Helicity dependent cross sections for the photoproduction of ${\pi }^0{\pi }^{\pm }$ pairs from quasi-free nucleons

Abstract

Photoproduction of ${\pi }^0{\pi }^{\pm }$-pairs from quasifree nucleons bound in the deuteron has been investigated to study the helicity dependence of this reaction. Measurements with a liquid deuterium target were used to extract the unpolarized cross sections for reactions on protons and neutrons. A deuterated, longitudinally polarized solid-butanol target, together with a circularly polarized photon beam, determined the double polarization observable $E$. From these results the spin-dependent cross sections ${\sigma }_{1/2}$ and ${\sigma }_{3/2}$, corresponding to the anti-parallel and parallel spin configurations of the beam photon and target nucleon, have been derived. The measurements were performed at the Mainz MAMI accelerator with tagged, circularly-polarized photon beams produced via bremsstrahlung from longitudinally polarized electron beams. The reaction products were detected with an almost $4\pi$ solid-angle covering calorimeter composed of the Crystal Ball and TAPS detectors, supplemented by plastic scintillation detectors for charged particle identification. The results are sensitive to sequential decays of nucleon resonances via intermediate states and also to the decay of nucleon resonances by emission of charged $\rho$ mesons, and are compared to recent model results.

9 pages, 6 figures

References in corpus (10)

• Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C
• Photoproduction of pi0-mesons from nuclei
• Light Baryon Spectroscopy
• Quasifree photoproduction of $\eta$ mesons off protons and neutrons
• Photoproduction of pi0pi0 and pi0pi+-pairs off the proton from threshold to the second resonance region
• Insight into the narrow structure in {\boldmath{$\eta$}}-photoproduction on the neutron from helicity dependent cross sections
• First measurement of the polarization observable $E$ and helicity-dependent cross sections in single ${\pi }^0$ photoproduction from quasi-free nucleons
• Measurement of the beam-helicity asymmetry $I^{\odot }$ in the photoproduction of ${\pi }^0{\pi }^{\pm }$-pairs off protons and off neutrons
• Complete set of observables for photoproduction of two pseudoscalars on a nucleon
• Helicity-dependent cross sections for the photoproduction of ${\pi }^0$ pairs from nucleons