Overview of the Systematic Uncertainties on Measured Top Mass by the CDF Collaboration

Overview of the Systematic Overview of the Systematic Uncertainties on Measured Uncertainties on Measured

Top Mass by the CDF Top Mass by the CDF CollaborationCollaboration

Top Mass Conveners Top Mass Conveners

For the CDF Top Group For the CDF Top Group

Joint CDF and DO Workshop: Systematic Joint CDF and DO Workshop: Systematic Uncertainties on Top Physics MeasurementsUncertainties on Top Physics Measurements

September 8, 2008 September 8, 2008

Sep 08, 2008 2M. Datta, FNAL

OutlineOutline Introduction: Current status of Top mass Introduction: Current status of Top mass

measurementsmeasurements General philosophy about the systematic uncertaintiesGeneral philosophy about the systematic uncertainties Status of systematic uncertaintiesStatus of systematic uncertainties

Quick overview and prescriptionsQuick overview and prescriptions Work in progress and to do listWork in progress and to do list

Color reconnectionColor reconnection NLONLO

SummarySummaryNote: The same systematic prescriptions are also Note: The same systematic prescriptions are also

used by all the Top analysesused by all the Top analyses


IntroductionIntroduction Top mass measurement Top mass measurement

has entered a new era of has entered a new era of precisionprecision Most of the measurement Most of the measurement

already systematics limitedalready systematics limited Unprecedented level of Unprecedented level of

precision even for each precision even for each single analysis single analysis Working hard for every Working hard for every

100 MeV improvement100 MeV improvement Investigating systematic Investigating systematic

effects from sources, which effects from sources, which might not taken into account might not taken into account


MMtoptopMMtoptop

In channel/analysis not using in-situ JES In channel/analysis not using in-situ JES Systematics Systematics dominated by the uncertainty on parton energies (JES)dominated by the uncertainty on parton energies (JES)

Other sources arise from the assumptions employed to infer MOther sources arise from the assumptions employed to infer M toptop

MMtop top

per CDF Analysisper CDF Analysis

Statistical Statistical

(Including in-situ JES (Including in-situ JES

for LJ& All-Had)for LJ& All-Had)

(GeV/c(GeV/c22))

JES (DIL) ORJES (DIL) OR

Residual JESResidual JES

(LJ and All-Had)(LJ and All-Had)

(GeV/c(GeV/c22))

Other Other

SystematicSystematicss

(GeV/c(GeV/c22))

Dilepton (1.9 fbDilepton (1.9 fb-1-1)) 2.72.7 2.52.5 1.51.5

Lep+Jets (2.7 fbLep+Jets (2.7 fb-1-1)) 1.3 1.3 0.50.5 0.90.9

All Jets (2.1 fbAll Jets (2.1 fb-1-1)) 3.83.8 0.80.8 1.51.5

Statistical and systematical sensitivities by channel


Systematic Uncertainties Systematic Uncertainties Syst. (GeV/cSyst. (GeV/c22)) Lep+JetsLep+Jets DileptonDilepton All HadAll Had

Residual JESResidual JES 0.50.5 -- 0.80.8

JESJES -- 2.52.5 --

b-JESb-JES 0.40.4 0.40.4 0.60.6

ISR and FSRISR and FSR 0.30.3 0.50.5 0.30.3

PDFsPDFs 0.20.2 0.60.6 0.40.4

GeneratorGenerator 0.50.5 0.90.9 0.50.5

In-time pileupIn-time pileup 0.10.1 0.20.2 0.30.3

Lept energy scaleLept energy scale 0.20.2 0.10.1 --

B-tag scale factorB-tag scale factor -- -- 0.40.4

Bkg fraction,Bkg fraction,

Sample comp, Sample comp,

Modeling, statModeling, stat

0.40.4 0.5 (stat), 0.5 (stat),

0.3 (Sample Comp),0.3 (Sample Comp),

0.2 (Modeling)0.2 (Modeling)

1.03 (Bkg Template),1.03 (Bkg Template),

0.26 (Sig Template)0.26 (Sig Template)

Calibration/MethodCalibration/Method 0.10.1 0.40.4 0.40.4

TotalTotal 1.01.0 2.92.9 1.71.7

othe

r


General philosophyGeneral philosophy ALL top mass analyses are calibrated to MC: pythia + CdfSim ALL top mass analyses are calibrated to MC: pythia + CdfSim

for signal.for signal. Data used to model some backgrounds.Data used to model some backgrounds.

