Les Houches

Photon people/mailing list:

Photon topics:

1. Measurements: gg, gg + jet, gg + 2jets

–All processes:Try for some calculation including direct and fragmentation contributions in as high orders as possible (something equivalent to joining of 2gammaNNLO and DIPHOX/Gamma2MC) In what areas in phase space is 'missing' (meaning wrt 2gammaNNLO) fragmentation important? What is the relationship with asymmetric pt cuts? Pertinence to ATLAS recent results and CMS results in progress, theory-data agreement in low DeltaPhi region for example

–gamma gamma + jet: Try GoSam gamma gamma + 1 jet + MG compared to SHERPA/aMC@NLO/POWHEG/ALPGEN/MG/PYTHIA (codes producing hadronised events) Is there a way to 'map' kinematic effects from fragmentation to experimental level (as we do today running for example PYTHIA with and without UE to correct results from the partonic codes for UE today), so as to be able to correct/extrapolate from purely partonic codes?

2. Understanding finely the background to the H125 or X125 (or 126!) –Make 2d reweighting of LO/LO+ codes used for prompt diphoton irreducible backgrounds to 2gammaNNLO(+gamma2MC) –Make 2d reweightings of LO/LO+ codes used for photon + jet and jet-jet (pure QCD) backgrounds to DIPHOX in gamma-h and h-h modes (above are for training of multivariate methods in Hgg analysis)

–An obstacle to the use of physics motivated truth models from partonic/hadron-level calculations for background modelling in Hgg is the 'sculpting' of distributions at the experimental level by acceptance/other selection criteria not possible to model at parton- or hadron-level, can we work on techniques for these extrapolations?

–Precise measurements of the different background components (gamma-gamma, gamma-jet, jet-jet) *in the nbd of the H125/6*

3. Isolation –For or against trying to use or at least evaluating Frixione isolation on experimental level? Other cones? –Use in Vgamma –Prior LH studies, which Frixione parameters are the best –Same as usual question of surviving collinear (to photon) radiation

4. Hgg signal/background –Propagate new knowledge on the gg-ggf background-signal interference (Martin,Dixon et al) to the exps. signal modelling (mass shifts..) –Investigate new possible observables for greater S/B sensitivity (using knowledge from 2. above)