Measurement of Lepton and Pion Pair Production in Photon - Photon Collisions at Dci

Courau, A. ; Falvard, A. ; Haissinski, J. ; et al.
Phys.Lett.B 96 (1980) 402-406, 1980.
Inspire Record 153776 DOI 10.17182/hepdata.49087

We report a photon-photon experiment performed at the Orsay storage rings. 300e + e − , μ + μ − and π + π − pairs produced with low invariant masses have been observed. For each event, one or both protons have been tagged at a very small angle. The γγ→μ + μ − and γγ→π + π − cross-sections have been measured near threshold, the γγ→e + e − process being used as a normalization. The observed invariant mass distribution is compared to theoretical calculations for each of the three processes. The μ + μ − data are in good agreement with QED predictions. The π + π − cross-section, in our experimental acceptance, is somewhat larger than the one expected from the Born terms only.

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