Precision measurement of the matrix elements for η → π+π-π0 and η → π0π0π0 decays

Ablikim, M.; Achasov, M. N.; Adlarson, P.; Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I.; Ban, Y.; Batozskaya, V.; Becker, D.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi, F.; Bianco, E.; Bloms, J.; Bortone, A.; Boyko, I.; Briere, R. A.; Brueggemann, A.; Cai, H.; Cai, X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.; Chang, W. L.; Che, G. R.; Chelkov, G.; Chen, C.; Chen, Chao; Chen, G.

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摘要

A precision measurement of the matrix elements for eta -> pi(+)pi(-)pi(0) and -> pi(0)pi(0)pi(0) decays is performed using a sample of (10087 +/- 44) x 10(6) J/psi decays collected with the BESIII detector. The decay J/psi -> gamma eta is used to select clean samples of 631, 686 eta -> pi(+)pi(-)pi(0) decays and 272, 322 eta -> pi(0)pi(0)pi(0) decays. The matrix elements for both channels are in reasonable agreement with previous measurements. The nonzero gX(2)Y term for the decay mode eta -> pi(+)pi(-)pi(0) is confirmed, as reported by the KLOE Collaboration, while the other higher-order terms are found to be insignificant. Dalitz plot asymmetries in the eta -> pi(+)pi(-)pi(0) decay are also explored and are found to be consistent with charge conjugation invariance. In addition, a cusp effect is investigated in the eta -> pi(0)pi(0)pi(0) decay, and no obvious structure around the pi(+)pi(-) mass threshold is observed.

关键词

CHARGE ASYMMETRY DYNAMICS 3-PI