techincolor and heavy top/b search

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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.