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 18 3 × 64 lattice, using the O ( α )-improved SW-Clover action. From the study of the matrix element 〈 K − |J μ |D 0 〉, we obtain f + (0) = 0.78 ± 0.08 and from the matrix element 〈 K ∗0 |J μ |D + 〉 we obtain V (0) = 1.08 ± 0.22, A i (0) = 0.67 ± 0.11 and A 2 (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 A 2 (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.