Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities

Abstract

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\Delta (1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields ${\gamma }_{E1E1}=-3.5\pm 1.2$, ${\gamma }_{M1M1}=3.16\pm 0.85$, ${\gamma }_{E1M2}=-0.7\pm 1.2$, and ${\gamma }_{M1E2}=1.99\pm 0.29$, in units of $10^{-4}$ fm${}^4$.

5 pages, 3 figures, 2 tables

References in corpus (5)

• Using effective field theory to analyse low-energy Compton scattering data from protons and light nuclei
• Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C
• Compton scattering from the proton in an effective field theory with explicit Delta degrees of freedom
• Proton spin polarizabilities from polarized Compton scattering
• Incoherent pion photoproduction on ${}^{12}$C

Cited by in corpus (6)

• The Present and Future of QCD
• Generalized polarizabilities of the nucleon in baryon chiral perturbation theory
• Proton scalar dipole polarizabilities from real Compton scattering data, using fixed-t subtracted dispersion relations and the bootstrap method
• Chiral Effective Theory Methods and their Application to the Structure of Hadrons from Lattice QCD
• QCD and Hadron Physics
• First concurrent extraction of the leading-order scalar and spin proton polarizabilities