EPJ

2024 Impact factor 4.8
EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 13, 141-150
DOI 10.1007/s100520000268

$\gamma^* \gamma^*$ reactions at high energies

A. Donnachie1 - H.G.Dosch2 - M. Rueter3

1 Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
2 Institut für Theoretische Physik der Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany
3 School of Physics and Astronomy, Department of High Energy Physics, Tel Aviv University, 69978 Tel Aviv, Israel

Received: 19 August 1999 / Published online: 3 February 2000 - © Springer-Verlag 2000

Abstract
The total hadronic $\gamma^* \gamma^*$ cross sections at high energy are calculated as a function of energy and photon virtuality in a model combining Reggeon exchange, the quark box diagram (a fixed pole in Regge language) and soft and hard pomeron exchanges evaluated in the context of dipole-dipole scattering. Good agreement is obtained with the data for the real $\gamma\gamma$ cross section and for the real photon structure function $F_2^\gamma$. However the model prediction for the $\gamma^* \gamma^*$cross section is too small. This is attributed to an incorrect extrapolation of the Q2 dependence of the hard pomeron adopted here. Parametrising it independently shows that the hard part of the cross section can be well represented by a simple Regge pole with intercept $\sim 1.3$.

Copyright Società Italiana di Fisica, Springer-Verlag 2000

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