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Analyses of light higgs decays for the CLIC CDR

Tomas Lastovicka (Czech Academy of Sciences ) Christian Grefe (CERN and University of Bonn ) Jan Strube (CERN ) Frederic Teubert (CERN ) Blai Pie Valls (University of Barcelona). Analyses of light higgs decays for the CLIC CDR. Overview. CLIC environment H  bb

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Analyses of light higgs decays for the CLIC CDR

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  1. Tomas Lastovicka(Czech Academy of Sciences) Christian Grefe (CERN and University of Bonn) Jan Strube (CERN) Frederic Teubert (CERN) BlaiPie Valls (University of Barcelona) Analyses of light higgs decays for the CLIC CDR

  2. Overview • CLIC environment • H bb • Largest BF in the Standard Model • Flavour Tagging (in the presence of background) • H  μμ • Coupling to second-generation fermions • Momentum resolution (in the forward region) • Summary Light Higgs Decays - LCWS11

  3. The CLIC environment • CLIC_SID detector • Similar toSiDdetector • 27 mm radius inner vertex layer • 7.5 λ W-HCAL barrel • Tracking coverage down to 10° Light Higgs Decays - LCWS11

  4. The CLIC beams • 0.5 ns bunch spacing • 312 bunches / train • 50 Hz train repitition rate Light Higgs Decays - LCWS11

  5. Backgrounds at CLIC • 19 TeV from • 1.2 TeV in a 10ns readout window Light Higgs Decays - LCWS11

  6. The CDR benchmark point Signal channel Standard Model mH=120 GeV Light Higgs Decays - LCWS11

  7. Setup • Whizard 1.95 for generation of signal events • Pythia 6.4 for hadronisation • 60 BX mixed in • GEANT 4 simulation • Full reconstruction (PandoraPFA) • 100 ns readout window in HCAL barrel • 10 ns everywhere else • 2 / ab measurement Light Higgs Decays - LCWS11

  8. Higgs decays to bottom and charm Light Higgs Decays - LCWS11

  9. Pre-selection • FastJetkt algorithm, Rmax=0.7 • Try to force into two jets • Durham algorithm fails in presence of background Light Higgs Decays - LCWS11

  10. Flavour Tagging • LCFI with FastNN neural net Light Higgs Decays - LCWS11

  11. Event selection • Supplement flavour tagging network w/ additional variables Light Higgs Decays - LCWS11

  12. Results • Cut-and-count method • Measure signal and background events in “signal box” (NN cut) • Change definition from b to background and c to signal to measure h  cc Light Higgs Decays - LCWS11

  13. Higgs decays to muons Light Higgs Decays - LCWS11

  14. Higgs decay to muons • Rare decay, BF ~ 10-4  Testsexcellent momentum resolution Light Higgs Decays - LCWS11

  15. Analysis Strategy • Reconstruct two identified muons • Boosted Decision trees classifier • Likelihood fit Bonus • Electron Tagging study • Muon momentum resolution study Light Higgs Decays - LCWS11

  16. Results • BDT helps with low signal efficiency of rectangular cuts • Average of three independentlikelihood fits Light Higgs Decays - LCWS11

  17. Electron Tagging in the forward region • LumiCal (Θ > 3.5°) • Assume 95% rejection • BeamCal (Θ > 1.7°) • Assume 50% rejection Light Higgs Decays - LCWS11

  18. Momentum resolution Light Higgs Decays - LCWS11

  19. Summary • CLIC background adds a significant challenge to reconstruction • Benefits of large cross sections still outweigh • Measurements of SM Higgs decays serve as excellent tools for detector (and reconstruction) benchmarking Light Higgs Decays - LCWS11

  20. Supplementary Material Light Higgs Decays - LCWS11

  21. Muon identification Light Higgs Decays - LCWS11

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