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Search for GMSB SUSY at DØ

Search for GMSB SUSY at DØ. Latest Results and Prospects. Tim Christiansen Munich University. SUSY 2003, Tucson, Arizona June 5-10, 2003. Bino-like NLSP Higgsino-like NLSP Slepton (Stau) NLSP Squark as NLSP Gluino as NLSP. GMSB-SUSY. (GMSB = gauge-mediated supersymmetry breaking).

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Search for GMSB SUSY at DØ

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  1. Search for GMSB SUSY at DØ Latest Results and Prospects Tim Christiansen Munich University SUSY 2003, Tucson, Arizona June 5-10, 2003

  2. Bino-like NLSP Higgsino-like NLSP Slepton (Stau) NLSP Squark as NLSP Gluino as NLSP GMSB-SUSY (GMSB = gauge-mediated supersymmetry breaking) New messenger field(s) introduced to mediate SUSY-breaking at low energy scale O(100 TeV) M( ) << 1 MeV, almost massless small -coupling (depending on SUSY-breaking scale)  NLSP is meta-stable, might/might not decay within detector Phenomenology driven by NLSP: Focus of this presentation Outlook Tim Christiansen, Munich LMU

  3. „GMSB candidate“ event from CDF Run-I ee+gg+Et (both selectron and chargino inerpretations excluded) GMSB SUSY in pp Collisions In case of Bino-like NLSPs: Assuming prompt decay of NLSP  perform an inclusive search forgg + Et + X (X = jets and/or leptons) Motivation: Tim Christiansen, Munich LMU

  4. p Booster TeVatron p Main Injector & Recycler p Source TeV  s(tt) ~ 35% increased The TeVatron Run II The TeVatron Accelerator at the Fermilab Collisions every 396 ns (36 x 36) First data taken in 2001 pp collisions @ 1.96 TeV Tim Christiansen, Munich LMU

  5. The DØ Run-II Detector: Central Calorimeter EM Shower EM4 EM3 EM2 EM1 End Solenoid Calorimeter Central Fiber Tracker Z EMVTX The DØ Detector Tue DØ Detector The DØ Calorimeter Preshower detectors give a very precise position measurement: fit shower axis  Photon pointing (not yet used) New DAQ & Trigger System Increased lepton acceptance New tracking detectors (Silicon + scintillating fibers) in a magnetic solenoid … Preshowers are still in commissioning. -pointing no used yet. MC estimates are: Central: sR = 1.4 cm sz = 2.2 cm Forward: sR = 1.2 cm sz = 2.8 cm Tim Christiansen, Munich LMU 5

  6. Search for GMSB SUSY in gg+MEt Events ~ 41 pb-1 of data (Sept. ’02 - Jan. ‘03) • Event selection: • Trigger • 1-EM and 2-EM triggered events, 97% efficient for: • 2 photons in the central calorimeter: |h| < 1.1 • 90% of the cluster energy in the EM calorimeters • only little energy in hollow- • cone around the cluster: • g-consistent shower shape • e-veto: no matching track in central tracking system • Et > 20 GeV (allows reliable EM-scale & eff. (Zee); • above trigger threshold) • Et reconstruction • S over all cal.cells + correction for jet- and EM-E scales Tim Christiansen, Munich LMU

  7. Di-e Mass compared to Pythia-MC Data Pythia M(ee) [GeV] EM Reconstruction Reconstruction of Z  ee events (EM selection w/o track-veto) used to verify/study: • tracking efficiency • trigger efficiency • EM scale correction • Random overlap of • tracks and clusters: • rotation of e by f/2 in azimuth •  prob. for random • overlap in Z  ee • events: 3·10-3 From s(Z) analysis @ DØ DØ RunII Preliminary ee Data Histogram: fake-sample, normalized. to sidebands M(ee) [GeV] Tim Christiansen, Munich LMU

  8. Background contains the GMSB events?! • Background from wrong Et • QCD w/ direct g‘s • or mis-identif. jets • Drell-Yan (w/ jets) Z  ee, both • electrons mis-identified as photons • Background with true Et • Wgen g (dominant) • Wjen „g“ • Z tt  ee + X • tt, WW, WZ, etc. (small s) (dominant) gg-sample for the search + fake gg-sample to estimate QCD contribution (failed shower-shape cuts) eg-sample to estimate true-Et background with eg mis-identification + fake eg-sample to estimate QCD contribution Tim Christiansen, Munich LMU