Therefore we need systematic uncertainties for all and only Therefore we need systematic uncertainties for all and only those features of the data that may be incorrectly modeled by those features of the data that may be incorrectly modeled by our MC.our MC.

In principle:In principle: list such effectslist such effects determine variations that are consistent with data (ttbar or determine variations that are consistent with data (ttbar or

control samples)control samples) propagate those variations to uncertainty on Mpropagate those variations to uncertainty on Mtoptop..

But in practice…But in practice…


General philosophy General philosophy (Cont’)(Cont’)

Explicit evaluation of systematics is an art.Explicit evaluation of systematics is an art. Beware of double countingBeware of double counting Beware of under countingBeware of under counting What to do when we don’t have all the What to do when we don’t have all the

information (~always)? Make further information (~always)? Make further assumptions…assumptions…

In all systematics so far:In all systematics so far: Assume “prior” for systematic variations is Assume “prior” for systematic variations is

GaussianGaussian Assume a linear effect on MAssume a linear effect on Mtoptop

Results in symmetric Gaussian Results in symmetric Gaussian systematicssystematics

For each systematic variation determine the For each systematic variation determine the effect on measured top masseffect on measured top mass Perform data-size pseudo experiments, Perform data-size pseudo experiments,

including the appropriate signal and including the appropriate signal and background eventsbackground events

Most of the systematics are evaluated at top Most of the systematics are evaluated at top mass of 175 GeVmass of 175 GeV


General philosophy General philosophy (Cont’)(Cont’)

When +/-1 sigma can be somehow defined:When +/-1 sigma can be somehow defined: Evaluate slope using shift methodEvaluate slope using shift method

If +/-1 sigma shift results in measured top masses MIf +/-1 sigma shift results in measured top masses M++ and M and M--

Slope is |MSlope is |M++-M-M--|/2.|/2. When MWhen M++ < M < Mnominalnominal < M < M- - or M or M++ > M > Mnominalnominal > M > M- -

Otherwise slope: Larger of |MOtherwise slope: Larger of |M++-M-Mnominalnominal|/2 and |M|/2 and |M---M-Mnominalnominal|/2 |/2 Ignore uncertaintyIgnore uncertainty

When “1 sigma” is an elusive concept:When “1 sigma” is an elusive concept: Probe magnitude of our potential mis-modeling using whatever Probe magnitude of our potential mis-modeling using whatever

information we have at hand, then arbitrarily define 1 sigma and information we have at hand, then arbitrarily define 1 sigma and symmetrize.symmetrize.

Recognize that we have incomplete information, and the models we Recognize that we have incomplete information, and the models we use to probe don’t necessarily cover our potential mistakes.use to probe don’t necessarily cover our potential mistakes.


General philosophy (Cont’)General philosophy (Cont’) Analyses may be sensitive to modeling of some feature not in Analyses may be sensitive to modeling of some feature not in

the standard list of systematics. Of course you have to include the standard list of systematics. Of course you have to include these!these! Examples: Top mass measurement using lepton PExamples: Top mass measurement using lepton Ptt and L and Lxyxy

methodmethod

Prescriptions for Prescriptions for Systematic Systematic

UncertaintiesUncertaintieshttp://www-cdf.fnal.gov/physics/new/top/systematics/tevatron_systematics.htmlhttp://www-cdf.fnal.gov/physics/new/top/systematics/tevatron_systematics.html

Jet Energy Scale (including residual)Jet Energy Scale (including residual)b-jet energy scaleb-jet energy scale

MC GeneratorMC GeneratorISR/FSRISR/FSR

PDFPDFBackground fraction and shapeBackground fraction and shape

Lepton pLepton pTT

PileupPileupMethod/MC statisticsMethod/MC statistics


Jet Energy Scale (JES)Jet Energy Scale (JES) Details in Details in NIM A, 566, 375 (2006)

Relative uncertainty (L1) L1 correction applied for making

jet energy uniform along eta Multiple interaction uncertainty

(L4) Absolute correction (L5)

Correct jet back to the particle level

Underlying event uncertainty (L6) Out-of-cone uncertainty (L7)

Correct jet back to parton level Splash-out uncertainty (L8)

Leakage beyone radius=1.3 In-situ calibration applied for most

Lep+Jets and All-had analyses


JES/ Residual JESJES/ Residual JES Evaluate the separate uncertainties for ALL levels of the JES Evaluate the separate uncertainties for ALL levels of the JES

systematic (including higher levels in case analysis only systematic (including higher levels in case analysis only correct up to parton level (L5)). correct up to parton level (L5)). Add those pieces in quadrature to get the systematic on the top mass. Add those pieces in quadrature to get the systematic on the top mass.

