Improved measurement of B(D+ --> mu+nu) and the pseudoscalar decay constant fD+

Phys Rev Lett. 2005 Dec 16;95(25):251801. doi: 10.1103/PhysRevLett.95.251801. Epub 2005 Dec 16.

Abstract

We extract a relatively precise value for the decay constant of the meson by measuring B(D+ --> mu+nu) = (4.40 +/-0.66(+0.09)(-0.12) x 10(-4) using 281 pb(-1) of data taken on phi(3770) the resonance with the CLEO-c detector. We find fD+ = (222.6 +/- 16.7(+2.8)(-3.4)) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on B(D+e+nu)< 2.4 x 10(-5) which constrains new physics models.