$\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ in the Modified Perturbative Approach

Abstract

We investigate the transverse momentum effects in $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ at moderately large total center of mass energy $\sqrt{s}$ in the modified perturbative approach. The calculation of the differential cross section using different approximations shows that the inclusion of $k_{\perp }$ in the quark and gluon propagators cannot lead to a considerable improvement of the theoretical prediction.

6 pages, 3 figures, Talk given at the XVII Autumn School, ``QCD: Perturbative or Nonperturbative'', Lisbon, Portugal, 29. Sept. - 4. Oct. 1999, to appear in the proceedings. Missing figure added