A. SidotiUniversity of Pisa - INFN

Pisa

W Cross Section Measurements at CDF

CDF

1

Italo-Hellenic School of PhysicsThe Physics of LHC:

theoretical tools and experimental challengesMartignano, Grecìa Salentina (Lecce, Italy)

May 20-25, 2004

Goals & Outline

Goals:

•Present a “high-PT” cross section measurement with

details and technicalities (that you will hardly find in articles: “Dusty corners” )

•W bosons are high-PT well known processes, present

in many decays of interesting particles -> better to know them!•Measuring (pp->W) x BF(W->e)

Outline:

Physics of hadron collisions

Tevatron collider and CDF detector

W cross section measurements

Physics Processes at hadron colliders

LHC

TeVatron1033

<1032

Luminosity

[cm-2s-1]

10

0.3

∫L

[fb-1/y]

14 LHC (low lum)

2 TeVatron

√s

[TeV]

--

--

Electron:EM CalorimetersHigh Pt Track

Neutrinos:Large Missing EnergyOnly Transverse ( Met)

Muons:Muon DetectorsHigh PT Track

W Signature: Isolated Lepton and MET

Z Signature: Two Isolated Leptons (opposite charge)

W and Z bosons at hadron collidersAt hadronic collider W and Z bosons:decaying hadronically are overwhelmed by QCD background-> identification trough leptonic decays Can be produced with additional jets

Z(W)

e/

e/ ()

p

p

q

q

Cross Section: Physics

For a given physical process: =N events-Nbkg

x L dt

= Total efficiency (Trigger x Acceptance x Selection)

L dt = integrated luminosity

Nevents = Number of events

Nbkg = Number of background eventsStrategy of the analysis:1. Identify a clean sample of We events (Estimate

background contamination)2. Evaluate efficiencies (Includes trigger, kinematics,

electron ID and acceptances)3. Evaluate integrated luminosity4. Evaluate systematics

Luminosity, L, is a measurement of the brightness of the interaction region

The event rate, R, for a given process of x-section s is given by R = L*

The luminosity is a major machine parameterHigh luminosity sensitivity to small x-section

Instantaneous luminosity at colliders:f: frequency of collisionsn1,2 = number of particles in bunchx,y = transverse (Gaussian) dimensions of beam

Luminosity at Colliders

Or:

x,y= beam emittance

*x,y = amplitude functionBeam quality: bunch preparation, from source to storage

Beam optics parameter: related to magnets configuration

(.10-9 rad.m)(m)

2.2-1.4

0.35

0.5

0.5

Tev LHC

x F(z/*)

x F(z/*)

Tevatron

For RunII: New Main Injector:

• Improve p-bar production

Recycler ring (commissioning):

• Accumulate p-bars Center of mass energy

increase s RunI = 1.8 TeVNow s RunII = 1.96 TeV

CDFDØ

Main Injector

TevatronBoosterRecycler

ChicagoWorld’s highest energy p pbar collider.First accelerator with SC dipole magnets•Started operations in 1983•RunI(1992/93 and 1994/95)•RunII(2001/xx)

Instantaneous and Integrated Luminosity increase

Tevatron: LuminosityIntegrated Luminosity is a key ingredient for Tevatron RunII success.Analysis presented here (Mar2002- Jan2003) is based on integrated luminosity (72pb-1)

Record Peak Luminosity (05/02/2004) 6.11031 cm-2 s-1

CDF Takes efficiency at >85%Silicon integrated most of runs

CDF and DØ are collecting 1pb-1/day

CDF● CDF II during silicon installation

0

= 2.0n

= 3.0n

COT

0

.5

1.0

1.5

2.0

0 .5 1.0 1.5 2.0 2.5 3.0

END WALL HADRON CAL.

