supersymmetry at the tevatron - slac · susy p x 1 1 p x 2 2 f (x ) f (x ) i j 1 2 s^ ij (x x ) 1 2...
TRANSCRIPT
Supersymmetryat theTevatron
Marc Hohlfeld
Rheinische Friedrich–Wilhelms–Universitat Bonnon behalf of the CDF and DØ experiments
– p. 1/3
Outline
• Introduction• Tevatron collider and detectors• Physics at the Tevatron• Search for Supersymmetry
N Direct searchesI Search for supersymmetric Higgs bosonsI Search for Charginos and NeutralinosI Search for Squarks and GluinosI Search for long lived particles
N Indirect searchesI Search for Bs → µµ
• Summary and outlookt
χ~b~
χ~g~
2
1+
0
~
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 2/46
Particle ContentParticles in the Minimal Supersymmetric Model (MSSM)
R–parity = +1 R–parity = –1 R–parity = –1Particle Symbol Spin Particle Symbol Spin Particle Symbol Spin
Lepton ` 1
2Slepton ˜
L, ˜R 0
Neutrino ν 1
2Sneutrino ν 0
Quark q 1
2Squark qL, qR 0
Gluon g 1 Gluino g 1
2
Photon γ 1 Photino γ 1
29
>
>
>
>
=
>
>
>
>
;
Z Boson Z 1 Zino Z 1
2
W Boson W± 1 Wino W± 1
24 Neutralinos χ0
i1
2
Higgs H0, H± 0 Higgsino H01, H+
21
22 Charginos χ±
i1
2
h0, A0 0 H−
1, H0
21
2
• Assumptions in this talkN Consider mSUGRA model
I Relevant parameters: tan β, m0, m1/2, A0, sign(µ)N R–parity is conserved ⇒ LSP (Neutralino) is stable
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 3/46
Tevatron Parameters
• pp collisions at center of mass energy of √s = 1.96 TeV
Run I Run IIa Run IIb√
s (TeV) 1.8 1.96 1.96Bunches 6×6 36×36 36×36Bunch spacing 3500 396 396(ns)Luminosity 1.6 · 1030 9 · 1031 3 · 1032
(cm−2s−1)
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 4/46
Tevatron Performance
Run IIa Run IIb
Run IIa: 1.5 fb delivered
Run IIb: 1.6 fb delivered 1.3 fb recorded
1.4 fb recorded−1
−1−1
−1
• Tevatron coming close to design luminosity for Run IIbN Improved antiproton stacking rateN Peak luminosity ∼ 300 · 1030 cm−2s−1
• Integrated luminosity of 7–8 fb−1 by end of 2009 realistic projection
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 5/46
The Detectors
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Central Outer Tracker
Calorimeter
Silicon Strip Detector
Solenoid
Muon System
• Two multipurpose detectorsN Identification of electrons, muons,
taus, jets, missing transverse energy• Fast readout electronics
N Bunch spacing 396 ns• Dedicated trigger systems
N Rate reduction from 2.5MHz to 50Hz
• CDF detectorN Large tracking volume
• DØ detectorN Large acceptance for electrons
and muons
PP
NORTH SOUTH
H−DisksF−DisksSi−Barrels
Superconducting Coil CPSCFT
FPS
Toroid Solenoid
Central PreshowerTracker (CFT)Central Fiber
Detector (CPD)
Scintillators
Tubes (MDT)Mini Drift
Calorimeter
Tracker (SMT)Silicon Micro
Forward Preshower Detector (FPD)
Tubes (PDT)Proportional Drift
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 6/46
The Detectors (cont’d)
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 7/46
Physics at the Tevatron
• Physics at the Tevatron is characterized byN High center–of–mass energy of the collider
I Production of massive particles possibleI top–quark, Higgs, SUSY particles,
heavy gauge boson,...N Particles are produced in strong interaction
I Huge cross section for jet productionI Need large reduction to see signals
N 7 interactions/crossing at 3 · 1032cm−2s−1
0.1 1 1010 −7
10 −5
10 −3
10 −1
10 1
10 3
10 5
10 7
10 109 9
10 −7
10 −5
10 −3
10 −1
10 1
10 3
10
10 5
7
σjet(E Tjet > √s/4)
LHCTevatron
σt
σZ
