1. Physics Studies Update
FTK Meeting
01/26/06
Erik Brubaker
U of Chicago

2. Hhh4b analysis
Two algorithms for event selection in ATL-PHYS
Algorithm A
Algorithm B
NJETS >= 4
Consider leading 4 jets, pairing most consistent with 2 mh decays
Consider any 4 jets most consistent with 2 mh decays
Require b tag on all 4 jets
Require both pairs have mbb = mh ± 25 GeV.
Apply mh constraint, require mbbbb = mH ± 20 GeV.
Jan 26, 2006
FTK Meeting

3. Signal selection results
Algorithm A
Start
NJETS
4 b tags
mh cut
mH cut
# Events
960000
926038
8552
5425
4192
Cut eff.
96.5%
0.9%
63.4%
77.3%
97 study
0.6%
44%
81%
Algorithm B
7723
5803
4486
0.8%
75.1%
1.1%
73%
77%
Differences
9 years ago…
B-tagging efficiency
mh = 90
What is s?
Jan 26, 2006
FTK Meeting

4. Reconstructed masses mh = 130 GeV mH = 300 GeV. Jan 26, 2006
FTK Meeting

5. Background selection Algorithm A Start NJETS 4 tags Cut 3 Cut 4
Start
NJETS
4 tags
Cut 3
Cut 4
# Events
980000
153335
Cut eff.
8.9%
0.0%
97 study 4 tags eff: 10-3—2*10-5, depending on real b content
Need to weight events by tagging probability…
Is SHERPA really generating heavy flavor?
Jan 26, 2006
FTK Meeting

6. Background Selection (weighted evts)
eb = 0.5, ec = 1./10.9, eu = 1./231.
Algorithm B
Start
NJETS
4 b tags mh mH
# Events
980000
153335
Cut eff.
15.6%
2.2e-7
16.8%
2.7%
eb = 0.6, ec = 0.1, eu = 0.01
Algorithm B
Start
NJETS
4 b tags mh mH
# Events
980000
153335
Cut eff.
15.6%
6.1e-7
15.0%
7.0%
etot=1e-9  360 ev/fb-1
Jan 26, 2006
FTK Meeting

7. When revisiting the LVL1 parametrizations
Understand high-h triggers.
What is range of central jet trigger?
Can jets be clustered across central/forward boundary? (If not, is there a “dead spot” or a shoulder in response?)
Use “unfluctuated” ATLFAST jets as input.
Basically a truth jet of clustered hadrons.
Extend ET range past 300 GeV.
Parametrize 4x4 ET as well as 8x8.
Investigate h dependence of params.
Investigate response of g,q,c,b?
ATLFAST pT
LVL1 ET
Jan 26, 2006
FTK Meeting

8. SHERPA questions Are heavy quarks automatically included in ME?
What is recommended treatment or settings for MPI/underlying event at LHC?
Is there a good document that explains ycut well?
How does choice of ycut affect quantities that use low-pT jets, like MET?
Jan 26, 2006
FTK Meeting