YEE HSIUNGWEI-SHU HOU2019-12-272019-12-27200800319007https://scholars.lib.ntu.edu.tw/handle/123456789/442294https://www.scopus.com/inward/record.uri?eid=2-s2.0-45549098438&doi=10.1103%2fPhysRevLett.100.241801&partnerID=40&md5=157261f82e557eae2bea1b149e23df52We present a measurement of the branching fraction B(Ds+→μ+νμ ) using a 548fb-1 data sample collected by the Belle experiment at the KEKB e+e- collider. The Ds momentum is determined by reconstruction of the system recoiling against DKγX in events of the type e+e-→Ds*DKX, Ds*→Dsγ, where X represents additional pions or photons from fragmentation. This full-reconstruction method provides high resolution in the neutrino momentum and thus good background separation, equivalent to that achieved by experiments at the tau-charm factories. We obtain the branching fraction B(Ds+→μ+νμ)=[6.44±0.76(stat)±0.57(syst)] ×10-3, implying a Ds decay constant of fDs=[275±16(stat) ±12(syst)]MeV. © 2008 The American Physical Society.American Physical Society (APS); Background separation; BELLE experiments; Branching fractions; Data samples; Decay constants; E+e collider; High resolutions; neutrino momentum; Reconstruction methods; Computer networks; Experiments; Measurements; Microfluidics; Momentum; Restoration; Separation; Repairjournal article10.1103/PhysRevLett.100.2418012-s2.0-45549098438WOS:000256942400017https://www.scopus.com/inward/record.uri?eid=2-s2.0-45549098438&doi=10.1103%2fPhysRevLett.100.241801&partnerID=40&md5=157261f82e557eae2bea1b149e23df52