A QCD analysis of ZEUS diffractive data

Abstract

ZEUS inclusive diffractive-cross-section measurements have been used in a DGLAP next-to-leadingorder QCD analysis to extract the diffractive parton distribution functions. Data on diffractive dijet production in deep inelastic scattering have also been included to constrain the gluon density. Predictions based on the extracted parton densities are compared to diffractive charm and dijet photoproduction data.

Single-diffractive Drell–Yan pair production at the LHC

“…Factorisation has been shown to hold, as expected theoretically, in diffractive dijets production in DIS, where NLO predictions based on dPDFs well describe experimental cross sections [6,9] both in shape and normalisation. Factorisation breaking effects are expected to appear in diffractive photoproduction of dijets due to the resolved component of the quasi-real photon.…”

“…Since its dominant contributions appear in the large-y region, the fit x IP = 0.035 has been repeated with the cut y < 0.5 imposed. The second one addresses the issue, reported in previous analyses [5][6][7][8], of the inclusion in the fit of the lowest Q 2 points. For such a reason, the minimisation has been repeated by including only data points for which Q 2 > 6 GeV 2 .…”

“…In the deep inelastic regime, the presence of a hard scale enables the derivation of a dedicated factorisation theorem [1][2][3][4] which allows the investigation of the partonic structure of the colour singlet exchanged in the t-channel. From scaling violations of the diffractive Deep Inelastic Scattering (DDIS) structure functions, quite precise diffractive parton distributions functions (dPDFs) have been extracted by performing QCD analysis [5][6][7][8] of available data.…”

Diffractive dijet production with a leading proton in ep collisions at HERA

“…In each of these measurements diffractive events are selected by requiring a large rapidity gap. Different ratios of data to the NLO QCD prediction have been reported by H1 and ZEUS: while H1 reported their data to be suppressed by a factor of 0.6 with respect to the NLO QCD predictions [17,18], the ZEUS data are compatible with the theoretical expectations [20]. Various mechanisms of suppressing diffractive dijet photoproduction have been proposed [21,22].…”

Inclusive measurement of diffractive deep-inelastic scattering at HERA

“…The dependence of the DPDFs on the kinematic variables related to the proton vertex can be parametrised conveniently using Regge formalism, which amounts to a description of diffraction in terms of the exchange of a factorisable Pomeron (P) [21,22] with universal parton densities. Several authors have analysed diffractive DIS data to extract DPDFs [4,8,10,[23][24][25][26][27][28][29][30][31][32][33][34], with the conclusion that the data are compatible with proton vertex factorisation at low fractional proton energy losses, x P , and for photon virtualities Q 2 above ∼5 GeV 2 . The DPDFs extracted in these publications consistently find a dominant gluon contribution.…”