Precise measurements of the W mass at the Tevatron and...
Transcript of Precise measurements of the W mass at the Tevatron and...
Precise measurements of the W mass at the Tevatronand indirect constraints on the Higgs mass
Rafael Lopes de Safor the CDF and DØ Collaborations
March 11, 2012
Rencontres de MoriondQCD and High Energy Interactions
Precise measurement of the W-boson mass with the CDF II detector arXiv:1203.0275
Measurement of the W Boson Mass with the D0 Detector arXiv:1203.0293
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 1
Motivation
Electroweak theory
The W boson mass is not an input parameter, but can be calculated
MW
(1− M2
W
M2Z
)=
πα√2Gµ
(1 + ∆r)
Loop Corrections
∆r(MZ ,MH ,mt, αs, . . .) W+
t
W+
b
W W
H
Indirect dependence δMW
δMH = 13GeV [114→ 127] −6.2MeV
δmt = 1.8GeV [172.4→ 174.1] 10.8MeV
δ(∆α(5)HAD) = 0.0002 −3.6MeV
Current theoretical uncertainty 4MeV
SM prediction known to complete2-loop order (and some 3-loopparts)Phys.Rev.D69:053006,2004
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 2
Motivation
Direct Measurements (before February 2012)
(GeV)Wm80 80.2 80.4 80.6
LEP2 average 0.033±80.376
Tevatron 2009 0.031±80.420
D0 Run II 0.043±80.402
D0 Run I 0.083±80.478
Tevatron 2007 0.039±80.432
CDF Run II 0.048±80.413
CDF Run 0/I 0.081±80.436
World average 0.023±80.399
July 09
Top quark mass (GeV)165 170 175 180 185
W b
os
on
ma
ss
(G
eV
)
80.3
80.32
80.34
80.36
80.38
80.4
80.42
CMS excl.
Atlas excl.
Tevatron excl.
LEP excl.
References:
SM prediction: Phys.Rev.D69:053006,2004
0.9 GeV (arXiv:1107.5255)±Top Mass: 173.2
= 122.5HM
= 127.0HM
68%
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 3
Motivation
Global Electroweak Fit (before February 2012)
(TEV EWWG and LEP EWWG – July, 2011)
Does not include LHC direct exclusion.
Precision EW Measurements(Tevatron, LEP and SLD data)
W boson mass and width
Z boson mass, total and partial width
Z pole asymmetries and sin θW
Indirect measurementof the Higgs boson mass
MH = 92+34−26GeV
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 4
CDF Detector
General purpose detector. For thisanalysis, the important subdetectorsare:
Central Drift Chamber immersed ina 1.4T solenoid. Provides accuratelepton momentum measurementand position measurement.
Electromagnetic Calorimeter.Lead-aluminium-scintillatorcalorimeter. Provides showerenergy measurement as well asposition measurement via wirechamber embedded at the EMshower maximum.
Central tracker single muon resolution: 3.2% (for pT = 45GeV )
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 5
DØ detector
General purpose detector. For thisanalysis, the important subdetectorsare:
Central Tracker. Silicon andscintillating fiber trackers immersedin a 2T solenoid provide accurateposition measurement.
Electromagnetic Calorimeter.Highly segmented uranium-liquidargon calorimeter with good energyresolution and coverage.
Electromagnetic calorimeter single electron energy resolution (with E = 45GeV ): 3.33%at η = 0. Average over central cryostat with W → eν angular spectrum: 4.16%.
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 6
Measurement Strategy
The Tevatron was a pp collider with 1.96TeV of energy. In a hadron collision, it isimpossible to know the parton system initial longitudinal momentum and, therefore,to measure the longitudinal momentum of the neutrino from the W boson decay.
The transverse momenta carry part of the mass information. Both CDF and DØmeasurements use binned likelihood fits to extract the value of the W boson massfrom the following kinematical distributions:
Transverse mass mT =√
2 (pT (`)pT (ν)− ~pT (`) · ~pT (ν))
Lepton transverse momentum pT (`)
Neutrino transverse momentum pT (ν)
peT
electron
uT
/ET
pWT
Hadronic Recoil
UnderlyingEvent
peT
electron
peT
posit
ron
uT
pZT
Hadronic Recoil
UnderlyingEvent
1
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 7
Event Selection
CDF analysis
Analyzed 2.2 fb−1.
