Precision Measurement of the Decay Σ+ → pγ in the Process J/ψ→ Σ+(Σ)over-bar-

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.

Science Citation Index Expanded

摘要

Using (10 087 +/- 44) x 10(6) J/psi events collected with the BESIII detector, the radiative hyperon decay Sigma(+) -> p gamma is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be (0.996 +/- 0.021(stat) +/- 0.018(syst)) x 10(-3), which is lower than its world average value by 4.2 standard deviations. Its decay asymmetry parameter is determined to be -0.652 +/- 0.056(stat) +/- 0.020(syst). The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by 78% and 34%, respectively.

关键词

RADIATIVE HYPERON DECAYS BRANCHING RATIO ASYMMETRY PARAMETER