New Electroweak Results from DZero

1
New Electroweak Results from DZero
Wine Cheese January 28, 2005

• Z -gt tt Observation and Cross Section times
  Branching Fraction
• Diboson Studies Wg, Zg, WW, WZ

For the DØ Collaboration
Tom Diehl Fermi National Accelerator Laboratory
2
Outline

• DØ Run II Data
• The DØ Detector
• Inner tracker, calorimeter, muon systems
• sBr(Z-gttt) at 1.96 TeV
• Motivation
• Event Selection
• Tau reco, classification, ID
• Cross Section measurement
• Dibosons WW, WZ, Wg, Zg
• Motivation
• WWg and WWZ Couplings Anomalous Couplings
• WW (Dileptons)
• Cross Section _at_ 1.96 TeV

• WZ (Trileptons)
• Limit on s(WZ)s(WZ), and AC limits.
• Wg in e and m channels
• Wg Cross Section, Photon ET Spectrum, and limits
  on AC.
• Progress on Rad. Zero
• Zg in ee and mm channels
• Zg Cross Section, Photon ET Spectrum, Event
  Characteristics, and limits on ZZg and Zgg 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.

• pp collisions at sqrt(s) 1960 GeV

650 pb-1
Analyzed to here
520 pb-1
Monthly Effy
5
The DZero Detector in Run II Inner Tracker

• Tracker

6
The DZero Detector in Run II Calorimeter
Fine Longitudinal and Transverse Segmentation

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

7
The DZero Detector in Run II MUONS
Simulation
ms in Central Scint. Counters
Run II Data Unbiased Triggers
t(ns)
Run II
Run Ia

• Fitted Z(mm) peak has 8.1 GeV/c2 mass resolution
  in Run II.

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.

• What do we know about this?
• NNLO calculation predicts
  s(Z) 242-9 pb.
• Br(Z-gttt) is well measured.

from Hamberg, van Neervan, and Matsura, Nucl.
Phys. B359, 343 (1991), using CTEQ6L
9

• The analysis is complicated.

Start
Divide Events into OS and SS (For BKGD
Estimate) Lepton Pairs
Preselection single muon events
Reconstruct taus
Final Event Selection
Classify tau candidates
Extract Cross Section
10
Event Selection
Tau Decay Signature
For reference

• L226 pb-1 DL/L 6.5

• One t must decay to mnn.
• Event Selection starts with an isolated muon
• One m w/ pT(m)gt12 GeV/c
• This muon carries the sign of its tau lepton
• The other t can go to any of 3 decay modes

11
Reconstruct Tau Candidates

• Start with the Calorimeter
• CAL. ET (R0.5) gt 5 GeV ET (R0.3) gt 3 GeV
• Taus have narrow jets
• Then use the Tracker
• N(tracks w/ pTgt1.5 GeV/c in the narrow cone) gt 0
• Start with the highest pT track
• If theres a second track such that
  Mass(2-tracks)lt1.1 GeV/c2, add that track to the
  tau list
• If a third track such that Mass(3-tracks)lt 1.7
  GeV/c2, add it unless total charge 3 or -3.
• If total charge 0, discard the tau candidate.
• Require f(m)-f(t) gt 2.5 (These are low pT Zs)
• Reconstruct EM subclusters with ET gt 800 MeV

12
Tau Identification Classification

• 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

And there are selection criteria discriminating
them from each other And rejecting background.
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Tau Identification Classification

• 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

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Tau Identification Classification

• 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
• No attempt to separate hadron channels from
  electron channels.
• At this point we have the charge sign of m and t.

15
Tau Identification Neural Network

• 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 ts
• have higher track multiplicity
• have higher mass than M(t)
• be less isolated from other hadronic energy than
  are taus from Zs.
• 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.

One-Prong EM
One-Prong
Multi-Prong
All Types
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Tau Identification Candidates
TOTAL Number of Events

• Events predicted and events observed before and
  after P(NN)gt0.8 criteria for all 3 types.
• QCD background is scaled from same-sign data
• The other bkgds and expected Z(tt) from MC.
• Effy(NN)0.78 Signal/Bkgd 0.82
• Z(tt) Observed 865-55 after M(tt)gt60 GeV/c2
• P Effy 1.52 for M(tt) gt 60 GeV/c2.

