Uncertainty in the leading-order perturbative QCD calculations ofB-meson decays

Abstract

Uncertainty in the perturbative quantum chromodynamics (PQCD) calculation of $B$ decays is investigated in $B\ensuremath{\rightarrow}\ensuremath{\pi}$, $B\ensuremath{\rightarrow}D$ transition form factors and $B\ensuremath{\rightarrow}D\ensuremath{\pi}$ decay amplitudes. $B$-meson distribution amplitude dependence is studied by taking three kinds of distribution amplitudes suggested so far. It is found that almost the same ${q}^{2}$ dependence of the form factors can be obtained irrespective of the types of the $B$-meson distribution amplitudes by suitably choosing one parameter. The $B\ensuremath{\rightarrow}D\ensuremath{\pi}$ process shows the difference due to the distribution amplitude. The effect of the subleading component of the $B$-meson distribution amplitude is also studied in the three processes. The numerical results of calculations with the subleading component can be well approximated by the leading-order calculation with a suitable choice of the distribution amplitude parameters.