New Electroweak Results from DZero

1

New Electroweak Results from DZero

Observation and Cross Section times Branching Fraction

Diboson Studies: W, Z, WW, WZ

DD

Tevatron

Chicago

DØ

MainInjector

Tom DiehlFermi National Accelerator Laboratory

“Wine + Cheese” January 28, 2005

For the DØ Collaboration

2

Outline

DØ Run II Data The DØ Detector

Inner tracker, calorimeter, & muon systems

Br(Z) at 1.96 TeV Motivation Event Selection Tau reco, classification, & ID Cross Section measurement

Dibosons: WW, WZ, W, Z Motivation WW and WWZ Couplings &

Anomalous Couplings WW (Dileptons)

Cross Section @ 1.96 TeV

WZ (Trileptons) Limit on (WZ)(WZ), and AC

limits. W in e and channels

W Cross Section, Photon ET Spectrum, and limits on AC.

Progress on Rad. Zero Z in ee and channels

Z Cross Section, Photon ET Spectrum, Event Characteristics, and limits on ZZ and Z AC.

Summary

3

The DZero Collaboration

19 Countries 86 institutions ~620 physicists

4

DZero Run II Data

~700 pb-1 pp collisions at sqrt(s) = 1960 GeV since the start of Run II.

Since the end of the 2004 shutdown the Tevatron has returned to high-performance operation. Stores routinely in the 80-

100e30 cm-1 s-1 range. Peak luminosity increases

due to effort in A.D. Challenges DZero to adapt to

increasingly higher luminosities Trigger List Reconstruction

So far, so good.

650 pb-1

520 pb-1

Monthly

Eff’y

Analyzed to here:

pp collisions at sqrt(s) = 1960 GeV

5

The DZero Detector in Run II: Inner Tracker

Tracker

SMTSMT

SMT

6

The DZero Detector in Run II: Calorimeter

Fitted Z(ee) peak has 3.7 GeV/c2 mass resolution in Run II.

Fine Longitudinal and Transverse Segmentation

7

The DZero Detector in Run II: MUONS

Run IIRun Ia Fitted Z() peak has

8.1 GeV/c2 mass resolution in Run II.

No Shielding

D0 Shielding

’s in

Central Scint.

Counters

t(ns)

Simulation

Run II Data

Unbiased

Triggers

8

Physics Motivation Test consistency of SM couplings

to all leptons Benchmark our level of

understanding of the experiment. Tau is most difficult lepton to ID Develop Tau ID, Efficiencies,

backgrounds We use this signal to tune up our

triggers and algorithms for non-SM searches such as

certain parts of SUSY space New Phenomena such as heavy

resonances that decay with enhanced coupling to 3rd generation.

)(Br)( ZZ What do we know about this?

NNLO calculation* predicts (Z) = 242+-9 pb.

Br(Z) is well measured.

measured.been beforenever

has )(Br)( ZZpp*from Hamberg, van Neervan, and Matsura,

Nucl. Phys. B359, 343 (1991), using CTEQ6L

9

The analysis is complicated.

)(Br)( ZZ

Classify tau

candidates Extract

Cross Section

Preselection: single muon

events

Reconstruct

taus

Divide Events into

OS and SS

(For BKGD Estimate)

Lepton Pairs

Final Event

Selection

Start

10

One must decay to . Event Selection starts with an isolated muon

One w/ pT()>12 GeV/c This muon carries the sign of it’s tau lepton

The other can go to any of 3 decay modes

Event Selection

L=226 pb-1 L/L = 6.5%

hadronsor

e

XZ

)%07.0(20.15)prong" 3"Br(

)%13.0(71.84)prong" 1"Br(

)%06.0(84.17)Br(

)%06.0(37.17)Br(

e

Tau Decay Signature For reference:

Z

11

Start with the Calorimeter CAL. ET (R=0.5) > 5 GeV & ET (R=0.3) > 3 GeV Taus have narrow jets

Then use the Tracker N(tracks w/ pT>1.5 GeV/c in the narrow cone) > 0

Start with the highest pT track If there’s a second track such that Mass(2-

tracks)<1.1 GeV/c2, add that track to the tau list If a third track such that Mass(3-tracks)< 1.7 GeV/c2,

add it unless total charge = 3 or -3. If total charge = 0, discard the tau candidate.

Require > 2.5 (These are low pT Z’s) Reconstruct EM subclusters with ET > 800 MeV

Reconstruct Tau Candidates

I.P.

