Testing the chirality of b to u current with B^0 \to \rho^ - \ell^+ \nu
  We study the effects of a modest V+A admixture strength in $b\tou$ current in the decay $B \to\rho l \nu$. We have shown that the decay rate, lepton forward-backward distribution asymmetry $A_{FB}$ and polarization ratio are sensitive to the admixture. Future experimental studies of the decay at BaBar and BELLE could clarify the chirality of $b\to u$ current and might reveal hints for New Physics with right-handed quark currents. 
Yadong Yang, Hongjun Hao and Fang Su