Speaker
Dr
Uwe Schneekloth
(DESY)
Description
A combination is presented of all inclusive deep inelastic cross sections previously
published by the H1 and ZEUS collaborations at HERA for neutral and charged current ep
scattering for zero beam polarisation. The data were taken at proton beam energies of
920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond
to an integrated luminosity of about 1 fb$^{-1}$ and span six orders of magnitude in
negative four-momentum-transfer squared, $Q_2$, and Bjorken $x$. The correlations of the
systematic uncertainties were evaluated and taken into account for the combination. The
combined cross sections were input to QCD analyses at leading order, next-to-leading
order and at next-to-next-to-leading order, providing a new set of parton distribution
functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and
parameterisation uncertainties were assessed for these parton distribution functions.
Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and
using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was
extended by including HERA data on charm and jet production, resulting in the variant
HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous
determination of these parton distributions and the strong coupling constant possible,
resulting in alpha_s $(M_Z^2)$ = 0.1183 $\pm$ 0.0009(exp) $\pm$ 0.0005(model/parameterisation)
$\pm$ 0.0012(hadronisation) +0.0037 -0.0030 (scale). An extraction $of xF_3(\gamma Z)$ and
results on electroweak unification and scaling violations are also presented.
Primary author
Dr
Uwe Schneekloth
(DESY)
