Exclusive electroproduction of J/ψ mesons at HERA

Chekanov, S.; Grijpink, S.J.L.A.; Koffeman, E.; Kooijman, P.; Maddox, E.; Pellegrino, A.; Schagen, S.E.S.; Tiecke, H.; Wiggers, L.; Wolf, E. de

doi:10.1016/j.nuclphysb.2004.06.034

Cited by 207 publications

(233 citation statements)

References 77 publications

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“…The experimental data on J/ψ electroproduction mentioned in this paper are confirmed by the ZEUS data recently published [38].…”

Section: Experimental Datasupporting

confidence: 85%

Factorization of the dependence in electroproduction of vector mesons

Ferreira¹,

Baltar²

2005

Nuclear Physics A

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In a framework for nonperturbative QCD calculation of high energy processes, the amplitudes for photo-and electroproduction of vector mesons are written as integrals of the overlap product of photon and vector meson wave functions, multiplied by the amplitude for the scattering of qq dipole pairs off the proton. For sizes of the overlap functions that are smaller than the typical ranges of the interaction of the dipoles with the proton, the amplitudes factorize in the form of integrals, here called overlap strengths, formed only with the overlap of the wave functions times the square of the dipole separation. The integration is extended over the light front coordinates describing the qq dipoles. With this result, the overlap strengths contain all Q 2 dependence of the observables. We show the importance of this factorization in the description of the experimental data for all S-wave vector mesons.

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“…The experimental data on J/ψ electroproduction mentioned in this paper are confirmed by the ZEUS data recently published [38].…”

Section: Experimental Datasupporting

confidence: 85%

Factorization of the dependence in electroproduction of vector mesons

Ferreira¹,

Baltar²

2005

Nuclear Physics A

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“…At HERA, the distribution of the exclusive charmonium signal as a function of the candidate p 2 T was well described by an exponential function, exp(−bp 2 T ) [6,9]. The p 2 T distribution provides discrimination among various production sources because it approximates the squared four-momentum transfer, |t|, which depends on the production mechanism.…”

Section: Jhep09(2015)084mentioning

confidence: 99%

Measurement of the exclusive Υ production cross-section in pp collisions at s = 7 $$ \sqrt{s}=7 $$ TeV and 8 TeV

collaboration

Aaij²,

Adeva

et al. 2015

J. High Energ. Phys.

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A study is presented of central exclusive production of Υ(nS) states, where the Υ(nS) resonances decay to the µ + µ − final state, using pp collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range 2 < y(Υ) < 4.5 where the muons are reconstructed in the pseudorapidity range 2 < η(µ ± ) < 4.5. The data sample corresponds to an integrated luminosity of 2.9 fb −1 and was collected at centreof-mass energies of 7 TeV and 8 TeV. The measured Υ(1S) and Υ(2S) production crosssections are σ(pp → pΥ(1S)p) = 9.0 ± 2.1 ± 1.7 pb and σ(pp → pΥ(2S)p) = 1.3 ± 0.8 ± 0.3 pb, where the first uncertainties are statistical and the second are systematic. The Υ(1S) crosssection is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3S) production cross-section, including possible contamination from χ b (3P ) → Υ(3S)γ decays. The LHCb collaboration 15 IntroductionCentral exclusive production (CEP) of Υ(nS) (n = 1, 2, 3) resonances in pp collisions is thought to occur by photoproduction through the exchange of a photon and a pomeron (a colour-singlet system) between two protons, as illustrated in figure 1. Since the protons do not dissociate, typically only a small component of momentum transverse to the beam direction (p T ) is exchanged in the interaction. The photoproduction of Υ resonances at LHCb can be computed using perturbative quantum chromodynamics (QCD), given the high photon-proton centre-of-mass energy, W , and the cross-section depends on the square of the gluon parton-density function, g(x), where Bjorken-x is the fraction of the proton's momentum carried by the gluon [1]. Measurements of the production cross-sections for the Υ(nS) resonances in the forward region covered by the LHCb detector are sensitive to g(x) in the region of small x down to approximately 1.5 × 10 −5 , where the knowledge of g(x) is limited. Furthermore, predictions for the Υ(nS) cross-sections at leading order (LO) and next-to-leading order (NLO) in the strong-interaction coupling differ greatly for the values of W probed in Υ(nS) resonance production, and there are significant variations depending on the models used to describe the Υ wave function and the t-channel exchange [1][2][3]. Quarkonia photoproduction has been studied in exclusive production at HERA [4-9], the Tevatron [10] and the LHC [11][12][13]. At LHCb, exclusive production is associated with the absence of significant detector activity apart from that associated with the exclusive candidate. The background from proton dissociation occurring outside the detector acceptance is characterised as having a value of Υ candidate p T which is larger than that for exclusive production.-1 -

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“…A particularly clean probe of the two-gluon formfactor is J/ψ photoproduction, the t-dependence of which has been measured in experiments at the HERA collider (x ∼ 10 −2 − 10 −4 ) [29,30], the FNAL fixed-target experiment ( x ∼ 5 × 10 −2 ) [28], and a number of fixedtarget experiments at lower energies (x ∼ 10 −1 ); see Refs. [31,32] for a review of the data.…”

Section: Transverse Spatial Distribution Of Gluonsmentioning

confidence: 99%

Generalized parton distributions and rapidity gap survival in exclusive diffractiveppscattering

et al. 2007

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We propose a new approach to the problem of rapidity gap survival (RGS) in the production of high-mass systems (H = dijet, heavy quarkonium, Higgs boson) in double-gap exclusive diffractive pp scattering, pp → p + (gap) + H + (gap) + p. It is based on the idea that hard and soft interactions proceed over widely different time-and distance scales and are thus approximately independent. The high-mass system is produced in a hard scattering process with exchange of two gluons between the protons. Its amplitude is calculable in terms of the gluon generalized parton distributions (GPDs) in the protons, which can be measured in J/ψ production in exclusive ep scattering. The hard scattering process is modified by soft spectator interactions, which we calculate in a model-independent way in terms of the pp elastic scattering amplitude. Contributions from inelastic intermediate states are suppressed. A simple geometric picture of the interplay of hard and soft interactions in diffraction is obtained. The onset of the black-disk limit in pp scattering at TeV energies strongly suppresses diffraction at small impact parameters and is the main factor in determining the RGS probability. Correlations between hard and soft interactions (e.g. due to scattering from the long-range pion field of the proton, or due to possible short-range transverse correlations between partons) further decrease the RGS probability. We also investigate the dependence of the diffractive cross section on the transverse momenta of the final-state protons ("diffraction pattern"). By measuring this dependence one can perform detailed tests of the interplay of hard and soft interactions, and even extract information about the gluon GPD in the proton. Such studies appear to be feasible with the planned forward detectors at the LHC.

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Exclusive electroproduction of J/ψ mesons at HERA

Cited by 207 publications

References 77 publications

Factorization of the dependence in electroproduction of vector mesons

Factorization of the dependence in electroproduction of vector mesons

Measurement of the exclusive Υ production cross-section in pp collisions at s = 7 $$ \sqrt{s}=7 $$ TeV and 8 TeV

Generalized parton distributions and rapidity gap survival in exclusive diffractiveppscattering

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