Charged Particle

Cones of size R=0.3 and 0.5

25.0)(RMS2

ET

ETR iCalTowers

ii

12

Classify the tau candidates into three types

1. “One-prong”, a single track w/ no EM subclusters

2. “One-prong” + EM, a single track w/ EM subclusters (cleanest)

3. “Multi-prong”, more than one track

Tau Identification: Classification

TRK + CALType 1

o

no TRK, but EM sub-cluster

TRK + CAL

Type 2

1 TRK

+wide CAL cluster

Type 3

“One-prong” “One-Prong + EM” “Multi-Prong”

And there are selection criteria

discriminating them from each other

And rejecting background.

13

Classify the tau candidates into three types “One-prong”, a single track w/ no

EM subclusters “One-prong” + EM, a single track

w/ EM subclusters (cleanest) “Multi-prong”, more than one

track


TRK + CALType 1

o


TRK + CAL

Type 2

1 TRK

+wide CAL cluster

Type 3


7.0

/)(

GeV/c 5

GeV/c 7

GeV 5

GeV 10

5.05.0track

trkT

trkxCH

trksT

trksT

T

T

PEE

P

P

E

E

Gets rid of eventsw/ extra ’s

14

Classify the tau candidates into three types

1. “One-prong”, a single track w/ no EM subclusters

2. “One-prong” + EM, a single track w/ EM subclusters (cleanest)

3. “Multi-prong”, more than one track

No attempt to separate hadron channels from electron channels.

At this point we have the charge sign of and


TRK + CALType 1

o


TRK + CAL

Type 2

1 TRK

+wide CAL cluster

Type 3


7.0

/)(

GeV/c 5

GeV/c 7

GeV 5

GeV 10

5.05.0track

trkT

trkxCH

trksT

trksT

T

T

PEE

P

P

E

E

Gets rid of eventsw/ extra ’s

15

Divide 29,021 events into SS and OS lepton-lepton candidates.

We still have a large background from multijets. Jets tend to be wider than ’s have higher track multiplicity have higher mass than M() be less isolated from other hadronic energy than

are tau’s from Z’s. A Feed-forward neural network

8 input nodes (each a new criteria), a single hidden layer with 8 more nodes, and a single output (the answer). Not all inputs for all tau types.

Train the 3 types separately on expected signal and backgrounds.

Tau Identification: Neural Network

Jet-Background

q

o

o

1 TRK +wide CAL cluster + EM sub-cluster

“One-Prong”

“One-Prong”+ EM

“Multi-Prong” “All Types”

16

Events predicted and events observed before and after P(NN)>0.8 criteria for all 3 types. QCD background is scaled

from same-sign data The other bkgds and expected

Z() from MC. Eff’y(NN)=0.78 Signal/Bkgd ~

0.82 #Z() Observed = 86555

after M()>60 GeV/c2

Eff’y = 1.52% for M() > 60 GeV/c2.

Tau Identification: # Candidates

type contribution to signal:

13% Type1, 58% Type 2, 29% Type 3

TOTAL Number of Events

After NN

Before NN QCD 13881264 10024W 434153Z/* 117443SUM 15589309OS Events 15911

QCD 98446 7016W 5820Z/* 91424SUM 202657OS Events 2008

17

PT() PT()

ET()ET()

Systematic Uncertainties

Energy scale 2.5% NN MC inputs 2.6% Backgrounds 4.6% PDF’s 1.7% Eff’y & Accept. 2.6% Trigger Eff’y 3.5%

Total 7.5%

Figures show ET() and pT() for: MC vs. background subtracted data

UNCERTAINTY IN

18

Cross Section Calculation

Submitted to PRL.

hep-ex/0412020

FERMILAB-PUB-04/381-E

Theory: Matsura + van Neervan

)(Br)( ZZ

AL

bN)Br(Z

For m()>60 GeV/c2

After removing the * contribution

pb .)(19.)(16252

)Br(Z

sysstat

pb .)(15.)(18.)(15

237)Br(Z

lumsysstat

19

What else can we say about Taus?

Z mass peak We can find states

that decay to tau’s. Not some other large

source of tau pairs. Searches for Higgs,

SUSY etc with tau final states are available and more are coming

Lepton Universality Use DØ’s Run II

preliminary muon and electron results

Upper Left: Mass() for Bkgd vs. Signal MC for type 1 and type 2 tau tracks

Upper Right: Mass() for (OS events Bkgd) vs Signal MC

09.084.0)Br(Z and )eeBr(Z

)Br(Z--

-

1.96 TeV

20

Dibosons (Outline)

Dibosons: WW, WZ, W, Z Motivation WW and WWZ Couplings & Anomalous Couplings WW Dileptons

Cross Section @ 1.96 TeV WZ Trileptons in Run II

Limit on (WZ), (WZ), and AC limits. W in e and channels

W Cross Section, Photon ET Spectrum, and limits on AC. Progress on Rad. Zero

Z in ee and channels Z Cross Section, Photon ET Spectrum, Event Characteristics, and

limits on ZZ and Z Anomalous Couplings.

