Abstract
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.
| Original language | English |
|---|---|
| Article number | 470 |
| Pages (from-to) | 1-21 |
| Number of pages | 21 |
| Journal | European Journal of Physics C |
| Volume | 78 |
| Issue number | 6 |
| Early online date | 9 Jun 2018 |
| DOIs | |
| Publication status | Published - Jun 2018 |
Funding
Acknowledgements We thank Ulla Blumenschein, Ana Cueto Gómez, Jan Kretzschmar, Claudia Glasman, Matthias Schott, and Juan Ter- rón Cuadrado for information and discussions concerning the ATLAS direct photon measurements. JR and ES are grateful to our colleagues of the NNPDF collaboration for their support and useful discussions. ES thanks Rhorry Gauld for providing useful scripts and Alberto Guf-fanti for help with the production of APPLgrids. JR and ES are supported by the ERC Starting Grant “PDF4BSM”. The work of JR is also supported by the Dutch Organization for Scientific Research (NWO). CW is supported by a National Science Foundation CAREER award PHY-1652066. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the US Department of Energy, Office of Science, Office of High Energy Physics. We thank Ulla Blumenschein, Ana Cueto Gómez, Jan Kretzschmar, Claudia Glasman, Matthias Schott, and Juan Terrón Cuadrado for information and discussions concerning the ATLAS direct photon measurements. JR and ES are grateful to our colleagues of the NNPDF collaboration for their support and useful discussions. ES thanks Rhorry Gauld for providing useful scripts and Alberto Guffanti for help with the production of APPLgrids. JR and ES are supported by the ERC Starting Grant “PDF4BSM”. The work of JR is also supported by the Dutch Organization for Scientific Research (NWO). CW is supported by a National Science Foundation CAREER award PHY-1652066. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the US Department of Energy, Office of Science, Office of High Energy Physics.
| Funders | Funder number |
|---|---|
| Fermi Research Alliance, LLC | |
| National Science Foundation | 1652066, PHY-1652066 |
| U.S. Department of Energy | |
| Office of Science | |
| High Energy Physics | |
| Fermilab | DE-AC02-07CH11359 |
| H2020 European Research Council | ERC-StG-2012-335260 |
| Seventh Framework Programme | 335260 |
| European Research Council | |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek |
Keywords
- hep-ph
- hep-ex
