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…AT THE LHC

DARK MATTER …. …AT THE LHC. Alan Barr University of Oxford. On behalf of the ATLAS and CMS collaborations. PASCOS 2009 DESY 9 July 2009.

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…AT THE LHC

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  1. DARK MATTER … …AT THE LHC Alan BarrUniversity of Oxford On behalf of the ATLAS and CMScollaborations PASCOS 2009 DESY 9 July 2009

  2. You may have noticed there is a new collider starting operation

  3. 1/α +SUSY Log10 (μ / GeV) The value of prejudice rapidly decreasing stop higgs higgs Motivation

  4. Proton-proton controlled environment up to 14 TeV 109 collisions/second ~ decade operation The machine … ATLAS CMS 26.659 km circumference 9300 magnets Four experiments(two general purpose)

  5. Segment of 4π detector

  6. CMS Beam splash2008-09-10

  7. Events… From Steve Meyers More info: http://indico.cern.ch/conferenceDisplay.py?confId=62277

  8. Complete “event” Decay part Time heavyexotic lighterexotic standard Time = exotic = standard Dark Matter … Z2 ? Production part standard • Events build from blobs with 2 “exotic legs” • A pair of cascade decays results • Complicated end result 2 exotics Time Candidates include: {Supersymmetry, UED, Little Higgs}+ appropriate parity

  9. Example SUSY search Mass (GeV) Missing energy + Jets • Assume R-parity • Look for: • Jets from squark & gluino decays • Leptons from gaugino & slepton decays • Missing energy from (stable) LSPs “Typical” SUSY spectrum

  10. Prospino Cross-sections etc “Rediscover” Lower backgrounds WW ZZ “Discover” Higher backgrounds

  11. Caveats • Current public results mostly: • √S = 14 TeV • ∫L ≥ 1 fb-1 • no pile-up† • Initial conditions will be different • Work in progress for smaller √S, ∫L • 10 TeV • 10-100 pb-1 †some CMS physics TDR results include 5 pile-up events

  12. Signal BG Example 4 jet + pT distribution Typical search: inclusive distributions • Jet pT > {100, 50,50,50} GeV • pT > 100 GeV • pT > 0.2 meff • ST > 0.2 • Δφ(pT,j) > 0.2j = {1,2,3} • No e or μ • meff > 800 GeV

  13. Statistics limited Also use: W (μ) + jet γ + jet R: Z -> ννB: EstimatedR: Estimated • Measure in Z -> μμ • Use in Z -> νν Standard Model backgrounds

  14. W, t backgrounds Good match to “true” background Search region Control Region These are examples onlyLots of detail about Z, top, QCD, detectorBGs in further reading

  15. Multiple channels for discovery 1 fb-1, 14 TeV 1 fb-1, 14 TeV Systematics include BG determination Different final states accessible Below the lines = discovered

  16. SUS-08-001 Measuring masses • Large literature exists • Practical methods will be put to the test mll = ½ mllmax (1 – cos θ) • l+l- : pT > 10 GeV, |η|<2.4 • 3 jets |η|<3 ET>120,80,30 GeV • pTmiss > 200 GeV

  17. “Predict” relic density of observed LSPs Caveats: lifetimes beyond detector? optimistic case (light sparticles) many annihilation modes need to be checked Dark matter relic density? f f PoleselloTovey Drees, Kim, Nojiri hep-ph/0007202 Polesello, Tovey hep-ph/0403047 (cMSSM) Nojiri, Polesello, Tovey hep-ph/0512204 (MSSM) Moulin et al. arXiv:0712.3151 (Focus point)

  18. To find out more… CMSCERN-LHCC-2006-021J.Phys.G34:995-1579,2007 ATLASCERN-OPEN-2008-020arXiv:0901.0512 • New results will appear at: • https://twiki.cern.ch/twiki/bin/view/CMS/PhysicsResults • https://twiki.cern.ch/twiki/bin/view/Atlas/AtlasResults • Results for EPS and summer conferences in progress

  19. Conclusions

  20. Extras

  21. Et(miss) Lesson from the Tevatron Importance of detailed detector understanding • Simulation shows events with large fake missing energy • Vital to remove these in missing energy tails • Large effort in physics commissioning

  22. Neutralino spin from angles in decay chains ~ l+ _ q q θ ~ l- Spin measurements… Slepton spin from angles in Drell-Yan production

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