Tevatron Electroweak Results Tevatron Electroweak Results And Electroweak Summary And Electroweak Summary Sean Mattingly Brown University For the CDF and DZero Collaborations XXIV Physics in Collision Boston, MA 29 June 2004
Jan 09, 2016
Tevatron Electroweak ResultsTevatron Electroweak ResultsAnd Electroweak SummaryAnd Electroweak Summary
Sean Mattingly
Brown University
For the CDF and DZero Collaborations
XXIV Physics in Collision
Boston, MA
29 June 2004
Sean MattinglyXXIV PiC29 June 2004 2
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…
p
p
q’q W±
e,
p
p
qq Z0/
e+, +
e-, -
BR = ~10% BR = ~3%
( ) 0.25 nbZ BR ( ) 2.7 nb W BR
Electroweak Physics at the TevatronElectroweak Physics at the Tevatron
Sean MattinglyXXIV PiC29 June 2004 3
Tevatron Electroweak MeasurementsTevatron Electroweak MeasurementsW production
– Decays to e,, 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(w), quark couplings
Combined W/Z– Ratio of W/Z cross sections * BR indirect W width
Diboson production - WW/WZ/W/Z– Triple & quartic gauge couplings
W/Z/Diboson production are important backgrounds for top, Higgs and SUSY production
Sean MattinglyXXIV PiC29 June 2004 4
W/Z Event SignaturesW/Z Event Signatures
W production
?lM Can’t measure pZ of
80.425 0.034 GeVWM (LEP/TeV)
2( [1 cos( )])l miss l missT T TM E E
Z productione+,+
q
e-,-Hadronic Recoil
q
q’
e,Hadronic Recoil
q
2( ) 2( )l l l l l l l l
M p p E E p p ����������������������������
91.1876 0.0021 GeVZM (LEP)
Sean MattinglyXXIV PiC29 June 2004 5
DetectorsDetectors
= -1
= -2
Run II LuminosityTypically: ~6 x 1031 / cm2 sRecord: 8.5 x 1031 / cm2 sDelivered: ~570 pb-1
Recorded: ~400 pb-1 / expt~100K Zs, ~10M Ws /lept chan
Goal: 4.4 fb-1 by end FY 09
DZero Run II upgrades2T solenoid, inner trackingPreshower system/shieldingTrigger, DAQ
CDF Run II upgradesInner trackingForward calorimeterExtended systemTrigger, DAQ
CDF Analyses: 65-200 pb-1DZero Analyses: 42-162 pb-1
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Analysis MethodsAnalysis MethodsTriggers
– 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 > 25 GeV
ID efficiencies measured in Z eventsPrimary backgrounds determined using data jet events
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DZero: BR( ) 275 9 9 28 pbZ stat syst lumiee
5.55.4CDF: BR( ) 255.2 3.9 15.3 pbZ stat syst lumiee
*BR(Z *BR(Z ee) ee) Two electrons, ET > 25 GeV
– DZero: || < 1.1, CDF: full detector (1st EM central)
Small backgrounds from jets, Z ,(DY correction)DZero Run II Preliminary
BkgBkg+MC SignalData
No track matchL=42 pb-1
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*BR(Z *BR(Z ))Two opposite charged muons, pT > 15-20 GeV
– CDF: || < 1.0, DZero ||< 1.8
Very small backgrounds : jets(b), Z, cosmics, (DY corr.)
