Electroweak Physics at the Tevatron

Adam Lyon / Fermilabfor the DØ and CDF collaborations

15th Topical Conference on Hadron Collider PhysicsJune 2004

Outline Importance Methodology Single Boson Measurements Summary & Outlook W/Z+and Diboson Results

up next

2A. Lyon (HCP2004)

Learning from Electroweak Physics mW , mt , and mH are

related Constrain Higgs mass

Test of standard model couplings (and see M. Kirby's talk)

Study higher order QCD Many uses in detector

studies and luminosity determination

3A. Lyon (HCP2004)

Uncertainties in mW

Run 1 uncertainties (from hep-ex/0311039)

Source CDF m CDF e DØ eW statistics 100 65 60Lepton scale 85 75 56Lepton resolution 20 25 19p T (W) 20 15 15Recoil model 35 37 35Selection bias 18 — 12Backgrounds 25 5 9

Uncorrelated Uncertainties (MeV/c 2)

Source DØPDF & luminosity 7 4Radiative corrections 12G

W 101110

Correlated Systematics (MeV/c 2)

CDF15

Uncorrelated uncertainties scale with luminosity Correlated systematics improve as theory improves Perhaps can reach 40 MeV/c2 per channel & exp with 2 fb-1

4A. Lyon (HCP2004)

Collider: Tevatron for Run II

Base goal is 4.4 fbBase goal is 4.4 fb-1-1

(Design is 8.5 fb(Design is 8.5 fb-1-1) by end of FY09) by end of FY09

5A. Lyon (HCP2004)

Detectors: CDFSaved from Run I

SolenoidCentral CalorimeterCentral Muon System

New/Improved in Run II8 layer Si tracking (|| < 2)Central Outer Tracker (|| < 1)Plug Calorimeter (1.0 < || < 3.6)Extended muon coverage to || < 1.5New and improved trigger and DAQ

Luminosity~400 pb-1 on tapeAnalyses shown here use 65 - 200 pb-1

6A. Lyon (HCP2004)

Detectors: DØ

Saved from Run IHermetic LAr CalorimeterMuon Toroid and proportional drift

tubes

New in Run II2T Superconducting SolenoidInner Tracker (Si Microstrips and

Scintillating Fiber tracker)Preshower detectorsUpgraded muon system (including

better shielding)New and improved trigger and DAQ

7A. Lyon (HCP2004)

Detectors: DØ

Luminosity

370 pb-1 on tape

Analysis here use17-162 pb-

1

8A. Lyon (HCP2004)

W/Z Production and Event Topology

Use clean leptonic decays

W (energetic lepton + ET) Z0 (energetic opposite sign

leptons)

9A. Lyon (HCP2004)

W and Z events are extremely useful Measure cross sections

Calibration of detectors, luminosity measurements Lepton universality, W width

Measure W and Z properties (pT(W), pT(Z), y(Z), lepton angular distributions) Constrain PDFs, fit for couplings, look for new resonances

Measure W mT , lepton pT spectra Yields mW , W width

W/Z + Jets Backgrounds to Higgs and Top analyses

W/Z + , Dibosons Probe electroweak gauge structure Backgrounds to New Phenomena searches

10A. Lyon (HCP2004)

Analysis Methodologies Both DØ and CDF follow

similar strategies

Triggers: Calorimeter triggers for

electrons Track triggers for muons

Selection: W - a lepton and large

missing transverse energy Z - two opposite charge

leptons

Electron requirements: Isolated EM cluster Shower shape (CDF uses

shower max, DØ has finely segmented calorimeter)

Track pointing to calorimeter EM cluster

Muon requirements: Track matched to calorimeter

MIP trace and/or muon system track

Reject cosmics by timing and impact parameter

Track and calorimeter isolation

Measure identification efficiencies with Z events

Measure backgrounds with QCD Dijet events

Systematics Luminosity (~6%) PDF (use CTEQ6 and MRST) (1-

2%) Lepton ID (~1%) Backgrounds, E scale, Recoil

model, Detector Description

11A. Lyon (HCP2004)

Z ee Cross Section 2 EM objects with

pT > 25 GeV/c CDF: central + plug cal

(||< 2.8) DØ: central only

Small backgrounds QCD Z

pb2.159.32.254 5.54.5 lumsysstat

pb28992.275 lumsysstat

CDF:

DØ:

12A. Lyon (HCP2004)

Z mm Cross Section pT cut lowered to 15-20

GeV/c for muons DØ efficient for

mmm > 30 GeV/c2

DØ applies a Drell-Yan correction

Very small backgrounds:QCD (b-jets), Z

pb9.149.59.248 0.72.6 lumsysstat

pb2.269.80.58.261 lumsysstat CDF:

DØ:

13A. Lyon (HCP2004)

W e Cross Section Requirements:

1 electron with ET > 25 GeV

ET > 25 GeV(CDF plug analysis used 20 GeV)

CDF: central & plug DØ requires || < 1.1 Track match required Backgrounds

QCD, Z ee, W

14A. Lyon (HCP2004)

W e Cross Section

pb167142782 6156 lumsysstat

pb284128212844 lumsysstat

CDF (central):

DØ:

pb172167342874 lumsysstat CDF (plug):

15A. Lyon (HCP2004)

W m Cross Section Require m pT, ET > 20 GeV Backgrounds: QCD (b-jets),

Z mm, W

pb166162772 6460 lumsysstat

pb3221001283226 lumsysstat CDF:

DØ:

16A. Lyon (HCP2004)

