Separated cross sections in π^0 electroproduction at threshold at Q^2 = 0.05 GeV^2/c^2

Abstract

The differential cross sections σ_0=σ_T+εσ_L, σ_{LT}, and σ_{TT} of π^0 electroproduction from the proton were measured from threshold up to an additional center of mass energy of 40 MeV, at a value of the photon four-momentum transfer of Q^2= 0.05 GeV^2/c^2 and a center of mass angle of θ=90^\circ. By an additional out-of-plane measurement with polarized electrons σ_{LT'} was determined. This showed for the first time the cusp effect above the π^+ threshold in the imaginary part of the s-wave. The predictions of Heavy Baryon Chiral Perturbation Theory are in disagreement with these data. On the other hand, the data are somewhat better predicted by the MAID phenomenological model and are in good agreement with the dynamical model DMT.

6 pages, 4 figures

References in corpus (9)

• Chiral Dynamics in Nucleons and Nuclei
• A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
• Chiral perturbation theory
• Test of low-energy theorems for p(\vec{gamma},π^{0})p in the threshold region
• Pi0 photo- and electroproduction at threshold within a dynamical model
• Improved description of threshold pion electroproduction in chiral perturbation theory
• Observation of a unitary cusp in the threshold γp -> π^{0}p reaction
• Light Quark Mass Difference and Isospin Breaking In Electromagnetic Pion Production
• Neutral pion threshold production at Q^2=0.05 GeV^2/c^2 and Chiral Perturbation Theory

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• Progress Toward Understanding Baryon Resonances
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• Hadron structure at low Q^2
• Singularity structure of the pi N scattering amplitude in a meson-exchange model up to energies W < 2.0 GeV
• Exclusive ${\mathbf{\pi }}^0\mathbf{p}$ electroproduction off protons in the resonance region at photon virtualities 0.4~GeV${}^2$ $\le {\mathbf{Q}}^2\le 1$~GeV${}^2$
• Threshold pion electro- and photoproduction off nucleons in covariant chiral perturbation theory
• Role of $\omega$-meson exchange in scaling of the $\gamma p\to {\pi }^{0}p$ process from a Regge-type model with resonances
• A dispersive approach to pion photo- and electroproduction
• Pion electroproduction in a nonrelativistic theory
• Pion photo- and electroproduction and the chiral MAID interface
• The Dubna-Mainz-Taipei Dynamical Model for $\pi N$ Scattering and $\pi$ Electromagnetic Production
• Pion Photo- and Electroproduction and the Chiral MAID Interface
• Pion photo- and electroproduction in relativistic baryon ChPT
• Are narrow unflavoured mesons a signature of new physics?