7.06.2CDF: BR( ) 248.9 5.9 14.9 pbZ stat syst lumi
DZero: BR( ) 261.8 5.0 8.9 26.2 pbZ stat syst lumi
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6156CDF Central: BR( ) 2782 14 167 pbstat syst lumiW e
*BR(W *BR(W e e))One electron, pT > 25 GeV, missing ET > 25 GeV
– DZero: || < 1.1, CDF: central & plug
Backgrounds: jets, W, Zee
Points: Background Subtracted DataHistogram: We MC
L=42 pb-1
DZero: BR( ) 2844 21 128 284 pbW stat syst lumie
CDF Plug: BR( ) 2874 34 167 172 pbstat syst lumiW e
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*BR(W *BR(W ))One muon, pT > 20 GeV, missing ET > 20 GeV
– DZero: || < 1.6 (from initial lumi), CDF: || < 1.0
Backgrounds: Z, Wjets(b)
DZero: BR( ) 3226 128 100 322 pbW stat syst lumi 6460CDF: BR( ) 2772 16 166 pbstat syst lumiW
L=17 pb-1
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CDF/DZero ComparisonCDF/DZero Comparison
Similar efficiencies and purities– CDF: Includes forward electrons– DZero: Includes farther forward muons
Channel # eventsPurity
(%)Luminosity Used (pb-1)
* A (%)
We CDF 48.0K 94.0 72 23.1
DZero 27.4K 95.7 41 18.4
W CDF 31.7K 90.0 72 14.4
DZero 8.3K 88.0 17 13.2
Zee CDF 4242 98.5 72 22.7
DZero 1139 98.3 41 9.97
Z CDF 1785 98.5 72 10.2
DZero 6126 98.9 117 16.4
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W/Z Cross Sections SummaryW/Z Cross Sections Summary
Van Neerven, Matsuura
Van Neerven, Matsuura
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Indirect W WidthIndirect W Width
CDF combined electron & muon channels
( ) ( ) ( )
( ) ( ) ( )W W
Z Z
BR Z W lR
BR Z ll W
Tree level NNLO QCD calc (Van Neerven)
PDG(LEP)
SM EWK Calculation
10.93 0.15 0.13Combined stat systR ( ) (10.93 0.21)%BR W ( ) 2.071 0.040 GeVW
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Toward Higher PrecisionToward Higher PrecisionLuminosity 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 Physics with Zleptonic(1 pronghadronic
– Demonstrates visibility of resonances at the Tevatron– DZero: muonic decays + observe N 0, CDF: electronic decays
Visible Mass (GeV)
D0 Run II preliminary L=68 pb-1
CDF: BR( ) 242 48 26 15 pbZ stat syst lumi DZero: BR( ) 222 36 57 22 pbZ stat syst lum
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Physics with Physics with (cont)(cont)WCDF)
– Trigger on track + missing ET
– Count tracks in 10o cone, veto on tracks in 30o cone– Reconstruct 0 with detectors at shower max
– Combined mass < M
– Backgrounds: W, We, Z, jets
BR( ) 2.62 0.07 0.21 0.16 pbstat syst lumiW
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Forward-backward AsymmetryForward-backward Asymmetry
e− p
e+
p
)0(cos)0(cos
)0(cos)0(cos
fbA
Z/* e+e- (CDF)
– At Tevatron can measure at Z pole and above and below– Directly probes V-A, extract sin2W and u/d couplings to Z
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W Charge AsymmetryW Charge AsymmetryWe (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 W±’s direction (lost ) 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
( ) / ( ) /
( ) / ( ) /W
d W dy d W dyA
d W dy d W dy
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W Charge Asymmetry (cont)W Charge Asymmetry (cont)
Select W events and identify charge
– 50 < MT < 100 GeV, no other EM object with ET > 25 GeV
– Use calorimeter seeded tracking with forward silicon to determine charge out to |det| < 2
– Charge mis-ID rate measured using Zee– < 1% for |det| < 1.5, < 4% farther
forward
– Backgrounds bias asymmetry toward zero– Zee, W subtracted using MC, jets
using data
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Drell-Yan Invariant Mass SpectrumDrell-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
Di-EM Mass (GeV)
95% CL, M(Z’/SM) > 780 GeV
95% CL, M(Z’/SM) > 735 GeV
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Diboson ProductionDiboson Production
Tevatron collisions can produce W, Z, 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
Sean MattinglyXXIV PiC29 June 2004 22
Diboson Production: WDiboson Production: W
W(e/: Firstselect Wl events (CDF/DZero)– Add photon requirement: isolated EM, no track, shower max
– Photon ET > 7-8 GeV, lepton-photon R > 0.7, || < 1.1 – Backgrounds: W+jet, Z+, Z+jet, “leX”, W
Initial State Radiation Final State Radiation WW: Triple Gauge Coupling
D0 RunII preliminary W(e/)
L(e) = 162 pb-1
L() = 82 pb-1
Sean MattinglyXXIV PiC29 June 2004 23
Diboson Production: WDiboson Production: W Cross Sections Cross SectionsDZero ( ET > 8 GeV) CDF ( ET > 7 GeV)
