Diffractive photoproduction of ups at HERA

Frankfurt, L.; McDermott, M.; Strikman, M.

doi:10.1088/1126-6708/1999/02/002

Cited by 69 publications

(129 citation statements)

References 11 publications

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“…(1) and (2) have demonstrated that interactions at the upper range of HERA energies in gluon-induced processes may be fairly close to the BBL in a wide range of impact parameters (see, e.g., [8,10]). This is consistent with an analysis [11] of current fits to HERA diffractive data, which leads to diffractive gluon densities which are significantly larger than the quark ones (see also [12]). …”

supporting

confidence: 90%

Revealing the Black-Body Regime of Small-xDeep-Inelastic Scattering through Final-State Signals

et al. 2001

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We derive the major characteristics of inclusive and diffractive final states in deep-inelastic scattering off heavy nuclei for the-high energy (small-x) kinematics in which the limit of complete absorption is reached for the dominant hadronic fluctuations in the virtual photon (the black-body limit of the process). Both the longitudinal and transverse distributions of the leading hadrons are found to be strikingly different from the corresponding ones within the leading-twist approximation, and hence provide unambiguous signals for the onset of the black-body limit.The black-body limit (BBL) of deep-inelastic scattering (DIS) from a heavy nucleus

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supporting

confidence: 90%

Revealing the Black-Body Regime of Small-xDeep-Inelastic Scattering through Final-State Signals

et al. 2001

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“…Another critical test will be a measurement of the t-dependence of the Υ photoproduction at HERA which should be very close to the genuine two-gluon form factor. Note in passing that the t-slope of the elastic Υ photoproduction entered in the calculation of the total cross section of the γ + p → Υ + p reaction in [21]. Since at that time the data on the energy dependence of the slope of J/ψ production did not allow determination of α ′ for J/ψ we took it to be equal to zero.…”

Section: Comparison With the Datamentioning

confidence: 99%

Two-gluon form factor of the nucleon andJ/ψphotoproduction

Frankfurt¹,

Strikman²

2002

Phys. Rev. D

110

136

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We argue that the t-dependence of the two-gluon form factor of the nucleon should be given by Γ(t) = (1 − t/m 2 2g ) −2 with m 2 2g ≈ 1GeV 2 . We demonstrate that this form provides a good description of the t-dependence of the cross section of the elastic photoproduction of J/ψ-mesons between the threshold region of E γ = 11 GeV (Cornell), E γ = 19 GeV (SLAC) and E γ = 100 GeV (FNAL) including the strong energy dependence of the t-slope. It is also well matched with the recent HERA data. The same assumption explains also the t-dependence of φ-meson electroproduction near threshold at W = 2.3 GeV, Q 2 = 1.0 GeV 2 . Theoretical expectationsIt was demonstrated in [1] for the case of small x and in [2] in a general case that in the limit of large Q 2 the t-dependence of the process γ * L + N → V + N at fixed x is factorized into the convolution of a hard interaction block calculable in perturbative QCD, the short-distance qq wave function of the meson, and the generalized/skewed parton distribution (GPD) in the nucleon.In the scaling limit the t-dependence is originating solely from the GPD's since the meson wave function is highly squeezed in the direction transverse to the reaction axis. In the case of the valence quark exchanges these t-dependences are constrained by the sum rules for unpolarized [3] and polarized quarks [4] and could be also modeled in the chiral soliton models, see review in [5]. The t-dependence of GPD's provides unique information about the impact parameter distribution of the partons in nucleons. The knowledge of the transverse gluon distribution is especially important since it provides a key ingredient for the understanding of relative importance of soft and hard physics for high energy nucleonnucleon interactions at different impact parameters and has to be implemented in realistic Monte Carlo generators of nucleon-nucleon collisions at collider energies.In this paper we will first discuss theoretical expectations for the t-dependence of gluon GPD's. Next we will use the 11 ≤ E γ ≤ 100GeV data to check these expectations and hence 1

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“…We choose to plot results for the gluon since this is most relevant to small-x exclusive diffractive processes at HERA, for which it has been argued that the inclusion of skewedness (at least at LO in the unpolarized case) leads to an enhancement (see e.g. [21,22,33]). …”

Section: Fig 1 the Ratio Of The Unpolarized And Polarized Inputmentioning

confidence: 99%

Erratum: Next-to-leading order evolution of generalized parton distributions for DESY HERA and HERMES [Phys. Rev. D65, 056012 (2002)]

Freund¹,

McDermott²

2002

Phys. Rev. D

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The QCD evolution of both unpolarized and polarized generalized parton distributions (GPDs) to next-to-leading order (NLO) accuracy is presented, in both the DGLAP and ERBL regions, for two appropriately symmetrized input distributions based on conventional parton density functions. To illustrate the relative size of the NLO corrections a comparison is made with leading order evolution of the same distributions. For the first time, NLO results are given for both small and large values of the skewedness parameter, ζ = x bj , i.e. for all of the kinematic range relevant to HERA and HERMES.

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Diffractive photoproduction of ups at HERA

Cited by 69 publications

References 11 publications

Revealing the Black-Body Regime of Small-xDeep-Inelastic Scattering through Final-State Signals

Revealing the Black-Body Regime of Small-xDeep-Inelastic Scattering through Final-State Signals

Two-gluon form factor of the nucleon andJ/ψphotoproduction

Erratum: Next-to-leading order evolution of generalized parton distributions for DESY HERA and HERMES [Phys. Rev. D65, 056012 (2002)]

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