Semileptonic B Decays from an NRQCD/D234 Action
  Semileptonic, B --> pi, l nubar, decays are studied on quenched anisotropic lattices using tree-level tadpole improved Symanzik glue, NRQCD heavy quark and D234 light quark actions. Constrained fitting methods are applied to extract groundstate contributions to two-point and three-point correlators. We agree with previous lattice determinations of the form factors. The major source of systematic error here, as in previous work, comes from the chiral extrapolation to the physical pion mass. Future calculations must work at lighter quark masses to resolve this. 
J. Shigemitsu, S. Collins, C.T.H. Davies, J. Hein, R.R. Horgan, G.P.   Lepage