@article{ac68e568f5ba4205bb2ac6de57e46df6,

title = "Observation of D^{0}→K_{1}(1270)^{-}e^{+}ν_{e}",

abstract = "Using 2.93 fb^{-1} of e^{+}e^{-} collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} semileptonic decay is presented. The statistical significance of the decay D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} is greater than 10σ. The branching fraction of D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} is measured to be (1.09±0.13_{-0.16}^{+0.09}±0.12)×10^{-3}. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K_{1}(1270)^{-}→K^{-}π^{+}π^{-}. The fraction of longitudinal polarization in D^{0}→K_{1}(1270)^{-}e^{+}ν_{e} is determined for the first time to be 0.50±0.19_{stat}±0.08_{syst}.",

author = "{BESIII Collaboration} and M. Ablikim and Achasov, {M. N.} and P. Adlarson and S. Ahmed and M. Albrecht and R. Aliberti and A. Amoroso and An, {M. R.} and Q. An and Bai, {X. H.} and Y. Bai and O. Bakina and Ferroli, {R. Baldini} and I. Balossino and Y. Ban and K. Begzsuren and N. Berger and M. Bertani and D. Bettoni and F. Bianchi and J. Bloms and A. Bortone and I. Boyko and Briere, {R. A.} and H. Cai and X. Cai and A. Calcaterra and Cao, {G. F.} and N. Cao and Cetin, {S. A.} and Chang, {J. F.} and Chang, {W. L.} and G. Chelkov and Chen, {D. Y.} and G. Chen and Chen, {H. S.} and Chen, {M. L.} and Chen, {S. J.} and Chen, {X. R.} and Chen, {Y. B.} and Chen, {Z. J.} and Cheng, {W. S.} and G. Cibinetto and F. Cossio and Cui, {X. F.} and Dai, {H. L.} and Dai, {X. C.} and A. Dbeyssi and H. Muramatsu and R. Poling",

year = "2021",

month = sep,

day = "24",

doi = "10.1103/PhysRevLett.127.131801",

language = "English (US)",

volume = "127",

pages = "131801",

journal = "Physical review letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "13",

}