Before NN
QCD 13881-264 Z/g -gt mm
100-24 W-gtmn 434-153 Z/g-gttt
1174-43 SUM 15589-309 OS Events
15911 QCD 984-46 Z/g -gt mm
70-16 W-gtmn 58-20 Z/g-gttt
914-24 SUM 2026-57 OS Events
2008
After NN

• type contribution to signal
• 13 Type1, 58 Type 2, 29 Type 3

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Systematic Uncertainties
UNCERTAINTY IN

• Energy scale 2.5
• NN MC inputs 2.6
• Backgrounds 4.6
• PDFs 1.7
• Effy Accept. 2.6
• Trigger Effy 3.5
• Total 7.5

• Figures show ET(t) and pT(m) for Z-gttt MC vs.
  background subtracted data

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• Cross Section Calculation

• For m(tt)gt60 GeV/c2

• After removing the g contribution

Theory Matsura van Neervan
Submitted to PRL. hep-ex/0412020 FERMILAB-PUB-04/3
81-E
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What else can we say about Taus?

• Z-gttt mass peak
• We can find states that decay to taus.
• 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 DØs Run II preliminary muon and electron
  results

Upper Left Mass(m,t) for Bkgd vs. Signal MC for
type 1 and type 2 tau tracks Upper Right
Mass(m,t) for (OS events - Bkgd) vs Signal MC
1.96 TeV
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Dibosons (Outline)

• Dibosons WW, WZ, Wg, Zg
• Motivation
• WWg and WWZ Couplings Anomalous Couplings
• WW Dileptons
• Cross Section _at_ 1.96 TeV
• WZ Trileptons in Run II
• Limit on s(WZ), s(WZ), and AC limits.
• Wg in e and m channels
• Wg Cross Section, Photon ET Spectrum, and limits
  on AC.
• Progress on Rad. Zero
• Zg in ee and mm channels
• Zg Cross Section, Photon ET Spectrum, Event
  Characteristics, and limits on ZZg and Zgg
  Anomalous Couplings.

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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

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 doesnt decay to fermions.
• Or whatever.

hep-ph/9704448
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WWg and WWZ Couplings

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

• Cancellation of t- and u-channel by s-channel
  amplitude removes tree-level unitarity violation
  (in Wg, WW, and WZ, too). Textbook example
• t-channel At high energy limit and with massless
  quarks (simpler calculation). s violates
  unitarity.

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

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WWg and WWZ Anomalous Couplings

• Characterized by effective Lagrangian
• 5 CP Conserving SM Parameters
  lZ 0 lg 0
  
• DkZ 0 Dkg 0 (Dk k-1)
• Dg1Z 0 (Dg1Z g1Z -1)
  
• In Wg production, only the WWg 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
mW e(1kl) / 2MW
QeW - e (k-l) / M2W
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Effect of Non-SM WWg and WWZ Couplings

• Cross section increases especially for High ET
  bosons (W/Z/g).
• Unitarity Violation avoided by introducing a
  form-factor scale L, modifying the A.C. at high
  energy. e.g.

Events/20 GeV/c
PT(W)
(s(0.5)1800 GeV)
25
Anomalous Couplings LEP and Tevatron

• DØ and CDF put limits on anomalous WWg and WWZ
  Couplings in Run 1.
• WWg and WWZ couplings from WW
• WWg couplings from Wg analyses
• WWZ couplings from WZ
• DØ Combined Wg, WW, WZ (1999)

Tightest from the Tevatron

• LEP Combined (1D 95 CL)

HISZ SU(2)xU(1) coupling relations
LEP EWK Working Group hep-ex/0412015
(complementary in several ways)
Didnt use a form-factor dependence in their
couplings.
26
WW Production and Decay

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

Campbell Ellis

• s(WW) 13.5 pb-1 at Run II Tevatron energy.