σjet(E Tjet > 100 GeV)
σHiggs (M H = 150 GeV)
σW
σjet(E Tjet > √s/20)
σb
σtot
σ (
nb)
√s (TeV)
Proton−(Anti−)Proton Wirkungsquerschnitte
SUSY
p x1 1
p x2 2
f (x )
f (x )
i
j
1
2
σij (x x )21
Hadr
onis
atio
n
^
p
p
1
2
Spectators/ULE
hadronshard
interaction showerpartonincoming
N Final states are complicatedI Fragmentation of spectatorsI Additional jets due to gluon radiation
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 8/46
SUSY at the Tevatron
• There are three major areas to search for Supersymmetry at the TevatronN Search for supersymmetric Higgs bosons
I Search for Higgs bosons in τ final statesI Higgs bosons searches using b–jets
N Direct searches for other SUSY particlesI Squarks and GluinosI Charginos and NeutralinosI Long lived particles
N Indirect searches• Only a few selected topics will be covered in this talk• For a comprehensive overview please refer toCDF http://www-cdf.fnal.gov/physics/physics.htmlDØ http://www-d0.fnal.gov/Run2Physics/WWW/results.htm
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 9/46
Search for SUSY Higgs Bosons
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 10/46
Search for SUSY Higgs Bosons• 5 Higgs bosons are predicted in SUSY models
N MSSM Higgs sector specified by tanβ, mA
• Neutral Higgs bosons h/H/A can be produced via gluonfusion or in association with jetsN Coupling increases with tan2 β ⇒ Large cross section
• At high tan β the main decay modes areN h/H/A→bb: 90% h/H/A→ ττ : 10%
τ τhh
τ τµ h
τ τhe
τ τµ e
τ τe e
τ τ µ µ
• Focus on ττ final stateN Golden channels are τhτe and τhτµ
I Large branching fraction, moderate backgroundN Other channels are less important
I Fully leptonic channels: small branching fractionI Fully hadronic mode: huge multijet background
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 11/46
Search for SUSY Higgs Bosons (2)• Major backgrounds are Z/γ∗ → ττ and multijet production
N Require isolated lepton and isolated τ to reduce QCD contributionN Further reduce QCD by requiring large HT =
∑
pT
N Veto on events where E/T is aligned with visible τ decay products tosuppress W+jet events
• Finally reconstruct visible massN Mvis =
√
(E` + Eτ + E/T)2 − (p`x + pτ
x + E/xT )2 − (p`
y + pτy + E/
yT )2 − (p`
z + pτz )2
Visible Mass (GeV)0 50 100 150 200 250
Even
ts
1
10
210
0 50 100 150 200 250
1
10
210
ττ→M=160hττ→Z
QCDνµ→W
µµ→Zντ→W
ν lνl→WWtt
-1 Preliminary, 1.0 fb∅D
µe channel
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 12/46
Search for SUSY Higgs Bosons (3)
mvis (GeV)
-
• CDF (3 channels)N 2σ excess in τhτe and τhτµ channels
I mA ≈ 150 GeV, tanβ ≈ 50N No excess in τeτµ channel
• DØ (1 channel)N No excess in τhτµ channelN Expect results in τhτe and τeτµ channels
later this summer
100 150 200 250
10
1
100
0.1
mφ (GeV)
σ(pp
→φX
) x BR
(φ→
ττ)
(pb
)
95% CL upper limits
CDF Run II 1 fb-1
MSSM Higgs→ττ Search
Preliminary
Observed
Expected
1σ band
2σ band
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 13/47
Limits• Although there is excess seen by CDF, no evidence for Higgs production (yet)
N Set limits in the tan β–mA–plane
mA
(GeV/c2)
80
tan
β
100 120 140 160 180 2000
20
40
60
80
100
no mixing
LEP 2mh
max
˜–µ = -200 GeV, M
2 = 200 GeV, m
g = 0.8 M
SUSY
MSUSY
= 1 TeV, Xt = √6 M
SUSY (m
hmax), X
t = 0 (no-mixing)
CDFµ<0
expected
observed
no mixing
CDF Run II 1 fb-1
MSSM φ→ττ Search
Preliminary
mhmax
• What to expect in the futureN More data, more channels, combination with bh → bbb result