Uses W → eν and W → µν decaychannels.
Central leptons |η| < 1 with30 < pT < 55GeV
Missing transverse energy30 < /ET < 55GeV
Transverse mass60 < mT < 100GeV
Hadronic recoil momentumuT < 15GeV
DØ analysis
Analyzed 4.3 fb−1 (1 fb−1
analyzed before)
Uses W → eν decay channel.
Central electrons |η| < 1.05 withpT > 25GeV
Missing transverse energy/ET > 25GeV
Transverse mass50 < mT < 200GeV
Hadronic recoil momentumuT < 15GeV
W → eν candidates W → µν candidates Total
CDF 2.2 fb−1 470, 126 624, 708 1, 094, 834
DØ 4.3 fb−1 1, 677, 394 – 1, 677, 394(+1 fb−1) 2, 177, 224
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 8
Calibration Strategies
Full GEANT detector simulations are not fast nor accurate enough to describe thekinematical distributions used to measure the W boson mass.
Both CDF and DØ develop parametrized fast simulations of the detector response toW → `ν events. The parametrizations are calibrated with data, using very differentstrategies.
CDF strategy
Detailed model of leptoninteractions at the central tracker.
Precise alignment using cosmicrays.
Momentum scale calibrated usingJ/ψ → µµ, Υ→ µµ and Z → µµmass fits.
Use calibrated momentum scaleand E/p distribution in W → eνevents to calibrate the calorimeterenergy scale.
DØ strategy
Detailed model of the calorimeterresponse to electrons and photons.
Detailed model of the underlyingenergy flow.
Detailed model of efficiencies.
Calibrate the calorimeter energyscale using the dielectron invariantmass and angular distribution inZ → ee decays (electron energyscale α and energy offset β).
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 9
Calibration Results
)-1> (GeVµ
T<1/p
0 0.2 0.4 0.6
p/p
∆
-0.002
-0.0015
-0.001
-1 2.2 fb≈ L dt ∫CDF II
data (stat. only) µµ→ψJ/
data (stat. only) µµ→Υ
data (stat. only) µµ→Z
eventsνµ→ syst.) for W⊕ p/p (stat. ∆combined
)νe→E/p (W1 1.2 1.4 1.6
ev
en
ts /
0.0
1
0
10000
20000
/dof = 18 / 222χ
-1 2.2 fb≈ L dt ∫CDF II
αScale, 1 1.01 1.02 1.03 1.04 1.05
(G
eV
)β
Off
se
t,
0
0.075
0.15
0.225
0.31D0 Run II, 4.3 fb
L<0.72
0.72<L<1.4
1.4<L<2.2
L>2.2
(L in 1032 cm−2 s−1)
DØ tests the calibration method doing a closure testwith GEANT simulation treated as data. Theresults are consistent with the input value of MW
within statistical uncertainty (≈ 6MeV ) for a sampleequivalent to 24 fb−1!
CDF momentum scale and DØ energy scaleprecision: ≈ 0.01% (!!!)
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 10
Z Mass Fits
A very strict test of the calibration procedure
(GeV)µµm70 80 90 100 110
ev
en
ts /
0.5
Ge
V
0
2000
4000) MeVstat 12± = (91180 ZM
/dof = 30 / 302χ
-1 2.2 fb≈ L dt ∫CDF II preliminary
MZ(µµ) = 91180±12(stat)±10(syst)MeV
(GeV)eem70 80 90 100 110
ev
en
ts /
0.5
Ge
V
0
500
1000
) MeVstat 30± = (91230 ZM
/dof = 42 / 382χ
-1 2.2 fb≈ L dt ∫CDF II preliminary
MZ(ee) = 91230± 30(stat)± 14(syst)MeV
All values consistent with theprecisely measured value at LEP.
MZ = 91188± 2MeV
, GeVeem70 75 80 85 90 95 100 105 110
Ev
en
ts
/0
.2
5 G
eV
0
425
850
1275
1700Data
Fast MC
-1D0 Run II, 4.3 fb
Fit Region/d.o.f. = 153/1592!
, GeVeem70 75 80 85 90 95 100 105 110
!
-4
-2
0
2
4-1D0 Run II, 4.3 fbMZ(ee) = 91193± 17(stat)MeV
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 11
Systematic uncertainties
Comparison of systematic uncertainties in the mT (`, ν) measurement(values in MeV)
Source CDF mT (µ, ν) CDF mT (e, ν) DØ mT (e, ν)
Experimental – Statistical power of the calibration sample.
Lepton Energy Scale 7 10 16Lepton Energy Resolution 1 4 2
Lepton Energy Non-Linearity 4Lepton Energy Loss 4Recoil Energy Scale 5 5
Recoil Energy Resolution 7 7Lepton Removal 2 3
Recoil Model 5Efficiency Model 1
Background 3 4 2
W production and decay model – Not statistically driven.
PDF 10 10 11QED 4 4 7
Boson pT 3 3 2
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 12
CDF Results
Method (2.2 fb−1) MW (MeV) Method (2.2 fb−1) MW (MeV)
mT (µ, ν) 80379± 16(stat) mT (e, ν) 80408± 19(stat)pT (µ) 80348± 18(stat) pT (e) 80393± 21(stat)/ET (µ, ν) 80406± 22(stat) /ET (e, ν) 80431± 25(stat)
Combination (2.2 fb−1) 80387± 19MeV (syst + stat)
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 13
DØ Results
, GeVTm50 60 70 80 90 100
Ev
en
ts/0
.5 G
eV
0
5000
10000
15000
20000
25000
30000
35000
DATA
FAST MC
ντW>
Z>ee
MJ
1D0 Run II, 4.3 fb
Fit Region/dof = 37.4/492χ
, GeVTm50 60 70 80 90 100
χ
4
3
2
1
0
1
2
3
41D0 Run II, 4.3 fb
, GeVe
Tp
25 30 35 40 45 50 55 60
Ev
en
ts/0
.5 G
eV
0
10000
20000
30000
40000
50000
60000
70000
DATA
FAST MC
ντW>
Z>ee
MJ
1D0 Run II, 4.3 fb
Fit Region/dof = 26.7/312χ
, GeVe
Tp
25 30 35 40 45 50 55 60
χ
4
3
2
1
0
1
2
3
41D0 Run II, 4.3 fb
Method (4.3 fb−1) MW (MeV)
mT (e, ν) 80371± 13(stat)pT (e) 80343± 14(stat)/ET (e, ν) 80355± 15(stat)
Combination mT ⊕ pT (4.3 fb−1) 80367± 26(syst + stat)
Combination (5.3 fb−1) 80375± 23(syst + stat)
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 14
Comparing Results
Fitted W boson mass (MeV)80250 80300 80350 80400 80450
0
1
2
3
4
5
6
7
8
9
10
D0 (4.3/fb) mT(e,nu)
D0 (4.3/fb) pT(e)
D0 (4.3/fb) MET(e,nu)
CDF (2.2/fb) mT(mu,nu)
CDF (2.2/fb) pT(mu)
CDF (2.2/fb) MET(mu,nu)
CDF (2.2/fb) mT(e,nu)
CDF (2.2/fb) pT(e)
CDF (2.2/fb) MET(e,nu)
CDF 2.2/fb combination (stat+syts)
D0 4.3/fb combination (stat+syts)
D0 MET not included
in the combination
Very consistent results obtained with completely different calibration strategies!(uncertainties from individual measurements are only statistical)
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 15
Single Experiment Uncertainty
)-1Integrated Luminosity (pb210 310 410
W M
ass
un
cert
ain
ty (
MeV
)
50
100
150
200
250
300
350
400
Tevatron Single Experiment Uncertainties
)-1Integrated Luminosity (pb210 310 410
W M
ass
un
cert
ain
ty (
MeV
)
50
100
150
200
250
300
350
400
DZero (e)
CDF (e + mu)
Both experiments are getting close to the model and theoretical plateau.
Some work need to be done in this front as well!
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 16
Theoretical and modeling issues
Ideas and developments to improve the modeland theoretical uncertainties in the W mass measurement
Use a wider lepton η–acceptance to be lesssensitive to PDF uncertainties. It has been donebefore at the Tevatron (DØ RunI).Phys.Rev.D62:092006,2000
Use Tevatron W lepton charge asymmetry toconstrain the u/d PDF instead of low energyexperiments. Available: CT10W PDF set.Phys.Rev.D82:074024,2010
Explore lepton longitudinal momentum toextract the W mass. Concrete example:JHEP 1108:023,2011
Study QED uncertianties in the measurementusing NLO QCD ⊕ EW generators. Two recentimplementations in the POWHEG framework.arXiv:1202.0465, arXiv:1201.4804
|eη|0 0.5 1 1.5 2 2.5 3
Asy
mm
etry
-0.6
-0.4
-0.2
-0
0.2
-1DØ, L=0.75 fb
>25 GeVT
eE
>25 GeVT
νE
CTEQ6.6 central value
MRST04NLO central value
CTEQ6.6 uncertainty band
|eη|0 0.5 1 1.5 2 2.5 3
Asy
mm
etry
-0.8
-0.6
-0.4
-0.2
-0
0.2
-1(a) DØ, L=0.75 fb
<35 GeVT
e25<E
>25 GeVTν
E
CTEQ6.6 central value
MRST04NLO central value
CTEQ6.6 uncertainty band
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 17
Higgs Constraints
(Preliminary) New World Average
(GeV)Wm80 80.2 80.4 80.6
LEP2 average 0.033±80.376
Tevatron 2012 (prel.) 0.017±80.387
CDF II (prel.) 0.019±80.387
D0 Run II (prel.) 0.023±80.376
D0 Run I 0.083±80.478
CDF Run I 0.081±80.436
World average (prel.) 0.015±80.385
Winter 2012
Top quark mass (GeV)165 170 175 180 185
W b
os
on
ma
ss
(G
eV
)
80.3
80.32
80.34
80.36
80.38
80.4
80.42
CMS excl.
Atlas excl.
Tevatron excl.
LEP excl.
References:
SM prediction: Phys.Rev.D69:053006,2004
0.9 GeV (arXiv:1107.5255)±Top Mass: 173.2
= 122.5HM
= 127.0HM68%
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 18
(Preliminary) Global Electroweak Fit
0
1
2
3
4
5
6
10040 200
mH [GeV]
∆χ
2
LEPexcluded
LHCexcluded
∆αhad
=∆α(5)
0.02750±0.00033
0.02749±0.00010
incl. low Q2 data
Theory uncertainty
March 2012 mLimit
= 152 GeV
New (preliminary) indirect Higgs mass determination
MH = 94+29−24GeV (was MH = 92+34
−26GeV before)
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 19
Conclusions
CDF and DØ measured the W mass with precision at least as good as theworld average before.
The CDF measurement is now the single most precise measurement of the Wmass.
CDF and DØ measurements in excellent agreement.
Model and theory uncertainties begin to play an important role.
CDF analyzed 2.2 fb−1. DØ analyzed 4.3 fb−1 of integrated luminositycollected at high instantaneous luminosity runs of the Tevatron.
The measurements at CDF and DØ can reduce the world average uncertaintydown to 10MeV when all the rest of the data is analyzed.
The W mass will play an ever increasing role in the determination of theconsistency of the Standard Model.
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 20
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R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 21
Backup Slides
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 22
CDF Systematic Uncertainties
Source Uncertainty (MeV)
Experimental – Statistical power of the calibration sample.Lepton Energy Scale 7
Lepton Energy Resolution 2Recoil Energy Scale 4
Recoil Energy Resolution 4Lepton Removal 2
Background 3Experimental Total 10
W production and decay model – Not statistically driven.PDF 10QED 4
Boson pT 5W model Total 12
Total Systematic Uncertainty 15W Statistics 12
Total Uncertainty 19
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 23
DØ Systematic Uncertainties
Source mT MeV peT MeV /ET MeV
Experimental – Z statistics driven!Electron Energy Scale 16 17 16Electron Energy Resolution 2 2 3Electron Energy Nonlinearity 4 6 7W and Z Electron energy 4 4 4
loss differencesRecoil Model 5 6 14Electron Efficiencies 1 3 5Backgrounds 2 2 2Experimental Total 18 20 24W production and decay model – Not dependent on Z statistics!PDF 11 11 14QED 7 7 9Boson pT 2 5 2W model Total 13 14 17Total Systematic Uncertainty 22 24 29W Statistics 13 14 15
Total Uncertainty 26 28 33
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 24
Recoil Model
Hard recoil: Parametrized from
Z → `` events.
Soft recoil: Data min-bias (CDF)
or min-bias + zero-bias (DØ)
events.
Lepton removal: Hadronic
energy reconstructed as lepton.
Out-of-cone FSR: Photons
reconstructed as recoil.
CDF and DØ: Final tune with Z → ``
momentum imbalance.
(GeV)ee
Tp
0 5 10 15 20 25
Mean
(G
eV
)im
bη
0
1
2
3
4
5
6
7
8
9
10
Data
PMCS
1D0 Run II, 4.3 fb
(GeV)ee
Tp
0 5 10 15 20 25
χ
3
2
1
0
1
2
31D0 Run II, 4.3 fb
(GeV)ee
Tp
0 5 10 15 20 25 W
idth
(G
eV
)im
bη
3
3.5
4
4.5
5
5.5
6
Data
PMCS
1D0 Run II, 4.3 fb
(GeV)ee
Tp
0 5 10 15 20 25
χ
4
3
2
1
0
1
2
3
41D0 Run II, 4.3 fb
5
4
e−
e+
η
peeT · η
ξ
peeT
uTuT · η
x
y
FIG. 2. Graphical representation of η axis and observables used to fit the recoil model smearing parameters
the difference in the zero supression between the top and bottom parts of the DØ calorimeter is needed to the Full38
GEANT Monte Carlo closure part of this analysis III. The components uMBT and uZB
T are randomly selected from39
the minimum bias and zero bias libraries. The smearing is applied only on uMBT to cancel double counting that is40
unavoidable in the preparation of the minimum bias library.41
usoftT,smear =
√αMBuMB
T + uZBT + uTB
T (qT ,∆φ, SET ) (3)
where ∆φ is the angle between the uhadT and qT .42
To determine the smearing parameters, we split the set of parameters in two sets:43
(RelScaleA, RelScaleB, τHAD) which controls the relative response and (RelSampA,αMB) which controls the relative44
resolution.45
Both sets are determined from Z → ee events using a method first used by the UA2 collaboration [4]. The idea is46
to avoid introducing an explicit dependence on the electron energy scale by using an observable which depends only47
on the angular quantities. The observable used is the momentum imbalance in the direction of the bisector of the48
electron-positron system, which is labeled η, namely (peeT + uT ) · η 2.49
The imbalance is measured in 10 bins of reconstructed peeT = (pe
T + peT ) momentum with boundaries:50
(0, 1, 2, 3, 4, 5, 7, 10, 15, 20, 30) GeV . Following the UA2 method, only the mean and RMS of the eta imbalance distri-51
bution are used to determine the response and resolution parameters respectively.52
B. Fitting method53
The parameters are determined by a straightforward χ2 comparison between the parameterized model and either54
data or Monte Carlo. The W Mass analysis parameterized model is not always well suited to models such as the55
gradient method implemented in MINUIT, since discontinuities exist and, unless we are in a region very close to56
the minimum of the χ2 surface, it is safer, though much more time consuming, to determine the parameters by57
constructing the whole χ2 grid spanning a range around a physically well motivated set of values for the parameters.58
The χ2 grid, when sufficiently close to the minimum can be well fitted to a generic quadratic polynomial in either59
three dimensions (for the response parameters) or two dimensions (for the resolution parameters).60
From the fitted quadratic surface, the point of minimum and the hessian matrix at this point are calculated61
algebraically and interpreted as the best values and covariances matrix for the parameters. To improve the numerical62
stability of the algebraic manipulation, the parameters are rescaled to have all the principal curvatures in the same63
order of magnitude.64
This procedure is applied individually for the response and resolution parameters. Although the correlations65
between the two sets are small, they are not zero. Instead of dealing with a five-dimensional problem, which would66
FIG. 2. Graphical representation of η axis and observables used to fit the recoil model smearing
parameters.
