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Searches for New Physics at the Tevatron

Searches for New Physics at the Tevatron. B. Heinemann University of Liverpool. “From Tevatron to the LHC” Cosenor’s House, 24-25.04.2004. Outline. Introduction Higgs SUSY High mass dileptons: Z’ and LED’s Conclusions and Outlook

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Searches for New Physics at the Tevatron

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  1. Searches for New Physics at the Tevatron B. Heinemann University of Liverpool “From Tevatron to the LHC” Cosenor’s House, 24-25.04.2004 Searches for New Physics at the Tevatron

  2. Outline • Introduction • Higgs • SUSY • High mass dileptons: Z’ and LED’s • Conclusions and Outlook • Other results on: Leptoquarks, Magnetic Monopoles, ADD LED’s, Excited electrons, … • Difficulties: • XXX • YYY Searches for New Physics at the Tevatron

  3. The Tevatron: Run 2 • Run 2 started in June 01: • CMS energy 1.96 TeV • Delivered Lumi: 480/pb • Promising slope in 2004! • Data taking efficiencies about 90% • Physics Analyses: • Use about 200/pb (2x run 1) • But it’s still early days in Run 2! Expect 2 /fb by 2006 and 4.4-8.6 /fb by 2009  sensitivity to New Physics improved by>5 compared to Run 1 Searches for New Physics at the Tevatron 90% efficiency Data Recording Efficiency

  4. The Challenge • QCD and EWK cross sections 10-5 orders of magnitude larger than new physics! • Finding the needle in the heystack… • Good understanding of SM backgrounds • Use data and MC to estimate them • Useful: new enhanced LO MC’s (Alpgen, Madgraph) • NN and Likelihood methods require excellent modelling of BG Cross Sections (fb) WW, Wγ, Zγ, ? Higgs Searches for New Physics at the Tevatron

  5. Higgs • Standard Model • SUSY: • Enhanced production at high tanb • Bosophilic Higgs: • h→γγ • Doubly Charged Higgs • Backup slides Searches for New Physics at the Tevatron

  6. Standard Model Higgs H bb H  WW(*) Dominant decay modes Production Cross section • Cross sections small: 0.1 - 1 pb • MH 135 GeV: decay into bb • gg  H: QCD BG too large • HW and HZ associated production have lower (but still large!) BG • Best channels: • Wh→lνbb • Zh→ννbb • MH >135 GeV: decay into WW • gg  H WW(*)l+l- final states can be explored • BR only 1% • In this talk (both done by CDF and D0): • Wh→lνbb (CDF) • h→WW (D0) Searches for New Physics at the Tevatron

  7. Prospects for SM Higgs 2009 2006 • E.g. SM Higgs at 115 GeV • exclude at 95% C.L. in 2006 • 3s evidence in 2009 • Original study in 1998 confirmed in 2003 • Study still based on some extrapolations • No sensitivity expected with current Luminosity of 200/pb (not even on plot!) • But search now anyway: • Get ready for high Luminosity • Possibly new bright students develop smarter ideas than anticipated in studies • Understand systematic errors realistically (and start working on them!) Searches for New Physics at the Tevatron

  8. Event selection Central isolatede/m, pT > 20 GeV Missing ET > 20 GeV Two jets: ET > 15 GeV, |h| < 2 Veto Di-lepton, extra jet, etc.  Observe 2072 events in data Simulations performed with Alpgen plus Herwig passed through detailed detector response CDF: WH→lvbb (I) • Data in good agreement with Background expectation • Main Background: • W+light jets  now require b-tag Searches for New Physics at the Tevatron

  9. Require at leastone b-tagged jet  Observe 62 events in data  Expect 61 ± 5 events Main contributions to background Mass Resolution: 17% Expect0.3 evtsfrom Higgs Signal acceptance~1.8% forMH = 110 – 130 GeV CDF: Higgs: WH→lvbb (II) Searches for New Physics at the Tevatron

