Holographic Estimate of Electromagnetic Mass

TL;DR

This paper uses holographic QCD via gauge/gravity duality to estimate electromagnetic contributions to hadron masses, achieving results consistent with lattice calculations and providing insights into mass differences of protons, neutrons, and pions.

Contribution

It introduces a holographic approach to calculate electromagnetic mass contributions to hadrons, aligning with lattice results and revealing scale independence of pion electromagnetic mass.

Findings

Proton's electromagnetic mass is 0.48 MeV larger than neutron's.

Pion mass difference is approximately 1.8 MeV, about half the experimental value.

Electromagnetic pion mass is independent of N_c and 't Hooft coupling.

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 $0.48~{\rm MeV}$ larger than that of neutron, which is in agreement with recent lattice results. Similarly for pions we obtain $m_{\pi^{\pm}}-m_{\pi^0}=1.8~{\rm MeV}$, 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, $M_{\rm KK}=949~{\rm MeV}$.