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Nucleon Polarizibilities for Virtual Photons

J. Edelmann·N. Kaiser·G. Piller·W. Weise
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Abstract

We generalize the sum rules for the nucleon electric plus magnetic polarizability $Σ=α+β$ and for the nucleon spin-polarizability $γ$, to virtual photons with $Q^2>0$. The dominant low energy cross sections are represented in our calculation by one-pion-loop graphs of relativistic baryon chiral perturbation theory and the $Δ(1232)$-resonance excitation. For the proton we find good agreement of the calculated $Σ_p(Q^2)$ with empirical values obtained from integrating up electroproduction data for $Q^2<0.4 GeV^2$. The proton spin-polarizability $γ_p(Q^2)$ switches sign around $Q^2= 0.4 GeV^2$ and it joins smoothly the "partonic" curve, extracted from polarized deep-inelastic scattering, around $Q^2=0.7 GeV^2$. For the neutron our predictions of $Σ_n(Q^2)$ and $γ_n(Q^2)$ agree reasonably well at $Q^2=0$ with existing determinations. Upcoming (polarized) electroproduction experiments will be able to test the generalized polarizability sum rules investigated here.

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J. Edelmann, N. Kaiser, G. Piller, W. Weise. 1998-06-29. Nucleon Polarizibilities for Virtual Photons. https://doi.org/10.1016/s0375-9474(98)00467-9

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