Electromagnetic polarizabilities and the excited states of the nucleon (original) (raw)

The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α p (E 0+) = +3.2, α n (E 0+) = +4.1, the t-channel α t p,n = −β t p,n = +7.6 and the resonant β p,n (P 33 (1232)) = +8.3 contributions (in units of 10 −4 fm 3). The remaining deviations from the experimental data ∆α p = 1.2 ± 0.6, ∆β p = 1.2 ∓ 0.6, ∆α n = 0.8 ± 1.7 and ∆β n = 2.0 ∓ 1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions. This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms of twophoton coupling to the σ meson having the predicted mass m σ = 666 MeV and two-photon width Γ γγ = 2.6 keV.