Boson Pair Production + Triple Gauge Couplings
description
Transcript of Boson Pair Production + Triple Gauge Couplings
11 February 24, 1February 24, 1997997
Boson Pair Production + Triple Gauge CouplingsBoson Pair Production + Triple Gauge Couplings
Results from the Tevatron
San Miniato - April, 1997
WW/WWZ Couplings
W Production
WW/WZ Production
ZZ/Z Couplings
Z Production
Prospects for Run II
Summary Tom Diehl for the D0 and CDF Collaborations
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Standard Model Gauge Boson Interactions
Self-interactions are direct consequence of the non-abelian SU(2)L x U(1)Y gauge symmetry.
SM makes specific predictions. Cancellation of t and u -channel by s-channel
amplitude removes tree-level unitarity violation.
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Characterized by effective Lagrangian
CP Conserving SM Parameters:
g
Static Properties
Non-SM WWZ/WW Interaction
QeW =e/2 M2
W ()
W=e/2 MW
L W W V W V W
W W V
W W V
WWV WWV V†
V
V†
/ ( )
/
†
†
g g
MW
1
2
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Effect of non-SM Couplings
Cross section increases especially for High ET bosons (W/Z/).
Unitarity Violation avoided. e.g.:
WW Production
( )( / )
ss n
1 2
n 2 for WW ,WWZ
is a form factor
scale
PT(W)(WW)
n ZZ Z3 4, for and
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W Selection @ CDF + DO
CDF (67pb-1)
|e|<1.1 ||<0.6
||<1.1
GeV
D0 (93 pb-1)
|e|<1.1 ||<1.0
1.5<|e|<2.5
Same || as electron
Lepton ID
E T 20 E T 25E T 25
R l 0 7.
Photon ID
E T 15PT15
E T 7 E T10
E T 20 PT 20
GeV
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W Production
109 Candidates (75 e 34 )
Background: (W+jets,Z,W->) =
Signal vs. SM SM Signal = Candidates-Backgd
= 82.6 events
Anomalous Coupling
Limits: =1.5 TeV
@95% C.L.
CDF
26 4
2 7
.
.
753 8 0. .
18 2 0 0
0 7 0 7 0
. . ( )
. . ( )
Preliminary
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W Radiation Zero SM has “amplitude zero” at
where is angle between incoming quark and photon in the W rest frame (W polarization -> 73% correct rest frame).
Radiative events are background so increase R cut.
CDFcos( )*
1
3 *
Data subsample.
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W Production
= 1.5 TeV
D0 127 Candidates (57 e 70 )
Background: (W+jets, Z) = events.
Signal vs. SM SM: xBR = pb D0: xBR = pb.
43 5
12 5 10. .113 151 5
1 7. ...
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WW A.C. LimitsD0
Tightest WWg Coupling Limits available. 95% CL.
U(1)EM point excluded.
0 93 0 94
0 31 0
. . (
. .
= 0)
29 ( = 0)
= 1.5 TeV
Combined limits: together with
an earlier 14 pb-1 publicationPRL 75, 1034
(1995)
Require 3-body Transverse Mass
> 90 GeV/c2
for PT fit.
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WW->dileptons @ D0 and CDF
CDF (108pb-1)
|e|<1.1 ||<0.6
75<Mee or <105 GeV/c2
Veto events w/ jet of ET > 10 GeV
D0 (79pb-1)
|e|<1.1 1.5<|e|<2.5
ee:
e:
eR(,e)>0.5 |Mee-MZ| <15 GeV/c2
|ETrecoil|<40 GeV
E T 25 E Tl 20 E T 25E T
e 25 20,
Event ID
if GeV E T 50
PT15
|<1
E Te 25
E Tcal 25
PT 25 20, E T
30
E T 20Nearest Lepton
( , ) E lT 20 160 > ( , )E lT 20
e eee
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WW-> dilepton Results
3 e, 2 ee, 0
Drell-Yan, fake leptons
events
“Evidence for WW
Production”
=1000 GeV
2 e, 1 ee, 1
Drell-Yan, W,t-tbar, fake leptons
events
“Cross Section consistent w/ SM”
12 0 3. .