  10. Set limits on the Higgs production cross section times branching ratio: s(WH)×BR(W→lv, h→bb) < 5 pb (D0: <12.4 pb at mh=115 GeV) Systematics studies CDF: Higgs: WH→lvbb (III) • Difficulties: • 3rd jet veto introduces large syst. Error due to ISR/FSR • jet energy resolution: optimise in Z→bb • long term: need to use NN or so how reliable is MC? • Exceeds CDF’s Run I limits×BR < 14 – 19 pb • forMH = 70 – 120 GeVPRL 79, 3819 (1997) • Expect improvements due to • Di-jet mass resolution (17%→12-10%) • More sophisticated analysis techniques • Cut and b-tag optimisation Searches for New Physics at the Tevatron

  11. D0: H  WW(*)  l+l-nn • Event selection include • Isolated e/m • pT(e1) > 12 GeV, pT(e2) > 8 GeV • pT(e/m1) > 12 GeV, pT(e/m2) > 8 GeV • pT(m1) > 20 GeV, pT(m2) > 10 GeV • Reduce Drell-Yan background: • ET>20 GeV (ee, em); 30 GeV (mm) • Veto on Z resonance • Reduce top background • Veto energetic jets • Data correspond to integrated lumi. of ~ 180 (ee), 160 (em) and 150 (mm) pb-1 Higgs Signal Searches for New Physics at the Tevatron

  12. DØ: H  WW(*)  l+l-nn e+ n W+ n W- e- • Higgs mass reconstruction not possible due to two neutrions • Employ spin correlations to suppress the bkgd. • Df(ll) variable is particularly useful • Leptons from H  WW(*)  l+l-nn tend to be collinear Df(ll) between e and m (after preselection cuts) Higgs of 160 GeV Searches for New Physics at the Tevatron

  13. DØ: H  WW(*)  l+l-nn DØ Run II Preliminary Number of events after selections Dominant bkgd. in em sample • Expect 0.11 events for 160 GeV SM Higgs now Excluded cross section times Branching Ratio at 95% C.L. Higgs of 160 GeV Searches for New Physics at the Tevatron

  14. Higgs in SUSY at high tanb CDF Run I 95% C.L. • Standard Model: • σ(bbH) =1-10 fb: 100 x smaller than WH • SUSY: • Cross section enhanced at high tanβ: • σ(bbf)~ tanβ!(Willenbrook et al.) • E.g. for M(A)=120 GeV: • 5s discovery for tanb>30 • 3s evidence for tanb>20 • Experimentally: • 1 b-jet typically soft: • Require 3 jets with b-tags (=h,H,A) BR( ) ~ 90% Searches for New Physics at the Tevatron

  15. D0: Neutral Higgs at High Tan • Event Selection: • At least 3 jets:ET cuts on jets optimized for different Higgs mass values •  3 b-tagged jets • Look for signal in the invariant mass spectrum from the two leading b-jets • Main Background: • QCD multi b-production • Difficult for LO MC: determined from data and/or ALPGEN 1.2 • Signal acceptance about 0.2-1.5% depending on Mass ∫Ldt=131 pb-1 • Difficulties: • triggering: 3 b-jets, 4th jet soft: e.g. e=2 % in CDF • background: 3 b-jets beyond LO MC abilities and generating • enough MC challenging CPU wise • mass resolution: optimise and check in Z→bb AND FINAL STATE?????????? Searches for New Physics at the Tevatron

  16. D0: Non-SM Light H Some extensions of SM contain Higgs w/ large B(H) Fermiophobic Higgs : does not couple to fermions Topcolor Higgs : couples to only to top (i.e. no other fermions) Important discovery channel at LHC Event selection 2 Isolated ’s with pT > 25 GeV ||<1.05 (CC) or 1.5<||<2.4 (EC) pT () > 35 GeV (optimised) BG: mostly jets faking photons Syst. error about 30% per photon! Estimated from Data ∫Ldt=191 pb-1 Central-Central Central-Forward Searches for New Physics at the Tevatron

  17. Photon Fake Rate CDF (preliminary result) • Rate of jets with leading meson (pi0, eta) which cannot be distinguished from prompt photons: Depends on • detector capabilities, e.g. granularity of calorimeter • Cuts! • Systematic error about 30-80% depending on Et • Data higher than Pythia and Herwig • Pythia describes data better than Herwig Searches for New Physics at the Tevatron

