Update on e μ /e / μ  LFV resonance search

1. Update on eμ/e/μ LFV resonance search SUSY LFV group 06-05-2014

2. Updates since EB3 • fixed a bug on jet selection • Correct 2 inconsistency on object selection among different channels (mu isolation and tau overlap removal) • Apply suggestions/comments from EB3 and FAR • note structure and txt • Wjet & QCD further validation & Zμμbkgd check in μ channel • systematics & correlation • Bayesian Vs. Frequentist method for limit extraction • signal theoretical production cross-section calculation All numbers and plots are updated

3. updates Egamma trigger Muon trigger: barrel Muon trigger: endcap • Note edition • add a part for trigger efficiency (Sec. 2.1) • add a subsection for signal event selection after object selection(Sec. 3.5) • add subsections for signal production cross-section (Sec. 5.2 & 5.3) Trigger efficiency study are from Trigger performance group: [58] Tricoli, A. et al., Single Electron Trigger Performance Plots. ATL-COM-DAQ-2012-146, 20 Jun 2012. [59] Muontrigger performances in 2012 (approved plots for CHEP 2013).

4. updates • QCD further validation validate QCD shape with SS Vs OS (also ++ Vs. --) Reasonable agreement

5. updates • Construct a Wjet control region • invert the cut on the angle phi between the leptons: dphi> 2.7 1 <dphi< 2.7 • Missing Et > 30 GeV (enhance W). • Remove opposite sign requirement • Njet< 2 (reduce t‐tbar). • Remove Pt cut (increases statistics). • all other cuts are kept the same as signal event selection • Wjet further charge validation Reasonable agreement

6. updates It seems most of the Zμμbkgd events in μchannel are kept since a mu is mis-identified as a tau • Zμμbkgd study in μ channel • Good Z peak • truth level object match also tell us the tau is from a mu fake

7. updates • Systematics for signal search • correlations between different backgrounds • Systematics for signal search • systematics numbers from table 3 &7&9 in supporting note are mean values for Mll>200GeV, which are dominated by low mass region • it’s difficult to calculate systematics in each mass window for high mass region considering the statistics A correction factor from MC Constant number from data CR WW/Ttbar/Singletop/Zll Similar as: y = a0 – b*x x and y are anti-correlated

8. updates • Systematics for signal search • Construct a control region where signal events are rejected, comparing data Vs. MC and take the difference as systematics • invert the cut on the angle phi between the leptons: dphi> 2.7 1 <dphi< 2.7 • all other cuts are kept the same as signal event selection Put a 20% systematic uncertainty on total background in signal region

9. updates • Statistical methods test for limit extraction: Bayesian Vs. Frequentist • Bayesian method: the using one for this analysis • Frequentist method: a standard package also used by Zeμ group http://root.cern.ch/root/html/tutorials/roostats/StandardHypoTestInvDemo.C.html The central limit value is almost the same , but frequentist method gives smaller uncertainty bands

10. updates • signal theoretical production cross-section calculation Z prime K-factor and systematics are from Z’ group Reference:

11. updates • signal theoretical production cross-section calculation stau neutrino calculated with a NLO generator package Reference:

12. updates • signal theoretical production cross-section calculation stau neutrino calculated with a NLO generator package • Systematics: • PDF • factorization/renormalization scale • s Reference: SUSY group common definition https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/SUSYSignalUncertainties

13. Need to be discussed ? • How to address the 20% systematics for signal region ? • Systematics bands from Frequentist method ? • mu mis-identified as tau ? • Z’ k-factor: directly use Z’ group’s results?

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