Abstract
Due to multiple possible polarizations hard exclusive production of tensor mesons by virtual photons or in heavy meson decays offers interesting possibilities to study the helicity structure of the underlying short-distance process. Motivated by the first measurement of the transition form factor $\gamma^*\gamma \to f_2(1270)$ at large momentum transfers by the BELLE collaboration we present an improved QCD analysis of this reaction in the framework of collinear factorization including contributions of twist-three quark-antiquark-gluon operators and an estimate of soft end-point corrections using light-cone sum rules. The results appear to be in a very good agreement with the data, in particular the predicted scaling behavior is reproduced in all cases.
Highlights
Functions — tensor meson distribution amplitudes (DAs) — determined, or at least constrained
Motivated by the first measurement of the transition form factor γ∗γ → f2(1270) at large momentum transfers by the BELLE collaboration we present an improved QCD analysis of this reaction in the framework of collinear factorization including contributions of twist-three quark-antiquarkgluon operators and an estimate of soft end-point corrections using light-cone sum rules
Our work aims to match this experimental progress with a development of the robust QCD framework for the study of the transition form factor γ∗γ → f2(1270) in collinear factorization
Summary
Another possibility is to use the experimental result on the decay width Γ(f2 → ππ) and estimate fq assuming that the matrix element of the energy-momentum tensor π+π−|Θμν|0 is saturated by the tensor meson [23,24,25,26,27]. The “genuine” geometric twist-three contributions can be related to the three-particle DAs using EOM, see appendix C. The Wandzura-Wilczek-type twist-two contributions assuming the asymptotic expression for φ2(u) (3.16) have the form φW 4 W (u) = 100u2(1 − u)2(2u − 1) , g4W W (u) = 30u(1 − u)(2u − 1) We expect that these contributions are the dominant source of the power-suppressed corrections ∼ 1/Q2 because of the large mass of the f2(1270) and will neglect “genuine” geometric twist-three and twist-four contributions.
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