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SUSY Searches with jets at CDF

SUSY Searches with jets at CDF. Monica D’Onofrio IFAE-Barcelona 34 th International Conference High Energy Physics ICHEP08, Philadelphia. Outline. SUPER. Supersymmetry in few words SUSY Searches using jets: Inclusive production of squarks and gluinos

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SUSY Searches with jets at CDF

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  1. SUSY Searches with jets at CDF Monica D’Onofrio IFAE-Barcelona 34th International Conference High Energy Physics ICHEP08, Philadelphia

  2. Outline SUPER • Supersymmetry in few words • SUSY Searches using jets: • Inclusive production of squarks and gluinos • Search for third generation squarks: • sbottom from gluino decays • Stop in dilepton+jets sample • Summary and Conclusions ICHEP08, Philadelphia, 7/31/2008

  3. Supersymmetry • New spin-based symmetry relating fermions and bosons: Q|Boson> = |Fermion> Q|Fermion> = |Boson> gaugino/higgsino mixing • Minimal SuperSymmetric SM (MSSM): • Mirror spectrum of particles • Enlarged Higgs sector: two doublets with 5 physical states • Naturally solve the • hierarchy problem • Define R-parity = (-1)3(B-L)+2s • R = 1 for SM particles • R = -1 for MSSM partners If conserved, provides Dark Matter Candidate (Lightest Supersymmetric Particle) ICHEP08, Philadelphia, 7/31/2008

  4. MSSM phenomenology • SUSY must be broken • More than 100 parameters even in minimal (MSSM) models • Breaking mechanism determines phenomenologyand search strategy mSUGRA or Constrained MSSM used as benchmark  Squarks and gluinosheavy  1st and 2nd generation squarks are mass degenerate PROSPINO (pb) mixing of 3rd generation leads tolight stop and sbottommass m (GeV) ICHEP08, Philadelphia, 7/31/2008

  5. 2 fb-1 Inclusive search for squark/gluino mSUGRA: Low tan b scenario (=5) Assume 5-flavors degenerate q Final state: energetic jets of hadrons and large unbalanced transverse energy(due to presence of c0) ~ q ~ ~ ~ c c 0 0 g q g ~ A0 = 0, m<0 M0 [0,500 GeV/c2] m1/2  [50,200 GeV/c2] q 0 c ~ ~ q q ~ ~ c c 0 0 ~ ~ q q g g q ~ Mq ~ Mg qg final state dominates  3 jets expected ~ q ~ ~ ~ ~ c c 0 0 ~ q g ~ q q q ~ ~ q q 0 0 c Mq > Mg gg final state dominates  4 jets expected ~ ~ ~ ~ ~ ~ c c 0 0 Mq < Mg qq final state dominates  2 jets expected ~ ~ ~ q ~ ~ q q 3 different analyses carried out with different jet multiplicities Final selection based on Missing ET , HT = S (ETjets) and ET jets ICHEP08, Philadelphia, 7/31/2008

  6. DiBoson Background rejection Data sample Cleanup • at least one central jet with |h|<1.1 • minimum missing ET of 70 GeV • Reject beam-related backgrounds and cosmics Rejection of SM processes • min Df (missingET-jets) , to reject events with the ET due to jet energy mismeasurement. • Electromagnetic fractionof the jets < 90% to reject electrons mis-identified as jets • min Df (missingET-isolated track)to reject events with ET due to undetected e/m • Z veto • Define signal region based on selections that maximize background rejection ICHEP08, Philadelphia, 7/31/2008

  7. Results • Check DATA and SM predictions in control samples first • Then look at the signal regions: Good agreement between Observed and Expected events Syst. uncertainties dominated by (3%) Jet Energy scale uncertainty ICHEP08, Philadelphia, 7/31/2008

  8. Exclusion limits Use Bayesian approach 95% C.L. Exclusion limit on MgMq and M0M1/2 planes ~ ~ • When Mg=Mq → M > 392GeV/c2 • Mg < 280 GeV/c2 excluded in any case ~ ~ • LEP limit improved in the region where 75<M0<250 and 130<M1/2<170 [GeV/c2 ] ~ ICHEP08, Philadelphia, 7/31/2008

