364 articles – 2937 Notices  [english version]
 HAL : in2p3-00014416, version 1
 arXiv : hep-ex/9812024
 European Physical Journal C 13 (2000) 397-414
 Measurement of Dijet Cross-Sections at Low $Q^{2}$ and the Extraction of an Effective Parton Density for the Virtual Photon
 H1 Collaboration(s)
 (2000)
 The triple-differential dijet cross-section, d^3 sigma_{ep}/dQ2 dE_t2 dxgjets, is measured with the H1 detector at HERA as a function of the photon virtuality Q^2, the fraction of the photon's momentum carried by the parton entering the hard scattering, xgjets, and the square of the mean transverse energy, E_t2, of the two highest E_t jets. Jets are found using a longitudinal boost-invariant k_T clustering algorithm in the gamma* p center of mass frame. The measurements cover the ranges 1.6 Q^2 80 GeV\$^2 in virtuality and 0.1 y 0.7 in inelasticity y. The results are well described by leading order QCD models which include the effects of a resolved component to the virtual photon. Models which treat the photon as point-like fail to describe the data. An effective leading order parton density for the virtual photon is extracted as a function of the photon virtuality, the probing scale and the parton momentum fraction. The x_gamma and probing scale dependences of the parton density show characteristic features of photon structure, and a suppression of this structure with increasing Q^2 is seen.
 Thème(s) : Physique/Physique des Hautes Energies - Expérience
 Lien vers le texte intégral : http://fr.arXiv.org/abs/hep-ex/9812024
 in2p3-00014416, version 1 http://hal.in2p3.fr/in2p3-00014416 oai:hal.in2p3.fr:in2p3-00014416 Contributeur : Hélène Kerec <> Soumis le : Mardi 6 Juin 2000, 14:35:22 Dernière modification le : Mardi 6 Juin 2000, 14:35:22