Lattice calculation of D- and B-meson semileptonic decays, using the clover action at β = 6.0 on APE

We present the results of a high statistics lattice calculation of hadronic form factors relevant for D- and B-meson semi-leptonic decays into light pseudoscalar and vector mesons. The results have been obtained by averaging over 170 gauge field configurations, generated in the quenched approximation, at β = 6.0, on a 183 × 64 lattice, using the O(α)-improved SW-Clover action. From the study of the matrix element 〈 K−|Jμ|D0 〉, we obtain f+(0) = 0.78 ± 0.08 and from the matrix element 〈 K∗0|Jμ|D+ 〉 we obtain V(0) = 1.08 ± 0.22, Ai(0) = 0.67 ± 0.11 and A2(0) = 0.49 ± 0.34. We also obtain the ratios V(0)A1(0) = 1.6 ± 0.3 and A2(0)A1(0) = 0.7 ± 0.4. Our predictions for the different form factors are in good agreement with the experimental data, although, in the case of A2(0), the errors are still too large to draw any firm conclusion. With the help of the Heavy Quark Effective Theory (HQET) we have also extrapolated the lattice results to B-meson decays. The form factors follow a behaviour compatible with the HQET predictions. Our results are in agreement with a previous lattice calculation, performed at β = 6.4, using the standard Wilson action.