Jet Cross Sections In Photoproduction Research Articles

Heavy Flavour Production at HERA

Measurements of heavy-quark production at HERA constrain the structure of the proton, and have provided valuable indications of perturbative QCD. In this publication measurements of heavy-flavour jet cross sections in photoproduction and deep inelastic scattering (DIS), performed by the H1 and ZEUS collaborations, are presented using inclusive techniques for the signal extraction. The results are compared to next-to-leading order QCD calculations and found to be in reasonable agreement with theory predictions.

Inclusive jet cross sections and dijet correlations in [formula omitted] photoproduction at HERA

Inclusive jet cross sections in photoproduction for events containing a D ∗ meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb −1 . The events were required to have a virtuality of the incoming photon, Q 2 , of less than 1 GeV 2, and a photon–proton centre-of-mass energy in the range 130 < W γ p < 280 GeV . The measurements are compared with next-to-leading-order (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) models which incorporate leading-order matrix elements followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where contributions from higher orders are expected to be significant. The MC models give a better description than the NLO predictions of the shape of the measured cross sections.

Measurement of inclusive jet cross sections in photoproduction at HERA

Inclusive jet cross sections are measured in photoproduction at HERA using the H1 detector. The data sample of e+ p -> e+ + jet + X events in the kinematic range of photon virtualities Q^2 < 1 GeV^2 and photon-proton centre-of-mass energies 95 < W_gammap < 285 GeV represents an integrated luminosity of 24.1 pb^-1. Jets are defined using the inclusive k_T algorithm. Single- and multi-differential cross sections are measured as functions of jet transverse energy E_T^jet and pseudorapidity \eta^jet in the domain 5 < E_T^jet < 75 GeV and -1 < \eta^jet < 2.5. The cross sections are found to be in good agreement with next-to-leading order perturbative QCD calculations corrected for fragmentation and underlying event effects. The cross section differential in E_T^jet, which varies by six orders of magnitude over the measured range, is compared with similar distributions from p pbar colliders at equal and higher energies.

Dijet and multijet photoproduction at HERA/ZEUS

Recent results on high- E T dijet and three jet cross sections in photoproduction at HERA are reported. The measured cross sections are compared with the Next-to-Leading Order (NLO) QCD calculations. In general, the dijet cross sections show good agreement with the NLO calculations for the measured E T range (> 14 GeV). However, an excess over the NLO is observed even for the kinematic region where the theoretical uncertainties are small. The three jet cross sections show good agreement with NLO QCD and the Monte Carlo models. The data exclude parton shower (PS) models without colour coherence effects.

Three jet cross sections in photoproduction at HERA

We calculate three jet cross sections in photoproduction using exact matrix elements for the direct and resolved contributions. Numerical distributions are presented in a generic, irreducible set of variables that allows to disentangle the dynamics of partonic QCD subprocesses from each other and from pure phase space distributions. The results are compared to preliminary data from the ZEUS collaboration at HERA. It is found that the largest contribution comes from photon-gluon fusion in the mass range 36 GeV $< M_{\rm 3-jet} <$ 80 GeV. The measured leading jet scattering angle distribution is consistent with the $t$ -channel exchange of a massless fermion in $2\rightarrow 2$ scattering, where the third parton is assumed to arise from soft bremsstrahlung. The data are inconsistent with pure phase space and Rutherford scattering distributions.

Three jet cross sections in photoproduction at HERA

We calculate three jet cross sections in photoproduction using exact matrix elements for the direct and resolved contributions. Numerical distributions are presented in a generic, irreducible set of variables that allows to disentangle the dynamics of partonic QCD subprocesses from each other and from pure phase space distributions. The results are compared to preliminary data from the ZEUS collaboration at HERA. It is found that the largest contribution comes from photon-gluon fusion in the mass range 36 GeV $< M_{\rm 3-jet} <$ 80 GeV. The measured leading jet scattering angle distribution is consistent with the $t$-channel exchange of a massless fermion in $2\to 2$ scattering, where the third parton is assumed to arise from soft bremsstrahlung. The data are inconsistent with pure phase space and Rutherford scattering distributions.

High- $E_T$ inclusive jet cross sections in photoproduction at HERA

High- $E_T$ inclusive jet cross sections in photoproduction at HERA

Photoproduction of jets at DESY HERA in next-to-leading order QCD

A new next-to-leading order Monte Carlo program for the calculation of jet cross sections in photoproduction is described. The contributions from both resolved and direct components are included to O(\alpha \alpha_s^2). Properties of the predictions for various inclusive jet and dijet observables are discussed and comparisons with HERA data are presented.

Measurement of inclusive jet cross sections in photoproduction at HERA

The inclusive jet cross section in photoproduction has been measured as a function of transverse energy and pseudorapidity using the H 1 detector at the HERA electron-proton collider. The results are compared with leading order QCD calculations.