Measurement of beam spin asymmetry for exclusive pion electroproduction reactions at Jefferson Lab Hall C*

Hadron internal structure is incompletely understood, as intrinsic properties (e.g. mass, spin) cannot yet be fully understood within a QCD framework. The pion is a good candidate for studies leading to our improved comprehension, due to its relatively simple structure and its experimental accessibility. Experimental Hall C at Jefferson Lab is a unique facility that can host high precision studies of exclusive pion electroproduction reactions. The cross-section of this reaction is dictated by the longitudinal and transverse polarization of the virtual photon. Considering the recoil system in such a reaction, the ground state nucleon p(e, e’ π⁺)n reaction has been studied in detail but little is known about the nucleon-to-resonance (N→Δ) transition GPDs. The 12 GeV upgrade at Jefferson Lab provides a unique opportunity to study higher resonance of pion electroproduction reaction p(e, e’ π⁺)Δ⁰ at wide range of kinematics (Q², W and -t). This talk will present the first measurement of the beam spin asymmetry and cross-section ratio (σ_LT’/σ₀) for the higher resonance reaction from Kaon-LT Experiment (E12-09-011). This cross-section is then compared with the ground state reaction. The comparison of two reactions will be invaluable for our understanding of hadron GPDs.