Beam-Helicity Asymmetries in Double Pion Photoproduction off the Proton

TL;DR

This study measures beam-helicity asymmetries in double pion photoproduction off the proton at MAMI, providing sensitive data crucial for understanding the reaction dynamics in three isospin channels.

Contribution

It presents the first precise measurements of beam-helicity asymmetries in three specific double pion production channels, enhancing the understanding of reaction mechanisms.

Findings

Asymmetries are highly sensitive to reaction dynamics

Data covers three isospin channels

Results improve modeling accuracy of the process

Abstract

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels $\vec{\gamma}p\to \pi^{+}\pi^0n$, $\vec{\gamma}p\to \pi^{0}\pi^0p$ and $\vec{\gamma}p\to \pi^{+}\pi^{-}p$ . The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of $\pi^0$ mesons were detected in a $~4\pi$ electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.