Ohnemus (1991), (1994) and Campbell Ellis
(1999).
27
WW to Dileptons in Run I

• WW to dileptons _at_ DØ and CDF
• Cross section limit and anomalous coupling limits
  _at_ DØ (PRL and several PRDs)
• Evidence for WW Production and anomalous coupling
  limits _at_ CDF in 1997 PRL.
• Leptons jets channels provided more restrictive
  A.C. limits than dileptons at DØ and CDF but we
  couldnt isolate a signal from the much bigger
  Wjets background.

1D AC limits
28
Run 2 WW -gt Dileptons Event Selection

• Preselection Criteria
• Two oppositely-charged e or m w/ pTgt15 GeV/c. At
  least one has pTgt20 GeV/c.

• MET gt 30, 40, 20 GeV/c2 in ee, mm, em
  channels to remove Z/g.

Missing Transverse Energy After Preselection
Criteria Shows agreement between data and signal
plus backgrounds.
mm channel
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WW -gtemnn Event Selection

• em channel criteria
• No third lepton so that 61lt M(ll-) lt 121 GeV/c2.
• Minimal Transverse Mass gt 20 GeV/c2.
• Scaled MET gt 15 rootGeV
• HT(jets w/ ETgt20 hlt2.5) lt50 GeV.
• 3 silicon hits on electron if MT(mn)MT(W).
• Background is 3.81-0.17 events and is 71 Wj or
  g.
• Effy is 15.4-0.2.
• Expected signal is 11.1-0.1 events.
• 15 Candidates Observed.

REMOVES
WZ ZZ
multijets Z/g
All Cuts except MT(min)
Z/g -gt tt
D0
Top pairs
Wg
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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 isnt as high in
  these channels as in electronmuon.

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WW Cross Section Systematic Uncys

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

Bottom Line Systematic Uncy 8.7 -6.5
32
WW-gt Dileptons Cross Section

• For each channel
• We combine channels to extract s as minimum in

D0
33
WW-gt Dileptons Cross Section

• Submitted to PRL hep-ex/0410066

CDF Run II hep-ex/0501050 Also submitted to PRL
34
WZ Production and Decay
Campbell Ellis

• s(WZ) 4.0 pb at Run II Tevatron energy.

35
WZ _at_ Tevatron in Run I

• DØ Trileptons Results (92 pb-1)
• mnee and enee channels
• 1 candidate w/ background of 0.50-0.17 events
  (mostly Zjets).
• Expected 0.25-0.02 WZ events
• Model independent limits on Anomalous WWZ
  couplings in 1999 PRD.

• DØ CDF Results (leptons jets)
• Cannot distinguish between Wjets, WW, and WZ in
  those analyses.
• Limits on anomalous WWg 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 PRDs -gt 1999 (DØ)

1D limits
36
Run 2 WZ -gt Trileptons Event Selection

• At least 2 isolated es and/or ms with ETgt15
  GeV that make a Z boson
• 71ltM(ee)lt111 GeV/c2 or 50ltM(mm-)lt130 GeV/c2.
• A third isolated e or m with Etgt15 GeV
• DR(leptons)gt0.2

mm
Identify a Z boson
Only 65 events with 3
ee
Rejects Brems, W/Zg, Z-gttaus
WZ efficiency after these criteria is 15.
37
WZ -gt Trileptons Event Selection BKGD.
Z/gjet Background M.C. WZ (Z-gtmm) 3e Event

• METgt20 GeV
• ET(had) lt 50 GeV

For a W boson
Remove Top with B-gt isol. lepton
DiElectron Channel
MET

• Background (Mostly ZX)
• Total 0.71-0.08 bkgd. expected.
• 2 mmmn and 1 eeen Candidates

WZ efficiency after these criteria is 13.
M(ll)
s(ZZ)1.43 pb (EllisCampbell,Ohnemus)
38
WZ -gt Trileptons Event Selection BKGD.
Z/gjet Background M.C. WZ (Z-gtmm) 3m Events

• METgt20 GeV
• ET(had) lt 50 GeV

For a W boson
Remove Top with B-gt isol. lepton
Dimuon Channel
MET

• Background (Mostly ZX)
• Total 0.71-0.08 bkgd. expected.
• 2 mmmn and 1 eeen Candidates

WZ efficiency after these criteria is 13.
M(ll)
s(ZZ)1.43 pb (EllisCampbell,Ohnemus)
39
WZ Cross Section
Combined Ln(Likelihood)

• Cross section limit

D0 Prelim.

