Techincolor and Heavy TopB search Tulika Bose Meenakshi
Techincolor and Heavy Top/B search Tulika Bose Meenakshi Narain (Brown University) Work done in the context of Les Houches 2007 1
Exotic top partners (Bose, Narain) Some BSM theories predict the existence of: heavy top quark partner heavy bottom • Model suggested by Contino and Servant : ar. Xiv: 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: 2 Figures from slides of a presentation by R. Contino (TH-CERN)
Exotic top partners Some BSM theories predict the existence of: heavy top quark partner heavy bottom • Look for same-sign di-lepton states • reduces the ttbar background • Look for a resonant t. W invariant mass peak (T 5/3) Figures from slides of a presentation by R. Contino (TH-CERN) 3
Hunting for a heavy T • Signal & background samples generated using Madgraph • Pythia showering/hadronisation • Quark/Jet matching a la MLM Signal BKG 4 Table from Contino and Servant : ar. Xiv: 0801. 1679 (2008)
Hunting for a heavy T • • Samples processed via Fastsim CMSSW_1_6_8 Iterative 0. 5 Cone Jets Correct Jets (jet_corrections_16 X) Bkg combined according to expected cross sections 5
Hunting for a heavy T • . . • 2 same sign isolated leptons – (electrons or muons) with | | < 2. 4 • p. T > 50 Ge. V for the leading lepton • p. T > 25 Ge. V for the second leading lepton. • Missing transverse energy > 20 Ge. V. 6
Hunting for a heavy T • . . 1) • At least 5 jets with p. T > 30 Ge. V and | | < 5. 0. • p. T > 80 Ge. V for the second leading jet. • p. T > 100 Ge. V for the leading jet 7
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 T 5/3 + B: 5 observation: ~ 240 pb-1 with sys errors: 30% for signal and 50% for bkg with no sys errors: ~ 230 pb-1 # of Signal events 25. 8; bkg events: 0. 96 8
Reconstructing the heavy T • Reconstructing the first W (from top decay) (eff: 0. 84) – Take the two jets with invariant mass consistent within 20 Ge. V 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(p. T) > 50 Ge. V. • Reconstructing the second W (from heavy exotic top) – Remove jets associated with first W. – Take the two jets with invariant mass consistent within 25 Ge. V of W boson. – Require Rjet< 1. 5 and the W(p. T) > 30 Ge. V. W from top decay W from heavy top 9
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 Ge. V) – The top quark candidate is combined with the other W boson to yield the heavy top partner - T(-5/3) Recons. heavy Top and B top quark from heavy T 10
Reconstructing the heavy T • efficiencies for reconstructing 2 W candidates and one top candidate. • With Mass reconstruction: • Estimate the following for T 5/3 + B: 10 fb-1 3 evidence: ~ 250 pb-1 5 observation: ~ 650 pb-1 11
(Bose) Technicolor a. T; Extend TCSM 2 to include a. T 12
Technicolor (Multiple lepton signature) High mass di-boson resonance: Technicolor signal: TC W Z (clean with leptonic W & Z decays) Ge. V fb fb fb 13
Selection criteria 14
Technicolor (Multiple lepton signature) Triggers: Single, di-leptons Selection criteria: • 3 isolated leptons (electron or muon) – Electron p. T > 15 Ge. V, | | < 2. 5 – Muon p. T > 15 Ge. V, | | < 2. 5 • Missing transverse energy – ET > 40 Ge. V • Two oppositely charged leptons with Z invariant mass • Leptonic HT (scalar sum of transverse momenta of leptons) > 150 Ge. V • Z p. T > 65 Ge. V; • W p. T > 65 Ge. V (computed using lepton and missing Et) Event Selection Efficiencies: Mass (Ge. V) Efficiency 300 0. 20 400 0. 29 500 0. 34 15
CMS Discovery Potential 5 observation 10 fb-1 Promising LHC discovery channel with clean signature! Mass (Ge. V) Num of Signal events Number of Bkg events 300 36. 1 15. 1 400 36. 2 16. 1 500 33. 7 11. 9 16
T, a. T Mass Reconstruction The two mass peaks for T and a. T are not separated due to the Missing ET resolution. (ATLAS study sees a separation). After Reconstruction Generator Level Rho. T a. T 17
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. 18
- Slides: 18