Photon photon reactions

Berger, Christoph; Wagner, W.

doi:10.1016/0370-1573(87)90012-3

Cited by 166 publications

(58 citation statements)

References 109 publications

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“…V + p here generalizes to the`VMD elastic' process + p ! V + p : (7) The`truly elastic' (Compton) process +p! +p is of O( 2 ), compared with the O( ) VMD processes, and can safely be neglected in the following.…”

Section: Hadronic Event Classesmentioning

confidence: 99%

“…cross sections: (i) direct photon processes, where the photon couples directly to the partons within the proton, and (ii) resolved photon processes, which describe scatterings between partons in the photon and partons in the proton. The (QCD-evolved) parton distribution functions (PDFs) of the photon are extracted from two-photon physics [7]. In such a procedure the origin of the photon PDFs is wiped out, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…F 2 (x; Q 2 ) = 0 : 2 (1 x), the prejudice is that the VMD component contributes only to low-p ? physics [7]. Compared with the time when the VMD concept was originally formulated, our understanding of hadronic physics has increased substantially.…”

Section: Introductionmentioning

confidence: 99%

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Towards a complete description of high-energy photoproduction

1993

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A real photon has a dual nature, as a pointlike elementary particle and as a qq uctuation, in the latter case often with hadron-like properties. Therefore high-energy p i n teractions have a rich and not yet well explored structure. In this paper, we propose a consistent formulation, which is based on a subdivision of the total cross section into three distinct event classes: direct, VMD and anomalous. The VMD class, in its turn, contains the subclasses familiar from hadron{hadron physics. Within this approach, we calculate all the partial cross sections. Many other aspects of the event classes are also considered, such as proton and photon structure functions, jet rates and beam remnant structures. A major rôle is played by t w o distinct transverse momentum cut-o scales, which separate the classes. When all the ingredients are put together, we obtain a detailed model for photoproduction events. In order to test this approach, we also propose several alternative scenarios, each of which emphasizes di erent aspects of the photon. Predictions are presented for HERA events.

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Section: Hadronic Event Classesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Towards a complete description of high-energy photoproduction

1993

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“…The differential cross-section for the deep inelastic electron-photon scattering reaction, e(k) γ(p) → e(k ) γ(p) γ * (q) → e X, where the terms in brackets denote the four-momentum vectors of the particles, is proportional to F γ 2 (x, Q 2 ) [5]. Here Q 2 = −q 2 = −(k − k ) 2 and x = Q 2 /2p · q. Experimentally, in the single tag configuration, the value of x is obtained using…”

Section: Introductionmentioning

confidence: 99%

Comparison of deep-inelastic electron-photon scattering data with the HERWIG and PHOJET Monte Carlo Models

Aleph¹

2002

Eur. Phys. J. C

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Deep inelastic electron-photon scattering is studied in the Q 2 range from 1.2 to 30 GeV 2 using the LEP1 data taken with the ALEPH, L3 and OPAL detectors at centre-of-mass energies close to the mass of the Z boson. Distributions of the measured hadronic final state are corrected to the hadron level and compared to the predictions of the HERWIG and PHOJET Monte Carlo models. For large regions in most of the distributions studied the results of the different experiments agree with one another. However, significant differences are found between the data and the models. Therefore the combined LEP data serve as an important input to improve on the Monte Carlo models.Submitted to European Physical Journal C 1 For the members of the Collaborations see for example [1,3,4] 2 Contributions from P. Achard, V. Andreev, S. Braccini, M. Chamizo, G.

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“…In this generator, the two-photon luminosity function is calculated and events are generated at a specified γγ CM energy (W γγ ) using the equivalent photon approximation [18]. The efficiencies for detecting γγ → ppK + K − and its intermediate processes Λ(1520) 0p K + , Θ(1540) 0p K + and Θ(1540) ++p K − [19] at different fixed W γγ values are determined by assuming a phase space model.…”

mentioning

confidence: 99%