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SUSY Searches at the Tevatron

SUSY Searches at the Tevatron. Rencontres de Moriond, QCD March 2006 Else Lytken, Purdue University for the CDF and D0 collaborations. Outline. Brief intro to supersymmetry SUSY at the Tevatron Some selected analyses: Squarks and gluinos, incl scalar top and stopped gluinos

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SUSY Searches at the Tevatron

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  1. SUSY Searches at the Tevatron Rencontres de Moriond, QCD March 2006 Else Lytken, Purdue University for the CDF and D0 collaborations

  2. Outline • Brief intro to supersymmetry • SUSY at the Tevatron • Some selected analyses: Squarks and gluinos, incl scalar top and stopped gluinos Photon signatures Lepton signatures, incl Bs and RPV • Conclusion and outlook Else Lytken, Moriond QCD 2006

  3. Supersymmetry in 60 seconds Idea: extend SM with symmetry fermions  bosons If realized, lots of new particles to be found! Many attractions:Low scale supersymmetry protects higgs mass, provides dark matter candidate, unification @1016 GeV, and consistent with precision top mass fits Spin 0 1/2 1 3/2 5 higgsesgluino g gauge gravitino h0,H0,A, H±leptons bosons G sleptons l quarks 2 squarks qgauginos ± graviton 0 G ~ ~ ~ ~ ~ ~ +1 SM - 1 SUSY New quantum number often assumed conserved Else Lytken, Moriond QCD 2006

  4. Q C D mb b EWK nb top pb SUSY, Exotics SUSY searches at the Tevatron SUSY searches attractive from experimental point of view due to variety of signatures: - Missing transverse energy (MET) from stable LSP’s - multijets from cascade decays - multileptons Main challenge is the small expected production cross section  Need to model SM backgrounds very well  Most searches check predictions in control regions before looking at data containing possible signal Lightest Susy Particle Else Lytken, Moriond QCD 2006

  5. MET + jets: squark and gluino Generic squarks and gluinos strongly produced Cross section @ Tevatron: ~ a few pb Expect cascade decays Signature: lots of MET and  2 jets • Results from D0: (310 pb-1) 2, 3, or 4 jets CDF: (250 pb-1) 3 jets • Dominant backgrounds • Z+jets, W+jets, tt, QCD • QCD fitted or cross checked with data • MET cut > [75;175] GeV • Both experiments see no hints of SUSY Else Lytken, Moriond QCD 2006

  6. Limit combining with previous result in the µµ channel Search for Scalar top Look for pair production of lightest stop quark Assume equal BR to e, ,, and  LEP limit: m  45 GeV Event signature: 2 b-jets, e±µ + MET ~ ~ 0 1 ~ _ + Limit for eµ cut on N non-iso tracks Signal regions optimized for M=mt - m ~ ~ Else Lytken, Moriond QCD 2006

  7. Stopped gluinos • Assume MSUSY(scalars) >> MSUSY(fermions) •  gluino can have long lifetime and hadronize (”R-hadrons”) • If lifetime > 10 µs: • fraction of g’s stopped in calorimeters • stopped gluino  g +  • later bunch crossing: single high ET shower and high MET ~ ~ no good vertex 0 1 Background: cosmic muons M= 50, 90, 200 GeV (hep-ph/0506242) Theory prediction 3 1 Else Lytken, Moriond QCD 2006 2 4

  8. ~ LSP NLSP MET + photons In Gauge Mediated SUSY breaking models, LSP is gravitino. Typical signature from  decay: Assume prompt decay Signature: 2 energetic photons + MET NLO QCD background normalized to data below MET of 12 GeV Observe 4 events with MET45 GeV Expecting 2.1±0.7 with 760pb-1 Observed ~ New limit: m( ) 220 GeV Previous limit (CDF + D0): 209 GeV ± 1 Else Lytken, Moriond QCD 2006

  9. W* W* Z* MET + 3 leptons Expected signature from chargino-neutralino production Clean signature very attractive for the Tevatron D0, 6 channels: Expects: 3.85±0.75, Observes : 4. Signal would be 3-10 events Else Lytken, Moriond QCD 2006

  10. 3 leptons: continued CDF: All observations in agreement with SM predictions Stay tuned for updated limits! Else Lytken, Moriond QCD 2006

  11. ~ ~ ~    0 1 0 1 0 1 RP SUSY: Long-lived LSP / Scenario: Weak RP violation (inspired by NuTeV dimuon excess) Low mass LSP decays to 2+, r = [5;20]cm, other  escapes l q (~5 GeV) ~ ~  q - l q l • Bkg estimated from data • Several cross checks • Diff as systematics Now excluding that these events are SUSY  : L=383pb-1 Expect 0.8±1.5 events, observe 0 Else Lytken, Moriond QCD 2006

