Studies with Standard Model Background fast simulation Napoli

Studies with Standard Model Background (fast simulation) Napoli, 27/04/2006

Atlfast data samples: ttbar+jets • Data are available in: /castor/cern. ch/grid/atlas/datafiles/susy/atlfast/Feb 06/Top. Pairs. Alpgen Produced with Alpgen In the simulation all (? ) partons were required to have p. T>40 Ge. V and | |<5. The total ttbar cross section is 880 pb. BR(W->lnu)=1/3, BR(W->qq)=2/3 BR(tt->bblnulnu)=11. 1%, BR(tt->bblnuqq)=44. 4% Each of the files contains in average 3700 filtered events, on which it was already required: – Njets ≥ 4, Missing ET > 80 Ge. V, p. T(leading jet) > 80 Ge. V ×BR # files available Ldt tt (->bblnuqq) + 0 jets 196. 7 pb 106 124 fb-1 tt (->bblnuqq) + 1 jet 127. 9 pb 159 128 fb-1 tt (->bblnuqq) + 2 jets 52. 5 pb 51 118 fb-1 tt (->bblnuqq) + ≥ 3 jets 17. 0 pb 45 124 fb-1 tt (->bblnulnu) + 0 jets 49. 0 pb 86 180 fb-1 tt (->bblnulnu) + 1 jet 32. 0 pb 55 179 fb-1 tt (->bblnulnu) + 2 jets 13. 1 pb 15 130 fb-1 tt (->bblnulnu) + ≥ 3 jets 4. 2 pb 11 145 fb-1 MC Atlfast sample

Atlfast data samples: W+jets • Data are available in: /castor/cern. ch/grid/atlas/datafiles/susy/atlfast/Feb 06/Wjets. Alpgen • • Produced with Alpgen. In the simulation, BR(W->lnu)=1/3, BR(W->qq)=2/3. Only W->lnu is generated (all ) – Njets(p. T>40 Ge. V) ≥ 4 in | |<5, Missing ET > 80 Ge. V, p. T(leading jet) > 80 Ge. V (Few more details still to be known: cross section, ATHENA version, …) Number of partons: 3, 4, 5. Total samples’ luminosity expected 20 fb-1 (? ), Number of available files: 226 (3 jets), 94 (4 jets), 60 (5 jets) More information: https: //uimon. cern. ch/twiki/bin/viewauth/Atlas/Top. Pairs. Alpgen https: //uimon. cern. ch/twiki/bin/view/Atlas/Wplus. Jets. Alpgen • In none of these datasets the MC Truth exists: comparisons with our signal (SU 1, full, so far) are possible only at reconstruction level

Other Atlfast samples on /castor Other recent W+jets data samples to be considered are in: /castor/cern. ch/grid/atlas/datafiles/susy/atlfast/Apr 06/Wjets. Alpgen/Sample. B/ • aod. loosefilter (W+2 j, W+3 j 127 files) • aod. susyfilter (W+3 j, W+4 j, W+5 j 293 files) Reconstructed with 11. 0. 4 (should ask more to T. Lari) Recently also Z+jets samples should be available, in /castor/cern. ch/grid/atlas/datafiles/susy/atlfast/Feb 06/Zee. Njets. Alpgen_non. Default. Alp. Gen N=0, 1, 2, 3, 4, 5 jets. Many AOD files are actually empty. • CSC samples produced with ATHENA release 11 (few of them are available on the grid, but need reprocessing with 11. 0. 5 owing to bugs) cannot be run with the present version of Susy. Plot 10. 0. 2

Reconstruction details • Susy. Plot in ATHENA 10. 0. 2 • Run on lxplus. cern. ch using LSF queues (running in batch on the full statistics required just two days, but maybe it’s not the definitive solution) Actually signal and background should not be superimposable • SUSY (SU 1 point) full simulation • SM background (tt, W) fast simulation – We can run the larger SU 1 fast-simulation sample made in Napoli

Event selection Preselection cuts : • ETmiss > 100 Ge. V , • N(jet) ≥ 4 , • p. T(j 1) > 100 Ge. V, p. T(j 2, j 3, j 4) > 50 Ge. V Reconstruction cuts : Isolation criteria with Atlfast and • 2 OS isolated leptons: lack of further lepton cuts applied p. T>6 Ge. V, for the full-simulation studies with |η|<2. 5 SU 1 can provide discrepancies LEFT slepton: M(ll) < 57 Ge. V RIGHT slepton: 57 Ge. V < M(ll) < 100 Ge. V Both first 2 jets considered for llj and lj masses SFOS-OFOS subtraction After selection (but no OFOS subtraction): • # all SU 1 / # tt 1 events ~1/50 ~1/4 • # SU 1 signal/#SU 1 bckg evts ~1/60 ~1/3

Dilepton invariant mass SU 1 point ll tion u f la u m i s tt->lnqq + Njets W+Njets sim fa ul st at io n tt->lnln + Njets # of events normalized to 22 fb-1/10 Ge. V

ll-jet invariant mass SU 1 point tt->lnln + Njets tt->lnqq + Njets W+Njets

l-jet mass and asymmetry (SU 1) jhigh + jlow Left Near Left (N+F) 2. 1 1. 5 L 22 fb-1

l-jet mass and asymmetry (tt-lnln) Left Near Left (N+F) L 180 fb-1

l-jet mass and asymmetry (tt-lnqq) Left Near Left (N+F) L 120 fb-1

l-jet mass and asymmetry (tt-ln. X) Left Near Left (N+F) L 150 fb-1

l-jet mass and asymmetry (W+jets) Left Near Left (N+F) L 20 fb-1 (? )

Conclusions • After a first non-optimized run on (almost) all the “previously available” statistics, ttbar+jets and W+jets samples seem to give a negligible contamination to invariant mass distributions and their charge asymmetries. • A proper OFOS subtraction needs better knowledge of single lepton efficiencies (using ) our SM bckg sample should contain MC Truth • Run on recent SM and Napoli’s SU 1 fast samples • Running on CSC production: what to do? Patching Susy. Plot or moving to Event. View?

Electrons-Jets distance in SU 3 R between a reconstructed electron and its nearest reconstructed jet Running on just 1 AOD fast-simulation file (SU 3) produced in Napoli.