gamma, p => lhapdf

Asked by Igal on 2020-05-29

Hi,

I am using the DrellYanMatchingP.sin example and replace one of the proton beam by a photon beam and for this process: gamma, p => quark:antiq, p

And got this message

*** FATAL ERROR: The 'lhapdf' structure is intended only for protons and
*** pions, please use 'lhapdf_photon' for photon beams.

if I then use lhapdf_photon, I am getting this message

*** FATAL ERROR: This PDF set is not supported or not intended for photon beams.

Any ideas on what should be done to make it works?

Thanks, Igal.

Question information

Language:
English Edit question
Status:
Solved
For:
WHIZARD Edit question
Assignee:
Juergen Reuter Edit question
Last query:
2020-05-29
Last reply:
2020-08-19
Juergen Reuter (j.r.reuter) said : #1

Hi Igal,
seems you are testing out all corner cases^^
There are several things to watch when dealing with photons in hadronic environments.
Writing a statement like
beams = gamma, p
or
beams = A, p
actually demands photon on proton collisions. When you then define a process like e.g. Drell-Yan, so
q qbar -> e+e-
then you need the quark content inside the photon, and then you have to take the full beams statement
as
beams = A, p => lhapdf_photon, lhapdf
$lhapdf_file = "cteq5l.LHgrid"
$lhapdf_photon_file = "GSG961.LHgrid"
However, as far as I know such a photon PDF (quark content inside the photon) only exists in
and that is something which e.g. exists in the GSG961.LHgrid PDF from LHAPDF5.
For LHAPDF6 I don't know actually.
The other thing is to get the photon content inside the proton, which you can get e.g. from LUXqed PDFs:
then you have a process like
process aaww = A, A => Wp, Wm
and
beams = p, p => lhapdf
$lhapdf_file = "LUXqed_plus_PDF4LHC15_nnlo_100"

Cheers,
   JRR

Juergen Reuter (j.r.reuter) said : #2

Solved.