1. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 High Level Trigger for the ttH channel in fully hadronic decay at LHC with the CMS detector Daniele Benedetti On behalf of CMS Collaboration

2. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Outlook Reason for studying ttH channel Study of the data acquisition Current Higgs mass limits The role of the LHC collider CMS data acquisition system The Level 1 Trigger The High Level Trigger (HLT) ttH in fully hadronic decay

3. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Large Hadron Collider (LHC) Circumference: 27 Km Energy CM (p-p)=14 TeV Hadronic Calorimeter Electromagnetic Calorimeter Tracker  Chambers

4. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Higgs mass prevision From Lep measures Higgs mass > 114.1 GeV at 95% C.L. With the new world average for: M H <251 GeV (2  ) 95% C.L. M top = (178.0 ± 4.3) GeV And the best estimate for Higgs mass is: M H =117 GeV

5. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Interactions at LHC Production of quarks b Production of quarks top Production of Higgs 

6. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Higgs observability For M H  (120-130) GeV Cross Section Branching Ratio Expected Background Observability gg  H  bb P1+D1 No gg  H   P1+D2 Yes gg  ttH  ttbb P2+D1 ? P1 D2 D1 P2

7. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 The Channel ttH Fully hadronic final state 8 (or more) jets in the final state and 4 from quark b quark Hadronization jets M H =120 GeV Branching Ratio W  qq 67.6% H (120 GeV)  bb 71.3% Total hadronic 32.6%  (pb) ttH (LO) 0.5773 ttH(NLO) 0.7015 ttH hadronic (LO) 0.1881 ttH hadronic (NLO) 0.2286

8. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Background considered Cross Section (mb) Exepected rate at low Luminosity (2x10 33 cm -2 s -1 ) QCD(30<p T <50 GeV)0.195770~4x10 5 QCD(50<p T <80 GeV)0.025870~ 5x10 4 QCD(80<p T <120 GeV)0.003629~ 7.3x10 3 QCD(120<p T <170 GeV)0.000619~ 1.2x10 3 For the trigger study we used non resonant background. The QCD samples are datasets of the official CMS Production 2002

9. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 CMS Trigger 10 5 events/s (Hz) Use of  chamber and calorimeters 100 Hz Also using tracker Interaction p-p: 40 MHz Total reduction factor >10 5 L1 HLT

10. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Eff ttHRate QCD 4 E T > 40 GeV 80 % 1 KHz 4 E T > 50 GeV 65 %~200 Hz Rate(s -1 )=eff x  (mb) x 10 27 x L(cm -2 s -1 ) Luminosity=2x10 33 cm -2 s -1 p p T  E T Trigger L1 ttH hadronic

11. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Fast b-tagging for HLT jet vs vp d0d0 d0d0 Regional Tracking Conditional Tracking Only tracks within a jet cone  R=0.4  R 2 = (  jet  tracks ) 2 +(  jet  tracks ) 2  (  jet,  jet ) from L1 jet reconstruction Limited number of hits Pt tracks in pixel line > 2 Gev/c d o resolution p t resolution d o = impact parameter

12. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 High Level Trigger We use the Tracker information to recognise the jets from quark b Partial reconstruction 5 hits track reco 0.4 cone 2 GeV pxl line Pt cut Requiring SIP 2D > 2 We reject more QCD than signal SIP2D = Significance of impact parameter in 2D Sip2D tracks Black = ttH hadronic Red = QCD Sip2D= d 0  d 0

13. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 High Level Trigger The b-tagging is a track counting algorithm: 2 tracks at different SIP2D For 1 b-tagging jet 0.5 < Sip2D < 5 For 2,3,4 b-tagging jet 0.5 < Sip2D <2.5 2 tracks with Sip2D>2.0: 85% sig eff 25% QCD eff Preselection E T >10 GeV

14. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 2 tracks with Sip2D>2.0: 30 Hz QCD Rate with 60 % Eff High Level Trigger (100 Hz) 4 jets with E T >50 GeV 1,2,3,4 b-tagged jet Requiring: Energy Trigger + b-tagging

15. Daniele Benedetti CMS and University of Perugia Chicago 07/02/2004 Conclusions With the L1 Trigger (4 jets with E T >50 GeV) we obtain 65% signal efficiency at ~200 Hz of QCD rate. With the High Level Trigger we can decrease the QCD rate to 30 Hz still selecting 60% of signal events. …next steps Study the offline reconstruction and estimate the signal significance with respect to the resonant backgrounds.