1. Steps toward ttH (H->bb) in the Atlas ‘PhysicsAnalysis’ Environment. Chris Collins-Tooth Christian Shaw

2. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 Outline Begin with environment description –from ‘digi’ files to ESD, AOD and histograms –getting full (G4) and Atlfast output DC2 MC generation – Signal and BG –generators used, processes used, forced decays, status. DC2 data currently used (W+jets) –for practice in new PhysicsAnalysis env. Future: getting the ttH signal

3. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 Background Reminder: In DC2, there is no CBNT. Instead, in athena 8.7.0 we have ESD & AOD Atlfast can now run on GEN,SIM,DIGI and ESD – i.e. we can produce Combined AOD. SIM GEN AOD (G4+Fast) (~10k/event) ESD (~100k/event) DIGI Reconstruction MC

4. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 Environment – I. athena 8.7.0 with latest Atlfast releases –AtlfastUtils-00-01-33; AtlfastAlgs-00-01-60 –RecExCommon-00-02-59 –ParticleEventAthenaPool-00-00-57 –UserAnalysis-00-01-04. source share/RecExCommon_links.sh –Pitfall! - gets the distribution copy of RecExCommon_topOptions.py so re-copy it from your (checked out) RecExCommon-00-02-59/share area! run athena – several times! (ESD, AOD, analysis) –athena optRecExToESD.py RecExCommon_topOptions.py »Including CaloTowerContainer#* in JO makes ESD Extremely large! –athena optESDtoCombAOD.py RecExCommon_topOptions.py »produces COMBINED G4 + Fast output ! –athena AnalysisSkeleton_jobOptions.py »nb: set the OutputLevel to DEBUG to get ANY msgs !

5. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 Environment - II. Many ‘gen’, ‘sim’ or ‘dig’ files can be processed into the same ESD file. –PoolRDOInput= [ “rfio:/castor/cern.ch/atlas/project/dc2/...”, “rfio:/castor...” ] –Reco on LSF batch can take hours just to get from PEND to RUN. –Can UK group do better? UK sites? –Currently a 100 event input file produces ~300Mb ESD ! We assume multiple ESDs can then be processed into one AOD file. –Back navigation enabled in 3 rd run of athena (AnalysisSkeleton). We assume also that AOD -> ESD backnavigation works under a many-to-many scenario (not tested yet!!).

6. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 Output – histograms As yet, no ttH DC2 samples to work with (they are coming!) Analysis written in C++ using ‘UserAnalysis’ and ‘AnalysisTools’ packages. Simple output histograms to test AOD and backnavigation to ESD. FASTG4TRUTH

7. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 MC in DC2 – the story so far... Signal ttH (H->bb): 20000 events each at M H =100,110,120,130. Generator filter requires 1 lepton Pt > 10Gev. –efficiency ~65% Generated with Pythia ‘msub’ processes: –qq -> QQH –gg -> QQH Forced decays: –W+ leptons- Isolated high Pt lepton is the trigger. –W- quarks. Background MC – 100k ttbb, W+4jets also being generated as part of DC2.

8. UK Higgs MtgChris C-T + Christian ShawLondon 1.11.2004 Plans for ttH Reproduce previous analysis in paedm (Gen files will be ready before full simulation) Would like to look at Kt algorithm again (Previous results suggest may not be optimal for this channel) Some interesting ideas from top studies (Continuous jets, constraint fit for hadronic W) Much improvement in b-tqgging recently. Should be able to exceed TDR levels (5 % increase in b efficiency would give 50% increase in 4 b cut)