Background
D0CDF
2 6 0 4. .
( ) . ...WW
10 2 165 16 5 pb
Candidates
Results
11 13
0 8 0 9
. .
. .
@95% C.L.
| | .
| |
12
1.0
=1000 GeV
( )WW X 43 pb (95%CL)
Preliminary
Fermilab-Pub-96/311-E To be published in PRL
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WW/WZ Semi Leptonic Decay Modes @ CDF + D0
CDF (110pb-1)
|e|<1.1 ||<0.6
MT(e)>40 GeV/c2
2+ Jets 0.4 cone
GeV 60<Mjj<110 GeV/c2
ET(jj)>200 GeV
D0 (96pb-1)
|e|<1.1 1.5<|e|<2.5
MT(e)>40 GeV/c2
2+ Jets 0.5 cone
GeV 50<Mjj<110 GeV/c2
|ET(jj)-ET(e)| < 40 GeV
E T 20 E Tl 20 E T 25 E
T
e 25
Lepton ID
Jet Selection
E Tj 20E T
j 25
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WW/WZ Production
Effect of PT(W) Cut: Reduced Acceptance. Reduced Sensitivity
M(WW)>450 GeV/c2
CDF
95% CL Limits
=1000 GeV
Z
Z
0 49 0
0 35 0 32
. .
. .
54
=2000 GeV
0 67 0
051 051
. .
. .
85
Preliminary
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WW/WZ -> ejj Production
Run Ib, 82.3 pb
SM(WW) = 9.5 1.0 pb (BR = 1.4 pb)
SM(WZ) = 2.5 0.3 pb (BR = 0.2 pb)
D0
399 Candidates Background Source:
W+2 or more jets, t-tbar
= 387+-38 events
SM Pred = 18+-3 (WW+WZ) events
Preliminary
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WW/WZ->ejj Production
Limits from fit to PT(e)
033 036
043 059
. .
. .
Z
Z
Limits will superceed results of Run Iaanalysis [PRL 77, 3303 (1996)]
Another contour indicates W couples to Z
=2 TeV
D0
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ZZ/Z Interaction In SM all are couplings equal to zero Non-SM Characterized by an
effective Lagrangian w/ 8 coupling parameters.
CP Violating h1V and h2
V
CP Conserving h3V and h4
V
Transition Moments
de 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
( )
( )
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Z Selection @ CDF + DO
CDF (67pb-1)
|e1|<1.1 ||<0.6
|e2|<4.2 ||<1.2
Same || as Wg
DO (96,87,14) pb-1
(ee,, |e| as before,
|| <1, || < 1,2.4
Neutrino Channel
No Jets (ET>15 GeV)
Same || as Wg
Lepton ID
ETe 25
Photon ID
R l 0 7.ET 7 GeV ET
10 40, GeV
E Te1 20 PT 20
E Te2 20 15 10 , ,
P
P
T
T
GeV / c
GeV / c
15 10
15 2
,
,
ET 40 GeV
ee and ee and
tight
loose
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Zg ResultsZg Results 31 Candidates (18 ee, 13 )
Background (Z+jets) = events Signal vs. SM
SM signal = 24.9 events expected Candidates-Background = 29.6 events
A.C. Limits:
assuming only one
coupling at a time is non-zero
16 16
0 4 0 4
30 10
40 20
. ( ) .
. ( ) .
h h
h h
Z Z
Z Z
14 0 3. .
hn0 similar
CDF
500 GeV
Preliminary
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Z(ee,) Candidates vs. SM
29 Candidates (14 ee, 15 )
Background (Z+jets, W channel only)
Signal vs. SM SM signal = 29.1 Z events expected. Candidates-Background = 23.6 events.
D0
Preliminary
54 10. . events
E eeT ( )
M(ee)
M(ee)
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Z Candidates vs. SM
4 Candidates Background (W->e, Brems.)
SM signal = events expected.
