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Comparison of ttjj production at Tevatron and LHC

Comparison of ttjj production at Tevatron and LHC. Regina Demina University of Rochester 12/09/03. Outline. Motivation Production mechanisms Production rates and statistics Kinematics Monte Carlo verification Summary. Motivation. ttH – discovery mode at low M(H)

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Comparison of ttjj production at Tevatron and LHC

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  1. Comparison of ttjj production at Tevatron and LHC Regina Demina University of Rochester 12/09/03

  2. Outline • Motivation • Production mechanisms • Production rates and statistics • Kinematics • Monte Carlo verification • Summary CMS week, CERN

  3. Motivation • ttH – discovery mode at low M(H) • Tree level couplings at production and decay • Probes top-Yukawa coupling – particularly interesting since ~1 • Background processes • ttbb (dominates if 4 b-tags are required); • ttjj (comparable if >=3 b-tags=2 b’s from tt+1mistag) • Background processes are best calibrated in the absence of signal • Tevatron can help CMS week, CERN

  4. Production mechanisms • tt production • Tevatron (ppbar, 1.98 TeV): 85% quark annihilation, 15% gluon fusion • LHC (pp, 14 TeV) 100% gluon fusion • tt+jets • Initial state radiation • B-jet radiation • W-decay product radiation • t-radiation different similar CMS week, CERN

  5. Production rates and statistics • Production rates • Expected number of events in Wln +jets channel • Tevatron: L=5 fb-1 • LHC: L=104pb-1 • ttbb – the rate is too small to observe at Tevatron CMS week, CERN

  6. Production of tt+nj • Et(j)>10 GeV • ALPGEN, parton level CMS week, CERN

  7. CDF Run 1 result • Integrated luminosity 100 pb-1, W+njets (>=1b-tag) • Contributions: • W+jets; tt, tt+j • F(ttj)=5.1+8.4-5.9% • s(ttj)/s(ttX)<0.48 @90% • Theory 0.42 CMS week, CERN

  8. Kinematics • Good news – very similar jet Et spectrum: • <Et>(TeV)=30GeV • <Et>(LHC)=45GeV LHC Tevatron CMS week, CERN

  9. Tevatron contribution • Monte Carlo verification and tuning for ttjj production • Final state radiation is very similar to LHC • Initial state radiation must be studied on gluon fusion dominated processes, e.g. bb production • Separation can be done with invariant mass selection: • M(bWj)=~M(t) – b-jet radiation • M(jjj)=~M(W) – W decay products radiation • Forward jets - ISR • Analyses methods development and verification • B-tagging • B-charge tagging • Kinematic constraints CMS week, CERN

  10. Summary • Main background processes to ttH production are • ttjj • ttbb • ttjj production can be studied at Tevatron (ttbb rate is too small) • ISR and FSR can be separated statistically using invariant mass cuts • Jet kinematics is very similar at Tevatron and LHC CMS week, CERN

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