  18. Non-SM Light Higgs H Perform counting experiments on optimized sliding mass window to set limit on B(H) as function of M(H) • Difficulties: • jets faking photons: leading pi0’s • NLO MC of SM gg necessary: Pt(gg) cut Searches for New Physics at the Tevatron

  19. Supersymmetry Reminder • SM FermionsBoson Superpartners • SM Bosons Fermion Superpartners • Physical SUSY sparticles: neutralinos (Higgs, Photon, Z partners), charginos (Higgs, W partners), squarks (quark partners), sleptons (lepton partners) • Different SUSY models: • Supergravity:SUSY broken near GUT scale • GUT scale parameters: scalar mass m0 , gaugino mass m1/2 , ratio of Higgs v.e.v’s tanβ, Higgs mixing parameter μ • LSP is neutralino or sneutrinoν • Gauge-mediated models (GMSB):SUSY broken at lower energies – breaking scale L important parameter. • Gravitino G is the LSP (NLSP χ0 →Gγ ) ~ ~ ~ Searches for New Physics at the Tevatron

  20. “Trilepton” Search Chargino+neutralino production: three leptons and missing energy signature Main challenge - weak production  low cross sections LEP limits are very restrictive select two identified leptons, so far: ee eμ μ±μ± Add Et cut and topological cuts Require an additonal isolated track Sensitive to tau’s too At high tanb>10 stau may be light Chargino and neutralino decay into stau’s which then decay into tau’s 3-tau final state: dedicated analysis required (not covered here) / Searches for New Physics at the Tevatron

  21. D0: Trileptons: ee+lepton (I) 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 Conversion electrons • Anti top • Veto jets with ET>80GeV • Anti-Drell Yan • Missing ET>20GeV • Df(e,ET)>23 degrees • Isolated Track: Pt>3 GeV • ET x Pt > 250 GeV2 Potential signal / Cuts reduce BG by 4 orders of magnitude! ε(signal)=2-3% Searches for New Physics at the Tevatron

  22. D0: Combined tri-leptons Results: • 3(2) events compared to 2.9(0.9) expected • Run 1 cross section limit much improved • Soon will reach MSugra prediction (in the best scenario with low slepton masses) • Difficulties: • trigger: leptons are soft: 3rd lepton 3 GeV! • background: jets faking lepton, e.g. conversions • background: difficult to make enough b MC • understanding Missing Et: e.g. jet mismeasurements Searches for New Physics at the Tevatron

  23. Squarks and Gluinos • Stop quark: • Maybe best discovery potential in Run 2 • Theorists say “it should be light” • Searches so far only for stable stop • Unfortunately no result yet in promising decay modes in Run 2 but triggers in place and analyses ongoing! • Sbottom quark • pp→gg→bbbb→bbbbcc • pp→bb→bbcc • Search for b-jets + ET • Generic squarks • Search for jets + ET • Large QCD backgrounds must be suppressed LEP2 limit ~ ~ ~~ ~~ ~~ ~~ Searches for New Physics at the Tevatron

  24. D0: Squarks and Gluinos Final cuts: Missing ET>175 GeV HT>275 GeV • Squarks and gluions: • Strong production • large cross section, • but really large instrumental backgrounds (2 orders of magnitude over SM processes) 85 pb-1 2 jets ET>60 (50) GeV 30<Df(jet,MET)<165o • 4 events left 2.67±0.95 expected from SM sources: • 50% from Zjj -> vvjj • Other BG from Wjj • QCD background negligible (exponential fit to the data) • 17.1 event expected for M0=25,M1/2=100GeV Searches for New Physics at the Tevatron

  25. D0: Squarks and Gluinos • M0=25GeV; A0=0; tanb=3; m<0 M(gluino)>333GeV Run 1 – 310 GeV • Difficulties: • understanding Missing Et: e.g. jet mismeasurements • jet energy scale and resolution uncertainty • generating enough MC to estimate QCD BG! • handling large jet datasets M(squark)>292GeV Searches for New Physics at the Tevatron

