We measure the branching ratio of the purely leptonic decay of the D+ meson with unprecedented precision as B(D+→μ+ν)=(3.82±0. 32±0.09)×10-4, using 818pb-1 of data taken on the ψ(3770) resonance with the CLEO-c detector at the CESR collider. We use this determination to derive a value for the pseudoscalar decay constant fD+, combining with measurements of the D+ lifetime and assuming |Vcd|=|Vus|. We find fD+=(205.8±8.5±2.5)MeV. The decay rate asymmetry Γ(D+→μ+ν)-Γ(D-→μ-ν̄)Γ(D+→μ +ν)+Γ(D-→μ-ν̄)=0.08±0.08, consistent with no CP violation. We also set 90% confidence level upper limits on B(D+→τ+ν )<1.2×10-3 and B(D+→e+ν)<8.8×10-6.
|Original language||English (US)|
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|State||Published - Sep 11 2008|