1 / 20

Update on Search for light Higgs in SUSY cascades

SUSY-BSM meeting February 17 th 2006 CERN. Update on Search for light Higgs in SUSY cascades. Filip Moortgat (CERN) Philip Olbrechts (CERN) Alain Romeyer (Mons – Belgium). Simulated data and analysis techniques used Invariant mass and mass resolution

ianthe
Download Presentation

Update on Search for light Higgs in SUSY cascades

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SUSY-BSM meeting February 17th 2006 CERN Update on Search for light Higgs in SUSY cascades Filip Moortgat (CERN) Philip Olbrechts (CERN) Alain Romeyer (Mons – Belgium) • Simulated data and analysis techniques used • Invariant mass and mass resolution • Fitting procedure: extraction of Higgs mass and significance • Systematics: jet calibration • Conclusions and outlook

  2. Data samples / Reconstruction • ~ 98500 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. • 9 trials on GRID result in ~ 97000 events “su05_pyt_LM5”. • 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.

  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. • Take only that combination of reconstructed b tagged jets for which • the space angle is smallest and

  4. Overview of selection cuts applied • 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 • < 1.5 (See backup slides for individual distributions)

  5. Overview of selection/rejection efficiencies Number of events (weighted to the SUSY events) that pass the sequential cuts, starting with the trigger requirement. DATA TRIGGER NJET NBJET MET MAXPTJET MAXPT2JET MAXPT3JET DR SIGNAL 17480 17332 7234 5095 4950 4077 4033 1385 SUSY BG 62490 57489 7598 5755 5584 4547 4431 1175 TTBAR 234580 215720 44623 8384 7146 2860 2609 212 Z+JET 9.9e+06 1.7e+06 20176 6725 6725 0 0 0 W+JET 1.1e+08 2.2e+07 196395 78558 58919 39279 19640 0 DATA TRIGGER NJET NBJET MET MAXPTJET MAXPT2JET MAXPT3JET DR SIGNAL 100 99.2 41.3 29.1 28.3 23.3 23.1 7.9 SUSYBG 100 92.0 12.2 9.2 8.9 7.3 7.1 1.9 TTBAR 100 92.0 19.0 3.6 3.0 1.2 1.1 0.09 Z+JET 100 16.9 2.0 0.07 0.07 0 0 0 W+JET 100 19.8 0.18 0.07 0.05 0.04 0.02 0 The same number of events in %, normalised to the number of events that pass the trigger. Note: - due to limited statistics the , Z+jets and W+jets have the weights 7.8 , 6725.3 and 19639.5 respectively! - the hemisphere and b-tagging discr. cuts are not accounted for.

  6. Invariant mass distribution without SM bg # Events / 10 GeV SUSY signal + SUSY background SUSY signal Signal with two b jets coming from the Higgs SUSY background Invariant Mass (GeV)

  7. Invariant mass distribution with SM bg SUSY signal + SUSY background + W+jet + Z+jet + + QCD # Events / 10 GeV # = 482 # = 21 x 7.8 = 164 SUSY signal Signal with two b jets coming from the Higgs SUSY background Invariant Mass (GeV)

  8. The corresponding mass resolution # Events Reconstructed Higgs mass – Generated Higgs mass (GeV)

  9. Fitting procedure In order to extract the higgs mass and evaluate the signal significance, a simple fit method has been developed. # Events / 10 GeV polynom of order 5 with the following parameters: par 0 = -124.252 par 1 = 5.31716 par 2 = -0.0440705 par 3 = 0.000152914 par 4 = -2.44607e-07 par 5 = 1.49237e-10 Invariant Mass (GeV)

  10. Fitting procedure The global fit function F is where N is a normalisation factor and alpha is the fraction of signal in the global distribution. # Events / 10 GeV Invariant Mass (GeV) The significance S is extracted within a 2 sigma region around the fitted higgs mass and is defined as:

  11. Systematics: jet calibration Changing the correction factor of the “HepLorentzVector” of the jets by – 7.5 % and +7.5 % results in a shift of -6.8 GeV and + 8.2 GeV respectively. Number of events

  12. Conclusions and outlook • The SUSY event sample su05_pyt_LM5 is now complete (bug in PubDB). • The problem of the combinatorial background is solved by selecting • the combination of b-tagged jets with the smallest space angle. • The fitting procedure results in a higgs mass = 105.9 +/- 1.8 GeV while a • higgs mass = 116 GeV is expected (status b-jet calibration correction ?) • The higgs mass resolution is 17.4 +/- 1.9 GeV while a significance S ~ 20 • is obtained. • The analysis note is being finalized and is planned to be released • on the 28th of February 06. • 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.

  13. Number of jets 4 SUSY background SUSY signal Z + jet W + jet

  14. Number of b-jets 2 SUSY background SUSY signal Z + jet W + jet

  15. Missing Transverse Energy (MET) 200 GeV SUSY background SUSY signal Z + jet W + jet

  16. Highest “jet transverse momentum” 200 GeV SUSY background SUSY signal Z + jet W + jet

  17. 2nd Highest “jet transverse momentum” 150 GeV SUSY background SUSY signal Z + jet W + jet

  18. 3rd Highest “jet transverse momentum” 50 GeV SUSY background SUSY signal Z + jet W + jet

  19. Space angle between two b-tagged jets < 1.5 SUSY signal SUSY background Z + jet W + jet

  20. Backup: Jet resolution of the detector

More Related