paper

Form Factors from Light-Cone Sum Rules with -meson Distribution Amplitudes

arXiv:1701.01633 · doi:10.1007/JHEP05(2017)157

Abstract

We study form factors using QCD light-cone sum rules with -meson distribution amplitudes. These form factors describe the semileptonic decay , and constitute an essential input in and decays. We employ the correlation functions where a dipion isospin-one state is interpolated by the vector light-quark current. We obtain sum rules where convolutions of the -wave form factors with the time-like pion vector form factor are related to universal -meson distribution amplitudes. These sum rules are valid in the kinematic regime where the dipion state has a large energy and a low invariant mass, and reproduce analytically the known light-cone sum rules for form factors in the limit of -dominance with zero width, thus providing a systematics for so-far-unaccounted corrections to transitions. Using data for the pion vector form factor, we estimate finite width-effects and the contribution of excited -resonances to the form factors. We find that these contributions amount up to in the small dipion mass region where they can be effectively regarded as a nonresonant (-wave) background to the transition.

28 pages, 3 figures. A few comments added. Version published in JHEP

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