• Evidence for WZ Production
• P(0.71 bkgd) -gt 3 Candidates is 3.5
• Interpreting the Events as Signal Background

D0 Preliminary
CDF Run II hep-ex/0501021 submitted to PRD
40
WWZ Anomalous Trilinear Couplings

• Generate a grid of WZ MC using Hagiwara,
  Woodside, Zeppenfeld LO generator gt 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 _at_ 95 C.L.

-Ln(Likelihood)
L1 TeV Dg1z vs. lz
41
WWZ Anomalous Trilinear Couplings
1D Limits (holding the other to 0)
DØ Preliminary
95 C.L.

• Inner contours our 2D limits. Outer contours are
  from s-matrix unitarity.
• Best limits in WZ final states.
• First 2D limits in Dkz vs. lz using WZ.
• Best limits available on Dg1Z, Dkz, and lz from
  direct, model-independent measurements.
• The DØ Run II 1D limits are factor of 3 better
  than our Run I limits.

L1.5 TeV
L1 TeV
42
Wg Production
Initial State Radiation
Final State Radiation
WWg Vertex

• Sensitive only to WWg couplings
• Identify W boson decay to en or mn.
• We dont 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 _at_ low-ET.

Monte Carlo Prediction Baur Berger (1990)
43
Wg _at_ Tevatron in Run I

• D0 (1995 and 1997 PRLs) CDF (1995 PRL)
• s agrees w/ SM and Limits on Anomalous WWg
  couplings using the photon ET spectrum.

DR(lg)gt0.7 ET(g)gt 7 GeV (CDF)
DR(lg)gt0.7 ET(g)gt 10 GeV (DØ)
Anomalous Coupling Limits
DØ
Tightest WWg limits at hadron collider, (UP TO
NOW)!
1D limits
44
Run 2 Wg Event Selection en and mn
ID a W boson

• An isolated electron w/
  ETgt25 GeV in hlt1.1
• METgt25 GeV
• MT(en)gt40 GeV/c2.
• .NOT. 70ltM(eg)lt110 GeV/c2.

• One m, isolated, w/ pT gt 20 GeV/c.
• MET gt 20 GeV
• No MT cut at this stage

Eliminate Z bosons
Lumy eg (mg)162 (134) pb-1
ID a Photon (Both Channels)
ET(photon)gt8 GeV DR(l,g)gt0.7 hglt1.1

• An isolated EM object
• No track match (spatial)
• (Calorimeter j -width)2 lt 14 cm2
• If photon has tracks in a hollow cone of size
  0.05ltDRlt0.4 require

For g within fiducial coverage, Efficiency(ID)
0.81-0.03
45
Run 2 Wg Expected Backgrounds

• 
  Wg-gteng Wg-gtmng
• Wjet (jet mimics g) 58.7- 4.5
  61.8-5.1 events
• leX (Zs) 1.7-0.5
  0.7-0.2
• Wg-gttng 0.42-0.02
  1.9-0.2
• Zg (lost lepton) 0
  6.9-0.7

