We have studied the properties of hadron production in photon-photon scattering with tagged photons at the e + e − storage ring PETRA. A tail in the p T distribution of particles consistent with p T −4 has been observed. We show that this tail cannot be due to the hadronic part of the photon. Selected events with high p T particles are found to be consistent with a two-jet structure as expected from a point-like coupling of the photons to quarks. The lowest-order cross section predicted for γγ → q q , σ = 3 Σ e q 4 · σ γγ → μμ , is approached from above by the data at large transverse momenta.
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From a 98000-photograph exposure of the BNL 80-in. deuterium-filled chamber to a 14.6-GeV/c p¯ beam we have extracted those events that fit the channel p¯n→p¯pπ−. The cross section for this channel is measured to be 730 ± 50 μb. The cross section for the reaction p¯n→Δ¯−−(1238)p is determined to be 130 ± 30 μb. Evidence for target dissociation is presented. A comparison with the reaction π−n→π−pπ− at the same energy indicates agreement with factorization.
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