# Presentation: 125608

## New Electroweak Results from DZero

****** ****Observation and Cross Section times Branching Fraction**
**Diboson Studies:        W********, Z********, WW, WZ**

**Tom Diehl**
**Fermi National Accelerator Laboratory**

**“****Wine + Cheese” January 28, 2005**

- For the DØ Collaboration

## Outline

**D**Ø** Run II Data**
**The D**Ø** 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 E****T**** Spectrum, and limits on AC.**
**Progress on Rad. Zero**
**Z******** in ee and ******** channels**
**Z******** Cross Section, Photon E****T**** Spectrum, Event Characteristics, and limits on ZZ******** and Z******** AC.**
**Summary**

## The DZero Collaboration

**19 Countries**
**86 institutions**
**~620 physicists**

## DZero Run II Data

**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

## The DZero Detector in Run II: Inner Tracker

**Tracker**

## 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

## The DZero Detector in Run II: MUONS

**The DZero Detector in Run II: MUONS**

- Run II

- Run Ia

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

- ’s in
- Central Scint.
- Counters

- t(ns)

- Simulation

- Run II Data
- Unbiased
- Triggers

## 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.

**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                      ********(Z) =**** ****242+-9 pb.**
**Br(Z********) is well measured.**

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

## The analysis is complicated.

- 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

##                      Event Selection

**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%**

**Tau Decay Signature**

**For reference:**

## 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

- 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**

## 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

- “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

**Tau Identification: Classification**

- And there are selection criteria
- discriminating them from each other
- And rejecting background.

## 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

- “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

**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  and 

- “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 ******** and ******

**Tau Identification: Classification**

## 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 ’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**

- “One-Prong”

- “One-Prong”+ EM

- “Multi-Prong”

- “All Types”

## Tau Identification: # Candidates

- 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 = 86555 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            13881264
-         10024
- W            434153
- Z/*       117443
- SUM           15589309
- OS Events        15911
- QCD                98446
-         7016
- W            5820
- Z/*       91424
- SUM           202657
- OS Events        2008

## Systematic Uncertainties

**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

## Cross Section Calculation

- Submitted to PRL.
- hep-ex/0412020
- FERMILAB-PUB-04/381-E

- Theory: Matsura + van Neervan

**For m(********)>60 GeV/c****2**** **

**After removing the ********* contribution**

## 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

- 1.96 TeV

## 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.

## Dibosons: Introduction

**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.

## 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.

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

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

## WW and WWZ Anomalous Couplings

- QeW = e () / M2W

- W = e/ 2MW

**Characterized by effective Lagrangian**
**5 CP Conserving  SM  Parameters:                                           **********************
**********************        ****(******
**     ********g****************g****************g**************
****
**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**

## 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.:

- PT(W)

- (s^(0.5)=1800 GeV)

- # Events/20 GeV/c

## Anomalous Couplings – LEP and Tevatron

**D****Ø**** 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 *******
**D****Ø**** Combined W********, WW, WZ (1999)**

- Tightest from
- the Tevatron

**LEP Combined (1D 95% CL)**

- “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

## WW Production and Decay

**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).**

## 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.

- 1D AC limits

## 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 eee channels to remove Z/*.

- Missing Transverse Energy After Preselection Criteria
- Shows agreement between data and signal plus backgrounds.

-  channel

## 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 3.810.17 events and is 71% W+j or 
Eff’y is 15.40.2%. 
Expected signal is 11.10.1 events.
15 Candidates Observed.

**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 3.810.17 events and is 71% W+j or 
- Eff’y is 15.40.2%.
- Expected signal is 11.10.1 events.
- 15 Candidates Observed.

**WW ********e******** Event Selection**

**D0**

- All Cuts except MT(min)

- WZ & ZZ

- multijets & Z/*

- _REMOVES_

- Top pairs

- W

- Z/*  

## 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.

## 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: 

## WW Dileptons Cross Section

**WW******** Dileptons Cross Section**

**For each channel**
**We combine channels to extract ******** as minimum in   **

**D0**

## WW Dileptons Cross Section

- CDF Run II: hep-ex/0501050
- Also submitted to PRL

**Submitted to PRL **hep-ex/0410066

## WZ Production and Decay

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

- Campbell & Ellis

## DØ Trileptons Results (92 pb-1)
ee and eee 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.

- ee and eee 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.

