The Photon Content of the Proton

Aug 3, 2017
78 pages
Published in:
  • JHEP 12 (2017) 046
  • Published: Dec 11, 2017
e-Print:
Report number:
  • CERN-TH-2017-141

Citations per year

201720192021202320250102030
Abstract: (Springer)
The photon PDF of the proton is needed for precision comparisons of LHC cross sections with theoretical predictions. In a recent paper, we showed how the photon PDF could be determined in terms of the electromagnetic proton structure functions F2_{2} and FL_{L} measured in electron-proton scattering experiments, and gave an explicit formula for the PDF including all terms up to next-to-leading order. In this paper we give details of the derivation. We obtain the photon PDF using the factorisation theorem and applying it to suitable BSM hard scattering processes. We also obtain the same PDF in a process-independent manner using the usual definition of PDFs in terms of light-cone Fourier transforms of products of operators. We show how our method gives an exact representation for the photon PDF in terms of F2_{2} and FL_{L} , valid to all orders in QED and QCD, and including all non-perturbative corrections. This representation is then used to give an explicit formula for the photon PDF to one order higher than our previous result. We also generalise our results to obtain formulæ for the polarised photon PDF, as well as the photon TMDPDF. Using our formula, we derive the Pγi_{γi} subset of DGLAP splitting functions to order ααs_{s} and α2^{2}, which agree with known results. We give a detailed explanation of the approach that we follow to determine a photon PDF and its uncertainty within the above framework.
Note:
  • Deep Inelastic Scattering (Phenomenology)
  • QCD Phenomenology
  • p: structure function
  • electron p: scattering
  • higher-order: 1
  • photon: structure function
  • quantum electrodynamics: perturbation theory
  • quantum chromodynamics
  • hard scattering
  • DGLAP equation