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 14/47
Search for Charginos and Neutralinos
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 15/47
Search for Charginos and Neutralinos• Associated production of Charginos and Neutralinos
N Via W boson or Squark exchange• Decay of Chargino
N W bosons and lightest NeutralinoN Slepton and neutrino
• Decay of NeutralinoN Z bosons and lightest NeutralinoN Slepton and lepton
qqqq χ 0
1~χ 0
1~
~W +
Z
W+
l
l+
−
l+
ν
l+
l+
ν
χ~ 01
~ 0χ 1χ~+
χ02
~χ0
2~
χ 01
~
χ+~ χ 01
~
~~l+l+
q
+l
• Final state consists of three charged leptons, two Neutralinos and a neutrino
(GeV)Tp0 10 20 30 40 50 60 70 80 90 100
arbi
trary
uni
ts
0
200
400
600
800
1000
1200
1400
1600
1Tp2Tp3Tp
• Trilepton channel is the golden mode for the search ofCharginos and NeutralinosN Signature: three charged leptons plus
missing transverse energy• Challenges
N Leptons have low transverse momentaN Small cross sections: σ×BR < 0.5 pb
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 16/47
Backgrounds and Selection• Main background is QCD multijet production
N Very large cross section• Require two isolated leptons
N Main contributions from Z/γ production
)2) (GeV/c2,l1Invariant mass (l20 40 60 80 100 120 140 160 180
No. o
f eve
nts
-110
1
10
210
310
410
)2) (GeV/c2,l1Invariant mass (l20 40 60 80 100 120 140 160 180
No. o
f eve
nts
-110
1
10
210
310
410
ee+l+X→ ±1χ0
2χSearch for DataFake leptonDrell-Yantt
DibosonsγZ + γW +
SUSY
CDF Run II Preliminary-1 L dt ~ 1 fb∫
0.1 1 1010 −7
10 −5
10 −3
10 −1
10 1
10 3
10 5
10 7
10 109 9
10 −7
10 −5
10 −3
10 −1
10 1
10 3
10
10 5
7
σjet(E Tjet > √s/4)
LHCTevatron
σt
σZ
σjet(E Tjet > 100 GeV)
σHiggs (M H = 150 GeV)
σW
σjet(E Tjet > √s/20)
σb
σtot
σ (
nb)
√s (TeV)
Proton−(Anti−)Proton Wirkungsquerschnitte
SUSY
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 17/47
Backgrounds and Selection• Main background is QCD multijet production
N Very large cross section• Require two isolated leptons
N Main contributions from Z/γ production• Further possibilities to suppress background
N Require a third lepton or trackN Leptons must have same chargeN Diboson production main contributor
Trans. Mass (3rd Track,MET) (GeV)0 20 40 60 80 100 120 140
-210
-110
1
10D0 RunII Preliminary,1.1fb-1 data
ττ →Z QCD fakes W W
ν l→W µ e→tt
, eeµµ →Z WZ/ZZ SUSY point (131.232)
D0 RunII Preliminary,1.1fb-1
0.1 1 1010 −7
10 −5
10 −3
10 −1
10 1
10 3
10 5
10 7
10 109 9
10 −7
10 −5
10 −3
10 −1
10 1
10 3
10
10 5
7
σjet(E Tjet > √s/4)
LHCTevatron
σt
σZ
σjet(E Tjet > 100 GeV)
σHiggs (M H = 150 GeV)
σW
σjet(E Tjet > √s/20)
σb
σtot
σ (
nb)
√s (TeV)
Proton−(Anti−)Proton Wirkungsquerschnitte
SUSY
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 18/47
Backgrounds and Selection• Main background is QCD multijet production
N Very large cross section• Require two isolated leptons
N Main contributions from Z/γ production• Further possibilities to suppress background
N Require a third lepton or trackN Leptons must have same chargeN Diboson production main contributor
• Three different selection criteriaN Three identified leptonsN Two leptons plus additional track
I Higher efficiency, but slightlymore background
N Likesign selectionI Sensitive in regions with low pT third
lepton0.1 1 10
10 −7
10 −5
10 −3
10 −1
10 1
10 3
10 5
10 7
10 109 9
10 −7
10 −5
10 −3
10 −1
10 1
10 3
10
10 5
7
σjet(E Tjet > √s/4)
LHCTevatron
σt
σZ
σjet(E Tjet > 100 GeV)
σHiggs (M H = 150 GeV)
σW