21

Dibosons: Introduction Motivations

Multiple vector bosons provide a high-pT Standard Model process with a cross section and interesting physics

Cross sections are useful for New Phenomena search analyses.

a SM parameter to measure: the gauge boson “self-couplings”

hep-ph/9704448

SM Higgs Branching Fractions

More Motivation We are on the lookout for very

massive particles that decay to the heaviest gauge bosons.

Like the Higgs. Or the Higgs that doesn’t decay to

fermions. Or whatever.

22

WW and WWZ Couplings

Cancellation of t- and u-channel by s-channel amplitude removes tree-level unitarity violation (in W, WW, and WZ, too). Textbook example t-channel: At high energy limit and

with massless quarks (simpler calculation). violates unitarity.

t-channel u-channel

s-channel

)cot( we e

WW Coupling WWZ Coupling

s-channel: Term of opposite sign cancels unitarity violating part.

3)(

2 sGWW F

Self-interactions are direct consequence of the non-Abelian SU(2)L x U(1)Y gauge symmetry. SM specific predictions.

23

WW and WWZ Anomalous Couplings

VWW VWW

)WVWVWW(/L

†2

V†V

††1VWWVWWV

WM

gg

QeW = e () / M2

W

W = e/ 2MW

Characterized by effective Lagrangian 5 CP Conserving SM Parameters:

(

g

gg

In W production, only the WW couplings.

In WZ, only WWZ couplings.

In WW, both and one has to make an assumption as to how they are related.

W+ Boson Static Properties

24

Effect of Non-SM WW and WWZ Couplings

Cross section increases especially for High ET bosons (W/Z/). Unitarity Violation avoided by introducing a form-factor scale

, modifying the A.C. at high energy. e.g.:

WW Production

( )( / )

ss n

1 2n 2 for WW ,WWZ

PT(W)(s^(0.5)=1800 GeV)

# E

vent

s/20

GeV

/c

25

Anomalous Couplings – LEP and Tevatron

DØ and CDF put limits on anomalous WWg and WWZ Couplings in Run 1. WW and WWZ couplings from WW WW couplings from W analyses * WWZ couplings from WZ *

DØ Combined W, WW, WZ (1999) TeV 2

C.L. 95%

0.1918.0

53.029.0

Tightest from

the Tevatron

LEP Combined (1D 95% CL)

1cos2

1)-(g (D0) constraintw/

1)-(tang and

2Z1

2Z1ZZ

w

w

0.0340.051

0.026059.0

069.0105.0

1

Zg

“HISZ” SU(2)xU(1) coupling relations

Didn’t use a form-factor dependence in their couplings.

*(complementary in several ways)

LEP EWK Working Group hep-ex/0412015

26

WW Production and Decay

Dileptons

e and Br = 2.5 and 1.2%

Pure and efficientLow branching

Frac.

Lepton+jets

en+jets, +jets

Br = 15%

EfficientNot very pure

All-jets

All-jets

Br = 47%

Very EfficientNever Mind

Decay Modes are named like top pairs. In fact, WW is one of the top backgrounds.

(WW) ~ 13.5 pb-1 at Run II Tevatron energy*.

Campbell & Ellis

* Ohnemus (1991), (1994) and Campbell & Ellis (1999).

27

WW to Dileptons in Run I

WW to dileptons @ DØ and CDF Cross section limit and anomalous

coupling limits @ DØ (PRL and several PRDs)

Evidence for WW Production and anomalous coupling limits @ CDF in 1997 PRL.

Leptons + jets channels provided more restrictive A.C. limits than dileptons at DØ and CDF but we couldn’t isolate a signal from the much bigger W+jets background.

( ) . ...WW

10 2 165 16 5 pb

TeV 1

9.0 8.0

3.11.1

TeV 1

C.L. 95%

1.0||

2.1||

C.L.) (95% pb 37

)(

XWW

1D AC limits

28

Run 2: WW -> Dileptons Event Selection

Preselection Criteria Two oppositely-charged e or

w/ pT>15 GeV/c. At least one has pT>20 GeV/c.

MET > 30, 40, & 20 GeV/c2 in eee channels to remove Z/*.

Missing Transverse Energy After Preselection Criteria

Shows agreement between data and signal plus backgrounds.

D0 D0 D0

ee Channel Channel e Channel

channel

29

e channel criteria No third lepton so that 61<

M(l+l-) < 121 GeV/c2. Minimal Transverse Mass > 20

GeV/c2. “Scaled MET” > 15 rootGeV HT(jets w/ ET>20 &||<2.5)

<50 GeV. 3+ silicon hits on electron if

MT()~MT(W). Background is 3.810.17

events and is 71% W+j or Eff’y is 15.40.2%. Expected signal is 11.10.1

events. 15 Candidates Observed.

