We present the results of the first lattice QCD study of the strong coupling $g_{D^{*}D\pi }.$ From our simulations in the quenched approximation, we obtain $g_{D^{*}D\pi }=18.8\mathrm{}\pm {2.3}_{-2.0}^{+1.1\mathrm{}}$ and $g_c=0.67\mathrm{}\pm {0.08}_{-0.06}^{+0.04\mathrm{}}.$ Whereas previous theoretical studies gave different predictions, our result favors a large value for $g_c.$ It agrees very well with the recent experimental value by CLEO. $ĝ$ varies very little with the heavy mass and we find in the infinite mass limit $g_{\infty }=0.69\mathrm{}\left(18\right).$

• Received 25 June 2002

DOI:https://doi.org/10.1103/PhysRevD.66.074504