Unitary Limitations of the SMEFT Approach in Describing New Physics in the Processes of Single Top Quark Production

Using the optical theorem from the conditions of perturbative unitarity, we have established the upper bounds on the ratios of the Wilson coefficients to the square of the new physics scale for anomalous operators contributing to the processes of single t-quark production in hadron collisions. The limitations are found in an analytical form and are given numerically in the form of characteristic regions.