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Early SUSY discovery

Early SUSY discovery. How to best use early data poor knowledge of multi-jet backgrounds incomplete measurement of other backgrounds limited detector understanding. Alan Barr Claire Gwenlan. We wont be able to find SUSY quickly in the “16 jets + 4 leptons” channel!. UK SUSY/Exotics.

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Early SUSY discovery

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  1. Early SUSY discovery • How to best use early data • poor knowledge of multi-jet backgrounds • incomplete measurement of other backgrounds • limited detector understanding Alan BarrClaire Gwenlan We wont be able to find SUSY quickly in the “16 jets + 4 leptons” channel! UK SUSY/Exotics 29th February 2007

  2. Robust topologies LSP q squark q _ q _ q (and similar) LSP BACKGROUND topology (QCD) SIGNAL topology

  3. Small Njets + ET • Select a small number of high PT jets • Large signal cross-section • Large control statistics • Relatively well known SM backgrounds • Relatively model independent • Does not rely on leptonic cascades • Does not rely on hadronic cascades • Use kinematics rather than “busyness of event” to pick out SUSY

  4. Selection • Keep it simple • Two jets • ET (J1,2) > 150 GeV; |η1,2| < 2.5 • Plot MT2 • N.B. MT2→ 0 if: • ET→ 0 • ET parallel to either jet • Jet ET → 0 J.Phys.G29:2343-2363,2003, Phys.Lett.B463:99-103,1999 Characteristics of backgrounds

  5. Sample discrimination 1 fb-1 ! Full sim CSC AODs

  6. Requirements • Need: • Some understanding of ET and energy scale • Degree needs to be determined • Some lepton ID • Estimate Z→νν from Z→μμ • Some idea of ttbar background • Do not need: • B-tagging • Detailed understanding of jet resolution tails • Missing ET tails from multi-jets • To know much about loss of energy in cracks etc

  7. Summary & next steps • Idea • Use simple topology for rapid discovery of light sparticles • 2 jets + missing energy • Kinematic plot of MT2 gives good discrimination • Backgrounds under control • Excellent prospects if SUSY is light • Next: • QCD background from Alpgen (rather than Pythia) • Trigger • Backgrounds from control regions

  8. Backups

  9. Samples • CSC 11.0.x AODs (Full Simulation) SUSY (SU3): 5403 herwig (+jimmy) Jets (J1-J8): 5010->5017 pythia ttbar (no all-hadronic): 5200 MC@NLO (+jimmy) ttbar (only all-hadronic): 5204 MC@NLO (+jimmy) Zee : 5152 MC@NLO Zmumu: 5151 MC@NLO Wenu: 5100 herwig (+jimmy) More to add when R12 AODs available…

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