Measurement of the Absolute Branching Fraction and Decay Asymmetry of Λ → nγ

作者：Ablikim, M.; Achasov, M. N.; Adlarson, P.; Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai, X. H.; 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.; 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.; Chelkov, G.; Chen, C.; Chen, Chao; Chen, G.; Chen, H. S.

来源：Physical Review Letters, 2022, 129(21): 212002.

DOI：10.1103/PhysRevLett.129.212002

• RADIATIVE HYPERON DECAYS
• WEAK DECAYS
• BARYONS
• RATIO
• PARAMETER

The radiative hyperon decay Lambda -> n gamma is studied using (10087 +/- 44) x 10(6) J/psi. events collected with the BESIII detector operating at BEPCII. The absolute branching fraction of the decay Lambda -> n gamma is determined to be (0.832 +/- 0.038(stat) +/- 0.054(syst)) x 10(-3), which is a factor of 2.1 lower and 5.6 standard deviations different than the previous measurement. By analyzing the joint angular distribution of the decay products, the first determination of the decay asymmetry a. is reported with a value of -0.16 +/- 0.10(stat) +/- 0.05(syst).