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W properties AT CDFW properties AT CDF
J. E. GarciaJ. E. Garcia
INFN Pisa
OOutlineutlineC
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1.CDF detector
2.W cross section measurements
3.W mass and width
4.W charge asymmetry
5.Summary
Jose E. Garcia – INFN Pisa
W @ TW @ TevatronevatronC
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Precise Electroweak measurementsPrecise Electroweak measurements
Check Standard ModelCheck Standard Model
Provide evidence of physics beyond SMProvide evidence of physics beyond SM
Important input to LHC physics programImportant input to LHC physics program
Tevatron is for the next years the only accelerator than can produce Ws directly:
~ 90,000 W e () events per week. With a week luminosity of 15 pb-1.
Forward ElectroMagnetic and Hadronic calorimeters (“PLUG”).
(1 < || < 3)
Drift chamber (COT)Drift chamber (COT)
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CDFCDF II II
Silicon trackerSilicon tracker
a.a. L00 L00 (1 SS, r-(1 SS, r-))
b.b. SVXII SVXII (5 DS)(5 DS)
c.c. ISL ISL (2 DS |(2 DS || > 1, 1 DS || > 1, 1 DS || < 1)| < 1)
W PW Productionroduction
W decay signatures (lepton channels):
Isolated, high pT lepton with large missing
transverse momentum
Muon channel
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Electron channel
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W PW Productionroduction
MT (GeV/c2)
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W CW Crossross S Sectionection inin P Pluglug
Candidate events 64 pb-1
Estimated background
Acceptance efficiency
10,461 (8.7± 2.4) % (5.2 ± 0.2) %
BR(We) = 2.874 0.034stat 0.167sys 0.172lum nb
Update of the this measurement is in progress:
• Larger statistics ( ~ 220 pb-1)
• Much improved tracking efficiency
• Start re-blessing process this September
Candidate events 220 pb-1
Estimated background
Acceptance efficiency
61,309 10.4 % 8.7 %Preliminary
2874
W CW Crossross S SectionectionC
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Overall good agreement with the NNLO calculations
Accuracy limited by the systematic effects
Uncertainties dominated by luminosity measurements (~6%)
Other systematics dominated by PDF uncertainties (~2%)
LLeptonepton U UniversalityniversalityC
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From the measurements of the W W e e and W W μμ cross sections obtain cross section ratio U:
Many systematic uncertainties cancel out
In the same way from W W e e and W W ττ cross sections:
012.0998.0 eg
g
sysstateg
g04.002.099.0
2
2
)(
)(
)(
)(
eg
g
eW
W
eWBR
WBRU
W IW Indirectndirect W WidthidthC
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CDF II (e+)
CDF II ()
R: cross section ratio measurement:
Many systematic uncertainties cancel out (e.g. luminosity)
Allows for an internal consistency check of the Standard Model with direct Γ(W) measurement
)(
)(
ZBR
WBRR
Channel (W)(MeV)
e+ (72 pb-1) 2079 ± 41
(194 pb-1) 2056 ± 44
World Average 2118 ± 44
SM Prediction 2094 ± 3
)(
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)(
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)(
)(
W
W
Z
Z
Zpp
WppR
PRL94, 091803(2005)
W W Mass MeasurementMass MeasurementC
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Tevatron Run II has now 6 times Run I CDF, DØ data sets. CDF has analyzed first 200 pb-1 of data and determined uncertainties. Run II goal is to reduce uncertainty to less than 40 MeV.
LEP: 80,447 42 MeV Tevatron: 80,454 59 MeV (Run I)
ΔMW= 34 MeV
Precise knowledge of MW
constrains SM MH,
as well as hypothetical new particles.
W propagator includes H, tb and hypothetical new particle loops.
W W Mass MeasurementMass MeasurementC
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22 )()()()( TTTTT
pp EEWm
Calorimeter energy scale Tracking momentum scale
NLO event generator Model detector effects
DATA W Mass templates +
Backgrounds
Binned likelihood fitBinned likelihood fit
W Mass
W W Mass MeasurementMass MeasurementC
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CDF RUN IIPRELIMINARY
CD
F R
UN
II
PR
EL
IMIN
AR
Y
W W Mass MeasurementMass MeasurementC
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CDF RUN IIPRELIMINARY
mT fit
mT(μν)(GeV)
CDF RUN IIPRELIMINARY
mT fit
mT(eν)(GeV)
Using 200 pb-1 of Run II data CDF estimated the uncertainty on MW
Total uncertainty: Total uncertainty: 76 MeV76 MeV ( (e+e+ combined) already lower than CDF combined) already lower than CDF Run I (79 MeV)Run I (79 MeV)
Systematic Electrons (Run 1b) Muons (Run 1b)Lepton Energy Scale and Resolution 70 (80) 30 (87)
Recoil Scale and Resolution 50 (37) 50 (35)Backgrounds 20 (5) 20 (25)
Statistics 45 (65) 50 (100)Production and Decay Model 30 (30) 30 (30)
Total 105 (110) 85 (140)
In the collision u quark inside proton carries higher fraction of momentum than d. W production is sensitive to u(x)/d(x).
W CW Chargeharge A AsymmetrysymmetryC
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Use Ws to probe the proton structure
dyWddyWd
dyWddyWdyA w /)(/)(
/)(/)()(
pp
Observable quantity is electron rapidity
Convolution of W production asymmetry and V-A
decay
dyeddyed
dyeddyedA
/)(/)(
/)(/)()(
WXpp
W CW Chargeharge A AsymmetrysymmetryC
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PRD71, 051101(2005)
Identification of the lepton charge is the key
Probability of missId is around ~4% at || ~2
SSummaryummaryC
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Jose E. Garcia – INFN Pisa
RUN II CDF measurements are already better than results obtained RUN II CDF measurements are already better than results obtained in RUN I.in RUN I.
W mass has increased precision, expected to reach next year up to W mass has increased precision, expected to reach next year up to 30 MeV with 2 fb30 MeV with 2 fb-1-1
W charge asymmetry has been included in PDF’05 fitsW charge asymmetry has been included in PDF’05 fits
Direct W width measurement using Run II dataDirect W width measurement using Run II data
Results consistent with SMResults consistent with SM
BBackupackup S Slideslides
W properties AT CDFW properties AT CDF
J. E. GarciaJ. E. Garcia
Electrons
EM CalorimetersHigh PT Track
WW//Z IZ IdentificationdentificationC
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• At hadronic colliders W and Z bosons decaying hadronically are overwhelmed by QCD background.
Identification trough leptonic decays
W Signature: Isolated Lepton and Isolated Lepton and EETT
Z Signature: Two Isolated Two Isolated Leptons (opposite Leptons (opposite charge)charge)
Muons
Muon DetectorsHigh PT Track
Neutrinos
Large Missing EnergyOnly Transverse (ET)
PPhysics withhysics with W’s W’sC
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20 W boson identification is fundamental for many High-PW boson identification is fundamental for many High-PTT processes: processes:
W propertiesW properties
top searches ( tt top searches ( tt WW WW bbbb))
SM Higgs searchesSM Higgs searches
precision measurements sensitive to New Physics.precision measurements sensitive to New Physics.
It is a well known process, so it helps to set the basis for:It is a well known process, so it helps to set the basis for:
Understanding of the detector Understanding of the detector
Understanding of the backgroundsUnderstanding of the backgrounds
Lepton identification (e, Lepton identification (e, , , ))
Candidate events in 64 pb-1 Estimated background Acceptance efficiency
W e 10,461 (8.7± 2.4) % (5.2 ± 0.2) %
W W e e C Crossross S Sectionection in P in PluglugC
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MT (GeV/c2)ET (GeV/c2)
Major systematics : PDFs, Amount of material in the simulation, Plug ET scale, Recoil modeling
QCD Z ℓ +ℓ− W
W W e e C Crossross S SectionectionC
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BR(We) = 2.874 0.034stat 0.167sys 0.172lum nb
Working on an update of the measurement
• Bigger statistics ( ~ 220 pb-1)
• Much improved tracking efficiency
64 pb-1 sample
For comparison:
CDF - e (|| < 1.1) 2.782 0.014 + 0.167 (based on 72 pb-1)
CDF - (|| < 1.1) 2.772 0.016 + 0.166 (based on 72 pb-1)
+ 0.061- 0.056
+ 0.064- 0.060
W IW Identification in dentification in PPluglug R Regionegion
1.1 > > 2.8
(Electron energy corrected by offline corrections, Z vertex position and Ppr)
(Isorel corrected for leakage)
(corrected for Zvertex)
No PHOENIX electrons)No PHOENIX electrons)
• Match a track (PT > 1 GeV) such that track extrapolation to PES plane is
within a 3 cm window of PES cluster (|TrackX ,Y – PESX ,Y| < 3cm).
Electron selection requirements as in the W plug cross section (blessed 18/03/04).
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