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Di-Boson Physics @ the Tevatron

Di-Boson Physics @ the Tevatron. Liang HAN. University of Science & Technology of China (USTC). On behalf of the & Collaborations. P-Pbar @ 1.96 TeV, 2x10 32 cm -2 s -1 Vector Boson factory. CDF. DØ. ~ 0.7 million W ~ 0.15 million Z

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Di-Boson Physics @ the Tevatron

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  1. Di-Boson Physics @ the Tevatron Liang HAN University of Science & Technology of China (USTC) On behalf of the & Collaborations

  2. P-Pbar @1.96 TeV, 2x1032 cm-2s-1 • Vector Boson factory CDF DØ • ~ 0.7 million W • ~ 0.15 million Z • ~ 400 WW, ~ 120 WZ, ~50 ZZ Booster p Tevatron p at L~ 30 pb-1/week p source Main Injector & Recycler • 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) "Tevatron diBoson" @Moriond 2008

  3. 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) "Tevatron diBoson" @Moriond 2008

  4. 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) "Tevatron diBoson" @Moriond 2008

  5. 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) "Tevatron diBoson" @Moriond 2008

  6. 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) "Tevatron diBoson" @Moriond 2008

  7. 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) "Tevatron diBoson" @Moriond 2008

  8. 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) "Tevatron diBoson" @Moriond 2008

  9. 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) "Tevatron diBoson" @Moriond 2008

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

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

  12. 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) "Tevatron diBoson" @Moriond 2008

  13. 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) "Tevatron diBoson" @Moriond 2008

  14. 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) "Tevatron diBoson" @Moriond 2008

  15. Di-Boson Physics @ Tevatron • Precise measurement from O(102)pb • down to O(1)pb @ up to 2fb-1, • precise agreement to SM is observed (1) First evidence of Wg RAZ (2) Zg cross-section measurement (3) WW/WZlnjj semi-leptonic (4) WWZ TGC (5) First evidence of ZZ (1) (2) (3) • CDF results • http://www-cdf.fnal.gov/physics/ewk/ (4) (5) • D0 results • http://www-d0.fnal.gov/Run2Physics/ • WWW/results/ew.htm • More data coming, and digging hard for Higgs L.Han(USTC) "Tevatron diBoson" @Moriond 2008

  16. Backup Slides L.Han(USTC) "Tevatron diBoson" @Moriond 2008

  17. thrust axis pT2 al at di-lepton pT pT1 • To reduce the contribution of fake MET, no direct cut on MET → build a variable sensitive to “true MET” • decompose di-lepton pT in 2 components with respect to thrust axis: • al: sensible to pT mis-measurement • at: sensible to recoil activity mis-measurment • build a variable which gives more weight to at(add in quadrature with different weights) → • balance against activity in the opposite hemisphere and correct using the corresponding uncertainties • Result: • by construction all uncertainties and mis-reconstruction can ONLY reduce the valueof L.Han(USTC) "Tevatron diBoson" @Moriond 2008

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