luxqed recipe

Created by: scarrazza

In order to obtain a NNPDF fit using luxqed one needs the following:

Requirements

• provide QED evolution with eko.
• provide the photon PDF using fiatlux.
• provide F2, FL and F2LO contributions for a given input PDF set from yadism.

Algorithm (simplified version)

1. take an input QCD fit and generate the photon PDF using fiatlux, at large Q value.
2. down-evolve the photon obtained in 1 to Q=1GeV
3. use this photon as fixed parton in a new PDF fit, it should enters all FK tables
4. repeat 1 until the photon shape has converged.
5. care about the extra uncertainties identified by luxqed.

Missing software requirements

• fiatlux in python
• n3fit:
  • load the photon obtained in 2, e.g. using the T0 format, see here for loading and here for the convolution.
• validphys:
  • implement the T0/photon generation by integrating fiatlux/yadism, i.e. by following all the steps summarized here.