Meson-photon-photon transition form factors for S-, P -, and D-wave states are calculated, the meson being treated as a non-relativistic heavy-quarkantiquark pair. The full dependence on both photon virtualities is included. Cross-section formulas for charge-conjugation even mesons with J P = 0 − , 0 + , 1 + , 2 + , and 2 − in electron-positron collisions are presented and numerical results for LEP energies are given. In particular, we find two-photon event rates for χ c1 , η c (2S), and η b (1S) within reach of LEP. With minor modifications to incorporate SU(3)-flavour breaking we estimate rates for 18 light mesons as well, based on the observation that their two-photon decay widths agree remarkably well with measured data. Finally we point out that e + e − cross sections for 1 + states do not vanish at low Q 2 , the Landau-Yang suppression factors of the two-photon cross sections being compensated by the photon propagators.b Heisenberg Fellow.

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Motivated by the results of the electroweak precision experiments, studies of two-loop self-energy Feynman diagrams are performed. An algebraic method for the reduction of all two-loop self-energies to a set of standard scalar integrals is presented. The gauge dependence of the self-energies is discussed and an extension of the pinch technique to the two-loop level is worked out. It is shown to yield a special case of the background-field method which provides a general framework for deriving Green functions with desirable theoretical properties. The massive scalar integrals of self-energy type are expressed in terms of generalized multivariable hypergeometric functions. The imaginary parts of these integrals yield complete elliptic integrals. Finally, one-dimensional integral representations with elementary integrands are derived which are well suited for numerical evaluation.Comment: LaTeX, 21 pages, postscript files of four figures added as uuencoded tar-compressed file, to appear in Nucl. Phys. B (Proceedings Supplements), INLO-PUB-17/9