Transcript Searches for Supersymmetry at the Tevatron

Searches for
Supersymmetry in
Multileptonic Signatures at
the Tevatron
Workshop on Collider Physics
Argonne National Laboratory,
8-12 May 2006
Giulia Manca, University of
Liverpool
1
Outline
• Supersymmetry
• The Tevatron and its
•
•
•
experiments
Searching for SUSY
Conclusions
Outlook
8th May 2006
Giulia Manca, University of Liverpool
2
Supersymmetry
Extends the Standard Model (SM) by predicting a new symmetry:
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
Standard Model Particles
Susy Particles
g
Higgsino
Higgs
Higgs
e  
e


~
G~
G
Gravitino
G
Graviton
Quarks
8th May 2006
Leptons
Force particles
Squarks
Sleptons
Susy
Force particles
Giulia Manca, University of Liverpool
3
Supersymmetry
Extends the Standard Model (SM) by predicting a new symmetry:
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
Standard Model Particles
Susy Particles
g
Higgsino
Higgs
Higgs
e  
e


~
G~
G
Gravitino
G
Graviton
Quarks
8th May 2006
Leptons
Force particles
Squarks
Sleptons
Susy
Force particles
Giulia Manca, University of Liverpool
4
Supersymmetry
Extends the Standard Model (SM) by predicting a new symmetry:
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
Standard Model Particles
Susy Particles
g
Higgsino
~0
Higgs
Higgs
ci
e  
e


4 neutralinos
~c
i
2
~ charginos
G~
G
Gravitino
G
Graviton
Quarks
8th May 2006
Leptons
Force particles
Squarks
Sleptons
Susy
Force particles
Giulia Manca, University of Liverpool
5
Supersymmetry
Extends the Standard Model (SM) by predicting a new symmetry:
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
Standard Model Particles
Susy Particles
g
Higgsino
~0
Higgs
Higgs
ci
e  
e


4 neutralinos
~c
i
2
~ charginos
G~
G
Gravitino
G
Graviton
Quarks
Leptons
Force particles
Squarks
Sleptons
New Quantum Number R-Parity  Rp  (1)BL2s
Lightest Sparticle (LSP) stable!
8th May 2006
Susy
Force particles
+1 (SM particles)
-1 (Susy particles)
Giulia Manca, University of Liverpool
6
Supersymmetry
Extends the Standard Model (SM) by predicting a new
symmetry:
spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)
Standard Model Particles
Susy Particles
g
Higgsino
~0
Higgs
Higgs
ci
e  
e


4 neutralinos
~c
i
2
~ charginos
G~
G
Gravitino
G
Graviton
Quarks
Leptons
Force particles
Squarks
Sleptons
New Quantum Number R-Parity  Rp  (1)BL2s
Lightest Sparticle (LSP) stable!
8th May 2006
Susy
Force particles
+1 (SM particles)
-1 (Susy particles)
Giulia Manca, University of Liverpool
7
Limitations of Standard Model
• Stabilisation of Higgs mass at EW scale
• Couplings don’t unify at one scale
• Dark Matter
• Dark Energy
• Neutrino masses
• Gravity
f
H
H
f
Standard Model
8th May 2006
Giulia Manca, University of Liverpool
8
Limitations of Standard Model
SUSY
• Stabilisation of Higgs mass at EW scale

• Couplings don’t unify at one scale
• Dark Matter
• Dark Energy
• Neutrino masses
• Gravity
f
H
H
f
H
~
f
~
f
H
Standard Model
8th May 2006
Giulia Manca, University of Liverpool
9
Limitations of Standard Model
SUSY
• Stabilisation of Higgs mass at EW scale

• Couplings don’t unify at one scale

• Dark Matter
• Dark Energy
• Neutrino masses
• Gravity
f
H
H
f
H
~
f
~
f
H
Standard
Model
SUSY
8th May 2006
Giulia Manca, University of Liverpool
10
Limitations of Standard Model
SUSY
• Stabilisation of Higgs mass at EW scale

• Couplings don’t unify at one scale

• Dark Matter ->LSP

• Dark Energy
• Neutrino masses
• Gravity
f
H
H
f
H
~
f
~
f
H
Standard
Model
SUSY
8th May 2006
Giulia Manca, University of Liverpool
11
Limitations of Standard Model
SUSY
• Stabilisation of Higgs mass at EW scale

