  We present the first determination of parton distributions of the nucleon at
NLO and NNLO based on a global data set which includes LHC data: NNPDF2.3. Our
data set includes, besides the deep inelastic, Drell-Yan, gauge boson
production and jet data already used in previous global PDF determinations, all
the relevant LHC data for which experimental systematic uncertainties are
currently available: ATLAS and LHCb W and Z lepton rapidity distributions from
the 2010 run, CMS W electron asymmetry data from the 2011 run, and ATLAS
inclusive jet cross-sections from the 2010 run. We introduce an improved
implementation of the FastKernel method which allows us to fit to this extended
data set, and also to adopt a more effective minimization methodology. We
present the NNPDF2.3 PDF sets, and compare them to the NNPDF2.1 sets to assess
the impact of the LHC data. We find that all the LHC data are broadly
consistent with each other and with all the older data sets included in the
fit. We present predictions for various standard candle cross-sections, and
compare them to those obtained previously using NNPDF2.1, and specifically
discuss the impact of ATLAS electroweak data on the determination of the
strangeness fraction of the proton. We also present collider PDF sets,
constructed using only data from HERA, Tevatron and LHC, but find that this
data set is neither precise nor complete enough for a competitive PDF
determination.
