Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2

Abstract

The beam-helicity asymmetry has been measured simultaneously for the reactions (e p \to e p γ) and (e p \to e p π^0) in the $\Delta (1232)$ resonance region at $Q^2=$ 0.35 (GeV/c)${}^2$. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some ${\gamma }^{(\ast )}N\to \pi N$ multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels ($\gamma$ and ${\pi }^0$) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization.

arXiv comment7 pages, 8 figures, version to appear in EPJA

References in corpus (17)

• Generalized Parton Distributions
• A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
• Dispersion relations in real and virtual Compton scattering
• Pion cloud and the $Q^2-$dependence of ${\gamma }^{\ast }N\leftrightarrow \Delta$ transition form factors
• Virtual Compton Scattering and Generalized Polarizabilities of the Proton
• QED radiative corrections to virtual Compton scattering
• Single-Transverse Spin Asymmetry in Semi-Inclusive Deep Inelastic Scattering
• The first determination of Generalized Polarizabilities of the proton by a Virtual Compton Scattering experiment
• Measurement of the Polarized Structure Function ${\sigma }_{L{T}^{\prime }}$ for $p(\vec{e},e^{\prime }p){\pi }^o$ in the $\Delta (1232)$ Resonance Region
• Dispersion relation formalism for virtual Compton scattering off the proton
• Virtual Compton Scattering Off Protons at Moderately Large Momentum Transfer
• Measurement of the LT-asymmetry in π^0 electroproduction at the energy of the Δ(1232) resonance
• Measurement of the beam-helicity asymmetry in the p(e_pol,e'p)pi_0 reaction at the energy of the Delta(1232) resonance
• Measurement of the Generalized Polarizabilities of the Proton in Virtual Scattering at Q2=0.92 and 1.76 GeV2: I. Low Energy Expansion Analysis
• Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2= 0.92 and 1.76 GeV2
• Measurements of the Generalized Electric and Magnetic Polarizabilities of the Proton at Low Q2 Using the VCS Reaction
• Single--Spin Asymmetries in the Bethe--Heitler Process $e^{-}+p\to e^{-}+\gamma +p$ from QED Radiative Corrections

Cited by in corpus (14)

• Hadron structure at low Q^2
• Jülich-Bonn-Washington Model for Pion Electroproduction Multipoles
• Dispersion Theory in Electromagnetic Interactions
• Virtual Compton Scattering and the Generalized Polarizabilities of the Proton at Q^2=0.92 and 1.76 GeV^2
• Coupled-channel analysis of pion- and eta-electroproduction with the Jülich-Bonn-Washington model
• Virtual Compton Scattering measurements in the ${\gamma }^{\ast }N\to \Delta$ transition
• Real and Virtual Compton Scattering: the nucleon polarisabilities
• Virtual Compton Scattering and Nucleon Generalized Polarizabilities
• New Insight in the $Q^2$-Dependence of Proton Generalized Polarizabilities
• Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$
• Virtual Compton scattering at low energies with a positron beam
• Lepton mass effects in the Bethe-Heitler process
• The Proton Electromagnetic Generalized Polarizabilities
• Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles