Trigger studies for GMSB with photons (Internal note for approval)

1. Trigger studies for GMSB with photons(Internal note for approval) ShileiZang Bernadette Heyburn, UrielNauenberg University of Colorado, Boulder TSG Meeting, 19th Mar. 2008

2. Outline • GMSB with photons • Signal and background samples • Efficiency and rate for default triggers • A new method to optimize triggers • Optimization of 3 triggers • Results • Compare rate with other studies • Summary

3. GMSB with photons • Gauge Mediated SupersymmetryBreaking models • NLSP (neutralino)  LSP (gravitino) + photon • Prompt decay (ctau=0) g jet • Experimental signature q q jet • high pT photons • large MET due to gravitinos • multi-jets … p p q … jet q jet g

4. Λ: scale of the SUSY beraking • M: messenger mass scale • tanβ: the ratio of the Higgs vev • N5: number of messengers • sign(μ): the sign of Higgsino mass term • Cgrav : sets NLSP lifetime GMSB parameters

5. GMSB signal samples: • CSA07 samples of GMSB photons to estimate the signal efficiency. • GEN-SIM: 1_4_X; DIGI-RAW: 1_6_7. • 100k for each point: GM1b, GM1c, GM1e, GM1f, GM1g • Background samples: • 1_6_0-PreCSA07 (or 1_6_7-CSA07) samples are used to estimate the background rates, which include: • Photon jets (all pt bin) (CMSSW_160-PreCSA07) • QCD jets (all pt bin) (CMSSW_160-PreCSA07) • Wenu, Zee (CMSSW_167-CSA07) • Totally processed about15 million events to minimize the error of rate. • The study have been done under 1_6_0, and optimized for start-up luminosity of 1032 cm-2s-1. • HLTriggerOffiline/Egamma package is used for the study.

6. HLT paths for photons

7. Number of bkg events processed for rate estimation

8. Efficiency and rate for default triggers RS S H RD S S, RS S, RS, D S, RS, D, RD S, RS, D, RD, H all D VH

9. Strategy: • Three triggers for GMSB photons: • Optimize the two triggers: EMHighEt (H), and EMVeryHighEt (VH). • Choose another one from: D, RD, RS, MET, or Jets • How to optimize the triggers?

10. Optimize trigger thresholds • Usually the cuts are determined by eye to give reasonable values of efficiency and rate. Threshold, how to set? • Problem:How to optimize the trigger thresholds with figures of Efficiency vs. Rate in an objective way ?

11. Physics Analysis • Selection criteriaare optimized to maximize statistics (Optimize relative error of BR; Significance; 90% CL limit, etc) • Selection criteria are optimized to minimize the mass uncertaintyin mass measurement (e.g. top mass measurement) • Artificially reduced the error of physical result! • Not Really Blind !!

12. Information theory • N events, the amount of information :log2 N. • N is number of messengers; • physical results are the meaning of information taken by such N messengers. • For BR, number of messengers is the meaning of info.; • For width, mass, … , meaning of info. is taken by the messengers; depends on the kinematics (not just on the number of events). • Good property: log (xy)= log(x) + log(y).

13. Amount of information: log(NS ),log(NB ) • Signal efficiency ε and background efficiency b • After the cut: log(NSε), log(NB b) • Reductions of information: -log(ε), -log(b) • Ratio of the reductions: log(ε)/ log(b) • the smaller log(ε)/ log(b), the better • log(ε)/ log(b) <a  ε > ba (0< ε, b, a ≤1). • We can use statisticslog(ε)/ log(b) to optimize trigger thresholds! • Good property: Blind Analysis! • log(ε)/ log(b) depends on the amount of information; does not depend on the meaning of information.

14. a=0.01 ε a=0.05 ε a=0.02 a=0.1 (1.,1.) a=0.2 a=0.3 a=0.5 Trigger Study ε= ba a=0.7 a=1.0 b log(ε)/ log(b) <a  ε > ba . b (0.,0.) 1-b b MVA K ID ε ε

15. How to deal such a problem in Physics Analysis? • Solution: log(ε)/ log(b) to optimize selections with finalεandbafter the kinematics cut. • Our method will give worse physical results, but they are blind analysis and can be trusted.

16. log(ε)/ log(b) vs. Cuts (default EMHighEt) Min=0.129 0.129 • Et>80; Iecal<5; Ihcal<12; Itrack<4 • Itrack is better than Iecal and Ihcal. 0.035 Min=0.0047 0.102 Min=0.101 0.017 • Each figure is plotted with other cuts applied.

17. log(ε)/ log(b) vs. Cuts (proposed EMHighEt) Min=0.174 • Et>60; Itrack<2 • Itrack is better only when the Itrack cut point <5 0.022 Min=0.190 0.068

18. Et>40GeV Relaxed Single Photon candidates Et>40GeV Et>40GeV

19. Propose two new triggers: • p-EMHighEt (pH): Et>60GeV, Itrack<2 • p-EMVeryHighEt (pVH): Et>120GeV • Propose to use: pH, pVH, D for our physics. • Isolation is useful at low Et region to suppress bkg , but bad in high Et region for our signal. • Track isolation (cut position <6) is better than other isolaitons • GMSB points with small Lambda parameter (GM1b) have more events with two signal photons at generator level, so the Double trigger is helpful for them.

20. 2.14 Hz

21. Further possible improvement • D: Et>20; Iecal<2.5; Ihcal<8 or 6; Itrack<3 (0.26 Hz) • mD: Et>20; Itrack<3 (0.90 Hz) 0.64 Hz • It’s easy to reach 92% or 93% efficiency with 3.5 Hz, but difficult to reach 95% efficiency within 5.5 Hz! • 98.6% events have signal photons at generator level; after SusyAnalyzer, only 93.5% events have reconstructed photons.

22. Efficiency and Rates for each group of triggers pH, pVH, D pH, pVH, mD 10: pH, pVH 11: pH, pVH, RS 12: pH, pVH, RD 13: pH, pVH, D 15: pH, pVH, mD 0: H, VH 1: H, VH, RS 2: H, VH, RD 3: H, VH, D

24. Compare the rates with other studies in 13X and 16X Agree well Agree with error

25. Summary • We give the rates of all HLT paths on photons, which are comparable with 13X exercise and other studies in 16X. • Our rates have small errors. • We propose to modify EM1HighEt and EM1VeryHighEt tirggers (basically loosen the isolation variables and Et). • We propose to use 3 triggers for GMSB photons, which can reach ~93% efficiency with 3.2 Hz. • We find a new method for trigger study, and physics analysis. • The draft of the note: • http://www-hep.colorado.edu/~slzang/cmsnote_gmsb_trigger_v3.ps Thank you!