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Update on Search for light Higgs in SUSY cascades

SUSY-BSM meeting January 20 th 2006 CERN. Update on Search for light Higgs in SUSY cascades. Filip Moortgat (CERN) Philip Olbrechts (CERN) Alain Romeyer (Mons – Belgium). Used simulated data and analysis techniques Invariant mass and mass resolution for different cut series

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Update on Search for light Higgs in SUSY cascades

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  1. SUSY-BSM meeting January 20th 2006 CERN Update on Search for light Higgs in SUSY cascades Filip Moortgat (CERN) Philip Olbrechts (CERN) Alain Romeyer (Mons – Belgium) • Used simulated data and analysis techniques • Invariant mass and mass resolution for different cut series • Overview data sets and tracker misalignment • Conclusions and outlook

  2. Data samples / Reconstruction • ~ 61000 events - containing all SUSY channels - were produced at LM05. • ~ 20 % is the desired signal. • The main background contribution is expected to come from • the 80 % remaining SUSY events. • “su05_pyt_LM5” instead of “su03_msugra_lm5” • (4 trials on GRID result in ~ 61000 events of the ~98500 events available) • SM background events have been included. • ~ 1300000 events (PubDB: jm03b_Ttbar_inclusive) • Z+jet ~ 50000 events (PubDB: jm03b_Zjets_250_400) • W+jet ~ 50000 events (PubDB: jm03b_Wjets_250_400) • qcd ~ 200000 events (PubDB: jm03b_qcd_50_80) • qcd~197000 events (PubDB: jm03b_qcd_170_230) • qcd ~ 100000 events (PubDB: jm03b_qcd_300_380) • The jet reconstruction is based on the “iterative cone algorithm” • (cone size: 0.5) using the “SplittedEcalPlusHcalTowerUEInput” input. • The combined b-tagging algorithm was applied using jets with Pt > 30 GeV. • The Jet calibration is based on the official Jet calibration (GammaJet). • DST information was read, using ORCA_8_7_4. BUG FOUND!

  3. Analysis techniques • First selection is based on Level 1 trigger and JetMET HLT • trigger with a total signal selection efficiency of 79.5 % • Reconstruction of the b invariant mass spectrum: • Jet pairing is crucial as there are many possibilities. • Application of the ‘model independent’ hemisphere separation algorithm. • Try all possible combinations of reconstructed b tagged jets within • each hemisphere.

  4. Summary of former applied selection cuts • Number of jets 4 • Number of b-jets 2 • B-tagging quality estimator S > 1.5 • Missing Transverse Energy (MET) 200 GeV • Highest “jet transverse momentum” 150 GeV • 2nd Highest “jet transverse momentum” 100 GeV

  5. Old invariant mass distribution SUSY signal + SUSY background + W+jet + Z+jet + + QCD “Old data files” SUSY signal Signal with two b jets coming from the Higgs SUSY background Bug: cut on Pt of jet > 30 GeV not applied

  6. New invariant mass distribution SUSY signal + SUSY background + W+jet + Z+jet + + QCD # Events / 10 GeV SUSY signal Signal with two b jets coming from the Higgs SUSY background Invariant Mass (GeV)

  7. The corresponding mass resolution The width of the signal peak is mainly determined by the jet resolution of the detector as the intrinsic decay width varies from 3.3 MeV to 4.3 MeV. # Events # = 624 # = 180 Reconstructed Higgs mass – Generated Higgs mass (GeV)

  8. Optimising analysis cuts using “GARCON” (M. Spiropulu, A. Drozdetskiy, G. Karapostoli, et al.) • B-tagging quality estimator S > 1.5 The cuts remain fix for now! • Number of jets 4 • Number of b-jets 2 • Missing Transverse Energy (MET) 200 GeV • Highest “jet transverse momentum” 150 GeV • 2nd Highest “jet transverse momentum” 100 GeV GARCON • Missing Transverse Energy (MET) > 101 GeV • Highest “jet transverse momentum” > 283 GeV • 2nd Highest “jet transverse momentum” > 162 GeV “The softer cut on MET is compensated by hard cuts on the Pt jets” • 3rd Highest “jet transverse momentum” > 66 GeV • 4th Highest “jet transverse momentum” > 55 GeV • Highest “b-jet transverse momentum” > ~ 30 GeV • 2nd Highest “b-jet transverse momentum” > ~ 30 GeV

