Nucleon electric and magnetic polarizabilities in Holographic QCD

Abstract

We analyze the resonance contributions to the generalized Baldin sum rule, namely the sum of the generalized electric and magnetic nucleon polarizabilities ${\alpha }_E(Q^2)$ and ${\beta }_M(Q^2)$, within the Holographic QCD model by Witten, Sakai, and Sugimoto (WSS). In particular, we account for the contributions from the first low-lying nucleon resonances with spin 1/2 and 3/2 and both parities. After having extrapolated the WSS model parameters to fit experimental data on baryonic observables, we compare our findings with alternative predictions in literature, finding a qualitative agreement with all of them. Moreover, at least for the proton case, where data are available, our results are in qualitative accordance with resonance contributions extracted from experimental nucleon-resonance helicity amplitudes.

Comments: 11 pages, 6 figures, comments and references added, figure 6 updated