Electromagnetic mass splittings of pi, a(1), K, K-1(1400), and K*(892)

To one-loop order and O(alpha(EM)), the electromagnetic mass splittings of pi, a(1), K, K-1(1400), and K*(892) are calculated in the framework of U(3)(L) x U(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 f(pi), m(p), and m(a) 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 m(s) or m(K)(2). 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 gener alization 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.