  12. RP: 4 leptons / • Now assume prompt decay • 4 leptons from  decays Analysis also looked at 3 leptons ~~ • Yukawa term: • ijkLiLjEk Analysis accepts e and µ  sensitive to121 and122 _ Trilepton control regions Striking signature, virtually no SM background No cut on MET or N jets Expects 1.5±0.2 signal, <0.01 SM, observes 0  Limits on 121:  < 0.21 pb 122 : < 0.11 pb Else Lytken, Moriond QCD 2006

  13. hep-ph/0507233 Previous limit: Indirect constraint: BS • Rare decay, SM branching frac ~10-9 • Loop diagrams with sparticles (or direct decay if RPV) enhance orders of magnitude Important at high tan • Look for excess of µµ events in Bs and Bd • mass windows • Background estimation: linear extrapolation • from sidebands • Results compatible with SM backgrounds • Br(Bs)<1.0×10-7 @ 95%CL • --- Closing in on SUSY! --- Else Lytken, Moriond QCD 2006

  14. 1fb-1 Summary and outlook • CDF and D0 keep probing new areas of the SUSY parameter space! • Results can also constrain other models • It is only limits so far ..... • We have 1fb-1 ready for analysis and the • Tevatron is in great shape! • Expect 4-8 fb-1 by end of Run II The hunt continues ...! Else Lytken, Moriond QCD 2006

  15. Backup

  16. Indirect constraint: BS Rare decay, in SM branching frac ~10-9 Loop diagrams with sparticles (or direct decay if RPV) enhance orders of magnitude Important at high tan CDF also looks at Bd Background estimation: linear extrapolation from sidebands Normalizing using B+- +K+ - Results compatible with SM backgrounds Else Lytken, Moriond QCD 2006

  17. Look in the Bs and Bd Signal Window LR > 0.99 CMU-CMX Channel: Expect Observed Prob Bs0.39±0.21 0 68% Bd0.59±0.21 0 55% CMU-CMU Channel: Expect Observed Prob Bs0.88±0.30 1 67% Bd1.86±0.34 2 63% Else Lytken, Moriond QCD 2006

  18. ~ ~ ~ ~ ~ ~ Mg < Mq Mg ~ Mq Mg > Mq • D0 result: • 2, 3, or 4 jets for the cases: • and • Dominant background differ • Z+jets, W+jets, tt, QCD • MET > [75, 100, 175] GeV • Lepton veto MET + jets: squark and gluino Generic squarks and gluinos strongly produced Cross section @ Tevatron: ~ a few pb Expect cascade decays Signature: lots of MET and  2 jets 4 jets: Fit toQCD Else Lytken, Moriond QCD 2006

  19. MET+jets continue Expect 4.1 events, observe 3 • CDF: • Req.  3 jets and MET>165 GeV • Bkg dominated by Z + jets • Check: compare data and QCD MC in jet domimated region Else Lytken, Moriond QCD 2006

  20. ~ ~ ~ ~ ~ ~ Mg < Mq Mg ~ Mq Mg > Mq D0 STRATEGY Data pre-selection: Luminosity: 310 pb-1 ANALYSIS STRATEGY Distinguishes 3 approaches (dominant s ) Search for acoplanar dijet events (squark  jet + MET dominant) Search for events with at least 4 jets (gluino  2 jets + MET dominant) Search for events with at least 3 jets (2 jets from gluino and one from squark) JET BACKGROUND STRATEGY Cuts will remove its contribution. Otherwise, contribution extrapolated from data behavior at low missing ET region. Else Lytken, Moriond QCD 2006

  21. Else Lytken, Moriond QCD 2006

  22. MET CMUP CMIO CMX CDF Trilepton events Next-to-leading e-, pT = 12 GeV Leading electron e+, pT = 41 GeV MET, 45 GeV Isolated track, pT = 4 GeV Muon? Else Lytken, Moriond QCD 2006

  23. Limits Combine 3 lepton and 4+ lepton signal regions to set limits. Signal Point: M0 = 250, M1/2 = 260, tanb = 5, m > 0, s= 0.143 Excluded by DØ: σ≤ 0.116 (l121) with 238 pb-1 σ≤ 0.239 (l122) with 160 pb-1 Else Lytken, Moriond QCD 2006

  24. Conversion removal SF Else Lytken, Moriond QCD 2006

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