tth, (h→bb): Signal, Background & Comparisons

Chris Collins-Tooth

25-Jan-2007

Samples

• Signal tth(h→bb):

• 5340 (forced l + )• 5341 (forced l - )

• Backgrounds used: • 5855 AcerMC gg->ttbb (QCD)• 5214 AcerMC gg->ttbb (EW)• 5212 MC@NLO/Herwig ttjj (jj=bb removed).

Signal and BG Efficiencies.

• Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

• On the whole encouraging.• Problem with ttjj

• many events had >=4 unique b-quarks• Had to remove them, as ttjj(jj=bb) ttbb

Events Lepton >=6J >=4bJ 2topsSignal 5340 39600 26173 18645 1290 324

66% 47% 3.26% 0.82%Cammin 46% 3.80% 1.80%

ttjj (jj=bb removed) 452335 329790 163577 109 1773% 36% 0.024% 0.0038%

Cammin 15% 0.010% 0.0030%

ttbbQCD 45200 30804 18263 505 8468% 40% 1.12% 0.19%

Cammin 37% 1.50% 0.70%

Signal and BG Efficiencies.

• Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

• On the whole encouraging.• Problem with ttjj

• many events had >=4 unique b-quarks• Had to remove them, as ttjj(jj=bb) ttbb

Events Lepton >=6J >=4bJ 2topsSignal 5340 39600 26173 18645 1290 324

66% 47% 3.26% 0.82%Cammin 46% 3.80% 1.80%

ttjj (jj=bb removed) 452335 329790 163577 109 1773% 36% 0.024% 0.0038%

Cammin 15% 0.010% 0.0030%

ttbbQCD 45200 30804 18263 505 8468% 40% 1.12% 0.19%

Cammin 37% 1.50% 0.70%

higher jet mult.in MC@NLO?

Signal and BG Efficiencies.

• Latest “full sim” is Compared to Cammin [ATL-PHYS-2003-024]

• On the whole encouraging.• Problem with ttjj

• many events had >=4 unique b-quarks• Had to remove them, as ttjj(jj=bb) ttbb

Events Lepton >=6J >=4bJ 2topsSignal 5340 39600 26173 18645 1290 324

66% 47% 3.26% 0.82%Cammin 46% 3.80% 1.80%

ttjj (jj=bb removed) 452335 329790 163577 109 1773% 36% 0.024% 0.0038%

Cammin 15% 0.010% 0.0030%

ttbbQCD 45200 30804 18263 505 8468% 40% 1.12% 0.19%

Cammin 37% 1.50% 0.70%

cut on 2 tops too harsh?

higher jet mult.in MC@NLO?

Moving on.....• Look at signal and BG normalised to 30 fb-1

– Problem: BG samples not big enough!– No sensible distributions yet!

Optimisations/Cuts..• Lots of cut optimisations to consider; also new cuts

like PtJ1/J2>50/20 GeV on bJets forming Higgs