• Couplings don’t unify at one scale

• Dark Matter ->LSP

• Dark Energy
• Neutrino masses
• Gravity

8th May 2006
f
H
H
f
H
~
f
~
f
H
Standard
Model
SUSY
Giulia Manca, University of Liverpool
12
Supersymmetry: how ?
Wide range of signatures: look for SuSy specific signatures or
excess in SM ones; examples:
Rp
:
LSP Large Missing Energy ET
:
Isolated leptons
c0
˜ g˜ Multijets
qc±
…and many more!!
8th May 2006
Giulia Manca, University of Liverpool
13
Supersymmetry: how ?
Wide range of signatures: look for SuSy specific signatures or
excess in SM ones; examples:
Rp
:
LSP Large Missing Energy ET
:
Isolated leptons
c0
˜ g˜ Multijets
qc±
(fb)
…and many more!
1012
Remember :
VERY SMALL cross sections !!
8th May 2006
104
10
Giulia Manca, University of Liverpool
14
Supersymmetry: how ?
Wide range of signatures: look for SuSy specific signatures or
excess in SM ones; examples:
Rp
:
LSP Large Missing Energy ET
:
Isolated leptons
c0
˜ g˜ Multijets
qc±
(fb)
…and many more!
1012
Remember :
VERY SMALL cross sections !!
8th May 2006
104
10
Giulia Manca, University of Liverpool
15
•
•
mSugra: a working model
SUSY broken through gravity
Five parameters:
EW
scale
hep-ph/9311269
 M0:common scalar mass at
GUT scale
 M1/2:common gaugino mass at
GUT scale
(i.e. M1(GUT)=M2(GUT)=M3(GUT)= M1/2 )
 A0: common trilinear scalar
•
interaction at the GUT scale
(Higgs-sfermionR-sfermionL)
 tan: ratio of Higgs vacuum
expectation values
 Sign(), the higgsino mass
parameter
(determined by EWSB)
Lightest supersymmetric
particle(LSP) is the c01, stable
Radiative
EWSB
Corrections
GUT
scale
GRAVITY
Hidden
Sector
8th May 2006
Giulia Manca, University of Liverpool
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mSugra Existing Limits : LEP
• LSP ~ 50 GeV/c2
• Chargino > 103 GeV/c2 (heavy sneutrinos);
• Sleptons > 90-100 GeV/c2 for M(c01)<M(R);
8th May 2006
Giulia Manca, University of Liverpool
17
The Tevatron
•
p p at ECM 1.96 TeV
•
High Luminosity
 Tevatron ~1.5 fb-1!
 Record L=1.7x1032 cm-2 s-1
CDF and D0 running at
high efficiency
Mar01-Aug05
750 pb-1
8th May 2006
Giulia Manca, University of Liverpool
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The Tevatron
•
p p at ECM 1.96 TeV
•
High Luminosity
 Tevatron ~1.5 fb-1!
 Record L=1.7x1032 cm-2 s-1
CDF and D0 running at
high efficiency
Mar01-Aug05
750 pb-1
8th May 2006
Giulia Manca, University of Liverpool
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The Tevatron
•
p p at ECM 1.96 TeV
•
High Luminosity
 Tevatron ~1.5 fb-1!
 Record L=1.7x1032 cm-2 s-1
CDF and D0 running at
high efficiency
Still long way to go!
design goal
We are
here
Mar01-Aug05
750 pb-1
8th May 2006
base goal
Giulia Manca, University of Liverpool
Trileptons at the Tevatron
21
The trilepton signal
Higgsinos and
gauginos mix
CHARGINOS
NEUTRALINOS


Striking signature at Hadron Collider,
THREE LEPTONS
In mSUGRA Rp conserved scenario,
LARGE MISSING TRANSVERSE
ENERGY from the stable LSP+
 Low background
 Easy to trigger
~
c 10
~
c 1
p
p
~
c 20

~
c 10

GOLDEN SIGNAL AT THE
LOW MODEL DEPENDENCE TEVATRON !!
8th May 2006
Giulia Manca, University of Liverpool
Chargino-Neutralino
production…
22
 Low cross section
(weakly produced)
T. Plehn, PROSPINO
10
q
SUSY (pb) vs sparticle
mass(GeV/c2) for
√s=1.96 TeV
~
c 20
W*
1
~
c 1
q
t-channel
interferes
destructively
c0 c±
~
q
~
q
q'
10-1
c 20
~
c

1
10-2
10-3
100 150 200 250 300 350 400 450 500
Tevatron sensitive to the BULK
region in WMAP data
8th May 2006
Giulia Manca, University of Liverpool
23
…and decay
Leptons of 1st, 2nd
Leptons of 3rd generation
generation are preferred
are preferred
~
c
~
Chargino Decay
c

