Present: Beate, Jorge, Massimiliano, Pieter, Ruchi, Simone, Stefan, Yee
Selection details:
- 76 GeV <MZ→ℓℓ<106 GeV, pt(ℓ1)> 30 GeV, pt(ℓ2)> 20 GeV, |eta(ℓ)| < 2.5, DeltaR(ℓ,gamma)>0.4, pt(gamma)> 60 GeV, |eta(gamma)| < 2.5
Dynamic scales:
sqrt(MZ2+pt(Z->nunu/gamma)2)
Higher order QCD corrections:
- look at scale variations as well and compare with the k-factor uncertainty
-> make sure the k-factor uncertainty is larger than the scale variations, otherwise we might want to change our prescriptions
- change dynamic scale for ZZ to be consistent with Zgamma dynamic scale (Simone already sent instructions)
EWK corrections:
- ZZ ready, Zgamma on the scale of a few days
- DeltaR_{l, photon}<0.1 recombination (compatible with ATLAS), i.e. add photon to lepton. if 0.1<dR(l,gamma)<0.2, reject lepton as photon spoils isolation (can likely be neglected as the same for ZZ and Zgamma)
- jet-lepton overlap can probably be ignored since it plays a minor role and should impact the ZZ and Zgamma processes in the same way
- two close photons: maybe check whether there is a difference between using recombination and not (since it is a small amount of phase space)
Isolation uncertainties:
- calculate difference between Frixione and parton-level isolation with MCFM to get an estimate of the uncertainty
-> but could be a larger effect at NNLO
- see whether we can tune the epsilon parameter so that parton-level isolation and Frixione isolation behave similarly at NLO and then apply this range to NNLO
- epsilon parameter range chosen to cover the difference between parton-level isolation at truth-level and reco-level
PDF uncertainties
- use NLO MCFM with NNLO PDFs, this should be good enough
Future plans
- detailed discussion of how to obtain the central value and how to combine the uncertainties