Small x gluon from exclusive <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mi>J</mml:mi><mml:mo stretchy="false">/</mml:mo><mml:mi>ψ</mml:mi></mml:math> production

Martin, A. D.; Nockles, C.; Ryskin, M.G.; Teubner, T.

doi:10.1016/j.physletb.2008.02.067

Cited by 44 publications

(28 citation statements)

References 30 publications

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“…This lowenergy data set extends the kinematic region in W γp into the transition region between previous diffractive J /ψ measurements at HERA and fixed target experiments [26,27]. The elastic and proton-dissociative cross sections as functions of t and W γp are subjected to phenomenological fits, together with previous H1 data [4,24], and are compared with QCD based dipole models [14].…”

Section: Introductionmentioning

confidence: 90%

“…Following [14] the obtained value of δ can for large photon-proton centre-of-mass energies, W γp m J/ψ , be related to a leading-order gluon-density parametrised as x · g(x, μ 2 ) = N · x −λ via δ el ≈ 4 · λ. The scale of J /ψ photoproduction is often taken to be μ 2 = 2.4 GeV 2 .…”

Section: Energy Dependencementioning

confidence: 99%

“…The qq pair interacts with the proton via a coloursinglet exchange, which in lowest order QCD is realised as a colourless gluon pair [9][10][11][12]. The steep rise of the cross section with W γp is then related to the rise of the square of the gluon density towards low values of Bjorken x [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

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Elastic and proton-dissociative photoproduction of J/ψ mesons at HERA

et al. 2013

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Section: Introductionmentioning

confidence: 90%

Section: Energy Dependencementioning

confidence: 99%

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Elastic and proton-dissociative photoproduction of J/ψ mesons at HERA

et al. 2013

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“…At low E T the uncertainty in the cross sections linked to scales variations amounts to up to ±20% but it saturates at around ±10% above E γ T ≈ 15 GeV at central and forward rapidities. As aforementioned, global PDF fits do not reliably determine the gluon for x 10 −2 at low, yet perturbative, Q 2 20 GeV 2 scales [42]. This is due partly to the lack of precise structure function data for x < 10 −4 and mainly due to the fact that the copious DIS F 2 results probe the quark distribution, while the gluon density is constrained by the evolution, log(Q 2 ) dependence, of these data.…”

Section: Isolated Photon Production At the Lhcmentioning

confidence: 97%

Sensitivity of isolated photon production at TeV hadron colliders to the gluon distribution in the proton

Ichou

d’Enterria

2010

Phys. Rev. D

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We compare the single inclusive spectra of isolated photons measured at high transverse energy in proton-antiproton collisions at √ s = 1.96 TeV with next-to-leading order perturbative QCD predictions with various parametrizations of the parton distribution functions (PDFs). Within the experimental and theoretical uncertainties, the Tevatron data can be reproduced equally well by the recent CTEQ6.6, MSTW08 and NNPDF1.2 PDF sets. We present also the predictions for isolated γ spectra in proton-proton collisions at √ s = 14 TeV for central (y = 0) and forward (y = 4) rapidities relevant for LHC experiments. Different proton PDFs result in maximum variations of order ±30% in the expected E γ T -differential isolated γ cross sections. The inclusion of the isolated photon data in global PDF fits will place extra independent constraints on the gluon density.

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“…The heavy meson mass M V ensures that perturbative QCD can be applied to photoproduction. The calculation was performed some years ago to leading logarithmic (log(Q 2 )) approximation, assuming the produced vector meson quarkonium system to be nonrelativistic [16,17] and improved in distinct aspects [71,72]. Assuming a non-relativistic wave function for the vector meson the t = 0 differential cross section of photoproduction of heavy vector mesons in a leading-order approximation is given by [16,17] dσ γ h→V h dt…”

Section: Figmentioning

confidence: 99%

Probing the gluon density of the proton in the exclusive photoproduction of vector mesons at the LHC: a phenomenological analysis

2016

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The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken-x variable and low values of the hard scale Q 2 . An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon-hadron and hadron-hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrisations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalisation of the γ h cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small x and low Q 2 .One of the basic ingredients to estimate the hadronic cross sections are the parton distributions functions (PDFs). Theoretically, at large energies the hadrons are dominated by gluons, with its behaviour at small x being determined by the QCD dynamics at high parton densities. Consequently, a precise determination of the gluon distribution is fundamental to probe a possible transition between the linear and nonlinear regimes of the QCD dynamics [1]. Experimentally, our understanding about the partonic structure of the proton has been significantly improved by the results obtained in ep collisions at HERA, which have obtained very precise data in a broad range in photon virtualities Q 2 and Bjorken-x values, imposing the tightest constraints on the existing PDFs (for recent reviews see, e.g. Refs. [2][3][4]). However, the behaviour of the gluon distribution at small x is still poorly known as can be observed in Fig. 1, where we compare the predictions for the gluon distribution obtained by different groups a e-mail: barros@ufpel.edu.br [5][6][7][8][9] that perform the global analysis of the existing experimental data using the DGLAP evolution equations [10][11][12] in order to determine the parton distributions. Consequently, additional measurements are necessary to pin down the gluon distribution. An alternative is the analysis of the experimental results for the heavy quark production at forward rapidities in pp collisions at the LHC energies. Recent results [13][14][15] have analysed the impact of the LHCb data in the determination of the gluon distribution. Another promising observable is the cross section for the diffractive production of vector mesons, which in the leading logarithmic approximation is proportional to the gluon density squared [16,17]. This process was analysed at HERA and is currently been studied in photon-induced interactions at hadronic colliders. In recent years a series of experimental results at RHIC [18,19], Tevatron [20] and LHC [21][22][23][24][25][26][27][28][29] demonstrated that the study of ph...

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Small x gluon from exclusive J/ψ production

Cited by 44 publications

References 30 publications

Elastic and proton-dissociative photoproduction of J/ψ mesons at HERA

Elastic and proton-dissociative photoproduction of J/ψ mesons at HERA

Sensitivity of isolated photon production at TeV hadron colliders to the gluon distribution in the proton

Probing the gluon density of the proton in the exclusive photoproduction of vector mesons at the LHC: a phenomenological analysis

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