ttH(H->bb) background studies

1. ttH(H->bb) background studies C. Mattravers W. Murray

2. ttH (H->bb)

3. Signal 5870 (+ve lepton) • 5870 (+ve lepton) • 20000 events • 5871 (-ve lepton) • 20000 events

4. Backgrounds • ttbb (QCD) – v12 sample 5855 • 19000 events • ttbb (EW) – v12 sample 5214 • 3500 events • ttjj – v12 sample 5212 • 940000 events

5. tthhbb Analysis Code • Modifications to code Modifications made are included in versions 00-04- 02 onwards. Modified tthhbbClass so that it would reconstruct tt even when there were not enough b jets to make a Higgs. This was for background studies. Current version: 00-04-03

6. Present background studies • Studies in progress to study the shape of the background signal in mbb space and fit this to a statistical distribution. • No knowledge of normalisation. • Lots of information lost with this method.

7. What are we studying? • Estimation of ttbb cross-section, using a set of variables calculated from MC and reconstructed data. • Can we estimate ttbb cross-sections from the folowing factorisation? Where for example: fbb² = (Pbb)2 x Recon4 where (Pbb)2 is the prob of tagging both Bjets as Bjets, And fjj² = (Pjb x Pjj) x Recon3 Where these are the probabilities of tagging 1 light jet as a Bjet and tagging 1 light jet as a light jet. + + +

8. Mis-tag Probabilities • Using reconstructed data from various signal/background samples we are looking at MC Truth data for BTagging and top reconstruction to determine the likelyhood that a b-jet will be tagged as a light-jet and vice versa. • Also how does this compare to the likelyhood that 2 b-jets are mis-tagged etc.

9. 5870 signal sample

12. 5871 Signal Sample

15. 5214 ttbb (EW)

18. 5855 ttbb (QCD)

21. 5212 ttjj