Optimization of Isolation Cuts for WZ Searches in 10 TeV pp Collisions

1. Search for W′➟WZin 10 TeV pp Collisions

2. Backgrounds 200 pb-1

3. Proposed Cuts (from WZ note) • Muon ID • Isolation: 5 GeV threshold in calo, 2 GeV in tracker • Impact parameter significance: b/σb < 3 • Electron ID • SimpleLoose for Z, SimpleTight for W • Z Reconstruction • Both leptons: pT > 15 GeV • 81 GeV < MZ < 101 GeV • Veto on second Z candidate • W Reconstruction • ΔR(eZ,µW) or ΔR(eW,µZ) > 0.1 • MT cut > 50 GeV

4. Proposed Change toL2 Muon Calorimeter Isolation

5. HLT_IsoMu9 Path Prescaled L1 Candidates pT > 5 GeV? Thresholds vary according to |η| L1Filtered Calo Isolation Conesize = 0.24 2.0 < Thresh < 4.0 Refit with regional info (CSCs or DTs) L2PreFiltered Tracker Isolation Conesize = 0.24 0.8 < Thresh < 1.2 pT > 9 GeV (uses 90% CL) L2IsoFiltered Refit with tracker info L3PreFiltered d0 < 2.0 pt > 11.0 L3IsoFiltered

6. Existing Isolation Cut Region • Calorimeter towers excluded in a veto cone of Δr < 0.1 centered on the parameters propagated to the calorimeter • Calorimeter towers summed in a cone of Δr < 0.24 centered on the parameters at vertex • A threshold is applied based on the candidate’s eta value Isolated Candidates

7. Proposed Isolation • Abandon the eta-dependent threshold in favor of a pT-dependent cut that relaxes with higher pT • We choose a functional form quadratic in pT: • The plots show the full pT range, but the L2 pT cut of 7 GeV is enforced in efficiency calculations • No isolation is imposed for L2 candidates with pT > 15 GeV, where a non-isolated trigger would take over

8. Approach • Look at the interaction of isolated and non-isolated triggers • HLT_IsoMu9 has an L2 pt cut of 7 GeV • HLT_Mu15 has an L2 pt cut of 12 GeV • Want to maximize rejection and efficiencies in the pt range before the non-isolated trigger takes over

9. Samples Used • Summer08_IDEAL_V9_v1 • Plots are normalized by cross-section to correspond to the integrated luminosity of the Z sample (~1 fb-1) • We consider only L2 objects matched to a generated muon which is a daughter of desired event

10. Iso by Towers Cut Region Rate passed to L3 reduced by 30% L2 pT Cut Current Iso Threshold (approx.)

11. Iso by Ecal Crystals Cut Region Rate passed to L3 reduced by 38% L2 pT Cut Current Iso Threshold (approx.)

12. Efficiency of the Isolation Cut • The following slides show the efficiency of the tower-based isolation cut with pt-dependent threshold • The structure of the calorimeter leads to eta-dependent structure in the isolation deposits, so we want to relax our criteria in regions where calorimeter response is greatest

13. Efficiency of Isolation Cut vs. pT • The pt-based cut allows a smooth rise in efficiency with pt

14. Eta Distribution • The existing isolation uses a complex eta-dependent threshold to ensure a flat efficiency in eta • We would like to adjust the thresholds from the pt-dependent but to allow a flatter eta distribution as well

15. Efficiency of Isolation Cut vs. eta • Eta-Dependent • pt-Dependent

16. Threshold Scaling by eta • If we scale the pt-based thresholds up in proportion to the eta-based thresholds, we can restore a nearly flat distribution