1. 28/4/2006Chris Collins-Tooth tth, (h → bb) with EventViews Chris Collins-Tooth, Christian Shaw 03-May-2006

2. 28/4/2006Chris Collins-Tooth Introduction Report from UK Higgs mtg. in London last Friday Accessing the tth (h → bb) channel. Some output (for 20k Mh=130 GeV) MC Sample: Sim,Dig:9.0.4 Reco:10.0.4 Soon: CSC... –These are not even simulated yet.

3. 28/4/2006Chris Collins-Tooth Report from UK Higgs mtg Lots of interest in ttH H → bb. –WM,PTD,RG,NK,SD,CT If you are interested, join atlas-uk-higgs@cern.ch Made TWiki page for use by ttH H → bb, linked from: –https://uimon.cern.ch/twiki/bin/view/Atlas/HiggsWorkingGrouphttps://uimon.cern.ch/twiki/bin/view/Atlas/HiggsWorkingGroup I Decided to make code available on this page for 11.0.3 EventView-based ttH (H → bb) analysis. Focus for next meeting will be work for CSC. –We will undoubtedly need to re-make AOD, since no truth info. –I aim to concentrate on jet algorithms and muon purity..

4. 28/4/2006Chris Collins-Tooth The tth (h → bb) channel Event trigger is a high Pt lepton.

5. 28/4/2006Chris Collins-Tooth The tth (h → bb) channel Event trigger is a high Pt lepton. Aim: throw away most of the event leaving the correct two b-jets, allowing M h reconstruction.

6. 28/4/2006Chris Collins-Tooth The tth (h → bb) channel Event trigger is a high Pt lepton. Aim: throw away most of the event leaving the correct two b-jets, allowing M h reconstruction. Many combinatorical possibilities! Must keep them in the list of possible “Event Views” until we can judge which is the most accurate combination (from comparison to truth, t-mass reco.) EventView software tools suited to this..

7. 28/4/2006Chris Collins-Tooth Some Output: tth Trigger Lepton When only a trigger electron.. “Trigger electrons” are: –Pt>25 GeV –no soft electrons –IsEM applied –Isolation: no more than 15 GeV in cone 0.45 When there’s only a trigger muon.. “Trigger muons” are: –Pt> 20 GeV –Muon track Chi2NdofCut < 20 –We intend to implement an isolation cut. deltaR (electron only) deltaR (muon only)

8. 28/4/2006Chris Collins-Tooth Electron or Muon? When there’s a trigger electron and some muons which qualify as trigger candidates.. –use the electron!!! NB: events with >1 trigger electron candidate are very rare.

9. 28/4/2006Chris Collins-Tooth b-jet Energy Look at Ebjet/Ebquark Adding soft  ’s back in to the jet helps. Using Kt alg. also helps.. Kt R-param=0.45. –BEWARE there’s a bug! –Value actually given in JobOpts=0.2 (=0.45**2). Seems like a small effect, but b-jet combinatorics sensitive to small energy shifts! Add Muons Cone Kt

10. 28/4/2006Chris Collins-Tooth b-jet Energy Look at Ebjet/Ebquark Adding soft  ’s back in to the jet helps. Using Kt alg. also helps.. Kt R-param=0.45. –BEWARE there’s a bug! –Value actually given in JobOpts=0.2 (=0.45**2). Seems like a small effect, but b-jet combinatorics sensitive to small energy shifts! Add Muons Cone Kt better mean, more symmetric

11. 28/4/2006Chris Collins-Tooth Higgs Masses Cone 0.7 simply not applicable to this channel..too many jets! Cone 0.4 not calibrated. Input M h =130 GeV. Use Kt with  ’s added. Mass peaks: –Cone4, no  ’s ~118 GeV –Kt4, with  ’s ~125 GeV Cone Kt Add Muons

12. 28/4/2006Chris Collins-Tooth More detail... With Kt 0.4, and soft muons resummed into the b-jets, we see an improvement in the reco’d higgs mass. If you want to see exactly how the tth (h → bb) analysis is run, you can see my online log at: MhMh Fit Mean 1.25e+05 https://uimon.cern.ch/twiki/bin/view/Atlas/HiggsWorkingGroup

13. 28/4/2006Chris Collins-Tooth Finally Looking at TruthJet energies... –Ebjet/Ebquark has many effects folded in. –Where there is a good match, Interesting to look at Ebjet/Etruthjet and Etruthjet/Ebquark. Backgrounds –We simulated gg->ttbb with AcerMC –Other Backgrounds tbd with Atlfast. –Significances to follow soon – haven’t had time yet!

14. 28/4/2006Chris Collins-Tooth