ttH Report

1
ttH Report

• S. Uozumi (Kobe)
• R. Yonamine (GUAS)
• K. Fujii (KEK)
• Feb-16 2008 PhysicsWG meeting

2
Introduction

• Goal is to estimate sensitivity of the Top-Yukawa
  coupling with ttH channel at ILC first stage.
• Take advantage of NLO Threshold effect and e
  polarization which enhance the s(ee- ? ttH) by
  factor 4.
• Targer parameter space
• cms 500 800 GeV
• mH120 200 GeV ? Ethre 2mtmH 470 550
  GeV
• s(Ethre a) O(0.1) fb ? O(100) events with 1000
  fb-1
• Decay
• ttH ? bWbW (bb, WW or ZZ) ? 8 / 10 fermions
• High jet multiplicity
• Expected main Backgrounds
• ttg ? ttbb for H ? bb case
• ttWW / ttZZ for H ? WW/ZZ case

3
Status

• Signal generator with threshold enhancement is
  done (Ishikawa).
• Signal cross-section is calculated.
• Some main BG cross-section are calculated by
  MadGraph (Uozumi).
• Ishikawa-san is gone, and Yonamine-san is joining
  to take over the signal part.
• Both signal / BG are Entering to the quick
  simulation phase.
• Joining us is still highly welcomed!

4
Signal Monte Carlo (H ? bb)
Threshold enhancement

• Threshold enhancement is implemented.
• Beam polarization gives rather large effect.
• If MH gt 140 GeV, it will be difficult to measure
  Yt around cms 500 GeV.

Effect of beam polarization
MH dependence (with P(-0.8,0.6))
5
Background Cross-section
non-gluon ttbb BGs

• No selection is applied yet.
• At this level ttbb BG has comparable x-section
  with the signal.
• In the ttbb BG, ttg-gtttbb is x2 larger
• than other ttbb BG.

6
Effect of beam polarization to BG
ttbb BG

• cases of P(0,0), (-0.8,0.6) are examined.
• Slight improvement can be seen with the
• ttbb BG.

Signal cross-section (by Ishikawa-san)
ttWW BG
ttZZ BG
7
Plans

• First event generation is done for both signal /
  BG.
• Proceed to the quick simulation.
• Compare / cut on kinematical quantities with
  signal events.
• di-jet mass
• b-Jet energy
• etc