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High Level Trigger for the ttH channel in fully hadronic decay at LHC with the CMS detector

High Level Trigger for the ttH channel in fully hadronic decay at LHC with the CMS detector. Daniele Benedetti On behalf of CMS Collaboration. Outlook. Reason for studying ttH channel Study of the data acquisition. Current Higgs mass limits The role of the LHC collider.

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High Level Trigger for the ttH channel in fully hadronic decay at LHC with the CMS detector

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  1. 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. Outlook Reason for studying ttH channel Study of the dataacquisition • 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. Large Hadron Collider (LHC) Circumference: 27 Km Energy CM (p-p)=14 TeV m Chambers Hadronic Calorimeter Electromagnetic Calorimeter Tracker

  4. Higgs mass prevision From Lep measures Higgs mass > 114.1 GeV at 95% C.L. With the new world average for: Mtop = (178.0 ± 4.3) GeV MH<251 GeV (2 s) 95% C.L. And the best estimate for Higgs mass is: MH=117 GeV

  5. Interactions at LHC TeVatron LHC 109 1010 tot 107 108 b 105 106 104 103 R@L=1034 cm-2s-1 [Hz] jet(ETjet>s/20) W 102 101  [nb] Z jet(ETjet>100 GeV) 100 10-1 t 10-2 10-3 jet(ETjet>s/4) H(mH=120 GeV) 10-4 10-5 H(mH=500 GeV) 10-6 10-7 .1 1 10 s [TeV] Production of quarks b Production of quarks top sg Production of Higgs

  6. Higgs observability For MH (120-130) GeV D1 P1 P2 D2

  7. The Channel ttH Hadronization jets quark Fully hadronic final state MH=120 GeV 8 (or more) jets in the final stateand 4 from quark b

  8. Background considered For the trigger study we used non resonant background. The QCD samples are datasets of the official CMS Production 2002

  9. CMS Trigger Interaction p-p: 40 MHz 105 events/s (Hz) Use ofm chamber and calorimeters L1 100 Hz Also using tracker HLT Total reduction factor >105

  10. Trigger L1 ttH hadronic p Luminosity=2x1033 cm-2 s-1 Rate(s-1)=eff x s(mb) x 1027x L(cm-2 s-1) pT ET

  11. Fast b-tagging for HLT do = impact parameter do resolution jet vs d0 vp d0 Pt tracks in pixel line > 2 Gev/c • Regional Tracking • Conditional Tracking Only tracks within a jet cone DR=0.4 DR2= (hjet-htracks)2+(fjet-ftracks)2 (hjet, fjet) from L1 jet reconstruction pt resolution Limited number of hits

  12. High Level Trigger We use the Tracker information to recognise the jets from quark b Black = ttH hadronic Red = QCD tracks Partial reconstruction 5 hits track reco 0.4 cone 2 GeV pxl line Pt cut d0 Dd0 Sip2D= SIP2D = Significance of impact parameter in 2D Requiring SIP 2D > 2 We reject more QCD than signal Sip2D

  13. High Level Trigger Preselection ET>10 GeV 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

  14. High Level Trigger (100 Hz) Energy Trigger + b-tagging Requiring: • 4 jets with ET>50 GeV • 1,2,3,4 b-taggedjet 2 tracks with Sip2D>2.0: 30 Hz QCD Rate with 60 % Eff

  15. Conclusions • With the L1 Trigger (4 jets with ET>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.

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