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2015:groups:sm:photons [2015/06/04 16:19]
suzanne.gasconshotkin created
2015:groups:sm:photons [2015/07/14 08:28]
philippe.gras Added instructions for CERN account
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 ====== Photon studies (isolation, fragmentation,​ resummation...) for direct photon measurements ====== ====== Photon studies (isolation, fragmentation,​ resummation...) for direct photon measurements ======
-under construction+//If you are interested in contributing please subscribe to the [[https://​​e-groups/​​searchValue=houches-2015-topics-sm-photon|mailing list]]. You will be asked to log in with your CERN account. If you don't have a CERN account, please fill [[https://​​account/​Externals/​RegisterAccount.aspx|this form]] to create a lightweight account.//
-  * Topics, meetings, etc.+still under construction
 +2nd meeting: Saturday June 6 at 9AM in Auditorium
 +  * List of presentations and discussion items:
 +  * Leandro Cieri: Discussion topics, recall of 2013 LH studies and slides (linked to program)
 +  * Gudrun Heinrich: Recall of 2013 LH studies and plots
 +  * Ciaran Williams: triphoton and quadriphoton cross sections measurements and isolation comparisons
 +  * Mauro Chiesa: Isolated photon production in the POWHEG+MiNLO framework: the W \gamma example
 +Very interesting but timescale not compatible with LH proceedings:​
 +  * Completion of work of Jean-Philippe Guillet (with Catani, Michel Fontannaz and Eric Pilon) in JHEP09(2013)007 (1306.6498) on resumming LL dependence on isol. cone size. Implementation of resummation of ln r terms in JETPHOX for hollow-cone case should enable to compare smooth to hollow-cone and see if the difference is still O(~1%) as shown for solid-cone by Leandro in LH2013 proceedings.
 +What could be accomplished for the proceedings?​ (Blackboard discussion)
 +  * Survey of current/​planned isol. criteria used in LHC exps for direct photon measurements
 +  * to be continued....
 +References for above presentations (to be completed):
 +  *Catani Fontannaz Guillet Pilon arXiv:​1306.6498 [hep-ph].
 +  *T. Gehrmann, N. Greiner, and G. Heinrich, Photon isolation effects at NLO in gamma gamma + jet final states in hadronic collisions, JHEP 1306 (2013) 058,​arXiv:​1303.0824 [hep-ph].
 +3nd meeting: Tuesday June 9 at 11AM in Auditorium
 +  * Ciaran Williams: Extension of sigma vs. epsilon plots for smooth vs. fixed cones to smaller epsilon values
 +  * Preliminary Draft of work plan for the proceedings and discussion:
 +A) Smooth vs. Exp'l Isolation Cone Comparison
 +1) Study additional processes similar to what was done by L. Cieri and D. de Florian for inclusive diphotons in LH2013, see if also obtain agreement within O(1)% for generalisation of LH Photon Isolation Accord."​one could define the isolation to be tight enough when the contribution from the fragmentation component does not exceeds ~15−20% of the total cross section"​ true for all processes?:
 +--Wgamma (and maybe later Zgamma) with POWHEG+MinLO: ​ Total cross-section vs Etmax and vs epsilon, and differential in Et_gamma, M_lnu(ll)gamma for 1-2 choices [e.g. epsilon=0.05,​ cone size](Mauro C. and Fulvio)
 +--Gamma + jet JETPHOX: Total cross-section vs Etmax and vs epsilon, and differential in Et_gamma for 1-2 choices[e.g. epsilon=0.05,​ cone size 0.2, 0.4, 0.7? ] (Gudrun H...)
 +--triphoton (and maybe later quadriphoton) production with MCFM: Total cross-section vs Etmax and vs epsilon, and differential in some variables (Et_gamma 1(2)(3)(4)...)Extend range of epsilon in sigma vs. epsilon plots down to epsilon=0.05 and add scale variations(Ciaran)
 +2) Is unphysical behaviour under '​mismatch'​ of direct and frag component orders (as reported in LH2013 by Cieri and deFlorian) for gamma gamma, gamma gamma + jet and W/Zgamma also generalized to other processes?
 +--Gamma + jet with JETPHOX shown June 6 (Gudrun)[yes] (Is it possible to have 'LO fragmention function-LO matrix element'​ to check?)
 +--LO fragmentation function possible in time horizon for proceedings (Jean-Philippe,​ Michel F.)?
 +B) Fragmentation: ​ How important is the '​transverse'​ (or non-collinear) vs. '​longitudinal'​ (or collinear) fragmentation?​
 +FO calculators (e.g. PHOX family, MCFM, GoSam, ...) only have longitudinal,​ HO codes with PS (e.g. POWHEG with MiNLO) have both.  While waiting for gamma gamma in POWHEG with MiNLO (probably not for proceedings),​ use Vgamma (and maybe later Zgamma), MCFM vs. POWHEG + MiNLO, as 'test bench' to evaluate difference in integrated xs, differential observables and comparison with CMS/ATLAS data (Mauro/​Fulvio,​ Ciaran et al, all) 
 +    ​
 +C) Experimental Survey (experimentalists):​
 +  ​
 +1) size and character of cones used/​planned for use in CMS + ATLAS (size, hollow/​solid,​ Fixed or normalized (epsilon or fixed value)), disc. Frixione?)
 +2)Survey of direct photon measurements esp Vgamma ​
 +  * Discussion of what to include in a few slides for the summary session tomorrow
2015/groups/sm/photons.txt · Last modified: 2015/07/14 08:28 by philippe.gras