  26. Jet Energy Scale @ CDF • Use test beam to set charged pion scale • Use in situ Z ee to set pi0 scale • Account for MI and UE • Correct for jet to hadron level • Correct for hadron to parton level (e.g. top mass) • Cross checks: • gamma-jet: 5% difference between Pythia and Herwig after full simulation • Z-jet: statistically limited • Z bb and W jj in top at Et of 50 GeV or so • calibration at high Et relies on MC tuning of • Response to single particles • Fragmenation/radiation in MC • Difficulties: • understand large difference between Pythia and Herwig • no calibration process in interesting region: Et>400 GeV! • will be dominant error on e.g. top mass Searches for New Physics at the Tevatron

  27. Sbottom: B-jets and ET • 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 • Difficulties: • understanding Missing Et: e.g. jet mismeasurements • b-tagging efficiency and purity • QCD background: LO MC unreliable for multi-b production Searches for New Physics at the Tevatron

  28. Long Lived Particles! • 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: NEW in Run 2 for CDF • Ensure efficient tracking: βγ>0.4 (Pt>40 for M=100 GeV) • Efficiency about 1-3% • BG: 2.9±3.2 • Data: 7 observed • Use dE/dx and COT timing in future • Difficulties: • cosmic background • track efficiency for massive/slow particles (v≠c) Searches for New Physics at the Tevatron

  29. GMSB Model: ggMet New D0 event taken recently: 2 γ, 1e, large Et: Et(γ)=69 GeV, Et(γ)=27 GeV Et(e)=24 GeV Et=63 GeV / Missing ET>40 GeV • Gauge mediated SUSY breaking scale L • Gravitino – LSP • NLSP (neutralino) g LSP • Dominant SUSY mode: c20 c1+ 185 pb-1 Signature – 2 photons, missing energy PT(photon)>20 GeV in |h|<1.1 1 event survived 2.5±0.5 expected from SM Searches for New Physics at the Tevatron

  30. GMSB Model: ggMet • Data consistent with SM background • Derive upper limit on cross section • Compare to NLO cross section • Result: • Difficulties: • understanding QCD BG due to Et mismeasurement • instrumental (cosmic/beam-halo) BG Searches for New Physics at the Tevatron

  31. CDF: Bs->μ+μ- SM vs e.g. SUSY • New Physics can enhance branching ratios of B-mesons: • Measure BR in decay modes suppressed in SM • E.g. Bs→μμ: • Bs = bound state of b and s quark • SM: BR(Bs→μμ)~10-9 • SUSY: BR may be A LOT higher at high tanb • Blind analysis with a priori optimisation: • 1 event observed, ~1+-0.3 expected 90% CL limits: • BR(Bs→μμ)<5.8 X 10-7 • BR(Bd→μμ)<1.5 X 10-7 Searches for New Physics at the Tevatron

  32. SUSY Sensitivity: Bs->μμ 90% CL limit: BR(Bs→μμ)<5.8 x 10-7 • SO(10) GUT model (R. Dermisek et al.: hep/ph-0304101) : • accounts for dark matter and massive neutrinos • largely ruled out by new result • mSugra at high tanβ (A. Dedes et al.: hep/ph-0108037): • Just about scratching the corner of parameter space • In direct competition with • Higgs • (g-2)μ • Expect <1x10-7 by end of year start exceeding limits set by higgs Searches for New Physics at the Tevatron

  33. Physics Potential of Tau’s • Light higgs decays to tau’s 8% of the time: • E.g. for 120 GeV higgs have already 20 H→ττ events on tape • Decay to tau’s enhanced in MSSM at high tanb • At high tanb the stau is light: • Charginos and Neutralinos can decay into stau’s • Stau may be LSP • Tau’s are difficult at pp machines… • No search result yet though but building foundations measure: • Z-> tau tau • W-> tau nu Searches for New Physics at the Tevatron

  34. W→τν and Z→τ+τ− Signals 2345 W→τν candidates in 72/pb • Look for hadronic tau decays • Narrow isolated jet • Low track multiplicity • Identify π0 candidate in ShowerMax detector • invariant mass of tracks and π0 < m(τ) • Efficiency about 50% • Difficulties: • triggering: CDF has new trigger “lepton + track” • jets faking hadronic taus: about 0.3% right now • tau ID efficiency: no clean way to get from data NNLO prediction: 2.73 nb • Z→τ+τ− signal: • 1 hadronic tau decay (jet) • 1 τ→eν or τ→μν decay • Backgrounds from Z→l+l−, QCD Searches for New Physics at the Tevatron

