Signal and Background Modeling for H → 4l Peter Vankov UK Higgs Meeting, RAL

Peter Vankov 2/13  Study of the Signal and Background shapes in Higgs → 4l (2µ2e, 4µ, 4e)  Define a model (PDF)  Extract the parameters of the model  Extract the Higgs signal significance Overview Goal:  Signal: So far - Heavy Higgs, M=300 GeV  Background: ZZ → 4l Analysis tools: - Athena, HiggsToFourLeptons package - Standard CSC selection

Peter Vankov 3/13 RooFit What is it? A powerful toolkit for modeling the expected distribution(s) of events in a physics analysis Primarily targeted to high-energy physicists using ROOT Originally developed for the BaBar collaboration by Wouter Verkerke and David Kirkby. Included with ROOT v5.xx Documentation: – for latest class descriptions. RooFit classes start with “Roo”. – for documentation and tutorials Statistical tool

Peter Vankov 4/13 Choosing models Signal PDF(Sig): Breit-Wigner PDF(Sig): Bifurcated Gaussian Background PDF(Bkg): Exponential function

Peter Vankov 5/13 Applying the chosen models H(300 GeV) 30/fb

Peter Vankov 6/13 Total PDF(Signal+Background) = PDF(Bkg) * (1-SB_frac) + SB_frac * PDF(Sig) 30/fb Creating a total (Sig+Bkg) model

Peter Vankov 7/13 Toy MC experiments Performing 200 Toy MC experiments Model 1Model 2 Using RooMCStudy

Peter Vankov 8/13 Sensitivity to model parameters Model 1

Peter Vankov 9/13 Sensitivity to model parameters Model 1

Peter Vankov 10/13 Sensitivity to model parameters Model 2

Peter Vankov 11/13 Sensitivity to model parameters Model 2

Peter Vankov 12/13 Signal Significance Model 1 Model 2 CSC note (7 june’2008): σ = 13.8 H(300 GeV) 30/fb

Peter Vankov 13/13  Work in progress  Looking at other Higgs masses  Experiment with other models  Use custom analysis (alternative to HiggsToFourLeptons) Gauss + Landau BiFurGauss + Landau Summary and To Do