σjet(E Tjet > √s/20)
σb
σtot
σ (
nb)
√s (TeV)
Proton−(Anti−)Proton Wirkungsquerschnitte
SUSY
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 19/46
Selection with Two Leptons
• PreselectionN Two good reconstructed leptons
• Anti–Z/γ∗ → ee, Z/γ∗ → µµ cutsN Small invariant massN Not back–to–back leptons
χ
χν
Lepton 1
Lepton 2
Lepton 3
Lepton 1
Lepton 2Jet 1
missing ET
missing ET
• Significant missing transverse energy
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
-310
-210
-110
1
10
210
310
410
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
-310
-210
-110
1
10
210
310
410
Data mumu→Z
QCD tautau→Z mu nu →W
mumu→Y(1s) W gammastarZZ 4l tt 2l 2b WW 2l + 2nuWZ 3l + nuZ bbW bbSUSY
Delta phi electrons, Stack_05
)µ, µ (φ ∆
-1DØ Preliminary, 1fb
(GeV)TMissing E0 20 40 60 80 100 120
No. o
f eve
nts
1
10
210
(GeV)TMissing E0 20 40 60 80 100 120
No. o
f eve
nts
1
10
210+l+Xµ e→ ±
1χ02χSearch for Data
Fake leptonDrell-Yan
tt Dibosons
γZ + γW +
SUSY
CDF Run II Preliminary-1 L dt ~ 1 fb∫
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 20/46
Cuts using E/T
• E/T related cutsN Cut on E/T itselfN Transverse mass cut: mT =
√
pT · E/T · (1 − cos∆Φ(e, E/T))
I Rejects events with mismeasured lepton energies
BackgroundSignal
true pT
true pT
reco pT
missing ET
T reco psmall angle
reco pT
T reco p true pT
true pT
missing ET
large angle
0 10 20 30 40 50 60 70 80 90 100
-310
-210
-110
1
10
210
310
410
0 10 20 30 40 50 60 70 80 90 100
-310
-210
-110
1
10
210
310
410
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
) [GeV]2
, Mtr1
min(MtrEv
ents
/ 1
GeV -1DØ RunII Preliminary 1.1 fb
N Significance of E/T: Sig(E/T) = E/Tr
P
jetsσ2(Ejet
T ||E/T)
I Only defined for events with jetsI Rejects events with mismeasured jet energies
Lepton 1
Lepton 2Jet 1
missing ET0 20 40 60 80 100 120 140 160 180 200
-310
-210
-110
1
10
210
310
410
0 20 40 60 80 100 120 140 160 180 200
-310
-210
-110
1
10
210
310
410
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
)TESig(
Even
ts
-1DØ RunII Preliminary 1.1 fb
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 21/46
Cuts using E/T
• E/T related cutsN Cut on E/T itself
N Transverse mass cut: mT =√
pT · E/T · (1 − cos∆Φ(e, E/T))
I Rejects events with mismeasured lepton energies
BackgroundSignal
true pT
true pT
reco pT
missing ET
T reco psmall angle
reco pT
T reco p true pT
true pT
missing ET
large angle
0 10 20 30 40 50 60 70 80 90 100
-310
-210
-110
1
10
210
310
410
0 10 20 30 40 50 60 70 80 90 100
-310
-210
-110
1
10
210
310
410
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
) [GeV]2
, Mtr1
min(MtrEv
ents
/ 1
GeV -1DØ RunII Preliminary 1.1 fb
N Significance of E/T: Sig(E/T) = E/Tr
P
jetsσ2(Ejet
T ||E/T)
I Only defined for events with jetsI Rejects events with mismeasured jet energies
Lepton 1
Lepton 2Jet 1
missing ET0 20 40 60 80 100 120 140 160 180 200
-310
-210
-110
1
10
210
310
410
0 20 40 60 80 100 120 140 160 180 200
-310
-210
-110
1
10
210
310
410
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
)TESig(
Even
ts
-1DØ RunII Preliminary 1.1 fb
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 21/46
Third Track Selection• Select high quality track to account for the third lepton
N Track must be isolated in tracker and calorimeterI Efficient for electrons, muons and taus, suppresses tracks in jets
N Use hollow cone for isolationI Also efficient for (3 prong) tau decays
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(1 prong)TauElectron Muon Tau
