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)${}^2$

Abstract

The cross section of the $ep\to e^{\prime }{p}^{\prime }\gamma$ reaction has been measured at $Q^2=0.33$ (GeV/c)${}^2$. The experiment was performed using the electron beam of the MAMI accelerator and the standard detector setup of the A1 Collaboration. The cross section is analyzed using the low-energy theorem for virtual Compton scattering, yielding a new determination of the two structure functions $P_LL}-P_{TT}/epsilon$ and $P_{LT}$ which are linear combinations of the generalized polarizabilities of the proton. We find somewhat larger values than in the previous investigation at the same $Q^2$. This difference, however, is purely due to our more refined analysis of the data. The results tend to confirm the non-trivial $Q^2$-evolution of the generalized polarizabilities and call for more measurements in the low-$Q^2$ region ($\le$ 1 (GeV/c)${}^2$).

9 pages, 10 figures. EPJA version. slight revisions in the text and figures

References in corpus (8)

• Global analysis of proton elastic form factor data with two-photon exchange corrections
• Dispersion analysis of the nucleon form factors including meson continua
• Quantum corrections to the string Bethe ansatz
• Electromagnetic Form Factors of the Nucleon and Compton Scattering
• Updated dispersion-theoretical analysis of the nucleon electromagnetic form factors
• Measurements of the Generalized Electric and Magnetic Polarizabilities of the Proton at Low Q2 Using the VCS Reaction
• New Predictions for generalized spin polarizabilities from heavy baryon chiral perturbation theory
• Monte Carlo simulation of virtual Compton scattering below pion threshold

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• 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
• Generalized polarizabilities of the nucleon in baryon chiral perturbation theory
• Measured proton electromagnetic structure deviates from theoretical predictions
• Real and Virtual Compton Scattering: the nucleon polarisabilities
• Virtual Compton Scattering measurements in the nucleon resonance region
• Virtual Compton Scattering and Nucleon Generalized Polarizabilities
• Spin-dependent sum rules connecting real and virtual Compton scattering verified
• New Insight in the $Q^2$-Dependence of Proton Generalized Polarizabilities
• Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton
• New approach to low energy Virtual Compton Scattering and generalized polarizabilities of the nucleon
• Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$
• Nucleon Polarizabilities: Theory
• Virtual Compton scattering at low energies with a positron beam
• Chiral effective field theories of the strong interactions
• 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