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Light Higgs search in SUSY cascades

Light Higgs search in SUSY cascades . Alain Romeyer (Mons - Belgium) Filip Moortgat (CERN). Introduction (Previous studies) Plans for this analysis Simulation chain Reconstruction and analysis framework Conclusion. LSP MET. Introduction. B tagging. h 0. b. Signature :.

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Light Higgs search in SUSY cascades

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  1. Light Higgs search in SUSY cascades Alain Romeyer (Mons - Belgium) Filip Moortgat (CERN) • Introduction (Previous studies) • Plans for this analysis • Simulation chain • Reconstruction and analysis framework • Conclusion Alain Romeyer - Sept. 2004

  2. LSP MET Introduction B tagging h0 b Signature : • It has been shown in CMS-note 1997/070 : • signal can be seen with • only few months of data • main bkg : SUSY • SM bkg very low • discrimination betweenSUSY signal and SUSY bkg is difficult Alain Romeyer - Sept. 2004

  3. Plans for this analysis • Using the Full simulation and reconstruction • On one particular MSUGRA point (LM5) • Background study : SUSY and SM (t, W, Z + jets…) • Optimise the reconstruction : • Trigger efficiency study • Jet reconstruction and calibration • B tagging efficiency • Reconstruct the bَb invariant mass and then… • If visible : using end-points try to estimate the squark masses • Using the Fast simulation study the CMS reach • Scan the MSUGRA parameter phase space • Provide a sensitivity region in the (m0,m1/2) plane for several luminosities Alain Romeyer - Sept. 2004

  4. MSUGRA Point Benchmark point LM5 Tan b = 10 AO = 0 µ > 0 M1/2 = 360 GeV M0 = 230 GeV MSUGRA 5 parameters : m0, m1/2,A, tan b, sign(µ) S. Abdullin – L. Pape Update II of the new MSUGRA test points proposal • All SUSY channel : 4.9 pb  150 000 evts/year Low Lumi. Alain Romeyer - Sept. 2004

  5. Masses and Branching ratios Branching ratio From Isajet ~ 20% of SUSY events contain our decay chain (~ 30 000 evts/year) Alain Romeyer - Sept. 2004

  6. Simulated events Isajet 7.69 + Pythia 6220 + CMKIN • Production of signal events and pile-up • Signal events : all SUSY channel (easier for later event reweighting) • Private production of 10 000 evts @ Mons(~25 days) • ~20% contains our decay chain • Digitisation : merge pile-up and signal • 100 000 evts production readyusing Digiswaiting for DST generator FULL SIMULATION CHAIN simulation OSCAR2_4_6 digitisation ORCA7_6_1 Low statistic -> only a first try Alain Romeyer - Sept. 2004

  7. « Reconstruction » strategy Reconstruction • II - Jet Reconstruction : • optimisation (large jet multiplicity) • calibration • Energy resolution • … Simulatedevents • Signal • Background : • SUSY • SM : top, QCD… • III - B tagging : • B tagging efficiency • mistagging rate • test of different algorithms • optimise for SUSY cascade (plenty of bs comming from tops and sbottom) I – L1 +HLT Efficiency tables • IV - MET • important for event selection Alain Romeyer - Sept. 2004

  8. Jet reconstruction • Test jet reconstruction and calibration with a Zbb sample (production of 50 000 events already asked) • Position of the peak • Energy resolution • Iterative Cone Algorithm perhaps not adapted to our problems • Splitting and merging of jets is not implemented • Midpoint Cone Algorithm could be an interesting solution Alain Romeyer - Sept. 2004

  9. Physics analysis • VII - Analysis • b ̅b inv mass reco. select the 2 b jets coming from the higgs decay •  reliable fit strategy •  higgs mass • CMS reach CMS sensitivity • VI - Event selection • Reject SM and SUSY bkg •  MET •  Number of jets • … • Optimisation !!! Alain Romeyer - Sept. 2004

  10. Conclusion • Full simulation of signal (and SUSY bkg) done for SUSY LM5 using : • ISAJET 7.69 • Pythia 6.220 • OSCAR_2_4_6 • ORCA_7_6_1 • Plans : • First step : full higgs analysis chain on LM5 • Study trigger efficicency (~95%) • Study jet reconstruction in SUSY cascade environment (calibration !!!) • B tagging efficiency (~50 – 60%) • Study background : SUSY and SM (top, Z+jets…) • Optimize selection criteria (MET, number of jets…) • Fit higgs mass Alain Romeyer - Sept. 2004

  11. Conclusion… • Second step : • Try to reconstruct masses of sparticles in the cascade decay chain using endpoints • Third step : CMS reach • Scan the MSUGRA parameter phase space with fast simulation (FAMOS) • For the moment we have used 10k events, now starting to run on 100k events •  We have already some first results !!! • will be shown in november SUSY BSM meeting. Alain Romeyer - Sept. 2004

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