  35. Di-lepton Production @ High Mass • Select 2 opposite sign leptons: ee or μμ (ττsoon) • Here ee channel: • 2 central e (CC) • 1 central and 1 forward e (CP) • NEW: 2 forward e’s (PP) • Good agreement with SM prediction Searches for New Physics at the Tevatron

  36. Model Independent Limits: spin-0, spin-1 and spin-2 particles spin-0 spin-1 • model-independent limits on σxBR for particles with spins 0, 1 and 2 • applicable to any new possible future theory • Observed limit consistent with expectation • New Plug-Plug result not yet included • Muon analysis also ongoing spin-2 Searches for New Physics at the Tevatron

  37. Limits on Several Models • Z’ occurs naturally in extensions of SM towards GUT scale, e.g. “E6” models • M(Z’)>570 GeV for E6 models (depends on exact model: couplings to quarks and leptons) • M(Z’)>750 GeV for SM coupling • Sneutrino in R-Parity violating SUSY may decay to 2 leptons: • M>600 GeV for couplingxBR=0.01 • Randall-Sundrum gravitons • Mass> 600 GeV for k/MPl >0.01 • Techni- pion’s, -omega’s G Z’ • Difficulties: • Mass dependent k-factor (NNLO) for Z’ signal recently provided by J. Stirling • No mass dependent k-factor for DY background versus di-lepton mass yet: will use MC@NLO ~ G ν Searches for New Physics at the Tevatron

  38. Summary of Black Boxes • Background Monte Carlo: • Enhanced LO MC’s (Alpgen, Madgraph etc.) being used more and more • Much better description of data than e.g. Pythia/Herwig: • Starting to use MC@NLO • CPU intense: often impractical to generate enough in remote corners of phase space • Jet energy scale and resolution crucial for many measurements: • Tuning of Pythia and Herwig required to describe jets better • Jets faking leptons, photons, tau’s: • Fake rate measurements big industry at CDF and D0: it is an art to correctly measure a fake rate! • Biggest experimental problems arise when data NOT modelled by MC • Generator • detector simulation Input and suggestions from theorists (or anybody) to maximise physics are very very welcome! Searches for New Physics at the Tevatron

  39. Conclusions and Outlook • Have done many searches and not found anything, but • This is just the beginning: • expect a factor of 10 more data by 2006/7 • Analyses can be optimised • Understanding of detector and techniques improving • New/better MC tools becoming available • Identify and solve experimental and phenomenological challenges • Invaluable experience for the LHC on • Background estimation • Jet energy and Missing Et measurements • Reliability and understanding of MC and it’s limitations • Commissioning the largest scale detectors to date • Optimising triggers and handling large data samples • Publishing papers now whenever result is competitive Searches for New Physics at the Tevatron

  40. WH: compare to HSWG Mh=115 GeV Searches for New Physics at the Tevatron

  41. It’s early days for searches… • Analyses not yet fully optimised for maximal sensitivity: • Extrapolation of current result to 2 fb-1 not valid • Legacy of Run 1: “going back to Run 1” required BEFORE making improvements upon Run 1 • Largest scale detectors world-wide • E.g. 720k RO channels for CDF Silicon detector • Commissioning and maintenance take a lot of resources • Optimisation of triggers still ongoing • Constantly increasing Luminosity requires frequent changes to optimise physics potential • Offline software and Data Handling permanent struggle • Monte Carlo statistics often limited, e.g. no full survey of SUSY parameter space • Development of offline tools • e.g. b-tagging, jet calibration, tracking algorithms vital for long term success • Requires people focussing on this rather than analyses • Many (good) people focused on EWK and top measurements instead to gain understanding of detectors (quite rightly!) Searches for New Physics at the Tevatron

