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 MeV larger than that of neutron, which is in agreement with recent lattice results. Similarly for pions we obtain m π ± − m π 0 = 1.8 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 KK = 949 MeV.

Instanton bags, high density holographic QCD, and chiral symmetry restoration

“…Upon substitution l = 3 7/4 π 1/2 2 1/4 /5 1/4 λ 1/2 which is consistent with the results in the literature[27][28][29][30].…”

Neutron-proton mass difference from gauge/gravity duality

“…Extrapolating the model parameters to fit real QCD hadronic data, we find that the mass splitting is about 0.25% of the average nucleon mass in the model, a result which approaches the lattice estimate in [9]. 2 Our result can be complemented with a previous estimate [15] of the electromagnetic contribution to the mass splitting in the WSS model, which turns out to be about −0.05% of the average nucleon mass. Thus, consistently with expectations, in the WSS model the strong sector contribution to the neutron-proton mass difference overcomes the electromagnetic contribution.…”