Tevatron Electroweak Results And Electroweak Summary

1
Tevatron Electroweak ResultsAnd Electroweak
Summary

• Sean Mattingly
• Brown University
• For the CDF and DZero Collaborations

XXIV Physics in Collision Boston, MA 29 June 2004
2
Electroweak Physics at the Tevatron

• W and Z production
• Well understood event signatures
• Leptonic decay modes avoid high jets backgrounds
• Increase understanding of detector by studying
  W/Z production
• Cross sections are relatively well known and
  high
• High statistics and clean event signatures ?
  precision measurements such as

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Tevatron Electroweak Measurements

• W production
• Decays to e,m,t ? lepton universality
• Charge asymmetry ? constrain PDFs
• Transverse mass distribution ? direct W mass
  width
• Constrain Higgs mass
• Z production
• Search for Z resonances
• Forward-backward asymmetry ? sin2(qw), quark
  couplings
• Combined W/Z
• Ratio of W/Z cross sections BR ? indirect W
  width
• Diboson production - WW/WZ/Wg(g)/Zg(g)
• Triple quartic gauge couplings
• W/Z/Diboson production are important backgrounds
  for top, Higgs and SUSY production

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W/Z Event Signatures
Z production
e,m
q
(LEP)
q
Hadronic Recoil
e-,m-
W production
n
? Cant measure pZ of n
q
q
(LEP/TeV)
Hadronic Recoil
e,m
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Detectors
DZero Run II upgrades 2T solenoid, inner
tracking Preshower m system/shielding Trigger,
DAQ CDF Run II upgrades Inner tracking Forward
calorimeter Extended m system Trigger, DAQ
CDF Analyses 65-200 pb-1
DZero Analyses 42-162 pb-1

• Run II Luminosity
• Typically 6 x 1031 / cm2 s
• Record 8.5 x 1031 / cm2 s
• Delivered 570 pb-1
• Recorded 400 pb-1 / expt
• 100K Zs, 10M Ws /lept chan
• Goal 4.4 fb-1 by end FY 09

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Analysis Methods

• Triggers
• Electrons EM calorimeter
• Muons track muon system
• Electron ID
• High ET isolated EM calorimeter cluster usually
  w/ track match
• Muon ID
• High ET isolated track matched to muon detector
  track or calorimeter MIP
• Z candidates
• 2 leptons w/ invariant mass consistent with Z
  mass
• W candidates
• 1 lepton missing ET gt 25 GeV
• ID efficiencies measured in Z events
• Primary backgrounds determined using data jet
  events

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sBR(Z ? ee)

• Two electrons, ET gt 25 GeV
• DZero h lt 1.1, CDF full detector (1st EM
  central)
• Small backgrounds from jets, Z ? tt,(DY
  correction)

DZero Run II Preliminary
Bkg BkgMC Signal Data No track match L42 pb-1
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sBR(Z ? mm)

• Two opposite charged muons, pT gt 15-20 GeV
• CDF h lt 1.0, DZero hlt 1.8
• Very small backgrounds jets(b), Z?tt, cosmics,
  (DY corr.)

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sBR(W ? en)

• One electron, pT gt 25 GeV, missing ET gt 25 GeV
• DZero h lt 1.1, CDF central plug
• Backgrounds jets, W?tn, Z?ee

Points Background Subtracted Data Histogram
W?en MC L42 pb-1
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sBR(W ? mn)

• One muon, pT gt 20 GeV, missing ET gt 20 GeV
• DZero h lt 1.6 (from initial lumi), CDF h lt
  1.0
• Backgrounds Z?mm, W?tn, jets(b)

L17 pb-1
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CDF/DZero Comparison
Channel events Purity () Luminosity Used (pb-1) e A ()
W?en CDF 48.0K 94.0 72 23.1
DZero 27.4K 95.7 41 18.4
W?mn CDF 31.7K 90.0 72 14.4
DZero 8.3K 88.0 17 13.2
Z?ee CDF 4242 98.5 72 22.7
DZero 1139 98.3 41 9.97
Z?mm CDF 1785 98.5 72 10.2
DZero 6126 98.9 117 16.4

• Similar efficiencies and purities
• CDF Includes forward electrons
• DZero Includes farther forward muons

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W/Z Cross Sections Summary
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Indirect W Width

• CDF combined electron muon channels

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Toward Higher Precision

• Luminosity error 10 ? 6.5
• CDF and DZero use same luminosity constants
• Added luminosity
• Improved statistical errors
• Smaller lepton ID systematics
• Refined background estimates
• Improved detector simulation
• Energy scale (EM and Hadronic), detector geometry
  and material description
• PDFs
• Using CTEQ6 and MRST sets w/ error sets
• Combine CDF and DZero results
• Tevatron Electroweak working group
• Standardized error reporting
• Account for error correlations
• http//tevewwg.fnal.gov

Use precision measurements in electroweak fits
(see 2nd part of talk)
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Physics with t

• Z?t(leptonic)t(1 prong hadronic)
• Demonstrates visibility of tt resonances at the
  Tevatron
• DZero muonic decays observe N p0, CDF
  electronic decays

