Bounds on scalar leptoquark masses from S,T,U parameters in the minimal four-color quark-lepton symmetry model

The contributions into radiative correction parameters S,T,U from the scalar leptoquarks are calculated in the minimal gauge model with the four-color quark-lepton symmetry. It is shown that the contributions into T and U from the scalar leptoquark doublets are not positive definite. Using the current experimental data on S,T,U the bounds on the scalar leptoquark masses are obtained. In particular, the existence of the relatively light scalar leptoquark with electric charge 2/3 is shown to be compatible with the current experimental data on S,T,U.