Abstract :
The decays D∗ → Dπ and D∗ → Dγ are well described by heavy meson chiral perturbation theory. With the recent measurement of B(D∗+ → D+γ), the D∗0, D∗+ and Ds∗ branching fractions can be used to extract the D∗Dπ and D∗Dγ couplings g and β. The D∗ → Dγ decays receive important corrections at order √mq and, from the heavy quark magnetic moment, at order 1/mc. Here all the decay rates are computed to one loop, to first order in mq and 1/mc, including the effect of heavy meson mass splittings, and the counterterms at order mq. A fit to the experimental data gives two possible solutions, g = 0.27−0.02−0.02+0.04+0.05, β= 0.85−0.1 − 0.1+0.2 + 0.3 GeV− or g = 0.76−0.03 −0.1+0.03+0.2, β = 4.90−0.3−0.7+0.3+5.0 GeV−1. The first errors are experimental, while the second are estimates of the uncertainty induced by the counterterms. (The experimental limit ΓD∗+ < 0.13 MeV excludes the g = 0.76 solution.) Predictions for the D∗ and B∗ widths are given.
