Measurement of inelastic J/ψ and ψ′ photoproduction at HERA (original) (raw)

Measurements of inelastic J/psiJ/\psiJ/psi and psiprime\psi^{\prime}psiprime photoproduction at HERA

The European Physical Journal C - Particles and Fields, 2003

The cross sections for inelastic photoproduction of J/ψ and ψ mesons have been measured in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 38.0 pb −1 . The events were required to have 0.1 < z < 0.9 and 50 < W < 180 GeV, where z is the fraction of the incident photon energy carried by the J/ψ in the proton rest frame and W is the photon-proton centre-of-mass energy. The ψ to J/ψ cross-section ratio was measured in the range 0.55 < z < 0.9. The J/ψ data, for various ranges of transverse momentum, are compared to theoretical models incorporating colour-singlet and colour-octet matrix elements. Predictions of a next-to-leading-order colour-singlet model give a good description of the data, although there is a large normalisation uncertainty. The J/ψ helicity distribution for z > 0.4 is compared to leading-order QCD predictions.

Measurement of inelastic J/psi photoproduction at HERA

Zeitschrift Fur Physik C-Particles and Fields, 1997

We present a measurement of the inelastic, non diffractive J/ψ photoproduction cross section in the reaction e + p → e + J/ψX with the ZEUS detector at HERA. The J/ψ was identified using both the µ + µ − and e + e − decay channels and events were selected within the range 0.4 < z < 0.9 (0.5 < z < 0.9) for the muon (electron) decay mode, where z is the fraction of the photon energy carried by the J/ψ in the proton rest frame. The cross section, the p 2 T and the z distributions, after having subtracted the contributions from resolved photon and diffractive proton dissociative processes, are given for the photon-proton centre of mass energy range 50 < W < 180 GeV; p 2 T is the square of the J/ψ transverse momentum with respect to the incoming proton beam direction. In the kinematic range 0.4 < z < 0.9 and p 2 T > 1 GeV 2 , NLO calculations of the photon-gluon fusion process based on the colour-singlet model are in good agreement with the data. The predictions of a specific leading order colour-octet model, as formulated to describe the CDF data on J/ψ hadroproduction, are not consistent with the data.

Exclusive photoproduction of J/psiJ/\psiJ/psi mesons at HERA

The European Physical Journal C - Particles and Fields, 2002

The exclusive photoproduction reaction γ p → Υ p has been studied with the ZEUS experiment in ep collisions at HERA using an integrated luminosity of 468 pb −1 . The measurement covers the kinematic range 60 < W < 220 GeV and Q 2 < 1 GeV 2 , where W is the photon-proton centre-of-mass energy and Q 2 is the photon virtuality. These results, which represent the analysis of the full ZEUS data sample for this channel, are compared to predictions based on perturbative QCD.

Elastic and inelastic photoproduction of J/ψ mesons at HERA

Nuclear Physics B, 1996

Results on J/~ production in ep interactions in the H1 experiment at HERA are presented. The J/tp mesons are produced by almost real photons (Q2 ~ 0) and detected via their leptonic decays. The data have been taken in 1994 and correspond to an integrated luminosity of 2.7 pb -l. The yp cross section for elastic J/¢ production is observed to increase strongly with the center of mass energy. The cross section for diffractive JAb production with proton dissociation is found to be of similar magnitude as the elastic cross section. Distributions of transverse momentum and decay angle are studied and found to be in accord with a diffractive production mechanism. For inelastic JAb production the total yp cross section, the distribution of transverse momenta, and the elasticity of the J/¢ are compared to NLO QCD calculations in a colour singlet model and agreement is found. Diffractive ~b' production has been observed and a first estimate of the ratio to J/tp production in the HERA energy regime is given.

Measurement of J/ψ photoproduction at large momentum transfer at HERA

Journal of High Energy Physics, 2010

The proton-dissociative diffractive photoproduction of J/ψ mesons has been studied in ep collisions with the ZEUS detector at HERA using an integrated luminosity of 112 pb −1 . The cross section is presented as a function of the photonproton centre-of-mass energy and of the squared four-momentum transfer at the proton vertex. The results are compared to perturbative QCD calculations.

Inelastic production of J/ψ mesons in photoproduction and deep inelastic scattering at HERA

The European Physical Journal C, 2010

Inelastic photo-and electroproduction of J/ψ mesons is studied in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and helicity distributions of the J/ψ mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a k T factorisation ansatz describe the data well, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.

Measurement ofJ/ψ helicity distributions in inelastic photoproduction at HERA

Journal of High Energy Physics, 2009

The J/ψ decay angular distributions have been measured in inelastic photoproduction in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb −1. The range in photon-proton centre-of-mass energy, W , was 50 < W < 180 GeV. The J/ψ mesons were identified through their decay into muon pairs. The polar and azimuthal angles of the µ + were measured in the J/ψ rest frame and compared to theoretical predictions at leading and next-to-leading order in QCD.

Photoproduction of mesons in electron-proton collisions at HERA

Nuclear Physics B, 1996

At the electron-proton collider HERA the inclusive D *± meson photoproduction cross section has been measured with the H1 detector in two different, but partly overlapping, kinematical regions. For the first, where {Wrp ) ~ 200 GeV and Q2 < 0.01 GeV 2, the result is o-(yp c~X) = ( 13.2 + 2 2 +2"1 +9.9

Measurement of inelastic J/psiJ/\psiJ/psi production in deep inelastic scattering at HERA

The European Physical Journal C, 2005

The inelastic production of J/ψ mesons in ep collisions has been studied with the ZEUS detector at HERA using an integrated luminosity of 109 pb −1 . The J/ψ mesons were identified using the decay channel J/ψ → µ + µ − . The measurements were performed in the kinematic range 2 < Q 2 < 80 GeV 2 , 50 < W < 250 GeV, 0.2 < z < 0.9 and −1.6 < Y lab < 1.3, where Q 2 is the virtuality of the exchanged photon, W is the photon-proton centre-of-mass energy, z is the fraction of the photon energy carried by the J/ψ meson in the proton rest frame and Y lab is the rapidity of the J/ψ in the laboratory frame. The measured cross sections are compared to theoretical predictions within the non-relativistic QCD framework including colour-singlet and colour-octet contributions, as well as to predictions based on the kT -factorisation approach. Calculations of the colour-singlet process generally agree with the data, whereas inclusion of colour-octet terms spoils this agreement.

Exclusive photoproduction of mesons at HERA

Physics Letters B, 2002

The exclusive photoproduction reaction γ p → Υ p has been studied with the ZEUS experiment in ep collisions at HERA using an integrated luminosity of 468 pb −1 . The measurement covers the kinematic range 60 < W < 220 GeV and Q 2 < 1 GeV 2 , where W is the photon-proton centre-of-mass energy and Q 2 is the photon virtuality. These results, which represent the analysis of the full ZEUS data sample for this channel, are compared to predictions based on perturbative QCD.