Inner silicon6 layers

30

30

SOLENOID

Intermediate silicon1 or 2 layers

= 1.0

EN

D P

LUG

EM

CA

LOR

IMETER

EN

D P

LUG

HA

DR

ON

CA

LOR

IMETERn

m

m

Time of Flight

Larg

e v

olu

me w

ire-c

ham

ber

96

layers

ISL1m

SVXII

L00

Wedge of Central Calorimeter(CEM)(courtesy D. Lucchesi)

Pseudorapidity = -log tan (/2)

Looking for W->e Candidates

• W selection:– High energy electron– Electron is isolated

– Large missing ET

• MET = |vector sum of all calorimeter energy in transverse plane| ~ ET

– Jacobian peaks:

• Both lepton ET and MET peak at about ½ the W mass

– Expect correlation between ET of lepton and neutrino

W->e candidates are selected matching:•Calorimetric information Electron Cluster energy,•Track information from tracking detectors (COT and Silicon)

Cone() r=0.4

Variables(I)

Variables used for selecting events:

•ET: calorimetric energy of EM cluster with all corrections

and considering as event vertex in z the z0 of the track associated.•MET: Missing transverse energy -> Unbalance of energy in

the transverse plane MET = - ET

•Relative Calorimetric Isolation:

•Had/Em: Energy in Hadronic Calorimeter/ Energy in EM

Calorimeter

•E/P: ratio Calorimetric energy/total momentum of track•Lshr: Lateral shower profile of adjacent calorimetric towers, comparison with test beam data to electron•Track quality selection: number of hits in the COT

•|z0|: z coord. of closest approach of track with beam axis

EM energy in cone R()=0.4 around EM clusterEM cluster energy

Variables (II)Variables based on ShowerMax detector: a anode cathode strip detector plane inserted inside the EM calorimeter

Trackx

z

•Charge x X: Distance

between shower deposit

and track extrapolation

in x direction (local) times

the charge of the particle

• z: Distance between

shower deposit and track

extrapolation in z

direction

Selecting electrons(“Tight” Selection)

Variable||

Em Cluster ET

Relative Calo. Isolation (R=0.4)Ehad/Eem

E/P OR PT<50 GeV/c#Stereo COT SuperLayers#Axial COT SuperLayers

Track PT

|z0|Lshr

Charge x X2

strip

|z|Fiduciality

Cut<1.1 (CEM)>25 GeV

<0.1<0.055+0.00045 . E

<2.0≥3 with ≥7hits≥3 with ≥7hits

>10 GeV/c<60 cm

<0.2>-3.0 cm AND <1.5 cm

<10<3.0 cm

Energy Corrections

Energy Corrections

Other corrections need to be applied to electron-magnetic cluster energy:•Tower-to-tower gain corrections•Time dependent gain corrections•“Face” corrections dependent on the position of the EM shower (from Test beam data)

Check of overall energy scales are made requiring that the invariant mass of dielectron pairs peaks at the Z mass value Overall Energy scale is OK

Time Dependent CorrectionsTime-Dependent corrections are evaluated calculating the average E/P (E from calorimeter, P from track momentum measurement) as a function of run number. E/P is averaged for 0.9<E/P<1.1

Tower to Tower Corrections<

E/

P>

Tower Number

For each calorimetric tower E/P average is measured.A correction factor (corr)is evaluated to bring the <E/P> close to 1.For each tower tEE’ = E/corrt

Improvement on dielectron invariant mass resolution: 5.4 GeV/c2 4.0 Gev/c2

CES-x corrections A variation (max variation ~7%) in the energy scale is found as a function of the local x position of the CES.The <E/P> distribution is flattened using f(x).

f(x

)

After corrections

<E

corr/

Pco

rr>

Conversion RemovalElectrons coming from photon conversion are removedConversion algorithm looks for couple of opposite sign tracks with |xy|<0.2 cm AND |cot|<0.04

Transverse plane

xy Conversion radius distribution

But don’t throw the baby with the dirty water

These events (Trident) are good!

