10,122 research outputs found
Have we seen anything beyond (N)NLO DGLAP at HERA?
The evidence from HERA for parton saturation, and other low- effects
beyond the conventional DGLAP formalism, is recalled and critically reviewed in
the light of new data and analyses presented at the conference.Comment: 4 pages, 5 figures, Contribution to the discussion session at
Intenrational Symposium on Multiparticle Dynamics, ISMD08, Hambur
Including heavy quark production in ZEUS-PDF fits
At HERA heavy quarks may contribute up to 30% of the structure function
. The potential of including heavy-quark data in the ZEUS PDF fits is
explored, using double differential cross-sections as well as the
inclusive quantities , . The introduction of
heavy quarks requires an extension of the DGLAP formalism. The effect of using
different heavy flavour number schemes, and different approaches to the running
of , are compared.Comment: 4 pages, 4 figures. To be published in the Proceedings of the 16th
International Workshop on Deep Inelastic Scattering, DIS2008, London, April
7-11th 200
Extraction of the proton parton density functions using a NLO-QCD fit of the combined H1 and ZEUS inclusive DIS cross sections
The combined HERA-I data set, of neutral and charged current inclusive
cross-sections for and scattering, is used as the sole input for
a next-to-leading order (NLO) QCD parton distribution function (PDF) fit. The
consistent treatment of systematic uncertainties in the joint data set ensures
that experimental uncertainties on the PDFs can be calculated without need for
an increased tolerance. This results in PDFs with greatly reduced
experimental uncertainties compared to the separate analyses of the ZEUS and H1
experiments. Model uncertainties, including those arising from parametrization
dependence, are also carefully considered. The resulting HERAPDFs have
impressive precision compared to the global fits.Comment: 5 pages, 2 figures. Talk on behalf of H1 and ZEUS collaborations, to
be published in the Proceedings of the 16th Workshop on Deep Inelastic
Scattering, DIS2008, London, April 7-11th 200
HERA Collider Results
The final results on the combination of all inclusive deep-inelastic
scattering cross section data from the H1 and ZEUS experiments at HERA are
reviewed. The parton distribution functions (PDFs) extracted from these data
(HERAPDF2.0) and from HERA data on heavy flavour production and jet production
are also presented (HERAPDF2.0Jets). The use of various heavy flavour schemes
is compared and the sensitivity of the data to cuts on Q2 is explored. When jet
data are included in the fits, a competitive value of is extracted at NLO, excluding scale uncertaintiesComment: Plenary talk at the XXIII International Workshop on Deep-Inelastic
Scattering, 27th April-1st May 2015, Dallas, Texas. 14 pages, 18 figures.
Based on the analysis of the H1 and ZEUS collaboration
- β¦