280 f(-p1) + f(-p2) → γ(p3) + f(p4)

280.1 Direct γ production, processes 280–282

These processes represent the production a real photon. Since this process includes a real photon, the cross section diverges when the photon is very soft or in the direction of the beam. Thus in order to produce sensible results, the input file must supply values for both gammptmin and gammrapmax. This will ensure that the cross section is well-defined.

Currently the code computes this process up to NLO accuracy. The extension to NNLO [1, 2, 3] has not yet been made public.

280.2 Plotter

nplotter_dirgam.f is the default plotting routine.

280.3 Example input and output file(s)

input280.ini process280.out

References

[1]    J.M. Campbell, R.K. Ellis and C. Williams, Direct Photon Production at Next-to–Next-to-Leading Order, Phys. Rev. Lett. 118 (2017) 222001 [1612.04333].

[2]    J.M. Campbell, R.K. Ellis and C. Williams, Driving missing data at the LHC: NNLO predictions for the ratio of γ + j and Z + j, Phys. Rev. D 96 (2017) 014037 [1703.10109].

[3]    J.M. Campbell, J. Rojo, E. Slade and C. Williams, Direct photon production and PDF fits reloaded, Eur. Phys. J. C 78 (2018) 470 [1802.03021].