Constraints on ttH analysisConstraints on ttH analysis

Samir FERRAG

IntroductionIntroduction

• Theoretical uncertainties:– PDFs: 40+1 CTEQ6 PDF sets– Factorisation and renormalisation scale: 0.50<<20

• AlpGen v:2.06 used• Cross sections computation:

– 100M events for each PDF set 0.05% stat uncertainty

– 7 Hours on Desktop (8h on my laptop) • Feasibility of ttH

– Extract the constraints on the background uncertainty– If feasible: define the priorities on real data:

• PDF, Background, ttH…

Theoretical uncertainties on ttbb Theoretical uncertainties on ttbb

ttbb= 2.55 +/- 6% (PDFs) +/- 55% (energy scale)PDF: can be irreducible and constitutes a serious source to constraint the analysis

Constraint on ttHConstraint on ttH

BB

SN

)1( 2

Constraint:

Sensitivity:

2

2

2

2

411

NSS

SB

Constraint on ttH for 10fbConstraint on ttH for 10fb-1-1

5

4

3

2

6% of PDF uncertainties (on ttbb+ttjj)

S/B

systematic uncertainty on B (%)

Requested S/BFor 3 significaneFor 6% PDF uncertainty

Need 1 to 2 % of accuracyOn background to reach 2 significance

S/B=0.14 From Markus cuts

Constraint on ttH for 100fbConstraint on ttH for 100fb-1-1

6% of PDF uncertainties

S/B

systematic uncertainty on B (%)

Requested S/BFor 3 significaneFor 6% PDF uncertainty

5

4

3

2

Need 4% of accuracyOn background to reach 3 significance

S/B=0.14 From Markus cuts