D0 Run II preliminary L68 pb-1
mt Visible Mass (GeV)
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Physics with t (cont)

• W?tn (CDF)
• Trigger on track missing ET
• Count tracks in 10o cone, veto on tracks in 30o
  cone
• Reconstruct p0 with detectors at shower max
• Combined mass lt Mt
• Backgrounds W?mn, W?en, Z?tt, jets

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Forward-backward Asymmetry

• Z/g ? ee- (CDF)
• At Tevatron can measure at Z pole and above and
  below
• Directly probes V-A, extract sin2qW and u/d
  couplings to Z

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W Charge Asymmetry

• W?en (CDF)
• Up-type quarks carry more average momentum
• W boosted in p direction, W- boosted in p
  direction
• Charge asymmetry as function of rapidity
  constrains PDFs
• Cannot unambiguously determine Ws direction
  (lost n) but e direction carries W direction
  information
• Measure charge asymmetry using e rapidity
• Higher ET e more closely aligned with W
  direction
• Main constraints for forward rapidities
• Ratio of u/d PDFs

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W Charge Asymmetry (cont)

• Select W events and identify charge
• 50 lt MT lt 100 GeV, no other EM object with ET gt
  25 GeV
• Use calorimeter seeded tracking with forward
  silicon to determine charge out to hdet lt 2
• Charge mis-ID rate measured using Z?ee
• lt 1 for hdet lt 1.5, lt 4 farther forward
• Backgrounds bias asymmetry toward zero
• Z?ee, W?tn subtracted using MC, jets using data

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Drell-Yan Invariant Mass Spectrum

• CDF/DZero Compare to Drell-Yan
• Set limits on Z, extra dimensions, etc.
• Improve on Run I limits, test new models

95 CL, M(Z/SM) gt 780 GeV
95 CL, M(Z/SM) gt 735 GeV
Di-EM Mass (GeV)
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Diboson Production

• Tevatron collisions can produce Wg(g), Zg(g), WW,
  WZ, ZZ
• Probe the gauge structure of electroweak
• Search for anomalous couplings
• Improve diboson modeling
• Diboson production backgrounds in searches for
  new physics
• Leptonic decay modes
• Minimize jet backgrounds

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Diboson Production Wg

• Wg?(e/m)ng First select W?ln events (CDF/DZero)
• Add photon requirement isolated EM, no track,
  shower max
• Photon ET gt 7-8 GeV, lepton-photon DR gt 0.7, hg
  lt 1.1
• Backgrounds Wjet, Zg, Zjet, leX, W?tng

D0 RunII preliminary W?(e/m)ng
L(e) 162 pb-1 L(m) 82 pb-1
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Diboson Production Wg Cross Sections
DZero (g ET gt 8 GeV) DZero (g ET gt 8 GeV) CDF (g ET gt 7 GeV)
Wg?eng 162 pb-1 Wg?mng 82 pb-1 Wg?(e/m)ng 202 pb-1
Wjet 80.0 7.4 30.1 10.0 49.52 14.95
Zg 4.7 2.0 22.37 1.26
leX 3.7 0.5 0.6 0.6
Wg?tng 3.4 1.1 0.9 0.3 3.23 0.29
Total Bkg 87.1 7.5 37 10 75.12 15.01
Total SM 142 17 67 13 255.63 26.52
Data 146 77 259
sBR(lng) 19.3 2.7(stat) 6.1(sys) 1.2 (lumi) pb 19.3 2.7(stat) 6.1(sys) 1.2 (lumi) pb 19.7 1.7(stat) 2.0(sys) 1.1(lumi) pb
Baur NLO 16.4 0.4 pb 19.3 1.3 pb
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Diboson Production Zg

• Z?(e/m)g (CDF)
• Z selection photon
• Photon ET gt 7 GeV, DR(lg) gt 0.7,
  hg lt 1.1
• Relative backgrounds smaller than for Wg
• Main background Zjet

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Diboson Production Zg Cross Section
CDF Zg?(ee/mm)g 202 pb-1
Total Bkg 4.4 1.3
Total SM 70.5 4.0
Data 69
sBR(lng) 5.3 0.6(stat) 0.4(sys) 0.3(lumi) pb
Baur NLO 5.4 0.4 pb
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Diboson Production WW

• Two analyses from CDF
• High purity identify 2 leptons
• High efficiency identify 1 lepton 1 isolated
  track
• Backgrounds DY, WZ/ZZ/Wg, Z?tt, tt?llX, fakes
• H?WW (CDF/DZero) See E. Nagys talk

• Purity analysis
• 2 high pT leptons
• Opposite sign
• Missing ET gt 25 GeV
• Veto if any high ET jets
• Reject if dilepton mass near Z mass and (missing
  ET)/ (scalar summed ET) lt 3

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Diboson Production WW (cont.)

