<p>Hadron-to-two-hadron transition generalized parton distributions (GPDs) extend the concept of hadron-to-resonance transition GPDs and provide a unified description of non-diagonal hard exclusive reactions in the generalized Bjorken limit. We present the formalism for the case of spinless hadrons addressing the non-diagonal deeply virtual Compton scattering <i>γ</i><sup><i>*</i></sup><i>π</i> → <i>γππ</i> in terms of <i>π</i> → <i>ππ</i> transition GPDs, which generalize GPDs for <i>π</i> → <i>f</i><sub>0</sub>, <i>ρ</i>, <i>f</i><sub>2</sub>, ⋯ transitions. We work out the basic properties of <i>π</i> → <i>ππ</i> transition GPDs and establish the soft pion theorems at the 2<i>π</i> production threshold. We construct the partial wave expansion of <i>π</i> → <i>ππ</i> transition GPDs in the two-pion decay angles and employ the dispersive approach to constrain <i>π</i> → <i>ππ</i> transition GPDs in terms of <i>ππ</i>-scattering phases with help of the Omnès representation. We estimate the <i>e</i><sup><i>−</i></sup><i>π</i><sup>+</sup> → <i>e</i><sup><i>−</i></sup><i>γπ</i><sup>+</sup><i>π</i><sup>0</sup> cross section in the kinematics of the JLab@12 GeV incorporating the isolated <i>ρ</i>(770) resonance state and work out the angular distributions of the cross section, specifying the observables sensitive to the polarization states of the produced <i>ρ</i>(770) resonance.</p>

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Non-diagonal DVCS and transition GPDs: a unified framework for spinless hadron case γ*π → γππ

  • Sangyeong Son,
  • Kirill M. Semenov-Tian-Shansky

摘要

Hadron-to-two-hadron transition generalized parton distributions (GPDs) extend the concept of hadron-to-resonance transition GPDs and provide a unified description of non-diagonal hard exclusive reactions in the generalized Bjorken limit. We present the formalism for the case of spinless hadrons addressing the non-diagonal deeply virtual Compton scattering γ*πγππ in terms of πππ transition GPDs, which generalize GPDs for πf0, ρ, f2, ⋯ transitions. We work out the basic properties of πππ transition GPDs and establish the soft pion theorems at the 2π production threshold. We construct the partial wave expansion of πππ transition GPDs in the two-pion decay angles and employ the dispersive approach to constrain πππ transition GPDs in terms of ππ-scattering phases with help of the Omnès representation. We estimate the eπ+eγπ+π0 cross section in the kinematics of the JLab@12 GeV incorporating the isolated ρ(770) resonance state and work out the angular distributions of the cross section, specifying the observables sensitive to the polarization states of the produced ρ(770) resonance.