Relativistic corrections to kaon charge radii in quark model

Relativistic effects of the order of v2/c2 are considered in the wave functions of kaons treated as bound qq-bar-states. The ratio xi=absK0/K+abs is calculated for dynamical models with the direct interaction. As it is shown, in contrast to results by Greenberg, Nussinov and Sucher, corrections to the nonrelativistic xiNR=msub(s)2-msub(u)2/2msub(s)2+msub(u)2 may be positive both in the classical and quantum models of qq-bar-systems. (author)