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Supersymmetry at the Tevatron

CDF. D0. Supersymmetry at the Tevatron. R. Demina University of Rochester. Supersymmetry: Fermion-Boson symmetry. If R-parity is conserved the lightest neutralino is stable – an excellent dark matter candidate. SUSY. 20 years of SUSY. And still, no one is prettier…

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Supersymmetry at the Tevatron

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  1. CDF D0 Supersymmetry at the Tevatron R. Demina University of Rochester

  2. Supersymmetry: Fermion-Boson symmetry. If R-parity is conserved the lightest neutralino is stable – an excellent dark matter candidate. SUSY 20 years of SUSY And still, no one is prettier… “We like the way she walks, We like the way she talks” but… God damn it, where is she?

  3. Outline • Data sets • Tri-leptons • Jets and missing energy • Straight up • With heavy flavor • Gauge Mediated SUSY Breaking – photons with missing energy • Long-lived particles • Conclusions

  4. Run II data taking Presented analyses are based on pre-shutdown data <200pb-1

  5. SUSY production at Tevatron • 200 pb-1 • 1013collisions • 80 chargino/ neutralino (3l) events produced • 800 squark/gluino events produced • To control backgrounds searches based on “signatures”: 3 or more physics objects

  6. Chargino/neutralino production – three leptons and missing energy signature Main challenge - weak production  low cross sections LEP limits are very restrictive Need extremely well controlled backgrounds m±m± Tri-leptons ee(l) em(l) (l ) – isolated track = e, m, t • Leptonic branching are enhanced if sleptons are lighter than gauginos

  7. ee+lepton 175pb-1 2 Electrons: EM cluster+track match • PT>12 (8) GeV • |h|<1.1 (3.0) • Anti-Z • 15<Mee<60 GeV • Df(ee)<2.8 • Anti-W(en)+g • >=1hit in silicon or tighter electron likelihood • Anti tt • Veto jets with ET>80GeV • Anti-Drell Yan • Missing ET>20GeV • Df(eMET)>0.4 Potential signal

  8. ee+lepton • Lepton = isolated track: • PT>3GeV • Etmiss x PT(track)>250GeV e(signal)=2-3%

  9. Tri-leptons • Summary after all cuts: Add isolated track with PT>3 GeV

  10. Run 1 cross section limit much improved Soon will reach MSugra prediction (in the best scenario with low slepton masses) Combined tri-leptons

  11. Jets and missing energy 85 pb-1 • Squarks and gluions: • Strong production • larger cross section, • but really large instrumental backgrounds (2 orders of magnitude over SM processes) Final cuts: Missing ET>175 GeV HT>275 GeV 2 jets ET>60 (50) GeV 30<Df(jet,MET)<165o • 4 events left 2.67 expected from SM sources (Z/W production) • 17.1 event expected for M0=25,M1/2=100GeV

  12. Squarks and gluinos • M0=25GeV; A0=0; tanb=3; m<0 M(gluino)>333GeV Run 1 – 310 GeV M(squark)>292GeV

  13. B-jets and missing energy • High tan(b) scenario under study: sbottom is lighter than other squarks and gluino • 4b-jets+missing energy • >=3jets (ET>10 GeV) • Missing ET>35 GeV • 1 b-tag • 5.6+-1.4 events SM predicted - 4 observed • 2 b-tags • 0.5+-0.1 events SM predicted - 1 observed

  14. ggMet 185 pb-1 Missing ET>40 GeV • Gauge mediated SUSY breaking at scale L • Gravitino – LSP • NLSP (neutralino) g LSP • Dominant SUSY mode: c20 c1+ Signature – 2 photons, missing energy PT(photon)>20 GeV in |h|<1.1 1 event survived 2.5±0.5 expected from SM

  15. Long Live Particles! d • LSP – charged particle, or • NLSP – charged particle (e.g. stop) with long decay time • Signature – isolated track of a rather slow particle • Use TOF system (CDF) • BG prediction of 2.9 +/- 0.7 (stat) +/- 3.1 (sys), with 7 observed

  16. Conclusions • Tevatron detectors produce solid physics results based on datasets of up to 185 pb-1 • SUSY limits extended beyond run 1: • In trilepton signature • Missing energy and jets • Missing energy and b-jets • GMSB in diphoton final state • New system (TOF) used to search for long lived particles

  17. Personal remarks1 • By now the mass limits for SUSY partners of all particles with the exception of top quark exceed the masses of their SM partners • This means that SUSY is badly broken everywhere with possible exception of top-sector • In run 2 (with 2fb-1) Tevatron experiments will be able to probe stop masses all the way to top mass and above • Stop production xsection =~10% (top xsection) for the same mass • Tevatron experiments will be able • Either discover SUSY • Or verify if SUSY is broken for all SM particles 1Not necessarily representing the views of CDF and DØ collaborations

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