W->e eventsAfter applying the selectionNumber of observed Events: 37584

Some kinematical distributions:

Electron ET Missing Transverse Energy

Transverse MassTransverse Mass:

MT = √2(ET . MET(1-cos ))Some good properties: invariant under W boson PT (if cut not applied) -> used for W mass measurement

Digression: Z->ee Sample•One of the most useful calibration sample for high PT objects (other calibration samples are J/ee, ee):•Clean sample of electron from Z->ee is obtained.•Will be used to evaluate efficiencies

Selection criteria:•At least one “Tight” electron selection•At least one “Loose” electron

•ET>25 GeV•Opposite sign track pointing to EM Cluster•PT>20 GeV/c•|z0|<60 cm

•Invariant mass of dielectron pair 75 GeV/c2<Mee<105 GeV/c2

Backgrounds

Two sources of backgrounds:•“EWK” Electroweak processes like Z->ee and W->that mimick a genuine W->e event

Evaluated from MC•“QCD” Dijet events where one jet is lost (cracks) and the other fakes an electron

Evaluated from data

Three methods for QCD bkg evaluation:•Relative Isolation vs Missing ET •Fake Rate•Angular Correlation

EWK BackgroundZ->ee cross section is related to W->e through R:

R=x BF(We)xBF(Zee)

One can use R from theory (Stirling et al.): R = 10.67 ±0.15

Therefore NZ, number of bkg events from Z->ee:

NZ = NWC – NOther-NZ

R(W/Z)

NOther = NQCD+N

R(W/Z) = R x (W->e)/(Z->ee)

Same idea for N

N = NWC – N’Other-N

R(e/)

N’Other = NQCD+NZ

R(e/) = (W->e)/(W->)

Iterative process to determine N and NZ

“QCD” Background: “IsoRel vs MET”

The simplest and most discriminating characteristics between an “isolated” electron as the one coming from the W decay and a jet is the Isolation.There is NO correlation between Missing Transverse Energy and Isolation for dijet events faking a W->e candidate.”Isorel vs MET” method

Bkg QCD = B x C

A

IsoRel vs MetContributions of signal and “EWK” bkg in regions A, B and Cshould be subtracted from region population.

Also consider possible trigger effects

SystematicsSystematic uncertainties are evaluated measuring the number of QCD events obtained modifying the Relative Isolation and MET cut.

Relative Isolation Cut

MET Cut

Red: # QCD evts RawBlue: # QCD evts after EWK processes removal

Systematic uncertainty is evaluated ~50%

#QCD = 587±52(stat)±294(syst)

QCD Bkg: Fake Rate methodFake Rate : Probability that jet fakes an electron (events collected by a trigger requiring at least one jet with ET>20 GeV)Parameterized as a function of ET

Denominator: Events with at least two jets with ET>15 GeV MET>15 GeV and not more than one “loose” electronNumerator: Denominator && one “tight” electron

Integrating the MET spectrum for MET>25 GeV and weighting for the “prescale” trigger factor one gets:

#QCD = 800±300 evts

QCD Bkg: Angular Correlation Method

Reconsider IsoRel vs Met method.Subtraction of signal and other EWK bkg is MC based.One can use a “data-driven” methodUse angular distributions to separate QCD from W->e signal

In QCD Bkg events jet faking an electron recoils against the jet

Jet faking an electron

“Genuine Jet”

In W->e Signal events W boson recoils against the jet

Jet

uncorrelated

“True” electron

Neutrino

Angular correlationsOperative method:O-jet events are assumed “background free”Calculate between sum of jet momenta and electron

QCD Bkg

W->e signal

MET distributions for:

QCD Bkg W->e Signal

for “Non Isolated” electron sample

Subtraction

“Pure QCD Bkg” MET distributionis used on isolated sample to estimate the number of QCD events:#QCD = 594±80(stat)

Background summary

All methods to evaluate QCD background are in agreementTotal number of W->en candidates: 37574

Backgrounds

QCD

Z->ee

W->

Total

587±29

9

317±14

752±17

1656±3

00Total background contamination less than 5%

Acceptance:Evaluated using MonteCarlo W->e ( generated with Pythia)

Efficiencies:Electron ID:

Evaluated from Data Z->ee sampleTrack Matching

Evaluated using a combination of Data and MC(Z->ee CC) EM Cluster Reconstruction

Evaluated using a combination of Data and MC (Z->ee CC) Trigger

Evaluated using back up triggers from data

3333

Acceptance and Efficiencies

Acceptance Measurement

•Acceptance is calculated using MC•W->e are simulated using Pythia MC (6.203) using CTEQ5L Parton Distribution Function•A full detector simulation is used to model the behavior of the CDF detector

It is crucial to tune MC to best match Data and MC

Selection cut considered:•ET>25 GeV•MET>25 GeV•||<1.1

Acceptance: Systematic Uncertainties

Systematic to acceptance are due to uncertainties in the simulation:

Energy Scale and Resolution

W Boson Transverse momentum

Material Estimate

Recoil Energy (Modeling energy deposition in the

Calorimeters)

Parton Distribution Function Uncertainties

Pythia ParametersSeveral “knobs” in Pythia are used to modify the Z Boson PT for tuning data to MC.

Z PT Distribution for data (points) and MC (histo)

2 between Z boson PT distribution data and MC

Generator level W boson PT variations shifting one of the Pythia parameter

Pythia Parameters: Summary

To evaluate the systematic uncertainty from tuning the Pythia parameters, MC generated with 3variation are used to evaluate acceptance.A relative systematic uncertainty is evaluated to be:A/A = 0.043 %

Material EstimateCorrect amount of material in the detector should be considered. Check material budget:E/P distribution is a good observableThe ratio of the number of events in the E/P peak (0.9<E/P<1.1) to the number of events in the tails of the distribution (1.5<E/P<2.0, 2.0<E/P<2.5).The amount of material (in X0) needed is evaluated in order to have the same ratio for Data and MC

~4±2% X0 of additional material (copper) has to be added

A/A = 0.73 %

Recoil Energy

Need to tune the MC model of energy deposition in We events to have the best possibile match of MET with data.•Hadronic showering•W boson recoil energy•Underlying event•Multiple interactionsCan be inaccurate for MC and need to be tuned.

leptonneutrino

U = -(ET + MET)

U

Compare projection parallel and perpendicular to electron and tune them.

UparU’par =Kpar x Upar + Cpar

UperpU’perp =Kperp x Uperp + Cperp

Recoil EnergyShift and scale parameters are obtained after minimizing the 2 for the distributions of U for data and MC.

Before tuning After tuning

MET is then recalculated using the tuned recoil energy U’:

MET’=-(ET+U’)

A/A = 0.25 %

PDF Uncertainties•Momentum distributions of quarks and gluons are required as an input for MC simulation•We will use the CTEQ6 PDF•CTEQ6 are determined after minimizing a 2 for global data.•After diagonalization of the covariance matrix a new set of CTEQ6 with “errors” can be extracted

20 sets of PDFs with ±1- are available

PDF systematic uncertainties are extracted from relative changes in the acceptances

It is not necessary to run the whole simulation.Can stop at generator level

A/A = +1.2/-1.4 %

Systematic Uncertainties for Acceptance: Summary

Source

Energy scale

Energy Resolution

Recoil Energy

W Boson PT

Material

PDF

Total

A/A (%)

0.34

0.03

0.25

0.04

0.73

+1.2/-1.4

+1.43/-1.64

A(%)

0.08

0.01

0.06

0.01

0.17

+0.28/-0.34

+0.34/-0.39

Total Acceptance = 23.96%

Efficiencies

Need evaluate efficiencies for:ID: electron ID (E/P, Lshr, etc…)Tracking: reconstructing the track of the high-pT lepton in the COTReconstructing: reconstructing EM cluster (calorimeter)TriggerAll these efficiencies are “conditional” efficiencies: i.e. provided that the requirements above are matched

In this way we are taking correctly into account correlations among variables

Order matters!

