1998/09/30 by Maxim V. Polyakov, M. V. Polyakov · 7 citations
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph
paper · pdf · doi:10.1016/s0550-3213(99)00314-4
published as Nucl.Phys.B555:231,1999 · 30 pages, one figure. Discussion of crossing relations between meson distribution amplitudes and quark densities is added
arxiv created 1999/03/20 · openalex publication_date 1999/08/01 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We study the hard exclusive production of two pions in the virtual photon fragmentation region with various invariant masses including the resonance region. The amplitude is expressed in terms of two-pion light cone distribution amplitudes (2πDA's). We derive dispersion relations for these amplitudes, which enables us to fix them completely in terms of ππ scattering phases and a few low-energy subtraction constants determind by the effective chiral lagrangian. Quantitative estimates of the resonance as well ππ background DA's at low normalization point are made. We also prove certain new soft pion theorem relating two-pion DA's to the one-pion DA. Crossing relations between 2πDA's and parton distributions in a pion are discussed. We demontrate that by studying the shape of the ππ mass spectra (not absolute cross section!) in a diffractive electroproduction one can extract the deviation of the meson (π,ρ, etc.) wave functions from their asymptotic form 6 z(1-z) and hence to get important information about the structure of mesons. Also we discuss how the moments of quark distributions in a pion can be measured in the hard diffraction. We suggest (alternative to Söding's) parametrization of ππ spectra which is suitable for large photon virtuality.