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Electroweak Physics and Searches for New Physics at CDF

This mini-symposium discusses the Standard Model of Particle Physics, the Higgs boson, and the limitations of the Standard Model. It explores possible extensions to the Standard Model such as Supersymmetry and Extra Dimensions. The search strategies for new physics at CDF, including high Pt leptons, high Et jets, and rare decays, are also discussed.

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Electroweak Physics and Searches for New Physics at CDF

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  1. Electroweak Physics and Searches for New Physics at CDF Beate Heinemann University of Liverpool Mini-Symposium on CDF @University of Chicago 5th of March 2004

  2. The Standard Model of Particle Physics • 3 generations of quarks and leptons interact via exchange of gauge bosons: • Electroweak SU(2)xU(1): W, Z, γ • Strong SU(3): g • Symmetry breaking caused by Higgs field • Generates Goldstone bosons • Longitudinal degrees of freedom for W and Z • 3 massive and one massless gauge bosons -Standard Model survived all experimental challenges in past 30 years! -electroweak and QCD precision data -No New Physics despite many efforts! Gauge Bosons Higgs Boson • Vacuum quantum numbers (0++) • Couples to mass • Mh = ? Beate Heinemann - University of Liverpool

  3. Why not the Standard Model? Coupling constants U(1) • Radiative corrections to Higgs mass: electroweak scale (100 GeV) much much lower than Planck Scale (1019 GeV): “hierarchy” or “naturalness” problem • No unification of forces at any scale • Higgs boson not yet found: is it there? • No explanation for matter/ anti-matter asymmetry in universe • No accounting for dark matter in universe • Many free parameters, e.g. masses of all particles: unsatisfactory SU(2) WMAP satellite Beate Heinemann - University of Liverpool

  4. What could be Beyond the SM? • Supersymmetry (SUSY): • Each SM particle has a “super”-partner with same quantum numbers apart from spin (top <-> stop, photon <-> photino, etc.) • Masses are O(1 TeV) • Unification of forces at GUT scale (1016 GeV) • Hierarchy problem solved • Extra Dimensions • String theory: links gravity to other forces • Could be large (0.1mm): probed at TeV scale • Hierarchy problem solved • The unexpected… Beate Heinemann - University of Liverpool

  5. Supersymmetry Intro • 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 χ0or sneutrinoν • Gauge-mediated models (GMSB):SUSY broken at lower energies – breaking scale F an important parameter. • Gravitino G is the LSP (NLSP χ0 →Gγ ) • If “R-Parity” conserved: • SUSY particles can only be pair-produced • Lightest SUSY Particle (LSP) stable and escapes detection • If conserved: LSP stable, carries away missing ET ~ ~ ~ Beate Heinemann - University of Liverpool

  6. Searches for New Physics: Strategy Cross Sections (fb) • Establish good understanding of data in EWK/QCD physics in Run 2: • Backgrounds to new physics searches • Indirect sensitivity to New Physics • Gain understanding of detector • Search for as many signatures as possible, involving: • High Pt leptons • Large imbalance in transverse momentum (e.g. due to neutrino or neutralino) • High Et jets • High Et photons • Rare decays of charm- and bottom-mesons • Interpret: • Provide cross section limits and acceptances (try to be as generic/model-independent as possible) applicable to future models! • In context of specific models of physics beyond the SM WW, Wγ, Zγ, ? Higgs Beate Heinemann - University of Liverpool

  7. The Tevatron: Run 2 • Run 2 started in June 01: • CMS energy 1.96 TeV • Delivered Lumi: 400/pb (run 1 was 110/pb) • Promising slope in 2004! • Data taking efficiency about 90%! • Physics Analyses: • Use about 200/pb taken between 03/02 and 09/03 Expect 2 /fb by 2006 and 4.4-8.6 /fb by 2009  sensitivity to New Physics improved by>5 compared to Run 1 Beate Heinemann - University of Liverpool 90% efficiency Data Recording Efficiency

  8. The CDF 2 Detector New for Run 2 Tracking System Silicon Vertex detector (SVX II) Intermediate silicon layers (ISL) Central Outer tracker (COT) Scintillating tile forward calorimeter Intermediate muon detectors Time-Of-Flight system Front-end electronics (132 ns) Trigger System (pipelined) DAQ system Retained from Run 1 • Solenoidal magnet (1.4 Tesla) • Central Calorimeters • Central Muon Detectors Beate Heinemann - University of Liverpool

  9. Outline • W and Z production • Establish understanding of detector • Alternative luminosity measurement • Test NNLO QCD calculations • Wγ, Zγ and γγproduction • Anomalous triple gauge couplings • SUSY? • High mass di-leptons • New physics: Z’, RS gravitons, etc. • Di-leptons + Di-jets • Leptoquarks, Squarks in RPV SUSY • Higgs boson • W mass • h→WW, double charged higgs • Bs→μμ • SUSY? Beate Heinemann - University of Liverpool

  10. Inclusive W cross section • W→μν and W→eν signal: • Backgrounds from QCD, Z→ℓ+ℓ−, W→τν and cosmic μ’s • Excellent description by MC simulation σ(pp→W→lν ) = 2777 ±10(stat) ± 52 (syst) ±167 (lum) pb J. Stirling: SM (NNLO)=2770 pb Beate Heinemann - University of Liverpool

  11. Z Production Cross Section • Z → e+ e− signal and Z →μ+μ− signals • 66 < m(ℓℓ)/GeVc-2 < 116 • Small backgrounds from QCD, Z/W→τ, cosmics μ’s: less than 1.5% SM: 250.2 pb For 66<m(l+l-)<116 GeV/c2 : σ(pp→Z/γ* →l+l-) = 254.3 ±3.3(stat) ± 4.3 (syst) ±15.3 (lum) pb Beate Heinemann - University of Liverpool

