Measurement of the cross-section ratio σ ψ(2S) / σ J/ψ(1S) in deep inelastic exclusive ep scattering at HERA

Abstract

The exclusive deep inelastic electroproduction of ψ(2S) and J/ψ(1S) at an ep centre-of-mass energy of 317 GeV has been studied with the ZEUS detector at HERA in the kinematic range 2 < Q 2 < 80 GeV 2 , 937 30 < W < 210 GeV and |t| < 1 GeV 2 , where Q 2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The data for 2 < Q 2 < 5 GeV 2 were taken in the HERA I running period and correspond to an integrated luminosity of 114 pb −1. The data for 5 < Q 2 < 80 GeV 2 are from both HERA I and HERA II periods and correspond to an integrated luminosity of 468 pb −1. The decay modes analysed were μ + μ − and J/ψ(1S) π + π − for the ψ(2S) and μ + μ − for the J/ψ(1S). The cross-section ratio σ ψ(2S) /σ J/ψ(1S) has been measured as a function of Q 2 , W and t. The results are compared to predictions of QCD-inspired models of exclusive vector-meson production.

Charmonium spectrum and diffractive production in a light-front Hamiltonian approach

“…[21] for coherent charmonium production in electron-lead collisions. The experiment data points are measurements by ZEUS collaboration [28] in electron-proton scattering at HERA.…”

“…[21] for details. � � (��� � ) Figure 2: Predictions of the BLFQ LFWF (solid curves) and the boosted Gaussian LFWF (dashed curves) compared with the HERA experimental data for the σ Ψ(2s) /σ J/Ψ cross-section ratio as a function of Q 2 in electron-proton scattering [28]. Error bars indicate the statistical uncertainties.…”

“…Fig. 2 shows the predictions of the BLFQ LFWFs (solid curve) and the boosted Gaussian LFWFs (dashed curve) for the σ Ψ(2s) /σ J/Ψ cross-section ratio as a function of Q 2 in electron-proton scattering measured at HERA [28].…”

Recent results on diffractive and forward physics at HERA

“…D * production in diffractive DIS [5] and prompt photon production in diffractive photoproduction [6] are compared to the models based on the diffractive PDFs. The production ratio ψ(2S )/ψ(1S ) in diffractive DIS [7] is compared to various models with approaches based on perturbative QCD in Section 4. Exclusive production of ρ 0 in photoproduction with a fast neutron [8] is reviewed in Section 5 in the context of the absorptive phenomena.…”

Measurement of the cross section ratioσψ(2S)/σJ/ψ(1S)in deep inelastic exclusiveepscattering at HERA

“…The predictions of the models FFJS, KNNPZZ and LM also provide fair descriptions of the measurements. The material described above has recently been published [29].…”