WW e Event Selection

D0

All Cuts except MT(min)

WZ & ZZ

multijets & Z/*

REMOVES

Top pairs

W

Z/*

30

WW (Dileptons) Quick Summary

The dielectron and dimuon channels have selection criteria along the same lines but with much more emphasis on rejecting Z bosons.

As a result, the efficiency isn’t as high in these channels as in electron+muon.

15 0.111.1 0.173.81 0.215.4 e

4 0.052.10 0.411.95 0.156.22

6 0.053.42 0.212.30 0.138.71 ee

Candidates # WW Bkgd. Eff.(%) ModeDecay

Expected Expected

31

WW Cross Section – Systematic Unc’ys

These are mostly correlated between channels (horizontally). These are added in quadrature for each channel (vertically).

Bottom Line Systematic Unc’y:

32

WW Dileptons Cross Section

For each channel

We combine channels to extract as minimum in

D0

BrL

NN)pp bkgdobsWW(

bkgd

obs

N

NLBrWW

N

eobs

)(

! Likelihood

channelschannelLn2

pb .)(9.0

.)(.)(8.13)( 2.19.0

3.48.3

lum

sysstatWW

s.d. 5.2 tosCorrespond

103.2)fluc. background( 7P

33

WW Dileptons Cross Section

CDF Run II: hep-ex/0501050

Also submitted to PRL

Submitted to PRL hep-ex/0410066

pb .)(9.0

.)(.)(6.14)( 8.10.3

8.51.5

lum

sysstatWW

pb .)(9.0

.)(.)(8.13)( 2.19.0

3.48.3

lum

sysstatWW

34

WZ Production and Decay

All-jets

All-jets

Br = 49%

Very EfficientNever Mind

Trileptons

e’s and’s

Br = 1.5%

Pure and efficientVery Low

branching Frac.

Lepton+jets

e+jets, +jets

Br = 15%

EfficientNot very pureUse B-tagging

(WZ) ~ 4.0 pb at Run II Tevatron energy.

Campbell & Ellis

Measure (WZ) with “trileptons” “Leptons + jets” is stepping stone

for WH where H decays to bb.

35

DØ Trileptons Results (92 pb-1) ee and eee channels 1 candidate w/ background of

0.50 events (mostly Z+jets). Expected WZ events

Model independent limits on Anomalous WWZ couplings in 1999 PRD.

TeV 1

C.L. 95%

1.42||

63.1|| 1

Z

Zg

C.L.) (95% pb 47

)(

XWZ

1D limits

WZ @ Tevatron in Run I

DØ + CDF Results (leptons + jets) Cannot distinguish between

W+jets, WW, and WZ in those analyses.

Limits on anomalous WW and WWZ couplings using the ET spectrum of the dijets from WW and WZ combined.

1996 PRL (CDF) and 1996 + 1997 PRLs (DØ) and several PRD’s 1999 (DØ)

36

Run 2: WZ Trileptons Event Selection

At least 2 isolated e’s and/or ’s with ET>15 GeV that make a Z boson 71<M(ee)<111 GeV/c2 or

50<M()<130 GeV/c2.

A third isolated e or with Et>15 GeV

R(leptons)>0.2 24552 entries

32222 entriesIdentify a

Z boson

Rejects Brems,

W/Z+, Ztaus

Only 65

events with 3

WZ efficiency after these

criteria is ~15%.

ee

37

Background (Mostly Z+X)

Totalbkgd.expected.

andeeeCandidates

WZ Trileptons Event Selection + BKGD.

MET>20 GeV ET(had) < 50 GeV

)()( TTT ElhadE

Remove Top with

B isol. lepton

For a W boson


criteria is ~13%.

DiElectron Channel

*1.43 pb (Ellis+Campbell,Ohnemus)

Z/*+jet Background

M.C. WZ (Z)

* 3e Event

M(ll)

MET

38

Background (Mostly Z+X)

Totalbkgd.expected.

andeeeCandidates



)()( TTT ElhadE

Remove Top with

B isol. lepton

For a W boson


criteria is ~13%.

Dimuon Channel


Z/*+jet Background

M.C. WZ (Z)

* 3 Events

M(ll)

MET

39

WZ Cross Section

Cross section limit

C.L.) (95% pb 3.13

)(

XWZ

“Evidence” for WZ Production

P(0.71 bkgd) Candidates is 3.5%

Interpreting the Events as Signal + Background:

BrL

NN)pp bkgdobsZW(

pb 5.4 5.36.2

Combined Ln(Likelihood)

CDF Run II: hep-ex/0501021

submitted to PRDC.L. 95% @ pb 2.15)( ZZWZ

D0 Preliminary

D0 Prelim.