ID Efficiencies

ID efficiency are measured using the second leg of a Z->ee decay.•One leg is required to be tight•The other (probe electron) is required to pass:

•ET>25 GeV•Opposite sign track pointing to the EM Cluster with PT>10 GeV/c and |z0|<60 cm

•Invariant mass 75 GeV/c2<Mee<105 GeV/c2

NCC = #events passing cuts aboveNTT = #events with both electrons tightNTi = #events with one tight, one probe an passing i-th ID cutFor a single selection cut (i-th):

iID= NTi+NTT

NCC + NTT

Eff = 81.8±0.8 %

ID Distributions

ID Distributions

Track ReconstructionEfficiency is measured on a un-biased sample with respect to COT tracks.•Data collected with W_NOTRACK•MET>25 GeV AND ET>25 GeV•No extra jet in the event•Had/Em<0.05, Lshr<0.2, 2

strip<10,•Only Silicon reconstructed track pointing to EmCluster

Trk=#events passing above cuts

#events passing selection cut + COT track pointing to EM Cluster

Eff = 99.7±0.2 %

EMCluster reconstruction

The EM cluster reconstruction efficiency is defined as the efficiency to reconstruct a EMcluster corresponding to a high-pT electron. Possible inefficiencies in this procedure might come from:•Detector failures (dead towers, proton beam splashes)•Code inefficiencies (bugs)

Efficiency measured on sample obtained requiring a “very tight track” (high quality track)

Eff = 99.0±0.4 %

Physics Processes at hadron colliders

LHC

TeVatron1033

<1032

Luminosity

[cm-2s-1]

10

0.3

∫L

[fb-1/y]

14 LHC (low lum)

2 TeVatron

√s

[TeV]

--

--

Triggers ad CDF

Analyzed events have been collected by a three level trigger:•L1_CEM8_PT8: single central EM calorimetric tower with ET>8 GeV and a track with PT>8GeV/c pointing to it•L2_CEM16_PT8: Central EM clusters are clustered. Energy of cluster > 16 GeV and Had/Em<0.125•L3_CEM18_PT8: Reconstructed offline clusters with Energy>18 GeV and Had/Em<0.125 + other requirements (Analysis selection cuts).

Trigger Efficiency: Strategy

•Use data collected by trigger paths different from the one used for the analysis (backup triggers)•Apply offline selection cuts•Measure efficiency:

= #Events Triggers Fired (Data AND Backup) AND Offline cuts

#Events Trigger Fired (Backup) AND Offline cuts

Need to evaluate trigger efficiencies.We have a trigger simulation but prefer to evaluate trigger efficiencies from data.What we need is the “conditional trigger efficiency” i.e. Trigger efficiency provided that analysis selection passed:(Trigger|Analysis selection)

Track Trigger EfficienciesTrack Trigger Efficiencies:Evaluated using the W_NOTRACK trigger pathW_NOTRACK has no track requirement at trigger level but requires MET>25 GeV.

L1_PT8 efficiency vs L3_PT8 efficiency vs |

Calorimetric Trigger EfficienciesUse “prescaled” backup trigger paths with some “missing” trigger primitives

L1_EM8 efficiency vs Highest EM Tower ET L2_CEM16 Trig Eff. vs ET

Efficiency Summary

Selection

Tracking

EM Reco

ID

Trigger

Eff (%)

99.7±0.2

99.0±0.4

81.8±0.8

96.6±0.1

Luminosity at CDFII

Howto Measure Luminosity

Different methods have been used since ISR times.Will focus on CDF RunII method

For a defined physical process:

Nint = L x

Where:L is the instantaneous luminosityNint is the interaction rate for the process with cross section

Measuring Luminosity at CDFII

For RunII CDF build the CLC (Cherenkov Luminosity Counter) to measure instantaneous luminosity

For a defined selection criteria {}: x fBC = int x CLC x LWhere: = <# Interactions/Bunch Xing>fBC = Frequency of collisionsL = Inst. Luminosityint = cross section of physical processCLC = CLC efficiency{} Defines a collision (thresholds, timing, etc…)

Measuring Luminosity at CDFIIPhysics process is inelastic ppbar scattering.Operationally can be computed as: (other possibilities: no interactions / bunch Xing, etc.)

