Department of Physics, Kyungpook National University
경북대학교 물리학과

KNU Physics Seminars

# Exploring the 3D structure of nucleon resonances based on transition GPD measurements at JLAB

## by Dr Stefan Diehl (U. Giessen & U. Connecticut)

Asia/Seoul
Seminar Room 320 (BLDG #219)

### Seminar Room 320

#### BLDG #219

Description

The study of transition GPDs is a unique tool to understand the 3 dimensional structure and the mechanical properties of nucleon resonances for the first time. To extract transition GPDs, for example the non-diagonal DVCS process can be used. In this process a pion-nucleon system, originating from the decay of an $N^*$ resonance, is produced in addition to a real photon. In addition transition GPDs, especially the chiral-odd sector can be studied by non-diagonal meson production like the hard exclusive $\pi^- \Delta^{++}$ process. Because the factorisation of these process amplitude requires the constraints on Mandelstam variable $t$ and photon virtuality $Q^2 (-t/Q² \ll 1)$ and several final state particles have to be detected for a clean identification, CLAS12 in combination with the upgraded CEBAF accelerator at JLAB provides a unique opportunity to study these processes.
The talk will introduce the topic and present an on-going analysis effort on the recently collected CLAS12 data. In addition perspectives for a 20+ GeV JLAB energy upgrade will be discussed. The results will be discussed in the context of theoretical predictions for the $N \to \Delta^{++}$ transition GPDs which can help us to gain insights into the 3D structure of the $N$ to $\Delta$ transition.

Host: Yongseok Oh and Kirill Semenov-Tyan-Shansky