40

WWZ Anomalous Trilinear Couplings

Generate a grid of WZ MC using Hagiwara, Woodside, + Zeppenfeld LO generator => Fast Detector Simulation.

Form ln(Likelihood) for each grid point to match the observations using the BKGD-subtracted number of events.

Intersect the ln(Likelihood) with a plane at Maximum-3.0 to form 2D Limits @ 95% C.L.

=1 TeV

g1z vs. z

-Ln(Likelihood)

41

Inner contours: our 2D limits. Outer contours are from s-matrix unitarity.

Best limits in WZ final states. First 2D limits in z vs. z using WZ. Best limits available on g1

Z, z, and z from direct, model-independent measurements.

The DØ Run II 1D limits are ~ factor of 3 better than our Run I limits.

WWZ Anomalous Trilinear Couplings

=1 TeV

=1.5 TeV

95% C.L.

1D Limits (holding the other to 0)

DØ Preliminary

42

Sensitive only to WW couplings Identify W boson decay to e or . We don’t bother with hadronic W channel. The background from QCD

photons (qq annihilation and Compton at L.O.) and from “phony” photons swamps it.

Final state radiation is sort of a “background” w/ a collinear divergence @ low-ET.

W Production

Initial State Radiation Final State RadiationWW Vertex

pb 4.00.16)(

GeV 8)( and

7.0)R(For

T

l

E

lMonte Carlo Prediction

Baur & Berger (1990)TeV 1.96@ s

43

W @ Tevatron in Run I

D0 (1995 and 1997 PRL’s) + CDF (1995 PRL) agrees w/ SM and Limits on Anomalous WWcouplings

using the photon ET spectrum.

TeV 2 C.L. 95%

0.2931.0

94.093.0

1D limits

DØ

pb )1.5()4.2(13.2 syststat

pb )1.5()(11.3 1.71.5 syststat

R(l)>0.7 & ET()> 7 GeV (CDF)

R(l)>0.7 & ET()> 10 GeV (DØ)

Tightest WW limits at hadron collider,

(UP TO NOW)!

Anomalous Coupling Limits

44

Run 2: W Event Selection: e and

An isolated electron w/ ET>25 GeV in ||<1.1

MET>25 GeV MT(e)>40 GeV/c2. .NOT. 70<M(e)<110 GeV/c2.

ID a W boson One isolated, w/ pT > 20 GeV/c.

MET > 20 GeV No MT cut at this stage

An isolated EM object No track match (spatial) (Calorimeter -width)2 < 14 cm2

If photon has tracks in a hollow cone of size 0.05<R<0.4 require

ID a Photon (Both Channels)

tracks

T cP GeV/ 0.2

For within fiducial coverage,

Efficiency(ID) =

ET(photon)>8 GeV

R(l)>0.7

||<1.1

Lum’y: e:162 (134) pb-1Eliminate

Z bosons

45

Run 2 W Expected Backgrounds

WeW W+jet (jet mimics )*

events “leX” (Z’s) W Z

Total BKGD events

# Observed 112 161 candidates

# Observed – Background = 141 W

1.7x as many W as in Run 1

1.6x as much luminosity as in Run 1 (analyzed so far)

* Probability(jet mimics 5x10-3 anddecreases withjet

46

Decay Channel eLum’y 162 (6.5%) 134 (6.5%) pb-1.


Total BKGD events

Eff’y*Acc.

WCross Section & Event Characteristics

BrL

NN)pp bkgdobsW(

Three-body Transverse Mass

e channel

channel

Scales adjusted to same.

D0 Prelim.

D0 Prelim.

pb 1.31.18)W( ppFERMILAB-PUB-04-246-E => PRL ET()>7 GeV

CDF

pb .)(0.1.)(0.1

.)(6.18.14)W(

lumsys

statpp

Prelim.

ET() >8 GeV R>0.7

323 Candidates w/ ~114 BKGD. ~200 pb-1. R>0.7

D0

47

W Anomalous Couplings

ET()

D0 Prelim.

Combined channels Photon ET agrees w/ S.M. (last is overflow bin). Baur + Berger MC w/ A.C.

Form a binned-likelihood based on pT() in a vs. grid including bkgd on events w/ MT(3)>90 GeV/c2.

D0 Prelim. @ 1.96 TeV

0.2222.0

97.093.0

1D limits @ 95% C.L.

2D limits

1.5?TeV1D limits

Still the tightest at any Hadron Collider!

