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Electroweak Physics and Searches for New Physics at CDF

Electroweak Physics and Searches for New Physics at CDF. Beate Heinemann University of Liverpool Mini-Symposium on CDF @University of Chicago 5 th of March 2004. The Standard Model of Particle Physics. 3 generations of quarks and leptons interact via exchange of gauge bosons:

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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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