= <NH>

<N1H>

Average Number of hits in CLC per bunch Xing

Average Number of hits in CLC per single ppbar interaction

L = fBC . <NH>

in . CLC. <N1H>

Uncertainties:Efficiency of CLC (based on MC) Measuring average number of hits (PMT gains, detector stability)Inelastic ppbar cross section (2.8 between CDF and E811)Overall Luminosity uncertainty(~6%)

Luminosity at CDFII

59

For a high luminosity environment measurements based on Cherenkov radiators have advantages over Beam-Beam Counters (RunI):

•Can discriminate between particles from primary interaction and secondary interaction (beam-halo,…)•Can count number of hits Increased precision measuring multiple interactions•Insensitive to low momentum particles (Cerenkov threshold 2.2 GeV/c for )•Excellent time resolution (t~100ps) (can identify in-time collisions)

Luminosity Region CorrectionThe requirement that the event vertex fall within ±60 cm of the center of CDF limits the event acceptance to a portion of the full luminous region of p p collisions while the luminosity reported by the CLC detector is over the full luminous region in z.

Efficiency is measured on events collected by “Minimum bias” trigger.

pp beam luminosity function (~ z vertex distribution)

= 95.0±0.4 %

Z Vertex distribution

Measured Zvtx Distribution fit to the luminosity function n = 100 bins, 2 = 119

Summary

Other EWK measurement:Extension in the “Forward Region”

Extension of acceptance in the higher h region.EM cluster from “Plug” calorimeters.Larger role played by tracks reconstructed only with silicon (silicon standalone tracking algorithm)

Extended pseudorapidity electron coverage+Forward Tracking1.1<||Ele<2.8

Small background contamination (QCD, W,Z ee) (~6% e, ~11 % )Systematics from PDF, energy scales, material description

xBF = 2.874± 0.034 (stat) ±0.167(syst) ± 0.172(lum) nb

Z and W cross section x BR(W/Z->l/ll)

20 years of W and Z at hadronic colliders!

CDF Run II Electron 1.1<||<2.8

Measuring Ratio R of x BF

R BF(p p

_

W lv)

BF(p p_

Z ll )

(p p_

W )

(p p_

Z) (Z)

(Z ll)(W l l )

(W )

(W) can be extracted indirectely.

From LEP

From Theory:Rosner et al.

From Theory: Van Neerven

R Measurements:R e-channel:R -channel:R Combined(W)(MeV)

10.860.18 0.1611.100.27 0.1710.940.150.132071 40

10.340.5911.320.76

2187128

CDF

DØ Theory

10.66 0.05

2092 ± 40 World Average

2150 ± 90 LEP Direct

From R to W width Measurement

Lepton UniversalityFrom W decaying in e and :

2

2

)(

)(

We

W

e g

g

eW

W

R

RU

From W decaying in :

2

2

)(

)(

We

W

e g

g

eW

W

R

RU

g/ge

CDF measurement0.990.040.07

g/ge

CDF measurementWorld Average

1.0110.0180.9930.025

Z Forward Backward Asymmetry

...cos)cos1(

)0(cos)0(cos

)0(cos)0(cos

2

BA

dd

ddAFB

Probing (Unique at Tevatron):

• Z/* Interference in High Invariant

Mass Region (far from Z-pole)

Consistent with SM

Constraints on non-SM Z Couplings

soon!

SM Contributions

Beyond SM(Z’,New Interactions)

W gammaZ gamma

Non SM!

•DiBoson Coupling Measurements:•Probe ewk boson self-coupling•Sensitivity to physics BSM(Anomalous Couplings)

Triple Boson coupling

DiBoson Production

W- Z-

DiBoson Production

Non SM

W-gamma

Selection Cuts

•One High-PT lepton(e,)

•One Photon(R(,l)>0.7)

•Large Missing ET

SM @s=1.96TeV19.3 ± 1.4

19.7±1.7stat±2.0sys±1.1lum29%259e+

•B(Wl) (pb)BackEvents

Consistent with SM

ET()

probing anomalous couplings

5.5±1.7stat±0.6sys±0.3lum6.8%69

•B(Z-->ll) (pb)Back.