48

W Radiation Amplitude Zero

For COS(*), the angle between incoming quark and photon in the W rest frame, =1/3, SM has “amplitude zero”.

For events w/ MT(cluster)>90 GeV/c2. One could guess the W rest frame. We use charge-signed (l,)

M.C. We plot the background-subtracted muon data vs. MC (l,) => hints of the Rad. Zero.

It will help to extend the eta-coverage of electrons and especially of photons.

D0 Preliminary Muon Channel

49

ZProduction

Initial State Radiation Final State Radiation

Initial and final state radiation. Identifying Z boson decay to e+e or is

easiest. Z was done in Run 1A. It might be

possible to do it in Zbbar. We don’t bother with hadronic Z channel.

No SM ZZ or

Z interaction.

pb9.3)(

GeV 8)( & 7.0)R(

/GeV 30)(For

1.00.2-

T

2

ll

El

cllM

TeV 1.96@ s

Monte Carlo Prediction

Baur & Berger (1993)

50

ZZ/Z Anomalous Couplings

Non-SM Characterized by an effective Lagrangian w/ 8 form-factor coupling parameters called h1V, h2V, h3V, and h4

V whereV stands for and Z. CP Violating h1

V and h2V

CP Conserving h3V and h4

V

In SM all these couplings =0.

Transition Momentsd

e k

Mh h

e k

Mh h

ZZ

Z Z

ZZ

Z Z

T

T

2

2

2

3 30 40

2

3 10 20

( )

( )

( )( / )

ss n

1 2

n ZZ Z3 4, for and

51

Z in Run 1

05.0|)(|

37.0|)(|

2040

1030

hh

hh

CL 95%

GeV 750

DØ Results (97 + 87+ 13 pb-1) and e+eandchannels candidates agrees w/ SM and

Limits on anomalous couplings in 1995 & 1997 PRLs and 1998 PRD.

Combined 1D Run 1 limits:

CDF Results (20 pb-1) and e+echannels agrees w/ SM (~5.2 pb) and

Limits on anomalous couplings in a 1995 PRL.

pb )0.3()1.9(5.1 syststat ET()> 7 GeV (CDF)

Up to now the tightest ZZ & Z limits at hadron collider.These are still competitive w/ LEP.

DØ

Z and ZZ limits ~same

52

Run 2: Z Event Selection Two + isolated electrons w/

ET>15 GeV. One or more w/ ET>25 GeV.

All CC electrons must have a track match.

M(ee)>30 GeV/c2.

ID a

Z boson

Two or more isolated , w/ pT > 15 GeV/c.

M()>30 GeV/c2.

Same as the Wevent selection.

Photon ID

ET(photon)>8 GeV

R(l)>0.7

||<1.1

Lum’y: ee: 324 (286) pb-1

All data through June 2004.

Backgrounds

Z+jet (jet mimics )

ZeeZ

events

138 Zee 152 Candidates

53

ZPhoton Spectrum + Event Display

Highest ET() photon in electron channel is 105 GeV.

Highest ET () in muon channel is 166 GeV.

D0 Prelim. Candidate

The ’s are left out of this MET.

138 Zee 152 Candidates

54

Cross section agrees w/ SM Main unc’y is stat. Two largest sys. uncy’s are photon ID

eff’y, PDF’s

Decay Channel eeLum’y 324 (6.5%) 286 (6.5%) pb-1.


Total BKGD events

SM Z events

Eff’y*Acc.

BrL

NN)pp bkgdobsZ(

pb 6.06.4)Z( pp

FERMILAB-PUB-04-246-E => PRL R>0.7 ET()>7 GeV.

CDF

ZCross Section

70 Candidates w/ 3.5 BKGD. ~200 pb-1 M(l+l-)>40 GeV/c2.

pb .)(3.0

.).(4.02.4)Z(

lum

sysstatpp

D0 Preliminary

ET() >8 GeV M(l+l-)>30 GeV/c2 R>0.7

8.4 times as much Z signal as all of Run I in 3.1 times the Lum’y.

55

ZEvent Characteristics

DØ Data Z data shows FSR, Zg ISR, and DY ISR for the 1st time.

Require M(ll)>65 GeV/c2 & M(ll)>100 GeV/c2

117 Z events left MC indicates 80% are ISR

and predicts ~ 0.94 pb.

D0

Prelim.

D0

Prelim.

x

Z Bosons

Drell-Yan leptons

Final State

Radiation pb .)(07.0

.).(15.007.1

)Z(

lum

sysstat

pp

D0 Preliminary

ET() >8 GeV R>0.7

56

ZAnomalous Couplings

Using the full sample: Form a binned-likelihood

based on pT() in an h30 and h40 grid including bkgd.

The ZZ and Z

AC contours are similar.

