Holographic Estimate of Electromagnetic Mass

Abstract

Using the gauge/gravity duality, we calculate the electromagnetic contributions to hadron masses, where mass generates dynamically by strong QCD interactions. Based on the Sakai-Sugimoto model of holographic QCD we find that the electromagnetic mass of proton is $0.48\mathrm{MeV}$ larger than that of neutron, which is in agreement with recent lattice results. Similarly for pions we obtain $m_{{\pi }^{\pm }}-m_{{\pi }^0}=1.8\mathrm{MeV}$, roughly half of the experimental value. The electromagnetic mass of pions is found to be independent of $N_c$ and 't Hooft coupling and its scale is set only by the Kaluza-Klein scale of the model, $M_{\mathrm{KK}}=949\mathrm{MeV}$.

Comments: 15 pages, 6 figures: v2. minor change, typo corrected and reference added:v3 minor change, references added: v4. published version, pion mass recalculated