New Electroweak Results from DZero
description
Transcript of 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
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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
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The DZero Collaboration
19 Countries 86 institutions ~620 physicists
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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
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The DZero Detector in Run II: Inner Tracker
Tracker
SMTSMT
SMT
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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
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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
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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
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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
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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
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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
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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.
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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
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”
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
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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
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”
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
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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”
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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
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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
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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
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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
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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.
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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”
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.
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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.
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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
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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
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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
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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).
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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
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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
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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/*
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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 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
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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:
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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
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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
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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.
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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)
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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
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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
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
38
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
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
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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.
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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)
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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
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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.
# Observed 112 161 candidates
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)
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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.
# Observed 138 152 candidates
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
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”
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)
LEP EWK Working Group hep-ex/0412015
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
WZ Trileptons Event Selection + BKGD.
MET>20 GeV ET(had) < 50 GeV
)()( TTT ElhadE
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)
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.