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Electroweak measurement @ the Tevatron

Electroweak measurement @ the Tevatron. Liang HAN. University of Science & Technology of China (USTC). Tevatron, CDF and DØ. P-Pbar @ 1.96 TeV, 2x10 32 cm -2 s -1 Vector boson factor L ~ 30 pb -1 /week ~0.7 million W, ~0.15 million Z ~400 WW, ~120 WZ, ~50 ZZ, …

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Electroweak measurement @ the Tevatron

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  1. Electroweak measurement @ the Tevatron Liang HAN University of Science & Technology of China (USTC)

  2. Tevatron, CDF and DØ • P-Pbar @1.96 TeV, 2x1032cm-2s-1 • Vector boson factor L ~ 30 pb-1/week • ~0.7 million W, • ~0.15 million Z • ~400 WW, ~120 WZ, ~50 ZZ, … • Precise test on Standard Model & understand Higgs background • Two experiments perform with high efficiency L.Han(USTC)@HEP10 2008

  3. Single W and Z production -- Due to large jet background, W and Z events are typically reconstructed in lepton decay l=e,m -- Tools to calibration isolated high pT l=e,m and MET from Wen -- Physics : NNLO QCD test on Z pT, h distribution, Ztt, andMWmeasurement etc; and something that won’t be accessible at LHC… L.Han(USTC)@HEP10 2008

  4. dσ/dy (nb) √s = 1.96 TeV Rapidity y W charge asymmetry -- Up quarks carry more proton momentum than down quarks  more W-in anti-proton direction, and more W+in proton direction -- W charge asymmetry A(y) is sensitive to u(x)/d(x) -- Difficult to measure W boson A(y) directly; instead, convolute A(y) to W± V-A decay  lepton rapidity asymmetry A(hl): L.Han(USTC)@HEP10 2008

  5. Accepted by PRD arXiv 0709.4254 Lepton and W charge asymmetry • DØ, Wl: lepton charge asymmetry • CP folding  -A(-y)==A(y) • CDF, We: W charge asymmetry • Reconstruct yW using MW constraint DØ preliminary: We 1fb-1 -- Experimental uncertainties have already been smaller than orcomparable with the parton distribution function CTEQ uncertainties in most regions L.Han(USTC)@HEP10 2008

  6. Z/g*l+l-Forward/Backward Asymmetry • Standard Model neutral-current couplings of Z bosons to fermions as e- q • Electron charge forward/backward asymmetry AFBin Z e+ (measured as function of Mee) • --  as negatively charged e-relative to the incoming quark L.Han(USTC)@HEP10 2008

  7. Tevatron, the only place of q+qbare-+e+AFB precise measurement • Many systematic uncertainties cancelled • Complementary sensitivity to Z’ model-independently, via Z/g*/Z’ interference 500GeV Z’,Z, Zx AFB Mee(GeV) • Precise test on the SM, especially the weak mixing angle sin2qWmeasurement L.Han(USTC)@HEP10 2008

  8. SM fundamental parameters : a, GF, MZ, MWandsin2qW • The effective weak mixing angle , from Z-pole observables, e.g. AFB 0.23152±0.00014 -- LEP b-quark asymmetry：+2.4s from global EW fit, 3.2sfrom SLC -- NuTeVn-N scattering ：0.2277±0.0016,+3.1s from SM prediction [PRL 88, 091802(02)] L.Han(USTC)@HEP10 2008

  9. @ Tevatron • DØ 1fb-1 analysis: • Select Forward/Backward di-EM events in 50GeV<Mee<500GeV • Subtract background from QCD and SM predictions( Ztt etc) • Reweight Pythia Z/g*ee to, e.g. 1) EM energy scale and resolution calibrated at Z-pole • 2) NLO QCD Z-pT,h,Mee distribution at partonic level • Compare to s of different inputs 0.2327±0.0018±0.0006 (statistic) (systematic) -- uncertainty comparable to LEP and NuTeV -- systematic : + 0.0005CTEQ6 PDF + 0.0003EM scale/resolution 0.2238±0.0040±0.0030 • CDF 72pb-1 analysis: [PRD 71, 052002(2005)] L.Han(USTC)@HEP10 2008

  10. Unfolded AFBdistribution @ Tevatron • Correct detector resolution, acceptance & efficiency etc  comparable to prediction • Detector resolution  Mee migration  unfolding matrix, computed iteratively on rewighted MC • Detector geometric and kinematic cuts  correct acceptance ×efficiency CDF 72pb-1 -- Provide complementary information on heavy Z’ boson search L.Han(USTC)@HEP10 2008

  11. Di-Boson production • Wg (DØ 0.7 fb-1) • Zg(DØ 1 fb-1) • WZ (CDF 2 fb-1, DØ 1 fb-1) • WW/WZ ljj (CDF 1.2 fb-1) • ZZ (CDF 2 fb-1, DØ 1 fb-1) • Precise test of non-Abelian SU(2)L×U(1)Y • --complementary to LEP : higher c.m. energy, new couplings of charged currents • Probe TGC (trilinear gauge couplings) • -- sensitive to “low” energy remnants of new physics @ high scale • Background to hunting Higgs, top and SUSY • Topology : ≥2 isolated high pT(>15 GeV) lepton(l=e,m)/g, MET(>20 GeV) for W L.Han(USTC)@HEP10 2008

  12. WZ production @ Tevatron SM NLO : [ PRD 60, 113006 (1999) ] • Unique measurement on WWZ TGC -- non-SM anomalous as with form factor as -- Enhancement on production + excess at W/Z high pT spectrum • WZllln search channel : -- eee, eem, emm and mmm combined, Br~1.5% -- high pT isolated lepton + MET + di-lepton invariant mass around Z L.Han(USTC)@HEP10 2008

  13. Evidence of WZ3l @ DØ 1fb-1 • 13 candidates with 4.5 background ~ 3 significance (HWZ generator) • Anomalous WWZ TGC =1.5 TeV =2.0 TeV a -0.18<Z<0.22 -0.17<Z<0.21 -0.15<g1Z<0.35 -0.14<g1Z<0.34 -0.14<Z =g1Z<0.31 -0.12<Z =g1Z<0.29 [ PRD 76, 111104(R) (2007) ] L.Han(USTC)@HEP10 2008

  14. Observation of WZ3l @ CDF 2fb-1 • Cross-section measurement: 25 candidates [ PRL 98, 161801 ] • Constraint on anomalous WWZ =1.5 TeV =2.0 TeV a -0.14<Z<0.16 -0.13<Z<0.14 -0.17<g1Z<0.27 -0.15<g1Z<0.24 -0.86<Z<1.36 -0.82<Z<1.27 L.Han(USTC)@HEP10 2008

  15. WW/WZlnjj@ CDF 1.2fb-1 • First measurement of (l+MET+2jets) @Tevatron : • more statistic sensitive to TGC • similar to WHlnbb • huge background from W+jets, ~300pb s(WW+WZ)×Br = 2.09±0.14 pb • Analysis strategy : 2) likelihood fit  signal fraction 1) NN to increase S/B significance S/B<1% 3% xBr < 2.88pb@95%C.L. L.Han(USTC)@HEP10 2008

  16. Radiation-Amplitude Zero in Wg • SM : RAZ(Radiation Amplitude Zero) • Measured as Charge-Sign photon-lepton Rapidity • Difference Q[() - (l)] • Predicted at dip L.Han(USTC)@HEP10 2008

  17. Study of W(ln)g RAZ @ DØ 0.7fb-1 • First indication of RAZ : ET(g)>7GeV, R(l)>0.7, MT(lgn)>90GeV • Full covariance matrix c2/dof=17.0/12 • 2-Bin Statistical analysis : • unimodal hypothesis ruled out @ 2.6s Small Max Bin Dip Bin • Photon pT spectrum  anomalous WWgTGC L.Han(USTC)@HEP10 2008

  18. Precise Z(ll)g measurement @ DØ 1fb-1 • Event selections: ET(g)>7GeV, R(l)>0.9, M(ll)>30GeV ISR : M(llg) ≥ MZ ISR FSR : M(llg) ≤ MZ FSR ( Zgllg ) = 4.96±0.30(stat+syst)±0.30(lumi) pb. SM NLO : 4.74 ± 0.22 pb. [ PRD 57, 2823 (1998) ] L.Han(USTC)@HEP10 2008

  19. Anomalous ZZg/ Zgg TGC@ DØ 1fb-1 • Photon ET spectrum of selected events : [ PLB 653, 378 (2007) ] L.Han(USTC)@HEP10 2008

  20. First measurement of ZZ @ CDF 2fb-1 • Charged 4l channel: • 3 events with 0.1 background 4.2 significance L.Han(USTC)@HEP10 2008

  21. Adding the llnn channel: • leading order Elemental Matrix  likelihood ration • Combined 4l + llnnresult : 4.4 significance SM NLO :1.4 ± 0.1 pb. [ PRD 60, 113006 (1999) ] L.Han(USTC)@HEP10 2008

  22. Search for ZZ @ DØ • SM NLO : • --1.6  0.1pb [ PRD 62, 113011; PRD 60, 072002 ] • -- t-channel only, no tri-linear TGC • Charged4lchannel @1 fb-1: M(ll) > 30 GeV for eeee, eemm, mmmm • 1event observed with 0.13  0.03 background expected • Cross section (ZZ/Z*) < 4.4pb@95%C.L. • The first bounds on ZZZ/ZZg*anomalous couplings from Tevatron [ hep-ex/0712.0599 ] L.Han(USTC)@HEP10 2008

  23. Combined e and mchannel of llnn@2.2 fb-1: • Recoil of Z+X discriminating variable • Physics background  likelihood electron channel electron channel muon channel muon channel • Statistic test : 1.77σ significance predicted → 2.4σ significance observed • Cross section measurement : L.Han(USTC)@HEP10 2008

  24. EW Physics @ Tevatron • Precise measurement from O(104)pb • down to O(1)pb @ up to 2fb-1, • precise agreement to SM is observed (1) (2) (1) W charge asymmetry (2) Zee F/B asymmetry (3) First evidence of Wg RAZ (3) (4) (4) Zg cross-section measurement (5) WW/WZlnjj semi-leptonic (6) WWZ TGC (5) (7) First evidence of ZZ (6) (7) • More data coming, digging hard for Higgs, and something else as precise • measurement of AFB and L.Han(USTC)@HEP10 2008

  25. Backup slides L.Han(USTC)@HEP10 2008

  26. Integral Luminosity -- Collider performance -- Experiment performance L.Han(USTC)@HEP10 2008

  27. L.Han(USTC)@HEP10 2008

  28. Z inclusive cross section • DØ (1 fb-1): Z()(hadron) • 1527 candidates with 20% backgrounds •  (ppZ)xBr(Z) = 247 ± 8(stat.) ± 13(syst.) ± 15(lumi.)pb • Consistent with SM prediction 251.9+5-11.8pb • Experimentally important for all  studies such as H search - L.Han(USTC)@HEP10 2008

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