A high-statistics lattice calculation of lambda(1) and lambda(2) in the B-meson

We present a high-statistics lattice calculation of the kinetic energy -lambda(1)/2m(b) of the heavy quark inside the B-meson and of the chrome-magnetic term lambda(2), related to the B*-B mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at beta = 6.0, on a lattice volume 24(3) x 40 and using, for the meson correlators, the results obtained with the SW-Clover O(a) improved lattice action for the light quarks. For the kinetic energy we found -lambda(1) = [B(h) over bar(iD)(2)hB]/(2M(B)) = -(0.09 +/- 0.14) GeV2, which is interesting for phenomenological applications. We also found lambda(2) = 0.07 +/- 0.01 GeV2, corresponding to M(B*)(2) - M(B)(2) = 4 lambda(2) = 0.280 +/- 0.060 GeV2, which is about one half of the experimental value. The origin of the discrepancy with the experimental number needs to be clarified.