Speaker
Description
The exclusive photoproduction reactions γp→J/ψ(1S)p and γp→ψ(2S)p have been studied at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373 pb−1. The measurement has been made in the kinematic range 30 < W < 180 GeV, Q2 <1 GeV2, |t| <1 GeV2, where W is the photon--proton centre-of-mass energy, Q2 is the photon virtuality and t is the squared four-momentum transfer at the proton vertex. The decay channels used were J/ψ(1S)→μ+μ−, ψ(2S)→μ+μ− and ψ(2S)→J/ψ(1S)π+π− with subsequent decay J/ψ(1S)→μ+μ−. The ratio of the production cross sections R=σψ(2S)/σJ/ψ(1S) has been measured as a function of W and t and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production.
| Collaboration / Activity | ZEUS |
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