1. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search1 Status of the ZZ  llbb search for the zh-llbb Team S.B. Beri, S. Caughron, M.-C. Cousinou, S. Desai, S. Dutt, M. Mulhearn, E. Nagy, H. Nguyen, L. Welty-Rieger, T. Yasuda E. Nagy CPPM/Fermilab

2. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search2 Same analysis as the ZH  llbb search until the RF training RF training (Satish) - M bb = 91 GeV - WZ and ZZ considered as signal instead of background

3. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search3 More plots on: http://www-d0.fnal.gov/Run2Physics/higgs/zh_llbb/d0_private/plots/latest_summer2011/mva/all/

4. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search4 We decided to use collie: exampleXsecMeasurement.cc - since we use collie (exampleLimitCalculation.cc) already in the ZH search - WZ  lvbb and ZZ  vvbb analyses use also collie collie input files produced by Satish - usual file: data/bkgd/signal - signal injected file for test: data  signal+background

5. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search5 Result (CLfit2) on the usual data file was disappointing: Signal Scale Factor: 0.000, Err: 0.491 We have double checked the collie IO format: - took out one of the signals (WZ) - Satish has merged the 2 signals into 1 (as in the HZ case) Same result: Signal Scale Factor: 0.000 We have double checked the collie setup – thanks to Gabriel Gabriel suggested to use the signal injected pseudo data file: It should result in Scale Factor = 1 if collie is doing correctly And indeed: Signal Scale Factor: 0.988, Err: 0.681

6. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search6 Maybe the data don’t contain significant di-Boson signal? Based on the Maximum Likelihood method I have traced the likelihood and log-likelihood vs the signal scale factor, f (see next slide). The data, bkgd and signal were taken from collie. These functions have clear maxima for both real and pseudo data. The scale factors are above 0 by more than 1 st. dev: f = 0.85 +/- 0.5 for data 1.00 +/- 0.5 for data replaced with sig+bkgd (not including (yet) systematic uncertainties) Conclusion: we do have a ZZ  llbb signal in our data we have to figure out why collie doesn’t find it e.g. looking at the collie LLR distributions per channels and for Null and Test hypotheses (Gabriel proposes a long list to do)

7. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search7 Log-LikelihoodLikelihood Real Data Pseudo Data = Signal+Background

8. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search8 Backup slides

9. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search9 The log-likelihood L vs scale factor f d i – data or pseudo-data b i – background s i – signal in bin i

10. E. Nagy - Low Mass Higgs 28th July 2011 Status of the ZZ-->llbb search10