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ATLAS: Missing Transverse Energy in the Search for Supersymmetry

ATLAS: Missing Transverse Energy in the Search for Supersymmetry. Christine McLean The College of William and Mary University of Michigan REU Advisor: Dr. Richard Teuscher August 11, 2011. ATLAS – A T oroidal L HC A pparatu S. Multipurpose LHC Detector.

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ATLAS: Missing Transverse Energy in the Search for Supersymmetry

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  1. ATLAS: Missing Transverse Energy in the Search for Supersymmetry Christine McLean The College of William and Mary University of Michigan REU Advisor: Dr. Richard TeuscherAugust 11, 2011

  2. ATLAS – A ToroidalLHC ApparatuS • Multipurpose LHC Detector

  3. The Search for Supersymmetry - SUSY • Solve Standard Model Problems • Hierarchy Problem • What keeps the Higgs Mass from Blowing Up? • 100 GeV [Electroweak] vs. 10^19 GeV [Gravity] • Sparticles – Supersymmetric Partner Particles • Favored Model: mSUGRA

  4. Goal: Supersymmetry Detection • Found from missing transverse energy in the detector • MET left by SM background and neutralinos

  5. Missing ET – SM Background • W+Jets • Z+Jets • QCD jet (mismeasurement) • T Tbar

  6. Early Plots – Jet Sample

  7. Monte Carlo Plots – Background and Signal Jet Pileup Bug

  8. Cuts for Signal Region A • Different cuts on the data for different SUSY production processes • Focused on signal region A: light-˜q˜qproduction • Source: • Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in sqrt(s) = 7 TeV proton-proton collisions

  9. Important Cuts – Delta Phi and Effective Mass (Meff) • Meff = Jet Pt + MET; Meff >500 GeV • Delta Phi Absolute Value> 0.4

  10. Plots after Meff Cut

  11. Plots After Last Official Cut

  12. One Additional MET Cut – MET > 225 GeV

  13. Data and Future • Full Monte Carlo Analysis Can be used to Compare to LHC Data • Z->ee Data to Look for SUSY in Two Lepton Mode • MC needs to be scaled to Data Luminosity First ATLAS Work in Progress

  14. Travels and Food

  15. Acknowledgements • REU Leaders: Homer Neal, Steve Goldfarb, Jean Krisch, Junjie Zhu, and Lauren Rugani • Advisor: Richard Teuscher • ATLAS Canada Graduate Students: Travis Bain, NikolinaIlic, and ReyhanehRezvani • Fellow REU and CERN summer students • NSF and CERN

  16. Hierarchy Problem - Backup Source: Travis Bain

  17. Hierarchy Problem - Backup Source: Travis Bain

  18. Supersymmetry Unification - Backup Source: Travis Bain

  19. Monte Carlo - Backup • Event Generator– generates random numbers and decides whether event happens based on probability • ATLAS – after generating events, showers them through the detector to get a readout simulation

  20. SM Missing ET Background and Cuts- Backup Source: NikolinaIlic

  21. Cut Flow Table - Backup

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