The "total JES systematic" (all levels at once) can be used as a The "total JES systematic" (all levels at once) can be used as a cross-checkcross-check Cross check recommended for analyses without in situ calibration.Cross check recommended for analyses without in situ calibration.

If background is evaluated from MC, apply the same If background is evaluated from MC, apply the same 11 JES JES variations to dominant background sources simultaneously variations to dominant background sources simultaneously with the signal variationswith the signal variations

Syst. (GeV/cSyst. (GeV/c22): ): MMtoptop Lep+JetsLep+Jets DileptonDilepton All HadAll Had

Residual JESResidual JES 0.5-0.70.5-0.7 -- 0.80.8

JESJES -- 2.5-3.52.5-3.5 --


Residual JES : LJ+DIL Template Residual JES : LJ+DIL Template AnalysisAnalysis


b-jet Energy Scaleb-jet Energy Scale Recently revisedRecently revised Old method : Old method : 0.6% shift of b-jet energies0.6% shift of b-jet energies

The old method was a) statistics limited in the original estimate, b) The old method was a) statistics limited in the original estimate, b) transfer to other analyses involved lots of averaging and rules of transfer to other analyses involved lots of averaging and rules of thumb.thumb.

New Method: Three componentsNew Method: Three components semi-leptonic decay BRssemi-leptonic decay BRs

Reweight b and c BRs together +/- 1 sigma.Reweight b and c BRs together +/- 1 sigma. Fragmentation Fragmentation

Reweight to LEP/SLD Bowler parametersReweight to LEP/SLD Bowler parameters Full-sim sample using Bowler parameters from LEP (coming Full-sim sample using Bowler parameters from LEP (coming

soon)soon) Cal response effect (0.2%) Cal response effect (0.2%)

Shift b-jet energies by 1%, evaluate shift, multiply by 0.2.Shift b-jet energies by 1%, evaluate shift, multiply by 0.2.Syst. (GeV/cSyst. (GeV/c22)) Lep+JetsLep+Jets DileptonDilepton All HadAll Had

b-JESb-JES 0.2-0.40.2-0.4 0.2-0.40.2-0.4 0.3-0.60.3-0.6


b-jet Energy Scale (Con’t)b-jet Energy Scale (Con’t) From Z-peak physics summary:From Z-peak physics summary:

B(bB(bl) = 0.1071 ± 0.0022l) = 0.1071 ± 0.0022 B(bB(bccl) = 0.0801 ± 0.0018l) = 0.0801 ± 0.0018 B(cB(cl) = 0.0969 ± 0.0031l) = 0.0969 ± 0.0031

Our MC matches b→l exactly.Our MC matches b→l exactly. Use Use 23.9% +/- 0.7%23.9% +/- 0.7%

c→l not so clear, when we try to avg direct, cascade c decays.c→l not so clear, when we try to avg direct, cascade c decays. Use Use 18.82% +/- 2.0%18.82% +/- 2.0%

Fragmentation parametrization: (similar to D0 method)Fragmentation parametrization: (similar to D0 method) Using reweighting by the variable that includes just the non-Using reweighting by the variable that includes just the non-

perturbative part of the b fragmentation.perturbative part of the b fragmentation. Exactly what the Bowler function is used for in Pythia.Exactly what the Bowler function is used for in Pythia. Take larger shift from reweighting to 1) LEP, 2) SLD fits.Take larger shift from reweighting to 1) LEP, 2) SLD fits.

Still don’t understand why D0 sees large systematic (but only for Still don’t understand why D0 sees large systematic (but only for tagged analysis).tagged analysis).


b-jet Energy Scale : Contribution b-jet Energy Scale : Contribution from Different Sources from Different Sources

Letpon+Jets Matrix Element Analysis


MC GeneratorMC Generator If different generators describes our data equally well .. take the difference If different generators describes our data equally well .. take the difference

between them as systematicsbetween them as systematics Why consider this systematic uncertainty, given some of these effects Why consider this systematic uncertainty, given some of these effects

might already be included in other systematic categories (such as JES)?might already be included in other systematic categories (such as JES)? Cover effects of ttbar-like high multiplicity environment Cover effects of ttbar-like high multiplicity environment

