Observation of the Semileptonic D+ Decay into the K 1 (1270)0 Axial-Vector Meson

Abstract

By analyzing a 2.93 fb-1 data sample of e+e- collisions, recorded at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the first observation of the semileptonic D+ transition into the axial-vector meson D+→K̄1(1270)0e+νe with a statistical significance greater than 10σ. Its decay branching fraction is determined to be B[D+→K̄1(1270)0e+νe]=(2.30±0.26-0.21+0.18±0.25)×10-3, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of K̄1(1270)0→K-π+π0. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.