DØ Prelim.

95% CL2D

Unitary

ZZ Coupling Limits

019.0||

22.0||

40

30

h

h

GeV 1000

DØ

Prelim.

019.0||

21.0||

40

30

Z

Z

h

h

These are the new standard.

What about LEP?

Limits on h20 & h10 will be nearly identical to h40 & h30, respectively (CP-odd).

57

What about ZZ and Z@ LEP?

LEP Studies e+e-Z/* Z LEP results (no form factor)

included (again some correction)

12.005.0

07.020.0

071.0078.0

13.013.0

40

30

20

10

Z

Z

Z

Z

h

h

h

h

034.0002.0

008.0049.0

025.0045.0

055.0056.0

40

30

20

10

h

h

h

h

There’s a difference between LEP and Tevatron AC definitions

LEP is measuring the real part of the couplings and Tevatron is measuring the imaginary part

It’s documented that there is no or very little interference between SM and Anomalous couplings. Limits on real and imaginary parts should be the same.

LEP Results


D0 has most restrictive limits in “h4” and “h2”

LEP has most restrictive limits in “h1” and “h3”

58

Summary: D0 EWK results with power of Run II Luminosity

First measurement of:

pb .)(15.)(18.)(15

237)ZppBr(

lumsysstat

Measurement of (WW) @ 1.96 TeV using dileptons pb .)(9.0

.)(.)(8.13)( 2.19.0

3.48.3

lum

sysstatWW

Evidence for WZ production, (WZ) @ 1.96 TeV, tightest model-independant WWZ AC Limits

C.L.) (95% pb 3.13

)(

XWZ

pb 5.4ZW( 5.36.2

)pp Studies of W production,

tightest model-independant WW AC Limits, Hints of Rad 0. 0.2222.0

97.093.0

Studies of Z production (10x Run 1 sample), Characteristics, AC Limits 019.0||

22.0||

40

30

h

h

019.0||

21.0||

40

30

Z

Z

h

h

DØ Prelim.

59

Barrier Slide 1

This slide and all that follow are not part of my talk. Acknowledgements Previous Drafts of slide that I made in case there was

additional detail Some detailed slides that I didn’t use at all. Some “backup” slides with more information.

60

Acknowledgements

Thanks, as always, to DZero collaboration. Serban Protopopescu, Cristina Galea, Abid Patwa, Silke Nelson Thomas Nunneman, Johannes Elmsheuser, Marc Hohfeld Qichun Xu, Bing Zhou, James Degenhardt Sean Mattingly, Andrew Askew Yurii Maravin, Drew Alton Marco Verzocchi, Stefan Soldner, Tim Bolton, Dmitri Denisov,

Ia Iashvili, Avto Karchilava CDF

61

We still have a large background from multijets. Jets tend to be wider than ’s have higher track multiplicity have higher mass than M() be less isolated from other hadronic energy than

tau’s from Z’s. A Feed-forward neural network

8 input nodes, a single hidden layer with 8 more nodes, and a single output (the answer). Not all inputs for all tau types.

Divide 29,021 events into SS and OS lepton-lepton candidates.

Tau Identification: Neural Network

Jet-Background

q

o

o

1 TRK +wide CAL cluster + EM sub-cluster

“One-Prong”

“One-Prong”+ EM

“Multi-Prong” “All Types”Train 3 types separately

62

Events predicted and events observed before and after P(NN)>0.8 criteria for all 3 types. There’s correction factors fi on

the SS backgrounds of 3 to 9% determined from a non-isol sample.

The other bkgds are from MC. Eff’y(NN)=0.75 &

R(NN)=1.6 (14 if swap cut order)

Signal/Bkgd ~ 0.82 Eff’y = 1.52% for M()

> 60 GeV/c2.

Before NN

Tau Identification: # Candidates

type contribution to signal: 13% 58% 29%

After NN

TOTAL

63

Z Neural Network Input Params.

64

WW Dileptons @ Tevatron in Run I

D0 Results (97 pb-1) 5 candidates w/ background

of events (mostly Z’s and W+jets).

Expected WW events

Consistent with S.M. Limits on Anomalous WW

and WWZ couplings in 1995 PRL and 1998 PRD.

CDF Results (108 pb-1) 5 candidates w/ similar but

smaller backgrounds of 1.2+-0.3 events.

Expected 5.21.8 WW events. Limits on AC “Evidence for WW

Production” in a 1997 PRL.

( ) . ...WW

10 2 165 16 5 pb

TeV 1

9.0 8.0

3.11.1

TeV 1

C.L. 95%

1.0||

2.1||

C.L.) (95% pb 37

)(

XWW

Leptons + jets channels provided more restrictive A.C. limits than dileptons.

