Rong, G (reprint author), Inst High Energy Phys, Beijing 100049, Peoples R China.
The absolute branching fraction for the decay D+ -> mu(+)nu has been directly measured based on a data sample of about 33 pb(-1) collected around root s- = 3.773 GeV with the BES-II detector at the BEPC collider. A total of 5321 +/- 149 +/- 160 D- mesons are reconstructed in nine hadronic decay modes. In the system recoiling against these singly tagged D- mesons, 2.67 +/- 1.74 purely leptonic decay events of D+ -> mu+nu(mu) are observed. Those yield the branching fraction of BF(D+ -> mu+nu(mu)) = (0.122(-0.053)(+0.111) +/- 0.010)%, and a corresponding value of the pseudoscalar decay constant f(D+) = (371(-119)(+129) +/- 25) MeV. (c) 2005 Elsevier B.V. All rights reserved.