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arXiv · hep-ph/9703280

Color-Octet Contributions to J/psi Photoproduction via Fragmentation at HERA

Bernd A. Kniehl·Gustav Kramer
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Abstract

We study J/psi photoproduction via fragmentation at next-to-leading order in the QCD-improved parton model, using the nonrelativistic factorization formalism proposed by Bodwin, Braaten, and Lepage. We consider direct and resolved photoproduction of prompt J/psi mesons and chi_{cJ} mesons radiatively decaying to J/psi+gamma, taking into account the formation of both color-singlet and color-octet c anti-c states. Adopting the values of the long-distance color-octet matrix elements extracted from fits to prompt-J/psi data recently taken at the Fermilab Tevatron, we predict that measurements of J/psi photoproduction at DESY HERA should show a distinctive excess over the expectation based on the color-singlet model at small values of the inelasticity variable z. This is complementary to the expected enhancement at z close to 1 due to the color-octet contribution to photon-gluon fusion.

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Bernd A. Kniehl, Gustav Kramer. 1997-03-10. Color-Octet Contributions to J/psi Photoproduction via Fragmentation at HERA. https://doi.org/10.1016/s0370-2693(97)01126-x

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