Differential decay rate for $B to pi l u$ semileptonic decays

We present our study on $B to pi l u$ semileptonic decay form factors with NRQCD action for heavy quark from a quenched lattice QCD simulation at $beta$=5.9 on a $16^3times 48$ lattice. We obtain form factors defined in the context of heavy quark effective theory by Burdman et al. and find that their $1/m_B$ correction is small. The limit of physical heavy and light quark masses can be performed without introducing any model function, and we obtain a prediction for the differential decay rate $dGamma/dq^2$. We also discuss the soft pion limit of the form factors.