Total BKGD 60.8- 4.5
71.3-5.2 events Observed
112 161 candidates
Probability(jet mimics g) 5x10-3 and
decreases with ET(jet).
Observed Background 141 Wg 1.7x as many Wg
as in Run 1 1.6x as much luminosity as in Run 1
(analyzed so far)
46
Wg Cross Section Event Characteristics
Decay Channel eng mng Lumy
162 (6.5) 134 (6.5)
pb-1. Observed 112
161 candidates Total BKGD 60.8- 4.5
71.3-5.2 events EffyAcc.
0.023-0.001 0.044-0.002
Three-body Transverse Mass
en channel
D0 Prelim.
D0
Prelim.
mn channel
ET(g) gt8 GeV DRgt0.7
D0 Prelim.
323 Candidates w/ 114 BKGD. 200 pb-1. DRgt0.7
CDF
FERMILAB-PUB-04-246-E gt PRL ET(g) gt7 GeV
Scales adjusted to same.
47
Wg Anomalous Couplings
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(g) in a lg
  vs. DKg grid including bkgd on events w/ MT(3)gt90
  GeV/c2.

ET(g) D0 Prelim.
D0 Prelim. _at_ 1.96 TeV
1D limits _at_ 95 C.L.
2D limits
1D limits
Still the tightest at any Hadron Collider!
48
Wg Radiation Amplitude Zero

• For COS(q), the angle between incoming quark and
  photon in the Wg rest frame, -1/3, SM has
  amplitude zero.
• For events w/ MT(cluster)gt90 GeV/c2. One could
  guess the Wg rest frame. We use charge-signed
  Dh(l,g)

D0 Preliminary Muon Channel
M.C.

• We plot the background-subtracted muon data vs.
  MC Dh(l,g) gt hints of the Rad. Zero.
• It will help to extend the eta-coverage of
  electrons and especially of photons.

49
Zg Production
Initial State Radiation
Final State Radiation
No SM ZZg or Zgg interaction.
Monte Carlo Prediction Baur Berger (1993)

• Initial and final state radiation.
• Identifying Z boson decay to ee- or mm- is
  easiest.
• Zg-gtnng was done in Run 1A. It might be possible
  to do it in Z-gtbbar. We dont bother with
  hadronic Z channel.

50
ZZg/Zgg Anomalous Couplings

• Non-SM Characterized by an effective Lagrangian
  w/ 8 form-factor coupling parameters called h1V,
  h2V, h3V, and h4V whereV stands for g and Z.
• CP Violating h1V and h2V
• CP Conserving h3V and h4V
• In SM all these couplings 0.
• Transition Moments

51
Zg in Run 1

• DØ Results (97 87 13 pb-1)
• mm-g and ee-g and nng channels
• 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)
• mm-g and ee-g channels
• s agrees w/ SM (5.2 pb) and Limits on anomalous
  couplings in a 1995 PRL.

ET(g)gt 7 GeV (CDF)
DØ
Zgg and ZZg limits same
Up to now the tightest ZZg Zgg limits at hadron
collider. These are still competitive w/ LEP.
52
Run 2 Zg Event Selection

• Two isolated electrons w/ ETgt15 GeV. One or
  more w/ ETgt25 GeV.
• All CC electrons must have a track match.
• M(ee)gt30 GeV/c2.

• Two or more isolated m, w/ pT gt 15 GeV/c.
• M(mm)gt30 GeV/c2.

ID a Z boson
Lumy eeg (mmg) 324 (286) pb-1 All data through
June 2004.
138 Zg-gteeg 152 Zg-gtmmg Candidates
Photon ID
Backgrounds

• Same as the Wg event selection.

• Zjet (jet mimics g)
• Zg-gteeg Zg-gtmmg
• 23.6- 2.3 22.4-3.0 events

ET(photon)gt8 GeV DR(l,g)gt0.7 hglt1.1
53
Zg Photon Spectrum Event Display
138 Zg-gteeg 152 Zg-gtmmg Candidates
Zg -gt mmg Candidate
D0 Prelim.
m
m
g

• Highest ET(g) photon in electron channel is 105
  GeV.
• Highest ET (g) in muon channel is 166 GeV.

The ms are left out of this MET.
54
Zg Cross Section
Decay Channel eeg mmg Lumy
324 (6.5) 286 (6.5)
pb-1. Observed 138
152 candidates Total BKGD 23.6- 2.3
22.4-3.0 events SM Zg
109-7 128-8 events EffyAcc.
11.3-0.8 11.7-0.6

• 8.4 times as much Zg signal as all of Run I in
  3.1 times the Lumy.