1
0
1

W*


~
c 1

~

~
c 10
Neutralino Decay

~
c 1

~

c
c 10
0
2

~

~
0
2

Z*

8th May 2006
Leading lepton
~
~
c

~
c 10
~
c
0
1
Next-To-Leading lepton
Third lepton
Best reach Tevatron
for mass sleptons~mass
chargino
Giulia Manca, University of Liverpool
24
Finding SUSY at CDF
CENTRAL REGION
=0
=1
Muon system
e
Recover loss in
acceptance due
to cracks in the
detector if we
accept muons
with no hits in
the Muon
Chamber

Drift chamber


Missing Transverse Energy
(MET)
Real MET
 Particles escaping detection ( )
Em
Calorimeter
8th May 2006
Fake MET
Had Calorimeter
Muon pT or jet ET mismeasurement
Additional interactions
Cosmic ray muons
Mismeasurement of the vertex
Giulia Manca, University of Liverpool
25
DO detector
•Coverage to muons up to eta~2
=0
=1.0
=2.0
=1.0
=3.0
=3.6
8th May 2006
Giulia Manca, University of Liverpool
26
The SM Control Samples
Lepton ID efficiencies
Trigger efficiencies
Calibration
Lepton E and P Scale
Luminosity
8th May 2006
Fake rates
Jet Energy Scale
Giulia Manca, University of Liverpool
27
The tuning of the detector
response
The final plot!
Without
Minimum
bias
Generator
level MEt
Corrected Met
8th May 2006
MC Z/g
Raw Met after
reconstruction
Giulia Manca, University of Liverpool
28
Learning from Data: Z pT
Events in the tail
background to
SUSY events!
Tune for parton KT and QCD
scale in MC Generators
8th May 2006
Giulia Manca, University of Liverpool
Trileptons at CDF
30
How to investigate the different scenarios?
CHANNEL
LUM
TRIGGER PATH
 + e/
750
High pT Single Lepton
ee + e/
350
High pT Single Lepton
 + e/
312
Low pT Dilepton
e + e/
Ongoing
Low pT Dilepton
e + e/
Ongoing
High pT Single Lepton
High tan
e/e + track
Ongoing
Low pT Dilepton
region
ee + track
610
Low pT Dilepton
ee,e, 
710
High pT Single Lepton
Low tan
region
Full
acceptance
coverage
sensitive
to leptonic 
decay
sensitive
to all 
decays
Low tan scenario tan=5 , 38%
High tan scenario tan=20, 100%
High pT data-sample benchmark
to understand low pT data-sample
8th May 2006
Giulia Manca, University of Liverpool
How to investigate the different
scenarios ?
31
CHANNEL
LUM
TRIGGER PATH
 + e/
750
High pT Single Lepton
ee + e/
350
High pT Single Lepton
 + e/
310
Low pT Dilepton
e + e/
Ongoing
Low pT Dilepton
e + e/
Ongoing
High pT Single Lepton
High tan
e/e + track
Ongoing
Low pT Dilepton
region
ee + track
610
Low pT Dilepton
ee,e, 
705
High pT Single Lepton
Low tan
region
Full
acceptance
coverage
sensitive
to leptonic 
decay
sensitive
to all 
decays
Low tan scenario tan=5 , 38%
High tan scenario tan=20, 100%
High pT data-sample benchmark
to understand low pT data-sample
8th May 2006
Giulia Manca, University of Liverpool
32
Analysis Strategy
COUNTING EXPERIMENT
• Optimise selection criteria for best
signal/background value;
• Apply selection criteria to the data
•
Define the signal region and keep it
blind
Test agreement observed vs.
expected number of events in
orthogonal regions (“control
regions”)
•
•Look in the signal region and
count number of SUSY events !!
Or set limit on the model
8th May 2006
Giulia Manca, University of Liverpool
Backgrounds:
how
to
reduce
Backgrounds
them?
• DIBOSON (WZ,ZZ) PRODUCTION
• DRELL YAN PRODUCTION +
33
additional lepton
 Leptons have high pT
 Leptons have mainly high pT
 Leptons are isolated and separated
 Small MET
 MET due to neutrinos
e
 Low jet activity
The third lepton
originates from g
conversion
p

8th May 2006
• HEAVY FLAVOUR PRODUCTION
e
p
e
The third lepton is
a fake lepton
e
g
p
irreducible background
 Leptons mainly have low pT

e
 Leptons are not isolated
 MET due to neutrinos
0

p
p
p


Giulia Manca, University of Liverpool
34
Selection criteria: Mass
Rejection of J/,  and Z
Dimuon events
SUSY
SUS
Y
Dimuon Mass(GeV/c2)
 M<76 GeV & M >106 GeV