  42. Doubly Charged Higgs: H++/H-- • H++/H-- predicted in some extensions of SM: • Left-Right (LR) symmetric models • SUSY LR models : low mass (~100 GeV – 1 TeV) • Single and Pair production • Striking signature: decay into 2 like-sign leptons • ee channel: • M(ee)>100 GeV to suppress large BG from Z’s (conversions: e±→e±γ→e±e+e- ) • eμ and μμ channels • Sensitive to single and pair production of H++/H— CDF Searches for New Physics at the Tevatron

  43. Doubly Charged Higgs: H++/H-- • Blind analysis • search region: M>100 GeV • 0 events observed • 4.3±1.3 events expected • Result: 95% C.L. upper limit on • cross section x BR for pair production (pp→H++ H--→l+ l+ l- l-) Searches for New Physics at the Tevatron

  44. Perspectives: Stops and Sbottoms • Stopsmay be light due to mixing between partners of left, right-handed top • Similar for sbottoms • Look for direct pair production of stops or sbottoms • Stop mass reach up to ~175GeV/c2 • Sbottom sensitivity up to 250GeV/c2 Searches for New Physics at the Tevatron

  45. Lepton + Quark Resonances : Leptoquarks Apparent symmetry between the lepton & quark sectors: common origin ? • LQs appear in many extensions of SM • (compositeness, technicolor…) • Connect lepton & quark sectors • Scalar or Vector color triplet bosons • Carry both lepton and baryon number • fractional em. Charge: +-1/3, +-4/3, etc. • Braching ratio β unknown, convention: • β=1 means 100% BR LQ→l±q • β=0 means 100% BR LQ→νq • Also sensitive to e.g. squarks in RPV (exactly the same!) e e • Nice competition between world’s accelerators: • HERA, LEP and Tevatron • At Tevatron: independent of coupling λ Searches for New Physics at the Tevatron

  46. Leptoquarks: 1st generation • New analysis in run 2: • Search for LQ’s decaying LQ→νq (β=1) • 2 jets (Et>) and Et>60 GeV: • Experimentally challenging • Result: • 124 events observed • 118.3±14.5 events expected •  exclude LQ masses with 78<M<118 GeV • eejj channel: • M(LQ)>230 GeV for β=1 (72 pb-1 ) • Difficulties: • understanding Missing Et: e.g. jet mismeasurements • ISR and FSR uncertainties??? Searches for New Physics at the Tevatron

  47. Summary of 1st Generation Leptoquark Results Run 1 Run 2 Beta 1st 2nd 1.0 238 200 0.5 213 in progress 0.0 in progressin progress 1.0 230 240 0.5 197 in progress 0.0 117 117 Beta 1st 2nd 1 225 200 1/2 204 0 98 98 1 220 202 1/2 182 164 0 1231 3rd generation not shown 1 c c Searches for New Physics at the Tevatron

  48. eeg Analysis CDF has done a search for excited electron, predicted in many compositeness models Produce via contact or gauge mediated interactions The cross section depends on e* mass and L L = 200 pb-1 2 electron /g, At least one Central electron Expected 2.98 +0.4-0.3 ; observed: 3 first time search Contact interaction: At 95% C.L. Me*>889GeV (Me* = L) Gauge mediated: At 95% C.L. Me*>208GeV (Me*= L) Searches for New Physics at the Tevatron

  49. m + Jets Analysis Second generation LeptoQuarks • mmjj channel (b=1) • Two muons • 2 jets • Mmm>15 (J/y,Y) • Remove events in the Z peak • S(Et(j1)+ Et(j2) ) > 85 GeV • S(Pt(m1)+ Pt(m2)) > 85 GeV • √ Sj(Et )2+ Sm(Pt)2>200 GeV • CDF observe 2 events w/~200 pb-1 • CDF expects 3.15±0.17 • Upper limit at 95%C.L • MLQ> 240 GeV (b=1) Searches for New Physics at the Tevatron

  50. me Analysis • DØ has done model independent search in em channel • Search for an excess over the SM prediction in the kinematic space • Look at the Missing ET , sensitive to new Physics • Set upper limits at 95 % C.L. L = 98 pb-1 1 electron Et>25 GeV 1 muon Pt>25 GeV Good fiducial volume 0/1 jet Searches for New Physics at the Tevatron

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