A QCD analysis of HERA and fixed target structure function data

Abstract

The parton momentum density distributions of the proton are determined from a next-to-leading order QCD analysis of structure functions measured at HERA and by fixed target experiments. Also included are data on the difference of the up and down anti-quark distributions. The uncertainties in the parton densities, structure functions and related cross sections are estimated from the experimental errors and those on the input parameters of the fit. Several QCD predictions based on the parton densities obtained from this analysis are calculated and compared to data. * email: m.botje@nikhef.nl

Dynamical parton distributions of the nucleon

“…The experimental errors of the data induce an uncertainty in the determination of parton distribution functions (and therefore to any quantity calculated using them) which can be estimated now by linear propagation and other methods [142][143][144][145][146].…”

HIGH Q2 STRUCTURE FUNCTIONS AND PARTON DISTRIBUTIONS

“…Both fits handle the correlation of systematic errors in their parameters and errors estimations. Whereas ZEUS use the so-called offset method 19 , H1 use the Pascaud-Zomer method 20 . The gist is that only a proper treatment of the correlated systematic errors allows the application of the "standard" ∆χ 2 = 1 statistical criteria for error estimate 21 .…”

Questions on uncertainties in parton distributions

“…This method was used in early H1 fits [13] and in ZEUS fits [6,7]. Much the same method is used for polarized data in [8], as far as the information on correlated errors allows.…”