SUSY
SUSY
M> 15 (20,25) GeV
 min M < 60 GeV
8th May 2006
(dielectron+track analysis)
Giulia Manca, University of Liverpool
( , ) , Jet Veto, Missing
Rejection of DY and high jet Energy
35
multiplicity processes
SUSY
Analysis
Kinematic
Variable
Kinemati
c Cut
Trilepton
analyses
Jet ET > 20
GeV
n. Jets <
2
Dielectron
+ track
analysis
HT=
∑jetETj
HT < 80
GeV
8th May 2006
Giulia Manca, University of Liverpool
36
Understanding of the Data
-like sign
L=704 pb-1
MET
Each CONTROL REGION is investigated
 with different jet multiplicity-check NLO processes
 with 2 leptons requirement - gain in statistics
 with 3 leptons requirement - signal like topology
??
EWK
Diboson
low DY
Zmass
L=704 pb-1
10
15
SIGNAL
REGION
DY + g
15
8th May 2006
Z + fake
76
Invariant Mass
106
Very good agreement between SM prediction
observed
Giulia and
Manca,
University data
of Liverpool
37
Systematic uncertainty
Major systematic uncertainties affecting the
measured number of events
ee+lepton (high-pt)
 Signal
 Lepton ID 5%
Z->ee MC
 Muon pT resolution 7%
 Background
 Fake lepton estimate method 5%
 Jet Energy Scale 22%
 Common to both signal and background
 Luminosity 6%
 Theoretical Cross Section 6.5-7%
 PDFs 7%
8th May 2006
Giulia Manca, University of Liverpool
38
Results !
Look at the “SIGNAL” region
Analysis
Total
predicted
background
Example
SUSY
Signal
Observed
data
ee,e, 
6.801.00
3.180.33
9
 +e/ (lowpT )
0.130.03
0.170.04
0
ee+track
0.480.07
0.360.27
1
ee + e/
0.170.05
0.490.06
0
 +e/
0.640.18
1.610.22
1
e +e/
0.780.15
1.010.07
0
8th May 2006
Giulia Manca, University of Liverpool
39
Highest lepton-pt event
In the ee like-sign analysis, we observe one interesting event
e- : 103 GeV
Mass OS1
220 GeV/c2
Mass OS2
12 GeV/c2
MET : 25 GeV
e+ : 5 GeV
e- : 107 GeV
g : 15 GeV
8th May 2006
Giulia Manca, University of Liverpool
40
Limit
No SUSY :(
•Combined all analyses to
obtain a limit on the mass
of the chargino in mSugralike scenario
with no slepton mixing
slepton masses ~ neutralino
masses
• Observed limit:
M(c1) ~ 127 GeV/c2
xBR ~ 0.25 pb
• Sensitive up to masses
M(c1) ~ 140
2
GeV/c
xBR ~ 0.2 pb
Better than LEP and
Tevatron Run I
8th May 2006
Giulia Manca, University of Liverpool
41
Limit
But : we are model
dependent !
In “standard” mSugra
Sensitive to chargino
masses of ~ 116 GeV/c2
Not able to exclude this
particular region of
parameter space with
these results …
8th May 2006
Giulia Manca, University of Liverpool
Trileptons at DO
43
Chargino and Neutralino in 3+ET
PRL 95,151805 (2005)
In mSUGRA:3 leptons+ET
 Luminosity ~350 pb-1
 Use tau leptons
6 analyses:
-2l(l=e,,)+isolated track or 