in the preparation of the minimum bias library.50
usoftT,smear =
√αMBuMB
T + uZBT + uTB
T (uT , φ, SET ) (3)
where (uT , φ) are, respectively, the length and direction of the hadronic recoil vector in51
the transverse plane before the top-bottom asymmetry correction is applied and uT is top-52
bottom correction mentioned above and fully described later in this note.53
To determine the smearing parameters applied to both hard recoil and soft recoil, we split54
the set of parameters in two sets: (RelScaleA, RelScaleB, τHAD) which controls the relative55
response and (RelSampA,αMB) which controls the relative resolution.56
Both sets are determined from Z → ee events using a method first used by the UA257
collaboration [4]. The idea is to avoid introducing an explicit dependence on the electron58
energy scale by using an observable which depends only on the angular quantities. The59
observable used is the momentum imbalance in the direction of the bisector of the electron-60
positron system, which is labeled η, namely (peeT + uT ) · η (see Figure 2).61
The imbalance is measured in 10 bins of reconstructed peeT = (pe
T + peT ) momentum with62
boundaries: (0, 1, 2, 3, 4, 5, 7, 10, 15, 20, 30) GeV . Following the UA2 method, only the mean63
ee) (GeV)→(ZT
p0 5 10 15 20 25 30
(G
eV
)η
+ u
Z η0
.65
p
-3
-2
-1
0
1
2
3
/ DoF = 15.6 / 92χ
-1 2.2 fb≈ L dt ∫CDF II preliminary
ee) (GeV)→(ZT
p0 5 10 15 20 25 30
) (
Ge
V)
η +
uZ η
( 0
.65
pσ
3.5
4
4.5
5
5.5
6
/ DoF = 15.9 / 92χ
-1 2.2 fb≈ L dt ∫CDF II preliminary
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 25
DØ Consistency CheckInstantaneous Luminosity
Blinded W mass (GeV)
81.6 81.7 81.8 81.9 82 82.1
L > 6
4 < L < 6
2 < L < 4
L < 2
Tm
Tp
MET
Z mass (GeV)
91 91.05 91.1 91.15 91.2 91.25 91.3 91.35 91.4
(Blinded W mass) / (Z mass)
0.895 0.896 0.897 0.898 0.899 0.9 0.901
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 26
DØ Consistency Check – Time
Blinded W mass (GeV)
81.6 81.7 81.8 81.9 82 82.1
Early Run IIb1
Late Run IIb1
Early Run IIb2
Late Run IIb2
Tm
Tp
MET
Z mass (GeV)
91 91.05 91.1 91.15 91.2 91.25 91.3 91.35 91.4
(Blinded W mass) / (Z mass)
0.895 0.896 0.897 0.898 0.899 0.9 0.901
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 27
DØ Consistency Check – u‖
Blinded W mass (GeV)81.6 81.7 81.8 81.9 82 82.1
< 0 GeV||u
> 0 GeV||u
Tm
Tp
MET
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 28
DØ Consistency Check – Recoil uT
Blinded W mass (GeV)
81.6 81.7 81.8 81.9 82 82.1
< 10 GeVTu
< 20 GeVTu
Tm
Tp
MET
Z mass (GeV)
91 91.05 91.1 91.15 91.2 91.25 91.3 91.35 91.4
(Blinded W mass) / (Z mass)
0.895 0.896 0.897 0.898 0.899 0.9 0.901
R. Lopes de Sa (Stony Brook University) W Mass at the Tevatron March 2012 29