Many of the systematic corrections are derived from control Many of the systematic corrections are derived from control samples which are not so busy as the ttbar eventssamples which are not so busy as the ttbar events

Currently taking the difference between Herwig and Pythia:Currently taking the difference between Herwig and Pythia: Difference in the showering models Difference in the showering models Difference in jet-resolutionDifference in jet-resolution

There might be overlap between generator and other systematicsThere might be overlap between generator and other systematics Hard to separate overlapping and non-overlapping contributionsHard to separate overlapping and non-overlapping contributions

Syst. (GeV/cSyst. (GeV/c22)) Lep+JetsLep+Jets DileptonDilepton All HadAll Had

GeneratorGenerator 0.5-0.80.5-0.8 0.9-1.30.9-1.3 0.5-0.80.5-0.8


MC Generator (Cont’)MC Generator (Cont’)

Work in progress and plansWork in progress and plans Include ALPGEN ttbar sample (different diagrams): Include ALPGEN ttbar sample (different diagrams):

Compare ttbar+0p inclusive with ttbar+Compare ttbar+0p inclusive with ttbar+1P 1P Currently investigating the effect due to ALPGEN Currently investigating the effect due to ALPGEN

having zero-width for top and W masseshaving zero-width for top and W masses Include NLO ttbar sample Include NLO ttbar sample

MC@NLO samples have ~10% of events with negative MC@NLO samples have ~10% of events with negative weight! weight!

Look at other NLO generators (such as POWHEG)Look at other NLO generators (such as POWHEG)


Radiation (ISR/FSR)Radiation (ISR/FSR) Constrain the ISR/FSR Pythia Constrain the ISR/FSR Pythia

parameters from Drell-Yan eventsparameters from Drell-Yan events Works great for constraining ISR, but Works great for constraining ISR, but

not directly FSRnot directly FSR ISR and FSR are governed by the ISR and FSR are governed by the

same physical processes and same physical processes and essentially the same empirical model essentially the same empirical model as well. as well.

Constraints on ISR from D-Y events Constraints on ISR from D-Y events can thus be taken as constraints on can thus be taken as constraints on

FSR as wellFSR as well Since Since Pythia uses parallel sets of parameters to control both types of showers

In the current "IFSR" samples are just simultaneous variations of the ISR and FSR parameters by 1 sigma.

Treating these uncertainties as correlated should if anything result in a larger systematic


Radiation (ISR/FSR) : Radiation (ISR/FSR) : PlansPlans Update this study with more data including Update this study with more data including

other distributions sensitive to the other distributions sensitive to the radiation, e.g. Nradiation, e.g. Njets,jets, for different mass for different mass (M(Mllll) regions.) regions.

Needs more study on hard gluon radiation Needs more study on hard gluon radiation modeling.modeling. Overlaps with NLO effects.Overlaps with NLO effects.

Plan: study MC samples with different Plan: study MC samples with different componentcomponent Hard ISR: ALPGEN – ttbar+jetsHard ISR: ALPGEN – ttbar+jets Hard FSR: MadgraphHard FSR: Madgraph Loops: MC@NLOLoops: MC@NLO

Based on the outcome of these studies may Based on the outcome of these studies may need to revise ISR/FSR systematic.need to revise ISR/FSR systematic.

From Un-ki Yang

4<Et(L4)<15 GeV


ISR and FSRISR and FSR 0.2-0.30.2-0.3 0.2-0.50.2-0.5 0.3-0.60.3-0.6


Parton Density Function Parton Density Function (PDFs)(PDFs)

Part I : Add in quadrature the difference between CTEQ6M 20 pairs of Part I : Add in quadrature the difference between CTEQ6M 20 pairs of eigenvectors eigenvectors

Part II: Add in quadrature the difference between MRST with two different Part II: Add in quadrature the difference between MRST with two different values of ΛQCD (e.g. MRST72 ΛQCD=228MeV vs. MRST75 values of ΛQCD (e.g. MRST72 ΛQCD=228MeV vs. MRST75 ΛQCD=300MeV) ΛQCD=300MeV)

Part III: Add in quadrature the effect of reweighting gg contribution from Part III: Add in quadrature the effect of reweighting gg contribution from 5% (LO) to 20% (=15+5) (NLO) 5% (LO) to 20% (=15+5) (NLO) Answer to D0’s question: The re-weighting is done on the our standard

Pythia ttbar events, which uses LO PDF. Once we include systematic uncertainty from NLO, this might already

be covered there


PDFsPDFs 0.2-0.30.2-0.3 0.5-0.60.5-0.6 0.40.4


Background Fraction and Background Fraction and ShapeShape No common prescription. Varies from analysis to analysis.No common prescription. Varies from analysis to analysis.