• Efficiency analysis
• 1 high pT lepton 1 isolated high pT track
• Missing ET gt 25 GeV
• Veto if gt 1 high ET jet
• Reject (missing ET)/(scalar summed ET) lt 5.5

CDF Purity Analysis CDF Efficiency Analysis
WW 11.3 1.3 16.3 0.4
DY 1.1 0.4 1.8 0.3
WZZZWg 1.8 0.1 2.4 0.1
Top 0.05 0.02 1.8 0.1
Fakes 1.1 0.5 9.1 0.8
Total Bkg 4.8 0.7 15.1 0.9
Total SM 16.1 1.6 31.5 1.0
Data 17 39
s(WW) 14.2 5.6 4.9 1.6 0.9 pb 19.4 5.1 3.5 1.2 pb
NLO Ellis Campbell 12.5 0.8 pb
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ZZ/WZ Final States

• Look for leptonic final states (CDF)
• 2-4 high pT leptons in e and m channels (194
  pb-1)
• ZZ?llll or llnn and WZ?lnll
• Require one lepton pair to be consistent with Z
  mass
• 5.1 0.7 expected
• 4 observed
• 95 CL s(ZZ/WZ) lt 13.8 pb-1
• SM (Ellis Campbell) 5.2 pb

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Precision Electroweak Measurements And
Electroweak Radiative Corrections

• Large number of measurements from LEP, SLC and
  Tevatron
• W mass/width (Tevatron, LEP-2)
• Top quark mass (Tevatron)
• Z-pole measurements (LEP, SLD)
• Z lineshape parameters
• Polarized leptonic asymmetries
• Heavy flavor asymmetries and branching fractions
• Hadronic charge asymmetry
• In the SM, each observable can be calculated/fit
  in terms of
• Dahad, as(MZ), MZ, MW, sin2qW, Mtop, Mhiggs,
  etc
• Higgs top enter as
  
  1 radiative corrections
• LEP Electroweak Working Group
• ZFITTER, TOPAZ0

Recent and future updates
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W Mass/Width

• Tevatron W mass and width
• From fits to MT spectrum
• LEP-2 W mass and width
• From reconstructing Ws
• ee-?WW?qqqq or qqln
• Difference between two final states DmW 22
  43 MeV

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W Mass Prospects

• Final CDF/DZero Run I W mass 80.452 0.059 GeV

Errors decrease with larger Run II luminosity
and Run II detector upgrades

Run II measurements of W charge asymmetry and Z
rapidity distribution constrain PDF ? reduce PDF
uncertainty

• Run II uncertainty goal 40 MeV per experiment
• 25 MeV combined (TEVEWWG)

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Top Quark Mass

• DZero update on Run 1 result
• Mtop 180.1 5.3 GeV
• 15 smaller error than previous
• Preliminary CDF Run 2 results
• See talk by A. Hocker
• Not yet included in fits
• Expected Run 2 accuracy 2.5 GeV

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W and Top Mass in Electroweak Fit
LEPEWWG
(indirect)

• Z-pole measurements
• Use fit to indirectly predict W/top mass (LEP-1,
  SLD)
• Direct and indirect agree
• Test of SM
• Both favor lighter Higgs

(direct)
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Electroweak Fit Top Mass
LEPEWWG

• Predicted and measured Mtop in good agreement
• Measurement uncertainty half of prediction
  uncertainty

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Electroweak Fit W Mass
LEPEWWG

• Predicted and measured MW in agreement
• Measured MW not yet as accurate as prediction
• Combined CDF/DZero Run II W mass expect similar
  accuracy to prediction

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Electroweak Fit Higgs Mass
LEPEWWG
A. Quadt
Year

• Fit using high Q2 (LEP, SLC, Tevatron) data
• Most likely MHiggs 113 6242 GeV
• MHiggs lt 237 GeV (95 CL)

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Electroweak Fit Summary
LEPEWWG

• Fit to all observables
• c2/Ndof 16.3/13
• Largest pull from b AFB
• 2.5s effect in opposite direction of next largest
  pull Al(SLD)
• Accurately predicts low Q2 measurements
• Atomic parity violation
• Moller scattering
• NuTeV?

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NuTeVs Result

• Paschos-Wolfenstein relation neutrinos on
  isoscalar target
• sin2qW 0.22773 0.00135(stat)
  0.00093(syst) SM 0.2226 0.0004
• Orassuming sin2qW is in agreement (i.e. MW/MZ)
• rn 0.988 0.004
• 3s effect
• New physics? New particles, oscillations, etc
• Old physics? PDFs, non-isoscalar target, sea
  asymmetry, etc

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Conclusion

• Many Tevatron Run II electroweak measurements
• Detector understanding increasing
• 200pb-1 of luminosity analyzed per experiment
• Preliminary W mass measurements soon
• TEVEWWG will combine CDF and DZero measurements
• Standard Model describes large number of
  measurements with precision
• Discrepancies can be interpreted as statistical
  fluctuations
• Higgs mass constrained lt 237 GeV, most likely
  MHiggs 113 6242 GeV
• Upcoming Tevatron Run 2 top quark and W mass
  measurements important components in Higgs mass
  constraints