  9. Analysis results “GARCON” “Same colour code” # Events / 10 GeV # = 456 # = 81 Invariant Mass (GeV) # Events Reconstructed Higgs mass – Generated Higgs mass (GeV)

  10. Cross-check analysis results “GARCON” Increase cut value of MET cut from 200GeV to 250 GeV! • B-tagging quality estimator S > 1.5 • Number of jets 4 • Number of b-jets 2 • Missing Transverse Energy (MET) 250 GeV • Highest “jet transverse momentum” 150 GeV • 2nd Highest “jet transverse momentum” 100 GeV

  11. Results cross-check “Same colour code” # Events / 10 GeV # = 484 # = 84 Invariant Mass (GeV) # Events Reconstructed Higgs mass – Generated Higgs mass (GeV)

  12. Check influence of b-tagging quality estimator S Increase cut value of b-tagging quality estimator S from S > 1,5 to S > 2 ! • B-tagging quality estimator S > 2 • Number of jets 4 • Number of b-jets 2 • Missing Transverse Energy (MET) 250 GeV • Highest “jet transverse momentum” 150 GeV • 2nd Highest “jet transverse momentum” 100 GeV

  13. Results check b-tagging quality estimator S “Same colour code” # Events / 10 GeV # = 381 # = 55 Invariant Mass (GeV) # Events Reconstructed Higgs mass – Generated Higgs mass (GeV)

  14. Check the space angle between the two b-tagged jets is typically smaller for signal events • B-tagging quality estimator S > 1,5 • Number of jets 4 • Number of b-jets 2 • Missing Transverse Energy (MET) 200 GeV • Highest “jet transverse momentum” 200 GeV • 2nd Highest “jet transverse momentum” 150 GeV • 3rd Highest “jet transverse momentum” 50 GeV

  15. Results: cut on space angle “Same colour code” # Events / 10 GeV # = 289 # = 25 Invariant Mass (GeV) # Events Reconstructed Higgs mass – Generated Higgs mass (GeV)

  16. Overview data samples • SUSY events: • ~ 61000 SUSY events generated “su05_pyt_LM5” (= 7,5 pb) • SM background events: • ~ 1300000 events generated “jm03b_Ttbar_inclusive”( = 830 pb) • Z+jet ~ 50000 events “jm03b_Zjets_250_400” • W+jet ~ 50000 events “jm03b_Wjets_250_400” • qcd ~ 200000 events “jm03b_qcd_50_80” • qcd ~197000 events “jm03b_qcd_170_230” • qcd ~ 100000 events “jm03b_qcd_300_380” No event passes previously described series of cuts Tracker misalignment • the “short term” misalignment scenario (strips: 100 m / pixels: 10 m): • 17 % reduction in signal selection efficiency • the “long term” misalignment scenario (strips: 20 m / pixels: 10 m): • 10 % reduction in signal selection efficiency

  17. Conclusions and outlook • The analysis has been re-made using the latest SUSY signal events at LM5. • The bug “jet Pt > 30 GeV” is fixed! • Increasing the cut on the b-tagging quality estimator S reduces with • ~ 35 % while SUSY signal is reduced with ~ 21 %. • More Standard Model backgrounds ( , W + jet, Z + jet, QCD) are • included in the analysis results. • The problem of the combinatorial background might get solved by selecting • only that combination of b-tagged jets with the smallest for that event. • The work on the endpoint distributions - to extract the sparticle masses – is • progressing, but also other methods are being considered. • We will use FAMOS to study the CMS reach, i.e. scan the MSUGRA • parameter phase space so that a sensitivity region in the (m0,m1/2) plane • can be provided for several luminosities.

  18. Backup: Jet resolution of the detector

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