1D AC limits

65

Anomalous Couplings - Previous Results

D0 and CDF put limits on anomalous WWg and WWZ Couplings in Run 1. WW and WWZ couplings from WW WW couplings from W analyses WWZ couplings from WZ

D0 Combined W, WW, WZ TeV 2

C.L. 95%

0.1918.0

39.025.0

Z

Z

Tightest from

the Tevatron

LEP Combined (1D 95% CL)

1)-(tang and 2Z1ZZ w

0.0340.051

0.026059.0

069.0105.0

1

Zg

“HISZ” SU(2)xU(1) coupling relations

Didn’t use a form-factor dependence in their couplings.

(complementary in several ways)


66

ee channel criteria Minimal Transverse Mass > 60

GeV/c2. .NOT. 76<M(ee)<106 GeV/c2. “Scaled MET” > 15 rootGeV

HT(jets w/ ET>20 &||<2.5) <50 GeV.

Background is 2.300.21 events and is 60% W+jets, 40% mixed heavy.

Eff’y is 8.760.13%. Expected signal is 3.420.05

events. 6 Candidates Observed.

WW ee Event Selection

jetsT

jetjet

TScT

EjetE

EE

2)),(cossin(

D0

D0All but scaled MET*

All but

MT(min)

*Events with jet(s).

Remove

Z/*

Remove

Top pairs

67

channel criteria 20<M()<80 GeV/c2. Constrained fit to MET and

lepton PT’s. A “Z-fitter”. HT (jets w/ ET>20 &||<2.5)

<100 GeV.

Background is 1.950.41 events and is > 80% Z/*

Eff’y is 6.220.15%. Expected signal is

2.100.05 events. 4 Candidates Observed.

WW Event Selection

D0

All cuts except HT

Remove

Z/*

Remove

Top pairs

68

Background (events expected)ll+fake isolated e = ZZ(lost lepton) =

Z(fake e) = ll+fake isolated = ttbar(fake isol. e /) =

Totalbkgd.expected.

andeeeCandidates



)()( TTT ElhadE

Remove Top with

B isol. lepton

For a W boson

Z/*+jet Background

WZ Monte Carlo


criteria is ~13%.

Select these


69

WZ Candidates Summary D0 Preliminary

WZeeeCandidate

Three Candidates.

is the

most efficient channel.

70

WZ Event 194337

71

WZ @ Tevatron in Run I

D0 Trileptons Results (92 pb-1) ee and eee channels 1 candidates w/ background of

0.50 events (mostly Z+jets). Expected WZ events

Model independent limits on Anomalous WWZ couplings in 1999 PRD.

D0 + CDF Results (leptons + jets) Cannot distinguish between

W+jets, WW, and WZ in those analyses.

Limits on anomalous WW and WWZ couplings in 1996 PRL (CDF) and 1996 + 1997 (D0) and several PRD’s 1999 (D0).

TeV 1

C.L. 95%

1.42||

63.1|| 1

Z

Zg

C.L.) (95% pb 47

)(

XWZ

TeV 2

C.L. 95%

0.1918.0

53.029.0

Z

Z

All D0 Wg, WW, WZ

Channels Combined

1D limits

D0

Not quite model-independant

72

WZ Events Properties D0 Preliminary

WZCandidates:

73

W Radiation Amplitude Zero II

M.C.D0 Muon Data

Preliminary

D0 Muon Data

Preliminary

D0 Elec. Data

Prelim.

74

LEP Individual Experiments WW and WWZ

Central Value and 1 sigma

75

Z in Run 1

05.0|)(|

37.0|)(|

2040

1030

hh

hh

CL 95%

GeV 750

D0 Results (97 + 87+ 13 pb-1) and

e+eandchannels ET()> 10 (40) GeV 37 + 4 candidates w/ background of

events from channel dependant sources.

candidates agrees w/ SM and Limits on anomalous couplings in 1995 & 1997 PRLs and 1998 PRD.

Combined 1D Run 1 limits:

CDF Results (20 pb-1) and e+echannels ET()> 7 GeV 8 candidates w/ background

of 0.5 events (Z+jets). agrees w/ SM (~5.2 pb) and

Limits on anomalous couplings in a 1995 PRL.

pb )0.3()1.9(5.1 syststat ET()> 7 GeV (CDF)

Tightest ZZ & Z limits at hadron collider.Z and ZZ Limits ~same. Still competitive w/ LEP.

D0

76

LEP Z Anomalous Couplings

Note: LEP Nomenclature

77

LEP ZZ Anomalous Coupling Limits

Note: LEP Nomenclature

78

Barrier Slide 2

This slide and all that follow are not part of my talk.

Documents

New Electroweak Results from DZero