Electromagnetic mass splittings of π, a1, K, K1(1400), and K* (892)

To one-loop order and O(αEM), the electromagnetic mass splittings of π, a1, K, K1(1400), and K*(892) are calculated in the framework of U(3)LxU(3)R chiral field theory. The logarithmic divergences emerging in the Feynman integrations of the mesonic loops are factorized by using an intrinsic parameter g of this theory. No other additional parameters or counterterms are introduced to absorb the mesonic loop divergences. When fπ, mρ, and ma are taken as inputs, the parameter g will be determined and all the physical results are finite and fixed. Dashen's theorem is satisfied in the chiral SU(3) limit of this theory and a rather large violation of the theorem is revealed at the order of ms or mK2. Mass ratios of light quarks have been determined. A relation for electromagnetic corrections to masses of axial-vector mesons is obtained. It could be regarded as a generalization of Dashen's theorem. Comparing with data, it is found that the nonelectromagnetic mass difference of K* is in agreement with the estimation of Schechter, Subbaraman, and Weigel. copyright 1997 The American Physical Society