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Transition to perturbative QCD in two-photon collisions

Ron-Chou Hsieh·Hsiang-nan Li
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Abstract

We propose that the different angular distributions in two-photon collisions observed at low and high center-of-mass energies $W_{γγ}$ indicate the transition from nonperturbative to perturbative QCD. We calculate the differential cross sections of $γγ\toππ$, $KK$ in the angle $θ$ of one of the final-state mesons using QCD sum rules and the perturbative QCD approach based on $k_T$ factorization theorem. Our predictions from sum rules (perturbative QCD) decrease (increase) with $|\cosθ|$, consistent with the Belle data of $γγ\to K^+K^-$ for $W_{γγ}\approx 1.5$-1.7 (2.2-2.4) GeV.

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Ron-Chou Hsieh, Hsiang-nan Li. 2004-07-01. Transition to perturbative QCD in two-photon collisions. https://doi.org/10.1103/physrevd.70.056002

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