Measurement of the beam-helicity asymmetry in the p(e_pol,e'p)pi_0 reaction at the energy of the Delta(1232) resonance

Abstract

In a p(e_pol,e'p)pi_0 out-of-plane coincidence experiment at the 3-spectrometer setup of the Mainz Microtron MAMI, the beam-helicity asymmetry has been precisely measured around the energy of the Delta(1232) resonance and Q^2 = 0.2 (GeV/c)^2. The results are in disagreement with three up-to-date model calculations. This is interpreted as lack of understanding of the non-resonant background, which in dynamical models is related to the pion cloud.

arXiv comment5 pages, 2 figures, 2 tables

References in corpus (12)

• A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
• Dynamical Study of the Delta Excitation in N(e,e' pi) Reactions
• Electroproduction of the Delta Resonance at High Momentum Transfer
• Pion cloud and the $Q^2-$dependence of ${\gamma }^{\ast }N\leftrightarrow \Delta$ transition form factors
• Determination of the E2/M1 Ratio in the γN \to Δ(1232) Transition from a Simultaneous Measurement of p(\vecγ,p)π^0 and p(\vecγ,π^+)n
• Search for Quadrupole Strength in the Electro-excitation of the Delta(1232)
• Measurement of the recoil polarization in the p (\vec e, e' \vec p) pi^0 reaction at the Δ(1232) resonance
• Chiral symmetry and the Delta-Nucleon transition form factors
• Induced proton polarization for pi^0 electroproduction at Q^2 = 0.126 (GeV/c)^2 around the Delta(1232) resonance
• The electroproduction of the $\Delta$(1232) in the chiral quark-soliton model
• Proton Polarization in the $p(\vec{e},e^{\prime }\vec{p}){\pi }^0$ Reaction and the Measurement of Quadrupole Components in the N to $\Delta$ Transition
• A polarization relation and the measurement of the longitudinal response in pseudoscalar meson electroproduction off the nucleon

Cited by in corpus (33)

• Electromagnetic excitation of the Delta(1232)-resonance
• Electroexcitation of nucleon resonances
• Electromagnetic Meson Production in the Nucleon Resonance Region
• Study of Non-Strange Baryon Resonances with Meson Photoproduction
• Investigation of the conjectured nucleon deformation at low momentum transfer
• Recoil Polarization for Delta Excitation in Pion Electroproduction
• 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
• Quadrupole Moments of N and Delta in the 1/N_c Expansion
• Lowest Q^2 Measurement of the gamma*p -> Delta Reaction: Probing the Pionic Contribution
• Electromagnetic N->Delta transition and neutron form factors
• Measurement of the Polarized Structure Function ${\sigma }_{L{T}^{\prime }}$ for $p(\vec{e},e^{\prime }{\pi }^{+})n$ in the $\Delta (1232)$ Resonance Region
• Measurement of the LT-asymmetry in π^0 electroproduction at the energy of the Δ(1232) resonance
• Measurement of the Transverse-Longitudinal Cross Sections in the p (e,e'p)pi0 Reaction in the Delta Region
• Determination of quadrupole strengths in the gamma*p-->Delta(1232) transition at Q2= 0.20 (GeV/c)2
• Measurements of the gamma*p->Delta Reaction At Low Q^2: Probing the Mesonic Contribution
• Recoil Polarization Measurements for Neutral Pion Electroproduction at Q^2=1 (GeV/c)^2 Near the Delta Resonance
• Jülich-Bonn-Washington Model for Pion Electroproduction Multipoles
• Deviation of the Nucleon Shape From Spherical Symmetry: Experimental Status
• Study of polarized-e polarized-p --> e-prime p pi0 in the Delta(1232) mass region using polarization asymmetries
• Measurement of the R${}_{LT}$ response function for ${\pi }^0$ electroproduction at $Q^2$ = 0.070 (GeV/c)${}^2$ in the $N\to \Delta$ transition}
• Study of nucleon resonances with electromagnetic interactions
• Coupled-channel analysis of pion- and eta-electroproduction with the Jülich-Bonn-Washington model
• Electroexcitation of the ${\Delta }^{+}(1232)$ at low momentum transfer
• Measurements of the γ* p --> Δ(1232) reaction at low Q2
• Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance region at Q^2= 0.35 (GeV/c)^2
• Virtual Compton Scattering measurements in the ${\gamma }^{\ast }N\to \Delta$ transition
• On hadron deformation: a model independent extraction of EMR from pion photoproduction data
• Q^2-evolution of nucleon-to-resonance transition form factors in a QCD-inspired vector-meson-dominance model
• Relativistically invariant analysis of polarization effects in exclusive deuteron electrodisintegration process
• Measurement of the Partial Cross Sections s(TT), s(LT) and [s(T)+epsilon*s(L)] of the p(e,e' pi+)n Reaction in the Delta(1232) Resonance
• General analysis of polarization effects in coherent pseudoscalar mesons photo-- and electroproduction on deuteron
• Pion electroproduction measurements in the nucleon resonance region
• Relativistically invariant analysis of $\Delta$--isobar production in deuteron electrodisintegration: $e^{-}+d\to e^{-}+\Delta +N:$ general analysis of polarization effects