https://doi.org/10.1140/epjc/s10052-018-5944-4
Regular Article - Theoretical Physics
Direct photon production and PDF fits reloaded
1
Fermilab, P.O. Box 500, Batavia, IL, 60510, USA
2
Department of Physics and Astronomy, VU University, 1081 HV, Amsterdam, The Netherlands
3
Nikhef Theory Group, Science Park 105, 1098 XG, Amsterdam, The Netherlands
4
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, UK
5
Department of Physics, University at Buffalo, The State University of New York, Buffalo, 14260, USA
* e-mail: emma.slade@physics.ox.ac.uk
Received:
13
February
2018
Accepted:
29
May
2018
Published online:
9
June
2018
Direct photon production in hadronic collisions provides a handle on the gluon PDF by means of the QCD Compton scattering process. In this work we revisit the impact of direct photon production on a global PDF analysis, motivated by the recent availability of the next-to-next-to-leading (NNLO) calculation for this process. We demonstrate that the inclusion of NNLO QCD and leading-logarithmic electroweak corrections leads to a good quantitative agreement with the ATLAS measurements at 8 and 13 TeV, except for the most forward rapidity region in the former case. By including the ATLAS 8 TeV direct photon production data in the NNPDF3.1 NNLO global analysis, we assess its impact on the medium-x gluon. We also study the constraining power of the direct photon production measurements on PDF fits based on different datasets, in particular on the NNPDF3.1 no-LHC and collider-only fits. We also present updated NNLO theoretical predictions for direct photon production at 13 TeV that include the constraints from the 8 TeV measurements.
© The Author(s), 2018