• Cross section agrees w/ SM
• Main uncy is stat.
• Two largest sys. uncys are photon ID effy, PDFs

70 Candidates w/ 3.5 BKGD. 200 pb-1 M(ll-)gt40
GeV/c2.
CDF
FERMILAB-PUB-04-246-E gt PRL DRgt0.7 ET(g) gt7
GeV.
55
Zg Event Characteristics

• DØ Data Zg data shows FSR, Zg ISR, and DY ISR for
  the 1st time.
• Require M(ll)gt65 GeV/c2 M(llg)gt100 GeV/c2
• 117 Zg events left
• MC indicates 80 are ISR and predicts s 0.94 pb.

Z Bosons
Drell-Yan leptons
D0 Preliminary
ET(g) gt8 GeV
DRgt0.7
Final State Radiation
56
Zg Anomalous Couplings

• Using the full sample
• Form a binned-likelihood based on pT(g) in an h30
  and h40 grid including bkgd.

DØ Prelim.

• These are the new standard.
• What about LEP?

The ZZg and Zgg AC contours are similar.
Limits on h20 h10 will be nearly identical to
h40 h30, respectively (CP-odd).
57
What about ZZg and Zgg _at_ LEP?

• LEP Studies ee-?Z/g ?Zg
• LEP results (no form factor) included (again some
  correction)

• Theres a difference between LEP and Tevatron AC
  definitions
• LEP is measuring the real part of the couplings
  and Tevatron is measuring the imaginary part
• Its 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

LEP EWK Working Group hep-ex/0412015
58
Summary D0 EWK results with power of Run II
Luminosity

• First measurement of

• Measurement of s(WW) _at_ 1.96 TeV using dileptons

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

• Studies of Wg production, tightest
  model-independant WWg AC Limits, Hints of Rad 0.

DØ Prelim.

• Studies of Zg production (10x Run 1 sample),
  Characteristics, AC Limits

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 didnt 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
Tau Identification Neural Network

• We still have a large background from multijets.
  Jets tend to
• be wider than ts
• have higher track multiplicity
• have higher mass than M(t)
• be less isolated from other hadronic energy than
  taus from Zs.
• 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.

One-Prong EM
One-Prong
Multi-Prong
All Types
Train 3 types separately
62
Tau Identification Candidates

• Events predicted and events observed before and
  after P(NN)gt0.8 criteria for all 3 types.
• Theres correction factors fi on the SS
  backgrounds of 3 to 9 determined from a non-isol
  m sample.
• The other bkgds are from MC.
• Effy(NN)0.75 R(NN)1.6 (14 if swap cut
  order)
• Signal/Bkgd 0.82
• P Effy 1.52 for M(tt) gt 60 GeV/c2.

Before NN
TOTAL
After NN
t type contribution to signal 13
58 29
63
Z-gt tt Neural Network Input Params.
64
WW -gt Dileptons _at_ Tevatron in Run I

• D0 Results (97 pb-1)
• 5 candidates w/ background of 3.1-0.4 events
  (mostly Zs and Wjets).
• Expected 1.9-0.1 WW events
• s Consistent with S.M.
• Limits on Anomalous WWg 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 5.2-1.8 WW events.
• Limits on AC
• Evidence for WW Production in a 1997 PRL.

1D AC limits
Leptons jets channels provided more restrictive
A.C. limits than dileptons.
65
Anomalous Couplings - Previous Results

• D0 and CDF put limits on anomalous WWg and WWZ
  Couplings in Run 1.
• WWg and WWZ couplings from WW
• WWg couplings from Wg analyses
• WWZ couplings from WZ
• D0 Combined Wg, WW, WZ

Tightest from the Tevatron

• LEP Combined (1D 95 CL)

LEP EWK Working Group hep-ex/0412015
HISZ SU(2)xU(1) coupling relations
Didnt use a form-factor dependence in their
couplings.
(complementary in several ways)
66
WW -gteenn Event Selection

• ee channel criteria
• Minimal Transverse Mass gt 60 GeV/c2.
• .NOT. 76ltM(ee)lt106 GeV/c2.
• Scaled MET gt 15 rootGeV
• HT(jets w/ ETgt20 hlt2.5) lt50 GeV.
• Background is 2.30-0.21 events and is 60
  Wjets, 40 mixed heavy.
• Effy is 8.76-0.13.
• Expected signal is 3.42-0.05 events.
• 6 Candidates Observed.

