Trigger studies of SM 130 GeV Higgs  in the lepton+hadron channel First pass at estimating trigger efficiency Higgs mass reconstruction Catalin Ciobanu, Dovid Skversky, Kevin Pitts, Tony Liss Univ. of Illinois

Part I: Trigger Studies

Trigger tables – from Francesca’s talk LOW-LUMHIGH-LUM Notation: means the event fired MU20 and J200 triggers MU20(20) 2MU6 EM25I(30) 2EM15I(20) J200(290) 3J90(130) 4J65(90) J60+xE60( ) TAU25+xE30(60+60) MU10+EM15I

This will hurt efficiency Too few ATLFASTB  -jets!

ATLFASTB  -jets + lepton Wait! It’s even worse: 73% of events with an ATLFASTB  -jet have no leptons. Of the 536 evts that do have both a lepton and a  -jet, about 300 are below the lepton trigger. 1986/50k= 4% - very poor

Lepton and  -jet E T -integral spectra Investigated using one additional trigger: Lepton +  -jet. 3 variables: –Lepton E T –  -ID flag (ATLFASTB! Remember small efficiency) –  -jet E T

Default Efficiency Using Erik’s parametrization for the jets –Not for the  jets –For the  triggers use ATLFASTB info, not the ‘truth’ –Given N (N  7) choose the most efficient N triggers: Low luminosity regime: N= 1: (jet+MET) N= 2: (+muon) N= 3: (+electron) N= 4: (+taujet+MET) N= 5: (+1jet) N= 6: (+3jet) N= 7: (+4jet) High luminosity regime: N = (muon) N = (+electron) N = (+jet+MET) N = (+taujet+MET) N = (+1jet) N = (+3jet) N = (+4jet)

Adding  +lepton trigger LOLUM Max. increase: 0.5%= ( )/34.3 Max. increase: 2.1% = ( )/24.7 Plot: 100* [ eff ( )-eff ( )] / eff ( )

“Perfect”  -jet identification Max. increase: 6.1%Max. increase: 33.5% = ( )/28.6 Plot: 100* [ eff ( )-eff ( )] / eff ( )

Imperfect  -jet identification Plot: 100* [ eff ( )-eff ( )] / eff ( ) as  -ID efficiency is varied from 10% to 100%. E T (lep)>5GeV E T (  -jet)>5GeV perfect ID ATLFB

Conclusions Rough pass at trigger efficiencies for H  in the lepton+hadron channel Backgrounds? –Top pair production –Bottom pair production –W/Z+jets production –Z  Some (all?) exist; some may have to be generated Study improvements to S/B –Cut on  between lepton and  -jet

Part II: Higgs Reconstruction For this study, to improve statistics, we use the ATLFAST(not-*ATLFASTB*)  -jets, i.e. the ‘truth’  -ID: abs(KFJET[i])=15

Collinear Approximation  Assume the neutrinos ( ) that go with the lepton move along the same transverse direction as the lepton itself (no need to assume same  as well)  Similar for the  -jet and the other neutrino 3.  Conserve energy and momentum –Missing energy = transverse comp. of –Solve for the transverse comp. of ( ) and 3. –Solve for the longitudinal comp.: If complex solutions, then also assume the same  (fully collinear approximation). This means giving up the P z mom. conservation in 21% of the events e,   -jet 3 Transverse plane

Leptonic and hadronic  reconstruction Needs debugging

Higgs Mass Reconstruction 4.3% events have M H >300

More Higgs plots Collinear approximation gets better as momentum increases:

Conclusions II We got a mass peak! –There may be room for improvement? Fit in the range:  9.8 GeV Clean up the bugs New ideas for complex Pz solution cases?