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Light higgs decay in SUSY cascade - Status report

Light higgs decay in SUSY cascade - Status report. Introduction Trigger efficiency B tagging Jet calibration Invariant mass reconstruction Likelihood fit Conclusion . Filip Moortgat (CERN) Alain Romeyer (Mons - Belgium). LSP MET. Introduction. B tagging.

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Light higgs decay in SUSY cascade - Status report

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  1. Light higgs decay in SUSY cascade - Status report • Introduction • Trigger efficiency • B tagging • Jet calibration • Invariant mass reconstruction • Likelihood fit • Conclusion Filip Moortgat (CERN) Alain Romeyer (Mons - Belgium) Alain Romeyer - January 2005

  2. LSP MET Introduction B tagging Benchmark point LM5 Tan b = 10 AO = 0 µ > 0 M1/2 = 360 GeV M0 = 230 GeV h0 b MSUGRA 5 parameters : m0, m1/2,A, tan b, sign(µ) S. Abdullin – L. Pape Update II of the new MSUGRA test points proposal Signature : Alain Romeyer - January 2005

  3. Simulated events • Production of signal events and pile-up • Signal events : all SUSY channel (easier for later event reweighting) • ~20% contains our decay chain • Digitisation : merge pile-up and signal • official 100 000 evts production at CERNavailable • our reconstruction strategy launched on digis • First results Isajet 7.69 + Pythia 6220 + CMKIN generator FULL SIMULATION CHAIN simulation OSCAR2_4_6 digitisation ORCA7_6_1 Alain Romeyer - January 2005

  4. « Reconstruction » strategy • ORCA_8_6_1 Reconstruction Simulatedevents • II - Jet Reconstruction : • Iterative Cone Algo. • cone size : 0.5 • tower Et thr. : 0.5 GeV • seed Et thr. : 1 GeV I – L1 +HLT Efficiency ? Jet sel. Pt > 10 GeV • III - B tagging : • By Track Counting • Number of tracks above minimum significance : 2 • Analysis • event selection • IV - b ̅b inv mass reco. • MET : • MET from EcalHcalTower Alain Romeyer - January 2005

  5. Trigger efficiency • L1 : 99.9 % - HLT : 96 % Low Lumi. Non cumulative Trigger !!! ~ all events !!! Caveat : ~ same efficiency for SUSY bkg. Alain Romeyer - January 2005

  6. Btagging Track Counting Algo. (default setting) Global efficiency : 49.5 % Global inefficiency : 9.4 % Need to be optimised Filip Nhiggs = Nhiggs after HLT * ( Btag Eff. )² ~ 4700 evts Alain Romeyer - January 2005

  7. Efficiency / inefficiency Alain Romeyer - January 2005

  8. Efficiency / inefficiency… Alain Romeyer - January 2005

  9. Select b jets from h0 Select only b jets coming from h0 decay (from parton content in a 0.3 cone) No jet energy calibration Alain Romeyer - January 2005

  10. Jet reconstruction accuracy Alain Romeyer - January 2005

  11. Jet calibration • Jet calibration method following CMS-note 1999/066 • Association between rec. Jets and generated partons before hadro. (cone < 0.3) • 2 types of jets : b jets and other • Etruejet = sum(Equarks,gluons) • Correction Factor C = Etruejets / Erecjets • Fit of the correction factor surface in the E vs || plane : Alain Romeyer - January 2005

  12. E correction for b jets Alain Romeyer - January 2005

  13. E correction for non b jets Same operation is done with the jet momentum Alain Romeyer - January 2005

  14. Impact on Minv Select only b jets coming from h0 decay Calibrated jets Alain Romeyer - January 2005

  15. Impact on jet reco. accuracy Alain Romeyer - January 2005

  16. Invariant mass (no cuts) Alain Romeyer - January 2005

  17. Likelihood fit NormalisedGaussian Extract from background fit Fraction of signal • Follow the Z’  µµ strategy (CMS AN 2004/018) • Unbinned method • No constraints on the absolute background level only on the background shape • 3 parameters : mh, s and Alain Romeyer - January 2005

  18. Fit result (full stat) Unbinned fit Binned only when plotted Alain Romeyer - January 2005

  19. Various running time 50 000 evts – S = 10.9 100 000 evts – S = 14.1 25 000 evts – S = 7.95 15 000 evts – S = 5.8 Alain Romeyer - January 2005

  20. Conclusion • For the first time the full analysis chain is working • higgs peak visible with significance above 5 • ~15000 evts (~ 40 days of understood data) • Future : • Include SM background • Improve S/B ratio (cuts, b tagging optimisation…) • Reduce the width of the invariant mass • Run the code on the Zbb sample for cross check and optimisation of the reconstruction strategy • Fast simulation (FAMOS) in order to explore the SUSY parameter phase space • Contour plot for the CMS reach Alain Romeyer - January 2005

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