Measurement of the cross-section for the reaction gamma p ---> J / psi p with the ZEUS detector at HERA

The ZEUS collaboration Derrick, M. ; Krakauer, D. ; Magill, S. ; et al.
Phys.Lett.B 350 (1995) 120-134, 1995.
Inspire Record 393907 DOI 10.17182/hepdata.44897

This paper reports the cross section measurements for the process ep $\rightarrow$ e\jpsip for $Q~2 < 4$ GeV$~2$ at $\sqrt s = 296$ GeV, based on an integrated luminosity of about 0.5pb$~{-1}$, using the ZEUS detector. The \jpsiwas detected in its $\rm e~{+}e~{-}$ and $\rm \mu~{+}\mu~{-}$ decay modes. The photoproduction cross section was measured to be $52~{ \ +7}_{-12}\pm 10$nb at an average $\gamma$p centre of mass energy of 67 GeV and $71~{+13}_{-20}\pm 12$nb at 114 GeV. The significant rise of the cross section compared to lower energy measurements is not in agreement with VDM models, but can be described by QCD inspired models if a rise in the gluon momentum density at low $x$ in the proton is assumed.

1 data table

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Photoproduction of the psi Particles

Camerini, U. ; Learned, J.G. ; Prepost, R. ; et al.
Phys.Rev.Lett. 35 (1975) 483, 1975.
Inspire Record 100670 DOI 10.17182/hepdata.21149

The s and t dependence of incoherent ψ(3100) photoproduction from deuterium has been measured at the Stanford Linear Accelerator Center. ψ(3700) photoproduction and ψ(3100) photoproduction from hydrogen have also been measured.

3 data tables

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