  9. Assumption: Small-Et part of the gg-sample comes from QCD QCD sample (gg,gj,jj) (1 EM cluster fails shower shape)  normalized at Et < 20 GeV Et > 25 GeV Et > 30 GeV Et > 35 GeV gg events 3 1 0 QCD (w/ wrong Et) 6.0  0.8 2.5  0.5 1.6  0.4 e+n+g/j 0.6  0.4 0.2  0.2 0.0  0.2 Background Estimation • Wg  eng & Wj  enj • (1 EM cluster has matching track) • Subtraction of QCD • contribution (fake eg-sample) • Normalization by means of the • known tracking efficiency for e Tim Christiansen, Munich LMU

  10. Simulated Signal Distributions L = 60 TeV L = 45 TeV L = 35 TeV arbitrary vertical scale MET [GeV] Missing-Et Distribution of gg Events Background normalized at MET < 20 GeV Tim Christiansen, Munich LMU

  11. Several points on the GMSB Snowmass slope: L m(10) m(1) stot Acceptance (w/o eff. of EM-ID & vertex cut) [TeV] [GeV] [GeV] [pb] Et>25 GeV Et > 30 GeV Et > 35 GeV 35 40.8 69.2 10.3 0.046 0.038 0.027 45 56.8 98.4 2.07 0.121 0.108 0.090 60 79.3 141.4 0.45 0.186 0.174 0.163 Of course, every SUSY point has different optimal cut on Et, but for simplicity, final cut is chosen atEt > 30 GeV. Event Numbers and Signal Acceptance • No excess of data over background was found • limits on the cross section for GMSB-SUSY processes have been calculated for several points of the Snowmass slope. GMSB Snowmass slope: messenger mass scale M=2L, no. of messengers N=1, tanb=15, m>0 0.66  0.09 Tim Christiansen, Munich LMU

  12. Results from GMSB Search at DØ Run II Comparing the 95% C.L. limits on s with theor. calculations: 95% C.L. Limits L > 51 TeV m(10) > 66 GeV m(1) > 116 GeV Results from Run I using similar models at DØ (CDF): m(10) > 75 (65) GeV with more than double the luminosity than shown here. LEP2: m(10) > 95 GeV. Tim Christiansen, Munich LMU

  13. g1 Et =31 GeV g2 g2 jet jet g1 g1 Et(g1) = 116 GeV Et(g2) = 24 GeV Et(jet) = 21 GeV Et = 31 GeV g2 jet Highest EtCandidate Event Tim Christiansen, Munich LMU

  14. using a similar model: Prospects: Displaced Photons -coupling depends on scale of SUSY breaking If lifetime is long, the 2 g‘s don‘t come from interaction point from hep-ph/0008070 • use preshower detector with calorimeter for photon pointing: • projective geometry • high segmentation 2 fb-1 { ~ inner radius of DØ calorimeter Tim Christiansen, Munich LMU

  15. contribution from to small-Et hep-ph/0008070 Prospects: Quasi-stable Stau as NLSP Sleptons are lighter than other sparticles, and Stau life-time depends on scale of SUSY-breaking: Stau could be quasi-stable Stau: m-like with high dE/dx hep-ph/0008070 Stau-NLSP model line: N=2, m>0, M/L=3, tanb=15 Di-“Muon“ Mass [GeV] Missing-Et [GeV] Tim Christiansen, Munich LMU

  16. Stau NLSP with Prompt Stau Decay from hep-ph/0008070: For sufficiently low SUSY-breaking scale: prompt decay for leptonic t-decays, together with W*/Z* decays from the cascade decays: 2 or more leptons + jets +Et tri-lepton search same-sign-lepton search Tim Christiansen, Munich LMU

  17. DØ has searched (and still is searching) for GMSB • SUSY in gg+Et events in pp collisions at . • QCD and Standard Model background contribution has • been estimated using data. • No excess of data over background was found. • Upper Limits on the GMSB-SUSY cross section have • been determined and compared to theoretical predictions: • These limits are comparable to those from Run I, despite • the much lower statistics shown here. • Soon, this analysis will surpass Run I and complementary • analyses are underway. Summary Tim Christiansen, Munich LMU

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