We162 pb-1
W82 pb-1
W(e/)202 pb-1
W+jet 80.0 ± 7.4 30.1 ± 10.0 49.52 ± 14.95
Z+ 4.7 ± 2.0 22.37 ± 1.26
“leX” 3.7 ± 0.5 0.6 ± 0.6
W 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
*BR(l) 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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Initial State Radiation Final State Radiation ZZg: Triple Gauge Coupling
Diboson Production: ZDiboson Production: Z
Z(e/)(CDF)– Z selection + photon
– Photon ET > 7 GeV, R(l) > 0.7, || < 1.1
– Relative backgrounds smaller than for W– Main background: Z+jet
( )10
( )W
Z
BR
BR
( )3
( )W
Z
BR
BR
Sean MattinglyXXIV PiC29 June 2004 25
Diboson Production: ZDiboson Production: Z Cross Section Cross Section
CDF: Z(ee/)202 pb-1
Total Bkg 4.4 ± 1.3
Total SM 70.5 ± 4.0
Data 69
*BR(l) 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: WWDiboson Production: WWTwo analyses from CDF
– High purity: identify 2 leptons– High efficiency: identify 1 lepton + 1 isolated track– Backgrounds: DY, WZ/ZZ/W, Z, ttllX, fakes
HWW (CDF/DZero): See E. Nagy’s talk
Purity analysis– 2 high pT leptons
– Opposite sign
– Missing ET > 25 GeV
– Veto if any high ET jets
– Reject if dilepton mass near Z mass and (missing ET)/ (scalar summed ET) < 3
Sean MattinglyXXIV PiC29 June 2004 27
Diboson Production: WW (cont.)Diboson Production: WW (cont.) Efficiency analysis
– 1 high pT lepton + 1 isolated high pT track– Missing ET > 25 GeV– Veto if > 1 high ET jet– Reject (missing ET)/(scalar summed ET) < 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
WZ+ZZ+W 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
(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 StatesZZ/WZ Final States
Look for leptonic final states (CDF)– 2-4 high pT leptons in e and channels (194 pb-1)
– ZZllll or ll and WZlll
– Require one lepton pair to be consistent with Z mass
– 5.1 ± 0.7 expected– 4 observed
– 95% CL: (ZZ/WZ) < 13.8 pb-1
– SM (Ellis & Campbell) = 5.2 pb
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Precision Electroweak Measurements Precision Electroweak Measurements And Electroweak Radiative CorrectionsAnd 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– had, s(MZ), MZ, MW, sin2W, 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/WidthW Mass/Width
Tevatron W mass and width – From fits to MT spectrum
LEP-2 W mass and width – From reconstructing Ws– e+e-WWqqqq or qql
– Difference between two final states: mW = 22 ± 43 MeV
Sean MattinglyXXIV PiC29 June 2004 31
W Mass ProspectsW 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)
Sean MattinglyXXIV PiC29 June 2004 32
Top Quark MassTop 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
Sean MattinglyXXIV PiC29 June 2004 33
W and Top Mass in Electroweak FitW and Top Mass in Electroweak Fit
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
(indirect)
(direct)
LEPEWWG
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Electroweak Fit: Top MassElectroweak Fit: Top Mass
Predicted and measured Mtop in good agreement– Measurement uncertainty half of prediction uncertainty
LEPEWWG
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Electroweak Fit: W MassElectroweak Fit: W Mass
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
LEPEWWG
Sean MattinglyXXIV PiC29 June 2004 36
Electroweak Fit: Higgs MassElectroweak Fit: Higgs Mass
Fit using high Q2 (LEP, SLC, Tevatron) data– Most likely MHiggs = 113 ± 62
42 GeV– MHiggs < 237 GeV (95% CL)
LEPEWWG A. Quadt
Year
Sean MattinglyXXIV PiC29 June 2004 37
Electroweak Fit: SummaryElectroweak Fit: Summary
Fit to all observables– 2/Ndof = 16.3/13
– Largest pull from b AFB
– 2.5 effect in opposite direction of next largest pull: Al(SLD)
– Accurately predicts low Q2 measurements
– Atomic parity violation– Moller scattering– NuTeV?
LEPEWWG
Sean MattinglyXXIV PiC29 June 2004 38
NuTeV’s ResultNuTeV’s Result Paschos-Wolfenstein relation: neutrinos on isoscalar target
sin2W = 0.22773 ± 0.00135(stat) ± 0.00093(syst) [SM = 0.2226 ± 0.0004]
Or…assuming sin2W is in agreement (i.e. MW/MZ)– = 0.988 ± 0.004
3 effect– New physics? New particles, oscillations, etc…– Old physics? PDFs, non-isoscalar target, sea asymmetry, etc…
21 sinNC NCud W
CC CC
q qW±/Z
Sean MattinglyXXIV PiC29 June 2004 39
ConclusionConclusion
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 < 237 GeV, most likely MHiggs = 113 ± 62
42 GeV– Upcoming Tevatron Run 2 top quark and W mass measurements important
components in Higgs mass constraints