Cross section comparisons

Experiment Channel # events Purity Lum. (pb-1) e * A || coverage

CDF W e 48045 94.0% 72 23.1% 2.8DØ W e 27370 95.7% 42 18.4% central

CDF W m 31722 90.0% 72 14.4% centralDØ W m 8302 88.0% 17 13.2% 1.6

CDF ee 4242 98.5% 72 22.7% 2.8

DØ ee 831* 98.3% 42 10.0% centralCDF mm 1785 98.5% 72 10.2% centralDØ mm 1139 98.9% 117 16.4% 1.8

dtLA

NNBr bkg

e

* Track match required

CDF and DØ are rather similar, except in angular coverageCDF uses plug calorimeter for far e coverageDØ uses forward muon system for far mcoverage

17A. Lyon (HCP2004)

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W

W

Z

Z

Zpp

Wpp

Zpp

WppR

GG

GG

Use measured W and Z cross sections and R

Measured (CDF Preliminary)

Theory (NNLO, PDG)

LEP

Infer the W width (Preliminary)

sysstateR 16.018.086.10

sysstatR 17.027.010.11 m

024.0368.3)(/)( ZppWpp 0021.01093.0)( WBR

)%002.0366.3()(/)( GG ZZ

MeV 402071)( G W

18A. Lyon (HCP2004)

Analyses with Taus Reconstructing leptons

is challenging Must use hadronic decays

for ID (1 or 3 charged tracks plus 0's)

But these are hadronic jets; high QCD background

Look for tracks in a narrow 10° cone pointing toward a narrow calorimeter cluster

Require 30° cone isolation for tracks

Reconstruct 0's (in shower max for CDF)

Require effective mass of tracks and 0's to be < 1.8 GeV/c2 (m + resolution)

0n3)or 1(

19A. Lyon (HCP2004)

W (CDF Run II Preliminary) Start with track + ET trigger Require

ET > 25 GeV, ET > 25 GeV No other jets above 5 GeV

2345 candidates in 72 pb-1

Bkg = 612 61 events eID· A = 1.06 0.064 %

nb )16.021.007.062.2()( lumsysstatWBR

sysstateWBRWBR

egg 04.002.099.0/ )()(

20A. Lyon (HCP2004)

Z Look for 1-prong decays Look for other via e or m Understand tau ID Important for searches Proof of principle that

resonances are seen at the Tevatron

0Zm)or (e

0n

pb 152648242)/( * sysstatZpp CDF:

21A. Lyon (HCP2004)

Charge asymmetry in W e Goal is to improve understanding of PDFs using W charge asymmetry

Since u quarks on average carry more of the p momentum than d quarks, W + produced in ud W + are boosted along p W - produced in du W - are boosted along p

The e from the W decay carries information on the W direction, but

true W direction cannot be reconstructed due to unmeasured pz of Use the e

direction to measure AyW convoluted with V-A decay distribution

Results are sensitive to ratio of PDFs for u and d Do for low and high ET [NEW APPROACH]

(at higher e ET, e dir is closer to W dir; less cancellation with V-A) Sensitivity is best at high || where it is least constrained

dyWddyWd

dyWddyWdAyW /)(/)(

/)(/)(

22A. Lyon (HCP2004)

Charge asymmetry in W e Require

e ET and ET > 25 GeV 50 < mT < 100 GeV No other EM object

with ET > 25 GeV

In forward region, use "calorimeter seeded Si tracking" to utilize new forward Silicon This along with drift chamber

can determine charge within || < 2

Measure charge mis-id rate with data using Zs < ~1% within || < 1.5 < ~4% far forward

Backgrounds Z [MC], W [MC],

QCD [data]

23A. Lyon (HCP2004)

Drell-Yan Forward Backward Asymmetry

Interference of * and Z f = u, d, e

Leads to AFB in

Depends on uuZ, ddZ and

eeZ couplings Can probe couplings Near the Z resonance, AFB

is related to sin2 W

New interactions may modify the SM AFB prediction

Z*

f

f f ’

f ’+

f

f f ’

f ’ eeZpp */

)0(cos)0(cos

)0(cos)0(cos

dd

ddAFB

cos)cos1(cos 2 BAdd

q q

e-

e+

24A. Lyon (HCP2004)

Drell-Yan Forward Backward AsymmetryCDF Run II Preliminary Require 2 isolated

electrons with pT > 20 GeV/c

5211 candidates in 72 pb-1

No asymmetry seen in dijet background

Use Collins-Soper reference frame for measuring electron scattering angle Reduces uncertainty in

scattering angle due to pT of incoming partons

25A. Lyon (HCP2004)

Drell-Yan Forward Backward AsymmetryCDF Run II Preliminary Fit for weak mixing angle

Fits for couplings are in good agreement with world averages

No evidence of new interactions above the Z pole

0.14/71.12ndf/

0020.00046.02238.0sin2

2

sysstatW

26A. Lyon (HCP2004)

High Mass Drell-Yan Spectrum Sensitive to new physics

New gauge bosons (e.g. Z'), extra dimensionsRun 1 limits surpassed and new models explored

27A. Lyon (HCP2004)

Summary Current preliminary results consistent with

SM

(Theory lines NNLO from Hamberg, van Neerven, Matsuura)

28A. Lyon (HCP2004)

Outlook 1.96 TeV cross sections nearing publication Tevatron electroweak working group will make

combinations Stay tuned for further analyses; > 300 pb-1 on

tape Preliminary W mass measurements soon

29A. Lyon (HCP2004)

EXTRAS

30A. Lyon (HCP2004)

Z ee Cross Section

31A. Lyon (HCP2004)

Afb Acceptance

32A. Lyon (HCP2004)

Uncorrected Afb