ET and topological cuts (M,f, MT)
Selection
SM expected
OBSERVED
ee+t
0.21±0.12
0
et
0.31±0.13
0
t
1.75±0.57
2
±±
0.64±0.38
1
e+t
0.58±0.14
0
+t
0.36±0.13
1
SUM
3.85±0.75
4
8th May 2006
M(e) (GeV/c2)
Giulia Manca, University of Liverpool
44
Chargino Neutralino Limits
mSUGRA: M(c±)≈M(c02) ≈2M(c01)
“3l-max”
•
•
M(  ) > M(c02)
No slepton mixing
Limits :
 xBR < 0.2 pb
 M(c±1)>116 GeV/c2
mSugra
optimistic
scenario
A0=0
“Heavy Squarks”
M(c±)≈M(c02)3M(q)
 xBR < 0.2 pb
 M(c±1)>128 GeV/c2
•
“Large m0”
M()>>M(c02 ,c±)
 No sensitivity
•
8th May 2006
Analyses being updated with 1 fb-1
Giulia Manca, University of Liverpool
45
Chargino Neutralino Limits
mSUGRA: M(c±)≈M(c02) ≈2M(c01)
“3l-max”
•
•
M(  ) > M(c02)
No slepton mixing
Limits :
 xBR < 0.2 pb
 M(c±1)>116 GeV/c2
mSugra
optimistic
scenario
“Heavy Squarks”
M(c±)≈M(c02)3M(q)
 xBR < 0.2 pb
 M(c±1)>128 GeV/c2
•
“Large m0”
M()>>M(c02 ,c±)
 No sensitivity
•
8th May 2006
A0=0
M(slep)>>M(n
eutralino)=> 2
Bodies decay
region
3rd lepton
too soft
Only LS
analyses
sensitive
Neutralino decay invisible to neutrinos
3 Bodies
decay region
Giulia Manca, University of Liverpool
46
Summary and Outlook:
Chargino and Neutralino in mSugra
TRILEPTONS SIGNAL:
• CDF and D0 analysed first half of data and observed no excess :(
• Set limit already beyond LEP results ! (although model dependent )
• 1.5 fb-1 of data collected and ready to be analysed
• With 4-8 fb-1 by the end of RunII we should be sensitive to Chargino
masses up to ~250 GeV and xBR ~ 0.05-0.01 pb !!
Ellis, Heinemeyer, Olive, Weiglein,
hep-ph\0411216
now
Favoured
by EW
precision
data
8th May 2006
Giulia Manca, University of Liverpool
47
•
•
•
Susy at the LHC !
Will generally be found
fast!
But SUSY comes in very
many flavours
Hints from the Tevatron
would help on search
priorities, e.g.
 tan large:
 3rd generation
important
(’s, b’s)
 R-parity is violated
 No ET
 GMSB models:
 Photons important
 Split-SUSY:
 Stable charged
hadrons
 Can setup triggers
Inclusive search
STATISTICAL
reach only
up to 2.8 TeV
up to 2.3 TeV
up to 2 TeV
accordingly
8th May 2006
Giulia Manca, University of Liverpool
48
•
•
•
Susy at the LHC !
Will generally be found
fast!
But SUSY comes in very
many flavours
Hints from the Tevatron
would help on search
priorities, e.g.
 tan large:
 3rd generation
important
(’s, b’s)
 R-parity is violated
 No ET
 GMSB models:
 Photons important
 Split-SUSY:
 Stable charged
hadrons
 Can setup triggers
Inclusive search
STATISTICAL
reach only
up to 2.8 TeV
up to 2.3 TeV
up to 2 TeV
accordingly
8th May 2006
Giulia Manca, University of Liverpool
49
•
Production Cross-sections at the
LHC
In mSugra:
 squark-gluino dominate
•
(pb)
SUSY (pb) vs sparticle
mass(GeV/c2) for √s=14 TeV
(jets+met channel)
T. Plehn, PROSPINO
300k
events
in 3fb-1
Direct production crosssections small
 But could be the only way
•
to observe SUSY if
quark-gluinos are heavy
! (“focus point”)
In other regions trileptons
signal enhanced from
squark-gluino cascade
3,000
events
in 3fb-1
0 
c  c±
mass(GeV/c2)
But also :
6x106 Zs, 2.4x106 t-antitop and
150,000 WZ !
8th May 2006
Giulia Manca, University of Liverpool
50
•
•
Mass measurement at the LHC
Mass constraints
Invariant masses in
pairs
 Missing energy
 Kinematic edges
Observable:
Depends on:
Limits depend on
angles between
sparticle decays
8th May 2006
Giulia Manca, University of Liverpool
51
Building on leptons…
• Other possibilities with lepton
signatures in mSugra:
Jets+MET+leptons -> mass of the
sparticles in the cascade
Like-sign dileptons -> still sensitive to
chargino-neutralino but also on gluino pair
production ! (no jet veto)
R-parity violating scenarios
8th May 2006
Giulia Manca, University of Liverpool
52
Conclusions
• Chargino-neutralino are the golden
•
•
discovery model at the Tevatron !
Hints from the Tevatron can give
directions to the LHC
At the LHC, chargino-neutralino
production crucial in study the properties
of the new sparticles as their masses (but
only mSugra considered)
• Exciting times to come !!
8th May 2006
Giulia Manca, University of Liverpool