- 1D limits

**WZ  @ Tevatron in Run I**

**D****Ø**** + 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)

## Run 2: WZ  Trileptons Event Selection

**At least 2 isolated e’s and/or  ********’s with E****T****>15 GeV that make a Z boson**
**71<M(ee)<111 GeV/c****2 ****  or  50<M(********************)<130 GeV/c****2****.**
**A third isolated e or ******** with Et>15 GeV**
******R(leptons)>0.2**

- Identify a
- Z boson

- Rejects Brems,
- W/Z+, Ztaus

- Only 65
- events with 3

**WZ efficiency after these **
**criteria is ~15%.**

- ee

- 

## WZ  Trileptons Event Selection + BKGD.

**Background (Mostly Z+X)**
- Totalbkgd.expected.
- andeeeCandidates

**WZ ******** Trileptons Event Selection + BKGD.**

**MET>20 GeV**
**ET(had) < 50 GeV**

- Remove Top with
- B isol. lepton

- For a W boson

**WZ efficiency after these **
**criteria is ~13%.**

- DiElectron Channel

- *1.43 pb (Ellis+Campbell,Ohnemus)

**Z/*********+jet Background**
**M.C. WZ (Z********)**
*** 3e Event**

- M(*ll*)

- MET

## WZ  Trileptons Event Selection + BKGD.

**Background (Mostly Z+X)**
- Totalbkgd.expected.
- andeeeCandidates

**WZ ******** Trileptons Event Selection + BKGD.**

**MET>20 GeV**
**ET(had) < 50 GeV**

- Remove Top with
- B isol. lepton

- For a W boson

**WZ efficiency after these **
**criteria is ~13%.**

- Dimuon Channel

- *1.43 pb (Ellis+Campbell,Ohnemus)

**Z/*********+jet Background**
**M.C. WZ (Z********)**
*** 3******** Events**

- M(*ll*)

- MET

## WZ Cross Section

**WZ Cross Section**

**Cross section limit**

- “Evidence” for WZ Production
- P(0.71 bkgd)  Candidates is 3.5%
- Interpreting the Events as Signal + Background:

- Combined Ln(Likelihood)

- CDF Run II: hep-ex/0501021
- submitted to PRD

- D0 Preliminary

- D0 Prelim.

## 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)

## 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 g1Z, z, and z from direct, model-independent measurements. 
The DØ Run II 1D limits are ~ factor of 3 better than our Run I limits.

- Best limits in WZ final states.
- First 2D limits in z vs. z using WZ.
- Best limits available on g1Z, 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

## 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.

- 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 Radiation

- WW Vertex

- Monte Carlo Prediction
- Baur & Berger (1990)

## W @ Tevatron in Run I

**D0 (1995 and 1997 PRL’s) + ****CDF**** ****(1995 PRL)**
-  agrees w/ SM and Limits on Anomalous WWcouplings using the photon ET spectrum.

- 1D limits

**D****Ø**

- 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

## Run 2: W Event Selection: e and 

**An isolated ****electron****                          w/ E****T****>25 GeV in |********|<1.1**
**MET>25 GeV**
**M****T****(e********)>40 GeV/c****2****.**
**.NOT. 70<M(e********)<110 GeV/c****2****.**

- ID a W boson

**One ************isolated, w/ pT > 20 GeV/c.**
**MET > 20 GeV**
**No M****T**** 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)**_

- For  within fiducial coverage,
- Efficiency(ID) = 

**E****T(photon)****>8 GeV**
******R(*****l*********)>0.7**
- ||<1.1

- Lum’y: e:162 (134) pb-1

- Eliminate
- Z bosons

## Run 2 W Expected Backgrounds

**                                             ****W********e********W******
**W+jet (jet mimics ********)*      ** events
**“*****l*****eX” (Z’s)                         **
**W********                            **
**Z******

**Total BKGD                    ** events
**# Observed                     **112                     161 candidates

- # Observed – Background = 141 W
- 1.7*x* as many W as in Run 1
- 1.6*x* as much luminosity as in Run 1 (analyzed so far)

- * Probability(jet mimics 5x10-3 anddecreases withjet

## WCross Section & Event Characteristics

- Lum’y                 162 (6.5%)         134 (6.5%) pb-1.
- # Observed          112                     161     candidates
- Total BKGD          events
- Eff’y*Acc.        

**W********Cross Section & Event Characteristics**

- Three-body Transverse Mass

- e channel

-  channel

- Scales adjusted to same.

- D0 Prelim.

- D0 Prelim.

- FERMILAB-PUB-04-246-E => PRL    ET()>7 GeV

- CDF

- Prelim.

- ET() >8 GeV R>0.7

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

- D0

## 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

- 1D limits @ 95% C.L.

- 2D limits

- 1D limits

- Still the tightest at any Hadron Collider!

## 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

## ZProduction

- 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 Zbbar. We don’t bother with hadronic Z channel.

- No SM ZZ or
- Z interaction.

- Monte Carlo Prediction
- Baur & Berger (1993)

## ZZ/Z Anomalous Couplings

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

## Z in Run 1

**D****Ø**** Results (97 + 87+ 13 pb****-1****)**
- and e+eand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****)**
-  and e+echannels
-  agrees w/ SM (~5.2 pb) and Limits on anomalous couplings in a 1995 PRL.

- ET()> 7 GeV (CDF)

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

**D****Ø**

- Z and ZZ limits ~same

## Run 2: Z Event Selection

**Two + isolated ****electrons**** w/ E****T****>15 GeV. One or more w/ E****T****>25 GeV.**
**All CC electrons must have a track match.**
**M(ee)>30 GeV/c****2****.**

- ID a
- Z boson

**Two or more isolated ********, w/ pT > 15 GeV/c.**
**M(********)>30 GeV/c****2****.**

- Same as the Wevent selection.

