First observation of the semileptonic decay Λc+ → pK- e+ νe

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 D, 2022, 106(11): 112010.

DOI：10.1103/PhysRevD.106.112010

• LATTICE

Using 4.5 fb(-1) of e(+)e(-) annihilation data samples collected at the center-of-mass energies ranging from 4.600 GeV to 4.699 GeV with the BESIII detector at the BEPCII collider, a first study of the semileptonic decays Lambda(+)(c) -> pK(-)e(+)v(e), Lambda(+)(c) ->Lambda (1520)e(+)v(e) and Lambda(+)(c) -> Lambda (1405)e(+)v(e) is performed. The Lambda(+)(c) -> pK(-)e(+)v(e) decay is observed with a significance of 8.2 sigma and the branching fraction is measured to be B (Lambda(+)(c) -> pK(-)e(+)v(e)) = (0.88 +/- 0.17(stat) +/- 0.07(syst)) x 10(-3). We also report evidence of Lambda(+)(c) ->Lambda (1520)e(+)v(e) and Lambda(+)(c) -> Lambda (1405)e(+)v(e) with significances of 3.3 sigma and 3.2 sigma , respectively, and measure B (Lambda(+)(c) ->Lambda (1520)e(+)v(e) ) = (1.02 +/- 0.52(stat) +/- 0.11(syst) ) x 10(-3) andB (Lambda(+)(c) ->Lambda (1405) [-> pK(-)]e(+)v(e)) = (0.42 +/- 0.19(stat) +/- 0.04(syst)) x 10(-3). Combining these with the inclusive semileptonic Lambda(+)(c) branching fraction measured by BESIII, the relative fraction is determined to be [B (Lambda(+)(c) -> pK(-)e(+)v(e))/