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

Hhh4b analysis Two algorithms for event selection in ATL-PHYS-97-104. 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

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

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

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

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 0.0337464 0.00568473 0.000154646 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 0.093047 0.0139949 0.000978518 Cut eff. 15.6% 6.1e-7 15.0% 7.0% etot=1e-9  360 ev/fb-1 Jan 26, 2006 FTK Meeting

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

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