Speaker
Description
Transition generalized parton distributions (GPDs) can be accessed through several classes of hard exclusive reactions including the non-diagonal Deeply Virtual Compton Scattering (DVCS) and non-diagonal Deeply Virtual Meson Production (DVMP) in which the target hadron transforms into a resonating hadronic system. Transition GPDs encode valuable information on the dynamics of hadron excitations.
In this talk, we discuss the QCD collinear factorization approach for the non-diagonal DVCS reaction $\gamma^* \pi \to \gamma \pi \pi$, which is a subprocess of the Sullivan-type of reaction of $e N \to e N' \gamma \pi \pi$. We consider its description in terms of $\pi \to \pi \pi$ transition GPDs, which provide a useful spinless hadron test ground for developing the framework of transition GPDs.
We review the definition and basic properties of $\pi \to \pi \pi$ transition GPDs. We consider the non-diagonal $\pi \to \pi \pi$ DVCS reaction and the Bethe-Heitler background process for the $\pi \pi$ invariant mass corresponding to the intermediate $\rho$-meson resonance and work out the angular structure of the produced $\pi \pi$ system. We construct a phenomenological model for $\pi \to \rho$ transition GPDs and provide estimates of the differential cross section of the $e \pi \to e' \gamma \rho$ reaction.