Fermilab-Pub-97/047-E accepted by PRL Fermilab-Pub-97/088-E submitted to PRD
58 10. . events
D0
18 0 2. .
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(From Greg Landsberg's Wine(From Greg Landsberg's Wine&Cheese Talk - 9/6/96, Fermil&Cheese Talk - 9/6/96, Fermilab)ab)
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Limits on Anomalous ZV Couplings
Run Ia (ee,,):
Run Ib (ee,):
| ( )| . | ( )| .h h h hZ Z Z Z30 10 40 20136 0 26
500 GeV
750 GeV 500 GeV
| ( )| .
| ( )| .
h h
h h
Z Z
Z Z
30 10
40 20
0 78
019
| ( )| .
| ( )| .
h h
h h
Z Z
Z Z
30 10
40 20
0 44
0 06
D0
hn0 similar
95% CL Limits
Tightest ZV Limits Available
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Prospects for Run 2
Tevatron and detector upgrades provide 2 fb-1 data samples.
Quantitative Expectations Factor of 20X in luminosity provides ~ 2.5X
improvement in A.C. limit. (at fixed form factor scale). Numbers of events (CDF + D0) estimate.
W _> l ~ 3000
Z _> ee( ~ 700
WW _> ll ~ 100
WZ _> lll ~ 30
ZZ_> e’s and ’s a few
Qualitative Expectations Wg and WZ radiation zero. Tevatron Studies probe theoretical
expectations for A.C.’s.
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ZZ Candidate from CDF
Three Central Muons. One muon inferred from a high-PT track.
Expected 0.1 event. Backgrounds?
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WZ Candidate from CDF
Approx. 1 such event expected. Three high ET electrons and Missing
Transverse energy. Backgrounds?
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SummarySummary D0 + CDF study W,WW,WZ, and Z
diboson final states with a rich variety of techniques.
WW, WWZ, ZZ, Z interactions appear to be those of Standard Model. WWg and WWZ vertices observed. Hint of Radiation Zero in Wg (CDF). (CDF). Limits on anomalous WWV and ZVg
Couplings. Tightest Are:ZV: =750 GeV limits from D0.
WWV: =2000 GeV limits from D0 and CDF (comparable).
Run II Detector and Lum. Upgrades.
( ) . ...WW
10 2 165 16 5 pb
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LEP vs TevatronLEP vs Tevatron
LEP experiments use 3 variables to parameterize WWV anomalous couplings.
g
g
ZW
WZ
W
W Z
12
12
cos
cos
LEP sensitivity highest to W. Limits on W correspond to limits on .
Limits on W correspond to limits on
if B and W are fixed to zero.
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Z Candidate from D0
Run: 58766Run: 58766Event: 10750Event: 10750Recorded: 01/09/93Recorded: 01/09/93ET
= 67.9 GeVET = 56.6 GeV
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Z(ee) Candidate from D0
Run 79096, Event 15782, recorded 05/22/94Run 79096, Event 15782, recorded 05/22/94
ET = 73.3 GeV, Mee = 89.4 GeV,
Mee = 200.3 GeV
ee11
ee22
ee11
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Storage
Analysis (pb-1) Scale Limits
D0 WW(dilepton)
73 1.0 -2.6<<2.6-2.1<<2.1
D0 WW(ejetjet)
96 2.0 -2.6<<2.6-2.1<<2.1
D0 W 96 1.5 -2.6<<2.6-2.1<<2.1
Z():
| | . ,| | .,
,
,
,
30 10 40 200 8 0 2
Z Z
h h Z(ee):
| | . ,| | .,
,
,
,
30 10 40 200 9 0 2
Z Z
h h
@ 95% CL}
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Z Selection @ CDF + DO
CDF (67pb-1)
|e1|<1.1 ||<0.6
|e2|<4.2 ||<1.2
||<1.1
GeV
DO (73 pb-1)
|e|<1.1
1.5<|e|<2.5
Same || as electron
Lepton ID
E T 25
R l 0 7.
Photon ID
E T 7 E T10
E Te1 20 PT 20
E Te2 20 15 10 , ,
Channel
in progress
GeV