Measurement of the electric and magnetic polarizabilities of the proton

Abstract

The Compton scattering cross section on the proton has been measured at laboratory angles of 90 • and 135 • using tagged photons in the energy range 70-100 MeV and simultaneously using untagged photons in the range 100-148 MeV. With the aid of dispersion relations, these cross sections were used to extract the electric and magnetic polarizabilities,ᾱ andβ respectively, of the proton. We find α +β = (15.0 ± 2.9 ± 1.1 ± 0.4) × 10 −4 fm 3 ,in agreement with a model-independent dispersion sum rule, and α −β = (10.8 ± 1.1 ± 1.4 ± 1.0) × 10 −4 fm 3 ,

First extraction of the scalar proton dynamical polarizabilities from real Compton scattering data

“…We used two different data sets, i.e., all the available experimental data for the unpolarized cross sections below pion-production threshold, denoted as FULL data set 1 (for a total of 150 data points) [26,[31][32][33][34][36][37][38][39][40][41][42], and the data set given by the TAPS experiment alone (55 data points) [26], which is, by far, the most comprehensive available subset. "Improved" data sets have been defined in recent fits of RCS observables, by discarding some data points from different experiments [4,20,43].…”

Virtual Compton scattering off the nucleon

“…For the resonances, the most important contributions come from the ∆(1232) and D 13 (1520) for which the radiative couplings were taken from pion photo/electro production [Vdh95]. The model was tested against available data for real Compton scattering below pion threshold and yields for the proton polarizabilities at the photon point : α G = 7.29 · 10 −4 f m 3 and β G = 1.56 · 10 −4 f m 3 , which should be compared to the values extracted form experiment [MGi95] : α exp G = 12.1 ± 0.8 ± 0.5 · 10 −4 f m 3 and β exp G = 2.1 ∓ 0.8 ∓ 0.5 · 10 −4 f m 3 . The underestimation of α G is probably due to the simplicity of the present tree-level effective Lagrangian model which does not include non-resonant πN intermediate states.…”

Effective theory of theΔ(1232)resonance in Compton scattering off the nucleon

“…During the past decade a number of excellent experimental programs have been dedicated to these two processes (see Refs. [1][2][3][4][5] and [6][7][8][9][10], respectively). At low photon energies, these experiments probe the static properties of the nucleon, such as its electric charge, magnetic moment, and polarizabilities.…”