  9. Third squarks generation ICHEP08, Philadelphia, 7/31/2008

  10. 1.8 fb-1 Searches for sbottom quark b ~ ~ ~ b c c 0 0 ~ ~ ~ ~ g g b ~ • In large mixing scenarios light sbottom expected (large tan b) • Dedicated searches for b production (B.R. (bb c0) = 100%) • direct pair production or b from gluino decays • sgg ~ 10 sbb , consider region • Assume gluino mass larger than sbottom mass Final state: ET + 4 b-jets b ~ ~ ~ ~ ~ ~ c c 0 0 ~ ~ g g ~ b b B-jets identified via tagging algorithms • Main background processes: • QCD-multijets • light-flavor jets tagging (“mistag”) • Top production, W/Z+jets, diboson •  Predictions tested in Control Regions QCD-dominated region ICHEP08, Philadelphia, 7/31/2008

  11. Results ~ ~ • Two optimizations used to maximize S/√B, depending on the difference between m(g) and m(b) • Large Dm: • Missing ET>145 GeV • Njet >=3 • Small Dm: • Missing ET>175 GeV • Njet >=2 Good agreement between DATA and SM predictions ICHEP08, Philadelphia, 7/31/2008

  12. Exclusion limits Excluded s above 0.1 pb (M(g) ~ 350 GeV/c2) Translated into limits on the gluino-sbottom mass plane ~ ~ Sbottom masses up to 300 GeV/c2 are excluded for M(g)<340 Gev/c2 ICHEP08, Philadelphia, 7/31/2008

  13. 2.7 fb-1 Seaches for stop quark • Lightest of the squarks • 2-, 3- and 4-body decays possible: • c0 is the LSP, q, l, n are heavy, Rp conserved • Ifand , dominant stop decay mode is to b quark and chargino: ~ ~ ~ ~ • Signature: Missing ET, 2 b-jets and • twoopposite-sign leptons Topology depends on Dm = mt1 - mc ~ ~0 • Main background: top production ICHEP08, Philadelphia, 7/31/2008

  14. Exclusion limits • Depending on the SUSY parameters, c1± may decay • in several ways, potentially enhancing the di-lepton branching ratio ~ Limits in stop-neutralino mass plane ICHEP08, Philadelphia, 7/31/2008

  15. Summary and conclusions • Extensive searches for squarks and gluinos carried out in CDF dedicated analysis. • No evidence of SUSY in ~2 fb-1 of data • Most constraining direct limits on q and g masses to date • On-going searches on sbottom and stop production in other complementary final states • Tevatron is performing really well: more than 3.5 fb-1 recorded ~ ~ Itmaybethatthefirst SUSY hintis justaroundthecorner... ICHEP08, Philadelphia, 7/31/2008

  16. Back-up

  17. The CDF experiment Delivered: 4.46 fb-1 Acquired: 3.65 fb-1 Recording data with high efficiency (80-85%) and making full use of detector capabilities. ICHEP08, Philadelphia, 7/31/2008

  18. EWK GUT mSUGRA • New superfields in “hidden” sector • Interact gravitationally with MSSM • Soft SUSY breaking 5 parameters at GUT scale 1. Unified gaugino mass m1/2 2. Unified scalar mass m0 3. Ratio of H1, H2 vevs tanβ 4. Trilinear coupling A0 5. Higgs mass term sgn() In R parity conservation scenario, the LSP is the neutralino (c01 ) ICHEP08, Philadelphia, 7/31/2008

  19. 2.0 fb-1 Exclusive 2jets+MET • Signature-based search • select events with 2 jets (ETjet3 < 15 GeV) and missing ET in the final state • 2 regions defined: • A. HT > 125 GeV , Missing ET > 80 GeV • B. HT > 225 GeV, Missing ET > 100 GeV •  Background estimation performed with data-driven techniques SM predictions compared to data. A B Express results in terms of 95% CL upper limits 4 representative (ms,mg) points in the no-mSUGRA regions ● ● ● ● ruled out ICHEP08, Philadelphia, 7/31/2008

  20. Exclusion limits for stop searches • Depending on the SUSY parameters, c1± may decay • in several ways, potentially enhancing the di-lepton branching ratio ~ Limits in stop-neutralino mass plane Example of expected limit and systematic uncertainties ICHEP08, Philadelphia, 7/31/2008

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