Come up with something and convince the group that it makes sense.Come up with something and convince the group that it makes sense. Often includes pieces related to:Often includes pieces related to:

Overall bg normalization (aka S:B)Overall bg normalization (aka S:B) bg composition (vary component normalizations within uncertainties)bg composition (vary component normalizations within uncertainties) bg shapebg shape

W(+/-hf) +jets samples with varying QW(+/-hf) +jets samples with varying Q22

Generate ALPGEN samples with Q=0.5 and Q=2.0Generate ALPGEN samples with Q=0.5 and Q=2.0 fakes particularly poorly understood—deserve special treatmentfakes particularly poorly understood—deserve special treatment

Uncertainty on the background composition is from cross-section Uncertainty on the background composition is from cross-section measurement measurement Haven’t included in this talk. Topic for future workshops..Haven’t included in this talk. Topic for future workshops..

Lep+Jets ME analysis (2.7 fb-1) Mtop (GeV/c2)

Bkg fractionBkg fraction 0.360.36

Bkg compositionBkg composition 0.180.18

Bkg: QBkg: Q22 0.080.080.070.07

Bkg MC stat.Bkg MC stat. 0.050.05


Lepton PLepton PTT

For most analyses, shift e and For most analyses, shift e and energies (separately) by +/- energies (separately) by +/-1%1% This shift was originally assigned for e This shift was originally assigned for e

NIM A, 566, 375 (2006), also checked by other di-electron analyses

No strong evidence for No strong evidence for Take largest shift from nominalTake largest shift from nominal Work in progressWork in progress

New analysis looking at ZNew analysis looking at Zee, ee, data dataSyst. (GeV/cSyst. (GeV/c22)) Lep+JetsLep+Jets DileptonDilepton

Lept energy scaleLept energy scale 0.1-0.20.1-0.2 0.1-0.30.1-0.3


In-time PileupIn-time Pileup Luminosity profile increasing; this systematic becomes more important to Luminosity profile increasing; this systematic becomes more important to

understand preciselyunderstand precisely Two partsTwo parts

Part I : Part I : known discrepancy in lumi profile of data, MC.known discrepancy in lumi profile of data, MC. Part II : Even if lumi profile matched, there may be residual Part II : Even if lumi profile matched, there may be residual

mismodeling of extra interactions.mismodeling of extra interactions. Taken into account by the JES uncertainty due to MITaken into account by the JES uncertainty due to MI Possible uncounted effects due to high multiplicity environment Possible uncounted effects due to high multiplicity environment

Part I: Part I: Evaluate the magnitude of the effect for each analysis.Evaluate the magnitude of the effect for each analysis. Suggest to run PEs reweighting to data Ninteractions profileSuggest to run PEs reweighting to data Ninteractions profile If significant effect, take case by case. Otherwise, uncertainty on the If significant effect, take case by case. Otherwise, uncertainty on the

comparison can be added as a systematic.comparison can be added as a systematic. Part II:Part II:

MC-based study in ttbar dilepton jets shows response changes by 250 MC-based study in ttbar dilepton jets shows response changes by 250 MeV/vertex MeV/vertex afterafter MI corrections. MI corrections.

L4 jet systematic: 107 MeV/vertexL4 jet systematic: 107 MeV/vertex Probes magnitude of possible mis-modeling by scaling up the L4 (MI) Probes magnitude of possible mis-modeling by scaling up the L4 (MI)

systematic by a factor of 2.3. systematic by a factor of 2.3.


In-time Pileup (Cont’)In-time Pileup (Cont’) Part I : Perform pseudo experiments by dividing the events into sub-Part I : Perform pseudo experiments by dividing the events into sub-

samples with #Z vertex= 1, 2, 3, samples with #Z vertex= 1, 2, 3, 4 4 Examine the resulting slope Examine the resulting slope mmtoptop/vertex and multiply by difference in /vertex and multiply by difference in

average number of verticies for data-MC.average number of verticies for data-MC. MMtop top = (= (mmtoptop/vertex) * (<Nvtx/vertex) * (<Nvtxdatadata> -<Nvtx> -<NvtxMCMC>)>)

Part II:Part II: Check effect of x2.3 larger L4 systematic. Check effect of x2.3 larger L4 systematic.

