Measurement of the Generalized Polarizabilities of the Proton in Virtual Compton Scattering at Q2= 0.92 and 1.76 GeV2

Abstract

We report a Virtual Compton Scattering study of the proton at low CM energies. We have determined the structure functions $P_{LL}-P_{TT}/\epsilon$ and $P_{LT}$, and the electric and magnetic Generalized Polarizabilities (GPs) ${\alpha }_E(Q2)$ and ${\beta }_M(Q2)$ at momentum transfer Q2= 0.92 and 1.76 GeV2. The electric GP shows a strong fall-off with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a fall-off; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from $\pi N$ intermediate states.

4 pages, 2 Figs. Version for PRL after PRL cancelled their request for reducing length of paper

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Cited by in corpus (27)

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• Dispersion Theory in Electromagnetic Interactions
• A new measurement of the structure functions $P_{LL}-P_{TT}/epsilon$ and $P_{LT}$ in virtual Compton scattering at $Q^2=$ 0.33 (GeV/c)${}^2$
• Light-front interpretation of Proton Generalized Polarizabilities
• Virtual Compton Scattering and the Generalized Polarizabilities of the Proton at Q^2=0.92 and 1.76 GeV^2
• New Predictions for generalized spin polarizabilities from heavy baryon chiral perturbation theory
• 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
• Measured proton electromagnetic structure deviates from theoretical predictions
• Real and Virtual Compton Scattering: the nucleon polarisabilities
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• New Insight in the $Q^2$-Dependence of Proton Generalized Polarizabilities
• Chiral perturbation theory - Success and challenge
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• Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$
• Nucleon Polarizabilities: Theory
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• 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