We report the first absolute measurement of the branching fraction of Λc+→Λe+νe. This measurement is based on 567 pb−1 of e+e− annihilation data produced at s=4.599 GeV, which is just above the Λc+Λˉc− threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be B(Λc+→Λe+νe)=(3.63±0.38(stat)±0.20(syst))%, representing a more than twofold improvement in precision upon previously published results. As the branching fraction for Λc+→Λe+νe is the benchmark for those of other Λc+ semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.
@article{arxiv.1510.02610,
title = {Measurement of the absolute branching fraction for $\Lambda^+_{c}\to \Lambda e^+\nu_e$},
author = {BESIII Collaboration and M. Ablikim and M. N. Achasov and X. C. Ai and O. Albayrak and M. Albrecht and D. J. Ambrose and A. Amoroso and F. F. An and Q. An and J. Z. Bai and R. Baldini Ferroli and Y. Ban and D. W. Bennett and J. V. Bennett and M. Bertani and D. Bettoni and J. M. Bian and F. Bianchi and E. Boger and I. Boyko and R. A. Briere and H. Cai and X. Cai and O. Cakir and A. Calcaterra and G. F. Cao and S. A. Cetin and J. F. Chang and G. Chelkov and G. Chen and H. S. Chen and H. Y. Chen and J. C. Chen and M. L. Chen and S. J. Chen and X. Chen and X. R. Chen and Y. B. Chen and H. P. Cheng and X. K. Chu and G. Cibinetto and H. L. Dai and J. P. Dai and A. Dbeyssi and D. Dedovich and Z. Y. Deng and A. Denig and I. Denysenko and M. Destefanis and F. De Mori and Y. Ding and C. Dong and J. Dong and L. Y. Dong and M. Y. Dong and S. X. Du and P. F. Duan and E. E. Eren and J. Z. Fan and J. Fang and S. S. Fang and X. Fang and Y. Fang and L. Fava and F. Feldbauer and G. Felici and C. Q. Feng},
journal= {arXiv preprint arXiv:1510.02610},
year = {2015}
}