Higher-Twist Effects in Light-Cone Sum Rule for the $B\to \pi$ Form Factor

Abstract

We calculate the higher-twist corrections to the QCD light-cone sum rule for the $B\to \pi$ transition form factor. The light-cone expansion of the massive quark propagator in the external gluonic field is extended to include new terms containing the derivatives of gluon-field strength. The resulting analytical expressions for the twist-5 and twist-6 contributions to the correlation function are obtained in a factorized approximation, expressed via the product of the lower-twist pion distribution amplitudes and the quark-condensate density. The numerical analysis reveals that new higher-twist effects for the $B\to \pi$ form factor are strongly suppressed. This result justifies the conventional truncation of the operator product expansion in the light-cone sum rules up to twist-4 terms.

Comments: 14 pages, 2 figures, 1 table