Measurement of the Absolute Branching Fraction for Λ_c⁺ → Λe⁺ν_e


We report the first measurement of the absolute branching fraction for Λ_c⁺. This measurement is based on 567 pb⁻¹ of e⁺e⁻ annihilation data produced at √s = 4.599 GeV, which is just above the Λ_c⁺ Λ̅_c̅ threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be ℬ(Λ_c⁺ → Λe⁺ν_e) = [3.63 ± 0.38(stat) ± 0.20(syst)]%, representing a significant improvement in precision over the current indirect determination. As the branching fraction for Λ_c⁺ → Λe⁺ν_e is the benchmark for those of other Λ_c⁺ semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.



Semileptonic decays, Baryons, Quarks, Annihilation reactions, Branching fractions (Nuclear physics), Lambda baryons

This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contracts No. 11125525, No. 11235011, No. 11275266, No. 11322544, No. 11322544, No. 11335008, No. 11425524, and No. 11505010; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the CAS Center for Excellence in Particle Physics (CCEPP); the Collaborative Innovation Center for Particles and Interactions (CICPI); Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. 11179007, No. U1232201, and No. U1332201; CAS under Contracts No. KJCX2-YW-N29 and No. KJCX2-YW-N45; 100 Talents Program of CAS; National 1000 Talents Program of China; INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation DFG under Contract No. Collaborative Research Center CRC-1044; Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) under Contract No. 530-4CDP03; Ministry of Development of Turkey under Contract No. DPT2006K-120470; Russian Foundation for Basic Research under Contract No. 14-07-91152; The Swedish Resarch Council; U. S. Department of Energy under Contracts No. DE-FG02-04ER41291, No. DE-FG02-05ER41374, No. DE-SC0012069, and No. DESC0010118; U.S. National Science Foundation; University of Groningen (RuG) and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt; and WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.


©2015 American Physical Society