If important compared to first part above, use it instead. If important compared to first part above, use it instead. If existing L4 systematic evaluated with MC lumi profile, multiply If existing L4 systematic evaluated with MC lumi profile, multiply

also by: (<Nvtxalso by: (<Nvtxdatadata>-1)/(<Nvtx>-1)/(<NvtxMCMC>-1).>-1). No direct data-MC comparisons we can use that aren’t statistically No direct data-MC comparisons we can use that aren’t statistically

limited.limited.


In-time pileupIn-time pileup 0.10.1 0.1-0.20.1-0.2 0.3-0.80.3-0.8


MC StatisticsMC Statistics Most analyses take something like a calibration systematic or Most analyses take something like a calibration systematic or

an MC statistics systematic to account for the uncertainties in an MC statistics systematic to account for the uncertainties in the calibration process due to limited MC stats.the calibration process due to limited MC stats.

The bootstrap is the approved way to understand calibration The bootstrap is the approved way to understand calibration uncertainties due to MC sample stats.uncertainties due to MC sample stats.

Think a bit about how to do this; don’t over- or under-count Think a bit about how to do this; don’t over- or under-count background effects, etc.background effects, etc.

Additional Additional Sources : Not Sources : Not Included YetIncluded Yet


Non-perturbative Effects Non-perturbative Effects What about a color reconnection systematic?What about a color reconnection systematic?

Based on the paper by Skands & Wicke. Working to Based on the paper by Skands & Wicke. Working to evaluate the models they used for their rough generator-evaluate the models they used for their rough generator-level results in the context of a full analysis.level results in the context of a full analysis.

Already generated some ttbar samples with different Already generated some ttbar samples with different models from Skands & Wicke’s papermodels from Skands & Wicke’s paper

To drive a real systematic, the models need to be validated To drive a real systematic, the models need to be validated for consistency with Tevatron data, e.g. minbias.for consistency with Tevatron data, e.g. minbias.

In the long run, if these effects turn out to be important, In the long run, if these effects turn out to be important, constrain them using e.g. high-Qconstrain them using e.g. high-Q22 Drell-Yan and bbbar Drell-Yan and bbbar eventsevents..


NLONLO Pythia includes corrections for hard radiation in t→Wb and Pythia includes corrections for hard radiation in t→Wb and

W→jj vertices. Missing pieces are:W→jj vertices. Missing pieces are: loops - small effect on kinematics expected; loops - small effect on kinematics expected; higher-order radiation effects - should be “small”.higher-order radiation effects - should be “small”.

Ongoing work for understanding of NLO, including loops, Ongoing work for understanding of NLO, including loops, hard radiation, soft radiation and PDFs. hard radiation, soft radiation and PDFs. Mentioned in the plans for ISR/FSRMentioned in the plans for ISR/FSR

IssuesIssues Hard to separate to different piecesHard to separate to different pieces


Jet Resolution : Cross CheckJet Resolution : Cross Check D0 quotes an uncertainty due to jet D0 quotes an uncertainty due to jet

resolution. CDF does not.resolution. CDF does not. The generator systematic “Pythia VS The generator systematic “Pythia VS

Herwig” should cover a large part of Herwig” should cover a large part of this systematicsthis systematics From photon+jets studies, find From photon+jets studies, find

the resolution in Herwig is much the resolution in Herwig is much closer to that in data, and closer to that in data, and different from that in Pythiadifferent from that in Pythia

Currently all-hadronic analyses are Currently all-hadronic analyses are checking the effect by smearing the checking the effect by smearing the jets with Pjets with PTT dependent resolution dependent resolution

functionsfunctions If the effects are small, use just as If the effects are small, use just as

a cross checka cross check


SummarySummary Working towards the final systematic uncertainty on measured Working towards the final systematic uncertainty on measured

top masstop mass Many of the sources are already incorporatedMany of the sources are already incorporated

Continue studies for better understanding Continue studies for better understanding ISR/FSR, …. ISR/FSR, ….

Take into account possible missing sourcesTake into account possible missing sources Color reconnectionColor reconnection NLO effects NLO effects

Work with D0 Top group to come up with a final revisited Work with D0 Top group to come up with a final revisited systematic uncertainties by the end of the year.systematic uncertainties by the end of the year. Include systematics for other Top analysis (cross-section Include systematics for other Top analysis (cross-section

etc.) in the discussionetc.) in the discussion

Documents

Overview of the Systematic Uncertainties on Measured Top Mass by the CDF Collaboration