26-30 March 2012
University of Bonn
Europe/Berlin timezone

Quantitative constraints on the gluon distribution function in the proton from collider isolated-photon data

28 Mar 2012, 11:30
20m
Wolfgang Paul Lecture Hall (University of Bonn)

Wolfgang Paul Lecture Hall

University of Bonn

Kreuzbergweg 28, 53115 Bonn, Germany,
Structure functions Structure functions

Speaker

David d'Enterria (CERN)

Description

The impact of isolated-photon data from proton-(anti)proton collisions at RHIC, SppbarS, Tevatron and LHC energies, on the parton distribution functions of the proton is studied using a recently developed Bayesian reweighting method. The impact on the gluon density of the 35 existing isolated-gamma measurements is quantified using next-to-leading order (NLO) perturbative QCD calculations complemented with the NNPDF2.1 parton densities. The NLO predictions are found to describe well most of the datasets from 200 GeV up to 7 TeV centre-of-mass energies. The isolated-photon spectra recently measured at the LHC are precise enough to constrain the gluon distribution and lead to a moderate reduction (up to 20%) of its uncertainties around fractional momenta x~0.02. As a particular case, we show that the improved gluon density reduces the PDF uncertainty for the Higgs boson production cross section in the gluon-fusion channel by more than 20% at the LHC. We conclude that present and future isolated-photon measurements constitute an interesting addition to coming global PDF analyses.

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