neutron + Neutrino Collision

Asked by ouseph cj on 2020-11-05

Dear MadGraph Experts

Currently I am calculating the X-section of p v > p v, considering the proton is at rest ( Neutrino + Neutron collision ), Can I use the below script for the same.

I am not sure about pdlabel and lhaid.
if it is not correct please help me to find the correct one.

# PDF CHOICE: this automatically fixes also alpha_s and its evol. *
  nn23lo1 = pdlabel ! PDF set
  230000 = lhaid ! if pdlabel=lhapdf, this is the lhapdf number
# Heavy ion PDF / rescaling of PDF *
  0 = nb_proton1 # number of proton for the first beam
  1 = nb_neutron1 # number of neutron for the first beam
  0.93957 = mass_ion1 # mass of the heavy ion (first beam)
# Note that seting differently the two beams only work if you use
# group_subprocess=False when generating your matrix-element
  1 = nb_proton2 # number of proton for the second beam
  0 = nb_neutron2 # number of neutron for the second beam
  -1.0 = mass_ion2 # mass of the heavy ion (second beam)


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I'm not an lhapdf expert.

In principle you can check on the lhapdf website if you have neutron specific PDF.
This would be more accurate (maybe?) than using proton PDF and use symmetrry to get the neutron PDF.

If you use the proton PDF, then you have plenty of choice from the lhapdf website.
The default one that we set by default is not the most recent one and therefore not the most accurate one for today standard.
(Now accuracy also depends of the regime of the PDF obviously).

So it highly depends of the accuracy that you hope to get. (knowing that you also have other source of uncertainties obviously and theoretical error due to hypothesis that are done --the likely biggest one being the LO approximation)



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