Heavy quark symmetry relations for $B\rightarrow De\bar \nu_e$ and $B\rightarrow D^*e \bar \nu_e$ form factors receive corrections suppressed by powers of the charm quark mass. For small up and down quark massed the leading corrections of order $(1/m_c)^{ n+2}~n = 0,1,2,...$ have a nonanalytic dependence on the light quark masses of the form $\ell n m_\pi^2$ for $n = 0$ and $(1/m_\pi)^n$ for $n = 1,2, ...$~. These corrections arise from very low momentum physics (i.e., well below the chiral symmetry breaking scale) and are computed using chiral perturbation theory. They are typically of order a few percent.
Categories: hep-ph