Events

•Two High-PT Leptons(Opposite

sign)

•One Photon (R(l,) >0.7)

Process:

pp->Z->ll

Consistent with SM•B(Z-->ll)SM= 5.4 ± 0.3pb

e+

Z-gamma

Two complementary approaches:

•Sensitive to WWγ and WWZ vertex•Higgs discovery channel•Right place to look for new Physics

14.3 +5.6 –4.9 (stat) 1.6 (sys) 0.9(lum) pb

Data 39

WW signal

16.3 ± 0.4

Bkg 15.273.55

BR(WWℓ+ℓ- )Th = 12.50.8pb(NLO)

Ldt=200pb-1

19.1 5.0 (stat) 3.6 (sys) 1.1(lum) pb

Dilepton selection (l+l-) (small yield and background)

Tight Lepton + Isolated Track selection(larger yield and background)

WW Production

Data 17

WW signal

11.3 ± 1.3

Bkg 4.8 ±0.8

Consistent with SM

W Mass measurement: RunIThe Tevatron Run 1 combined W mass measurement was ready six years after end of RunI

In Run I larger uncertainties coming from:StatisticsDetector Energy responseW Transverse MomentumPDF (correlated between experiments)

Method: fit Transverse Mass distributions to MC varying MW, including:•detectors effects,•W decay•W production model

W Mass measurement: RunI

Run I Tevatron

New Run I Top Mass Combined Measurement

W Boson mass SM key parameter and for SM Higgs mass constraints

W Mass measurement: Run II Prospects

direct extractio

n of (W)(W)

Almost all systematic uncertainties will decrease with statistics(control samples)Goal for Run II (with 250 pb-1) CDF Run II estimate (μμ)): = X±55(stat)±80(sys) MeV/c2

We need to improve uncertainties:•Radiative corrections (electrons)•QCD effects in W/Z production

Tevatron Run II Predictions

Thanks!

I would like to thank the organizers of this first LHC School whishing many others and successful future editions!

Backup Slides

ID FormulaN: number of Z->ee eventsT: efficiency of one leg passing tight cutsi: efficiency for one probe leg passing i-th ID cutNCC = (2.T(1-T)+T

2) x NNTT = T

2 x NNTi = (2 T i – T

2) x N

Solving for T and i:

i=NTi+NTT

NCC + NTT

T= 2NTT

NCC + NTT

79

Met

(G

eV)

Et (GeV)

Starting dataset

After Selection

10461 Events

Background ~5%79

MET vs Electron EtAll candidatesSelected by trigger MET_PEM

After whole selection chain

W->e candidates

Transverse Mass

8080

Kinematical Distributions

81

Electron ET Missing Transverse Energy

81

Xsection: ResultsCDF RunII Preliminary result:

xBF = 2.874 0.034 (stat) 0.167(syst) 0.172(lum) pb-1

82

For comparison, measurements in Central region are:

xBF(W->e) 2.782 0.014 +0.061-0.056 0.167 nb

xBF(W-> )2.772 0.014+0.064-0.060 0.166 nb

First CDF measurement of W cross section in PLUG region

xBFTHeory

= 2.687 0.054 pb-1 (Stirling, NNLO)

82

Conclusions

83

Result for 64pb-1 was blessed on March 18

Analysis of 200 pb-1 already started

(will be used for publication)

Basic work to select a ttbar enriched sample started (T.Staveris)

Stay tuned for more physics to come from large eta

83

References

84

Some References:

Measurement of the s x BF(W->enu) in the Plug Region using Calorimetric and Forward Tracking (CDF Note 6535)

Trigger Efficiencies for Plug Electrons in Run II (CDF Note 6864)

Face energy corrections