H1prelim-11-042
ZEUS-prel-11-002
H1 and ZEUS

HERAPDF1.5 NNLO

Reference Preliminary Moriond2011, March 2011
Figures  (1a)  (1b)  (1c)  (2a)  (2b)  (2c)  (3)  (4a)  (4b)  (4c)  (5a)  (5b)  (5c)  (6a)  (6b)  (6c)
Contact V. Radescu, A. Cooper-Sarkar et al.
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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