1 Techincolor and Heavy Top/B search Tulika Bose Meenakshi Narain (Brown University) Work done in the context of Les Houches 2007
Feb 01, 2016
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Techincolorand Heavy Top/B search
Tulika Bose
Meenakshi Narain
(Brown University)
Work done in the context of Les Houches 2007
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Exotic top partners
Some BSM theories predict the existence of: heavy top quark partner heavy bottom
• Model suggested by Contino and Servant : arXiv:0801.1679 (2008) “Discovering the top partners at the LHC using same-sign dilepton final states”Perform a sensitivity study using CMS fast simulation samples:
Figures from slides of a presentation by R. Contino (TH-CERN)
(Bose, Narain)
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Exotic top partners
Some BSM theories predict the existence of: heavy top quark partner heavy bottom
Figures from slides of a presentation by R. Contino (TH-CERN)
• Look for same-sign di-lepton states • reduces the ttbar background
• Look for a resonant tW invariant mass peak (T5/3)
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Hunting for a heavy T
• Signal & background samples generated using Madgraph• Pythia showering/hadronisation • Quark/Jet matching a la MLM
BKG
Table from Contino and Servant : arXiv:0801.1679 (2008)
Signal
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Hunting for a heavy T
• Samples processed via Fastsim• CMSSW_1_6_8• Iterative 0.5 Cone Jets• Correct Jets (jet_corrections_16X)
Bkg combined according to expected cross sections
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Hunting for a heavy T
• ..
• 2 same sign isolated leptons – (electrons or muons) with || < 2.4
• pT > 50 GeV for the leading lepton• pT > 25 GeV for the second leading lepton.• Missing transverse energy > 20 GeV.
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Hunting for a heavy T
• ..
1)
• At least 5 jets with pT > 30 GeV and || < 5.0.
• pT > 80 GeV for the second leading jet.• pT > 100 GeV for the leading jet
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CMS Discovery Potential
• Background is under control for such a signal
• Triggers: Single lepton, di-lepton (including e+mu and same-sign triggers); Lepton + jets
• Estimate the following for T5/3 + B: 5 observation: ~ 240 pb-1
with sys errors: 30% for signal and 50% for bkgwith no sys errors: ~ 230 pb-1# of Signal events 25.8; bkg events: 0.96
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Reconstructing the heavy T• Reconstructing the first W (from top decay) (eff: 0.84)
– Take the two jets with invariant mass consistent within 20 GeV of W boson.
– If a btagged jet is found close to the second leading lepton, the jet is removed from consideration.
– Require Rjet< 1.5 and the W(pT) > 50 GeV.
• Reconstructing the second W (from heavy exotic top)– Remove jets associated with first W.– Take the two jets with invariant mass consistent within 25 GeV of W
boson.– Require Rjet< 1.5 and the W(pT) > 30 GeV.W from top decay W from heavy top
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Reconstructing the heavy T• Reconstructing the heavy Top (from top decay)
– Discard the four jets that were assigned to the two W bosons – Combine the btagged jet with one of the two W bosons to get the top
quark• Take the one that is closest to top quark mass (within 40 GeV)
– The top quark candidate is combined with the other W boson to yield the heavy top partner - T(-5/3)
top quark from heavy T
Recons. heavy Top and B
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Reconstructing the heavy T
• With Mass reconstruction:
• Estimate the following for T5/3 + B:
3 evidence: ~ 250 pb-1 5 observation: ~ 650 pb-1
10 fb-1
• efficiencies for reconstructing 2 W candidates and one top candidate.
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Technicolor
aT;
Extend TCSM2 to include aT
(Bose)
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High mass di-boson resonance:
Technicolor signal: TC W Z (clean with leptonic W & Z decays)
Technicolor (Multiple lepton signature)
GeV
fbfb
fb
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Selection criteria
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Technicolor (Multiple lepton signature)
Triggers: Single, di-leptons
Selection criteria:• 3 isolated leptons (electron or muon)
– Electron pT > 15 GeV, || < 2.5– Muon pT > 15 GeV, || < 2.5
• Missing transverse energy– ET > 40 GeV
• Two oppositely charged leptons with Z invariant mass • Leptonic HT (scalar sum of transverse momenta of leptons) > 150 GeV• Z pT > 65 GeV; • W pT > 65 GeV (computed using lepton and missing Et)
Event Selection Efficiencies: Mass (GeV) Efficiency
300 0.20
400 0.29
500 0.34
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CMS Discovery Potential
5 observation
10 fb-1
Promising LHC discovery channel with clean signature!
Mass (GeV) Num of Signal events Number of Bkg events
300 36.1 15.1
400 36.2 16.1
500 33.7 11.9
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T, aT Mass Reconstruction
The two mass peaks for T and aT are not separated due to the Missing ET resolution. (ATLAS study sees a separation).
Generator LevelAfter Reconstruction
RhoT
aT
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Conclusion
• CMS discovery potential for T(-5/3) and Technicolor decays to multileptons have been evaluated.
• Work done via fastsim
• Move to using full simulation and standard object IDs and corrections.