Analysis of electromagnetic mass shift in light-cone algebra

Within the framework of light-cone algebra, it is shown that a logarithmic divergence in the electromagnetic mass shift of a hadron arises precisely due to a mass term in the quark propagator. This divergence, therefore, can be removed by mass renormalization. The coefficient of this divergence is a scalar density which transforms as S₃ for the case of a nucleon. In our analysis, the gauge invariance to order $\frac{1}{q^2}$ is explicitly used.