Search for Narrow Resonance Decaying to Muon Pairs in 2.3 fb -1

1. Search for Narrow Resonance Decaying to Muon Pairs in 2.3 fb-1 Ye Li on behalf of CDF Collaboration University of Wisconsin-Madison

2. Motivation • Theory Driven • Standard Model successful but incomplete • Strong discovery potential in dimuon channel • New models predict narrow neutral resonance, e.g. • Additional U(1) symmetry: Z’ • Extra space-time dimension: Randall-Sundrum graviton • Focus on Z’ →  channel APS April Meeting, St. Louis - 14 April 2008

3. Motivation • Experiment Driven • Last Tevatron dimuon resonance searches performed with integrated luminosity 200 pb-1 → Our search: L ≈ 2.3 fb-1 of CDF Run II data • Significant increase of sensitivity to dielectron and diphoton channels • Excellent tracking resolution (Central Outer Tracker, Drift Chamber) APS April Meeting, St. Louis - 14 April 2008

4. Methodology • Model Drell-Yan background and signal resonance with PYTHIA + detector simulation • Use Z region for normalization • Remove uncertainty on luminosity • Easy accounting APS April Meeting, St. Louis - 14 April 2008

5. Methodology • Inverse Mass (1/m) Scan • Excellent angular resolution → negligible • High PT track curvature (~1/PT) resolution constant → constant 1/m resonance width CDF Run II Preliminary 1/m ≈ 0.16/TeV APS April Meeting, St. Louis - 14 April 2008

6. Methodology • Fit for NZ’ (number of Z’ candidate) • Calculate Binned Poisson likelihood L(NZ’;MZ’) for region 1/m < 10/TeV • Construct the narrowest possible interval in NZ’ at 95% C.L. • Scan for resonance • Significance determined byMonte-Carlo pseudo-experiments APS April Meeting, St. Louis - 14 April 2008

7. Dataset & Selection • Dataset from high PT muon trigger • Dimuon event selection • Two opposite-sign tight muons • At least one muon passing the trigger CDF Run II Preliminary APS April Meeting, St. Louis - 14 April 2008

8. Efficiency • Mass dependence • Track and muon-hit cuts independent of mass • Momentum dependence • Normalization of background expectation • Only consider P dependence • No P dependence of trigger eff. for PT > 30 GeV • Separate the sample into signal and normalization (Z-pole) regions APS April Meeting, St. Louis - 14 April 2008

9. Acceptance • Comparison of muon in W →  data vs. simulation for two muon detector regions CDF Run II Preliminary || < 0.6 (CMUP) 0.6 < || < 1.0 (CMX) APS April Meeting, St. Louis - 14 April 2008

10. Acceptance • Mass-dependent Acceptance • Larger mass → Lower boost → More central events → Larger acceptance CDF Run II Preliminary APS April Meeting, St. Louis - 14 April 2008

11. Background • Drell-Yan */Z →  • PYTHIA + Simulation • WW and tt-bar • PYTHIA + Simulation • Cosmic Rays • Identified Cosmic-ray samples • QCD Jets and Decays-in-Flight • Data APS April Meeting, St. Louis - 14 April 2008

12. Drell-Yan • Dominant source for background • Dominant source for systematic uncertainty • Mass spectrum affected by higher-order corrections • Calculate up to next-to-next-to leading order (NNLO) correction → k-factor • Different Calculations give different k-factors • Average k-factor; Difference as uncertainty APS April Meeting, St. Louis - 14 April 2008

13. Signal Scan • Pseudo-experiment: MZ’ = 250 GeV CDF Run II Preliminary Most likely distribution of NZ’ APS April Meeting, St. Louis - 14 April 2008

14. Signal Scan • Expected limits on NZ’ from 1000 pseudo-experiments on 50 Z’ masses Data: to be implemented …! CDF Run II Preliminary APS April Meeting, St. Louis - 14 April 2008

15. Summary • Use 1/m distribution for constant resolution to search for Z’ • Fitter and Simulation in place to study signal acceptance and identification efficiency • Systematic uncertainties to be determined • Signal scan performed on pseudo-experiments • Ready to unblind the data soon APS April Meeting, St. Louis - 14 April 2008