  12. W and Z Cross Sections: Summary Beate Heinemann - University of Liverpool

  13. Wγ Production • pp → Wγ → ℓνγ: • probes ewk boson self-coupling: direct consequence of SU(2)xU(1) gauge theory • new physics, e.g. composite W modifies coupling • Selection: • 1 high-PT lepton (e,μ) • 1 Photon with: ET>7GeV, ΔR(γ,ℓ)>0.7 • 1 neutrino: large missing-ET>25 GeV Separate WWγ vertex from (boring) Lepton Bremsstrahlung Beate Heinemann - University of Liverpool

  14. Di-boson production: Wγ MT (lγ,ν) /GeV • Data agree with SM expectation: ET(γ)/GeV NLO prediction (U. Baur): Next: extract WWγ coupling from Photon Et spectrum Beate Heinemann - University of Liverpool

  15. Zγ Production • pp → Zγ → ℓ+ℓ-γ • 2 leptons with Et>25 GeV • 1 photon with Et>7 GeV, ΔR(lγ)>0.7 • New physics at Zγ vertex? Beate Heinemann - University of Liverpool

  16. Di-boson production: Zγ • Data agree with SM expectation: sigma*BR=5.3+-0.6(stat)+-0.3(sys)+-0.3(lumi) pb NLO prediction (U. Bahr) (LO + ET(γ) dependent k –factors): Beate Heinemann - University of Liverpool

  17. W/Z+gamma+X: more exclusive channels • Run I: • found 1 event with 2 photons, 2 electrons and large missing Et • SM expectation 10-6 (!!!) • Run II: • Any new such event would be exciting! SUSY? Beate Heinemann - University of Liverpool

  18. Search for gg+ / ET e.g. ~ ~ • Gravitino is the LSP • NLSP: Neutralino c1 G • Experimental Signature: +ET ~ ~ ~ ~ ~ Run 1: eeggEt pp →XX + Y → ggGG + Y SUSY would show up as an excess of events with large Missing Energy For Missing Et>25GeV Expected background: 22 Observed: 2 • Search Selection: • 2 central photons w/ Et>13(25) • Cosmic/beam halo removal Set cross section limit Beate Heinemann - University of Liverpool

  19. GMSB Search in gg+ / ET Acceptance Set the lower mass limit on the lightest chargino in GMSB: Mc>113 GeV @ 95% C.L. Beate Heinemann - University of Liverpool

  20. 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 Beate Heinemann - University of Liverpool

  21. 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 Beate Heinemann - University of Liverpool

  22. 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’ ~ ~ ν ν Beate Heinemann - University of Liverpool

  23. Z→e+e−Forward-Backward Asymmetry P P θ e+ • Tevatron uniquely sensitive to Z-γ* interference at high invariant masses. • Shape of the Afb spectrum can be used to extract values for sin2(θW) and u, d couplings to Z • Agreement with SM prediction. angle between p and e− e− Beate Heinemann - University of Liverpool

  24. 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 Beate Heinemann - University of Liverpool

  25. 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 ) Beate Heinemann - University of Liverpool

  26. Leptoquarks: 2nd generation • Signature: • 2 high Pt muons • 2 high Et jets • Suppress Z→μμ background Expect 3.15±1.17 events, observe 2  Exclude LQ’s at M(LQ)<240 GeV Beate Heinemann - University of Liverpool

  27. TeVatron Run 2 The Higgs Boson: the missing piece? • Precision measurements of • MW =80.450 +- 0.034 GeV/c2 • Mtop=174.3 +- 5.1 GeV/c2 • Prediction of higgs boson mass within SM due to loop corrections, e.g. MW (GeV) Mtop (GeV) Indirect constraints versus direct searches! Will they agree? 193 GeV Beate Heinemann - University of Liverpool

  28. Towards W Mass Difficult measurement  Work in progress – no results yet • Use MC templates to fit to signal + background • CDF Run I mW = 80,465 ± 100(stat) ± 104(sys) MeV • CDF Run II for 500/pb estimate: = X ± 40(stat) ± 55(sys) MeV Beate Heinemann - University of Liverpool

  29. Towards Higgs: WW Production • Motivation: • Sensitive to WWγ and WWZ vertex • Higgs discovery channel • Anything new/unexpected? • 2 leptons +missing Et +no jet with Et>15 GeV: • Observed: 5 events • Expected: • WW: 6.89±1.53 • BG: 2.34±0.83 Beate Heinemann - University of Liverpool

  30. Doubly Charged Higgs: H++/H-- background • H++ (double charged higgs) predicted in some extensions of SM and SUSY: M=100…1000 GeV • 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— • Blind analysis • search region: M>100 GeV • 0 events observed Result: 95% C.L. upper limit on • cross section x BR for pair production (pp→H++ H--→l+ l+ l- l-) • M(H++)>130 GeV Beate Heinemann - University of Liverpool

  31. Rare Decays: Bs->μ+μ- • 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 (~tan6β ?) • 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 SM vs e.g. SUSY Beate Heinemann - University of Liverpool

  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 and (g-2)μ Beate Heinemann - University of Liverpool

  33. Conclusion and Outlook • Physics at CDF is back: • Have twice the Run I luminosity and excellent detector • Electroweak Measurements in good agreement with Standard Model: • W and Z cross section, Di-boson production • W mass in progress • Searches for New Physics have started: • Expect new physics at the TeV scale (hierarchy problem) • Z’, Large extra dimensions, Leptoquarks, SUSY, Higgs • Cover broad range of possible signals • no signals yet but constraining theoretical models • And many results I could not cover… Many New Exciting Results coming soon! Beate Heinemann - University of Liverpool

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