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Published byMaud Cooper Modified over 9 years ago
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Status Update: Search for Low Mass Strings at CMS Andy Yen
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Intro Superstrings can lead to the following non-SM process: gg→gγ Extra contribution to the SM gamma+jet. Ms ~ 1 TeV, 100 evt for 200pb-1 2
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Data Samples Strings Signal: 10k events, Ms=1 TeV, ckin(3)>200 GeV, correct kinematics, incorrect matrix element weights. CMSSW 3.2.x Photon+Jet/QCD Dijet (CMSSW 2.2.x) Ckin(3)>170, 1M/1.5M [19400pb-1, 24pb-1] Chin(3)>300, 300k/1M [71548, 273] Ckin(3)>470, 100k/3M [221484, 9500] Ckin(3)>800, 100k/3M [5000000,250000] Ckin(3)>1400, 100k/.5M
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Photon Reconstruction Require dR within 0.15 of MC. 32x eff (string signal): 95.465 [right] 22x eff (pt>470 GeV pho+jet): 96.406 [left]
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Jet Reconstruction Jets Objects used iterativeCone5CaloJet sisCone5PFJet iterativeCone algorithm Colinear unsafe Infrared unsafe sisCone algorithm “seedless infrared safe cone” Particle Flow Reconstruct ALL particles in event Uses all CMS subdetectors
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Jet Response (continued) iterativeCone5CaloJets CMSSW 2.2.x vs 3.2.1 Arbitrary normalization 6 Mean: 0.79 Sigma:.106 Mean: 0.77 Sigma:.123
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Jet Energy Response CMSSW 3.2.1 IterativeCone5CaloJets vs sisCone5PFJets Crystal Ball Fit with 2 polynomial tails 7 Mean: 0.77 Sigma:.123 Mean: 0.94 Sigma:.082
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Collinear Safety? Even in the PF Jet, there is still a tail at low values. Approximately 10% of reconstructed Jets have 2 nd Jet within dR<1 [for sisCone PF jets]
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Collinear correction Take the vector sum of the momentum of the two jets Use Pt-weighted average of eta and phi (account for phi discontinuity). Improvements in eta/phi and energy response!
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Response Improvements Mean: 0.95 Sigma:.0596
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Jet Reco Efficiency
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Event Selection Describe the selection here + cut efficiencies for signal and backgrounds
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