Beam spin asymmetry in deep and exclusive pi0 electroproduction

TL;DR

This study measures the beam spin asymmetry in exclusive pi0 electroproduction at high energies, revealing non-zero interference effects and discussing implications for theoretical models like GPDs and Regge formalism.

Contribution

It provides the first detailed measurement of pi0 BSA dependence on kinematic variables in the deep inelastic regime, testing theoretical frameworks.

Findings

Asymmetries are 0.04 - 0.11, roughly independent of t

Asymmetries fit well with a sin(phi) function, indicating interference effects

Results inform the applicability of GPD and Regge models at high Q2

Abstract

The beam spin asymmetry (BSA) in the exclusive reaction ep->ep pi0 was measured with the CEBAF 5.77 GeV polarized electron beam and Large Acceptance Spectrometer(CLAS). The xB, Q2, t and phi dependences of the pi0 BSA are presented in the deep inelastic regime. The asymmetries are fitted with a sin(phi) function and their amplitudes are extracted. Overall, they are of the order of 0.04 - 0.11 and roughly independent of t. This is the signature of a non-zero longitudinal-transverse interference. The implications concerning the applicability of a formalism based on generalized parton distributions, as well as the extension of a Regge formalism at high photon virtualities, are discussed.