| Abstract | A preliminary NNLO QCD analysis is presented using the NC and CC inclusive
DIS cross sections obtained from the combination of the measurements from H1
and ZEUS based on the published HERA I and the preliminary HERA II data.
The HERAPDF1.5NNLO fit is performed in the NNLO DGLAP scheme as implemented in
the evolution code QCDNUM 17. Heavy quarks are treated as massive using
the NNLO version of the Thorne-Roberts variable flavour number scheme.
In comparison to the most recent HERAPDF1.5 NLO, a more flexible
parameterisation for the present QCD fits has been chosen wich affects most
gluon distribution at low x. A full set of the PDF uncertainties for
HERAPDF1.5NNLO is determined. Experimental uncertainties, variation of model
parameters and assumptions on the parametrization of the PDFs are considered.
For the strong coupling constant a central value of $\alpha_s(M_Z)=0.1176$
is used but a series of PDFs by varying $\alpha_s(M_Z)$ in the range
$0.114 - 0.122$ are also available. |
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