D0
All but MT(min)
Remove Z/g
Remove Top pairs
D0
All but scaled MET
Events with jet(s).
67
WW -gtmmnn Event Selection

• mm channel criteria
• 20ltM(mm)lt80 GeV/c2.
• Constrained fit to MET and lepton PTs. A
  Z-fitter.
• Df(mm)lt2.4
• HT (jets w/ ETgt20 hlt2.5) lt100 GeV.
• Background is 1.95-0.41 events and is gt 80 Z/g
• Effy is 6.22-0.15.
• Expected signal is 2.10-0.05 events.
• 4 Candidates Observed.

All cuts except HT
D0
Remove Z/g
Remove Top pairs
68
WZ -gt Trileptons Event Selection BKGD.

• METgt20 GeV
• ET(had) lt 50 GeV

For a W boson
WZ efficiency after these criteria is 13.
Remove Top with B-gt isol. lepton
Select these

• Background (events expected)
• llfake isolated e 0.288-0.005
• ZZ(lost lepton) 0.199-0.075
• Zg(g-gtfake e) 0.147-0.020
• llfake isolated m 0.068-0.023
• ttbar(fake isol. e /m) 0.007-0.004
• Total 0.71-0.08 bkgd. expected.
• 2 mmmn and 1 eeen Candidates

Z/gjet Background WZ Monte Carlo
s(ZZ)1.43 pb (EllisCampbell,Ohnemus)
69
WZ Candidates Summary

• D0 Preliminary

WZ-gteeen Candidate

• Three Candidates.
• mmmn is the
• most efficient channel.

70
WZ _at_ Tevatron in Run I

• D0 Trileptons Results (92 pb-1)
• mnee and enee channels
• 1 candidates w/ background of 0.50-0.17 events
  (mostly Zjets).
• Expected 0.25-0.02 WZ events
• Model independent limits on Anomalous WWZ
  couplings in 1999 PRD.

• D0 CDF Results (leptons jets)
• Cannot distinguish between Wjets, WW, and WZ in
  those analyses.
• Limits on anomalous WWg and WWZ couplings in 1996
  PRL (CDF) and 1996 1997 (D0) and several PRDs
  -gt 1999 (D0).

1D limits
All D0 Wg, WW, WZ Channels Combined
D0
Not quite model-independant
71
WZ Events Properties

• D0 Preliminary

WZ-gtmmmn Candidates
72
Wg Radiation Amplitude Zero II
D0 Muon Data Preliminary
M.C.
D0 Elec. Data Prelim.
D0 Muon Data Preliminary
73
LEP Individual Experiments WWg and WWZ

• Central Value and - 1 sigma

74
Zg in Run 1

• D0 Results (97 87 13 pb-1)
• mm-g and ee-g (and nng) channels
• ET(g)gt 10 (40) GeV
• 37 4 candidates w/ background of 6-1 (6-1)
  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)
• mm-g and ee-g channels
• ET(g)gt 7 GeV
• 8 candidates w/ background of 0.5-0.2 events
  (Zjets).
• s agrees w/ SM (5.2 pb) and Limits on anomalous
  couplings in a 1995 PRL.

ET(g)gt 7 GeV (CDF)
D0
Tightest ZZg Zgg limits at hadron collider. Zgg
and ZZg Limits same. Still competitive w/ LEP.
75
LEP Zgg Anomalous Couplings
Note LEP Nomenclature
76
LEP ZZg Anomalous Coupling Limits
Note LEP Nomenclature
77
Barrier Slide 2

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