REMARK ON HIGH-ENERGY QUARK-QUARK SCATTERING AND THE EIKONAL APPROXIMATION

In this paper we calculate the high-energy quark-quark scattering ampl itude, first in the case of scalar QCD, using Fradkin's approach to de rive the scalar quark propagator in an external gluon field and comput ing it in the eikonal approximation. (This approach was also recently used by Fabbrichesi, Pettorino, Veneziano, and Vilkovisky to study the four-dimensional Planckian-energy scattering in gravity.) We then ext end the results to the case of ''real'' (i.e., fermion) QCD, thus deri ving again, in a rather direct way, the results previously found by Na chtmann. The Abelian case (QED) is also discussed in the Appendix.