Electron and muon reconstruction in single lepton tT events ( Analysis Note 2005-024 )

1. Electron and muon reconstruction in single lepton tT events(Analysis Note 2005-024) (short!) update of previous session new definition of some observables less sensititive to Pile-Up effects updated all results in discussion with referees ... focus on main updated items Jorgen D’Hondt (Vrije Universiteit Brussel) on behalf of also S.Lowette and J.Heyninck PRS General Meeting, CERN, 6th of December 2005 Referees : Anne-Sylvie Giolo-Nicollerat, Martin Grünewald

2. Illustration Used 5.41fb-1 of ttbar events Select correct lepton Jorgen D'Hondt (Vrije Universiteit Brussel)

3. Classifying the reconstructed lepton Classify the reconstructed objects identified as leptons in two categories via the Monte Carlo truth information. Determine for each lepton candidate in the final state. non-W-like W-like non-W-like 0.2 Takes into account double counted reconstructed electron candidates • distribution of the DR of all reconstructed lepton candidates (e/m) in the final state • robustness against the used metric was checked: (h,f) versus (q,f) DR=0.2 → where one distribution goes up on top of the background Jorgen D'Hondt (Vrije Universiteit Brussel)

4. Differentiating the two classes sensitive observables Jorgen D'Hondt (Vrije Universiteit Brussel)

5. Observables for the W→mnm decay 2.0 GeV (PU) log(pT) Eiso aiso SZ log(pTiso) • Distribution on the left • Likelihood Ratio S/(S+B) on the right Jorgen D'Hondt (Vrije Universiteit Brussel)

6. Observables for the W→ene decay 3.6 GeV (PU) log(pT) Eiso aiso SZ • Distribution on the left • Likelihood Ratio S/(S+B) on the right log(pTiso) Same tendencies for electrons and muons, as expected Jorgen D'Hondt (Vrije Universiteit Brussel)

7. Combined Likelihood Ratio Variable Second bump has disappeared due to new definitions linear scale muons electrons logarithmic scale Correct lepton is the one with the highest Combined LR value Jorgen D'Hondt (Vrije Universiteit Brussel)

8. Comparing with other methods muons electrons cut on the LR-value and scan this LR-cut Event selection efficiency of the Likelihood Ratio method much less sensitive to Pile-Up effects, which can reach 4% when using a sequential cut based approach. Jorgen D'Hondt (Vrije Universiteit Brussel)

9. Pile-Up influence on observables about 0.5GeV effect no effect Jorgen D'Hondt (Vrije Universiteit Brussel)

10. Energy deposits in the calorimeter Jet clustering algorithms usually start from the collection of calorimeter deposits, but also the lepton creates these deposits and can radiate photons. These calorimeter deposits should be removed before performing the jet clustering algorithm. It can be seen that there is an asymmetry between the deposits in f and q, due to the magnetic field along the z-direction. The deposits around the chosen lepton within an asymmetric cone of opening 0.1rad in q and 0.05rad in fshould be removed. muon electron Pile-Up included Plots have changed due to the propagation of the lepton to the calorimeter surface Jorgen D'Hondt (Vrije Universiteit Brussel)

11. Outlook in use cases • Update of previous presented studies (PRS meeting November) • Variable created which differentiates W-like and non-W-like leptons • also differentiates between fake electrons or muons • several sensitive observables are combined with a Likelihood Ratio method • it was shown that one can increase the event selection efficiency (wrt.HLT) • the definition of some variables were updated (= simplified) • Comments from referees were implemented and discussed thoroughly in the updating process • thanks to both Anne-Sylvie and Martin for their constructive and valuable comments Jorgen D'Hondt (Vrije Universiteit Brussel)