_**Photon ID**_

**E****T(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 ********)**
**      ****Z********ee********Z******
-  events

- 138 Zee   152  Candidates

## ZPhoton 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 Zee   152  Candidates

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

- Main unc’y is stat.
- Two largest sys. uncy’s are photon ID eff’y, PDF’s

- Decay Channel   ee
- Lum’y                 324 (6.5%)         286 (6.5%) pb-1.
- # Observed          138                     152     candidates
- Total BKGD          events
- SM Z                   events
- Eff’y*Acc.        

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

- CDF

**Z********Cross Section**

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

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

## ZEvent 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.

- Z Bosons

- Drell-Yan leptons

- Final State
- Radiation

- D0 Preliminary

- ET() >8 GeV

- R>0.7

## ZAnomalous 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.

**D****Ø**
**Prelim.**

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

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

## What about ZZ and Z@ LEP?

**LEP Studies e****+****e****-****Z/********* ****Z******
- LEP results (no form factor) included (again some correction)

- 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

- LEP EWK Working Group hep-ex/0412015

- D0 has most restrictive limits in “h4” and  “h2”
- LEP has most restrictive limits in “h1” and “h3”

## Summary: D0 EWK results with power of Run II Luminosity

**First measurement of: **

**Measurement of ********(WW) @ 1.96 TeV using dileptons**

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

**Studies of W******** production, tightest model-independant WW******** AC Limits, Hints of Rad 0.**

**Studies of Z******** production (10x Run 1 sample), Characteristics, AC Limits**

- DØ Prelim.

## 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.**

## 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

## Tau Identification: Neural Network

- 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**

- “One-Prong”

- “One-Prong”+ EM

- “Multi-Prong”

- “All Types”

- Train 3 types separately

## Tau Identification: # Candidates

- 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

## Z Neural Network Input Params.

## 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 5.21.8 WW events.
- Limits on AC
- “Evidence for WW Production” in a 1997 PRL.

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

- 1D AC limits

## 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**

- Tightest from
- the Tevatron

**LEP Combined (1D 95% CL)**

- “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

## 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 2.300.21 events and is 60% W+jets, 40% mixed heavy.
Eff’y is 8.760.13%. 
Expected signal is 3.420.05 events.
6 Candidates Observed.

**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 2.300.21 events and is 60% W+jets, 40% mixed heavy.
- Eff’y is 8.760.13%.
- Expected signal is 3.420.05 events.
- 6 Candidates Observed.

**WW ********ee******** Event Selection**

**D0**

**D0**

- All but scaled MET*

- All but
- MT(min)

- *Events with jet(s).

- Remove
- Z/*

- Remove
- Top pairs

##  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 1.950.41 events and is > 80% Z/*
Eff’y is 6.220.15%. 
Expected signal is 2.100.05 events.
4 Candidates Observed.

****** ****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 1.950.41 events and is > 80% Z/*
- Eff’y is 6.220.15%.
- Expected signal is 2.100.05 events.
- 4 Candidates Observed.

**WW ******** Event Selection**

**D0**

- All cuts except HT

- Remove
- Z/*

- Remove
- Top pairs

## WZ  Trileptons Event Selection + BKGD.

**Background (events expected)**
*ll*+fake isolated e = 
- ZZ(lost lepton) = 
- Z(fake e) = 
*ll*+fake isolated  = 
- ttbar(fake isol. e /) = 
- Totalbkgd.expected.
- andeeeCandidates

**WZ ******** Trileptons Event Selection + BKGD.**

**MET>20 GeV**
**ET(had) < 50 GeV**

- Remove Top with
- B isol. lepton

- For a W boson

**Z/*********+jet Background**
**WZ Monte Carlo**

**WZ efficiency after these **
**criteria is ~13%.**

- Select these

- *1.43 pb (Ellis+Campbell,Ohnemus)

## WZ Candidates Summary

**D0 Preliminary**

**WZ********eee********Candidate**

**Three Candidates.**
****** ****is the **
**most efficient channel.**

## WZ  @ Tevatron in Run I

**D0 Trileptons Results (92 pb****-1****)**
- ee and eee 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).

- All D0 Wg, WW, WZ
- Channels Combined

- 1D limits

**D0**

- Not quite model-independant

## WZ Events Properties

**D0 Preliminary**

**WZ********Candidates:**

## W Radiation Amplitude Zero II

**M.C.**

- D0 Muon Data
- Preliminary

- D0 Muon Data
- Preliminary

- D0 Elec. Data
- Prelim.

## LEP Individual Experiments WW and WWZ

**Central Value and ******** 1 sigma**

## Z in Run 1

**D0 Results (97 + 87+ 13 pb****-1****)**
- and e+eandchannels
- 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+echannels
- 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.

- ET()> 7 GeV (CDF)

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

**D0**

## LEP Z Anomalous Couplings

- Note: LEP Nomenclature

## LEP ZZ Anomalous Coupling Limits

- Note: LEP Nomenclature

## Barrier Slide 2

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