)×10−4, we obtain B[ηc(2S)→3(π+π−)]=(1.31±0.15 (stat)±0.17 (syst) (+0.64−0.47) (extr))×10−2, where the third uncertainty is from B[ψ(3686)→γηc(2S)]. We also measure the χcJ→3(π+π−) (J=0, 1, 2) decays via ψ′→γχcJ transitions. The branching fractions are B[χc0→3(π+π−)]=(2.080±0.006 (stat)±0.068 (syst))×10−2, B[χc1→3(π+π−)]=(1.092±0.004 (stat)±0.035 (syst))×10−2, and B[χc2→3(π+π−)]=(1.565±0.005 (stat)±0.048 (syst))×10−2.Received 19 June 2022Accepted 28 July 2022DOI:https://doi.org/10.1103/PhysRevD.106.032014Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasStrong interactionPhysical SystemsQuarkoniaTechniquesParticle data analysisParticles & Fields