(3 prong)
Signal Background
Jet
0 10 20 30 40 50 60 70 80 90 100
-310
-210
-110
1
10
210
0 10 20 30 40 50 60 70 80 90 100
-310
-210
-110
1
10
210
Data ee→Z tautau→Z e nu →W
ee→Y tt 2l 2b WW 2l + 2nuWZ 3l + nuZZ 4l or 2l + 2nuQCDSUSY
Transverse momentum [GeV]
Even
ts /
1 G
eV -1DØ RunII Preliminary 1.1 fb
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 22/46
Result• No evidence for Charginos and Neutralinos found
N Set limits on the production cross section times branching ratioN Translate these limits in mass limits
Chargino Mass (GeV)100 110 120 130 140 150 160
BR(
3l) (
pb)
×) 20 χ∼ 1± χ∼ (σ
0
0.1
0.2
0.3
0.4
0.5
)20χ∼)>M(l~); M(
10χ∼2M(≈)
20χ∼M(≈)
1±χ∼M(
>0, no slepton mixingµ=3, βtan
-1DØ Run II Preliminary, 0.9-1.7 fb
LEP
3l-maxheavy-squarks
0large-m
Observed LimitExpected Limit
Chargino Mass (GeV)100 110 120 130 140 150 160
BR(
3l) (
pb)
×) 20 χ∼ 1± χ∼ (σ
0
0.1
0.2
0.3
0.4
0.5
• Cross section limit: σ×BR∼0.06 pb• 3`–max scenario (m ˜
R& mχ±
1
)N mχ±
1
> 145 GeV
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
100 110 120 130 140 150 160Chargino Mass (GeV/c2)
σ(χ∼
0 2χ∼± 1)×
BR(3
lept
ons)
(pb)
σNLO×BRσNLO×BR Uncertainty95% CL Upper Limit: observed95% CL Upper Limit: expectedExpected Limit ± 2σExpected Limit ± 1σ
CDF Run II Preliminary: 700-1000 pb-1MSSM: tanβ=3, µ>0, M(χ
∼02)∼M(χ
∼±1)∼2M(χ
∼01); no slepton mixing
Excludedby LEP
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
• Cross section limit: σ×BR∼0.2 pb• mSUGRA model without ˜–mixing
N mχ±
1
> 130 GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 23/46
Search for Squarks and Gluinos
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 24/46
Search for Squarks and Gluinos
• Squarks and Gluinos can be producedvia strong interactionN Production depends on the masses
of the Squarks and GluinosI Either gg, qg or qq
N Decays of Squarks and GluinosI Squarks: q → qχ0
I Gluinos: g → qqχ0
⇒ Three different analysis scenarios1 qq: 2 jets + E/T (Dijet analysis)2 qg,qq: 3 jets + E/T (3–jet analysis)3 gg: 4 jets + E/T (Gluino analysis)
m( ) m( )
g~m( )
q~m
( ) ~>>q~ gm( ) m( )
=m( )
q~
g~
m( )
m( )>> q~g~m( )
~~
Gluino Mass
Squa
rk M
ass
~~
qg production dominantFinal state: 3 jets + E
~qq production dominantFinal state: 2 jets + E~
~ ~g q
gg production dominantFinal state: 4 jets + E~ ~
T
T
T
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 25/46
Squark and Gluino Selection• Common selection for all three analyses
N 2 acoplanar jets and large E/TI 1 or 2 additional jets (3–jet, Gluino analysis)
N Reject events with electrons or muonsI Suppress W and Z events
N Veto on events where E/T is aligned with jetsI Reject events with mismeasured jets
,any jet) (degrees)TE(min
φ∆0 20 40 60 80 100 120 140 160 180
Even
ts /
5
0
50
100
150
200
250
300
0 20 40 60 80 100 120 140 160 1800
50
100
150
200
250
300
DØ PreliminaryData
+ jetsν l→W + jetsνν →Z
ttWW,WZ,ZZ
+ jets-l+ l→Zsingle-tSignal
Neutralino
Missing E
Neutralino
T
Jet Jet
⇐ Signal configuration
QCD background ⇒
Jet 1
Jet 2missing ET
reco jet pT
reco jet pT
true jet pT
true jet pT
• At the end cuts on E/T and HT are optimized for every selection
(GeV)TE0 50 100 150 200 250 300 350 400 450 500
Even
ts /
20
1
10
210
310
410
0 50 100 150 200 250 300 350 400 450 500
1
10
210
310
410DØ Preliminary
Data + jetsν l→W + jetsνν →Z
ttWW,WZ,ZZ
+ jets-l+ l→Zsingle-tSignal ⇐ E/T distribution
HT distribution ⇒
[GeV]T H200 300 400 500 600 700 800 900
Eve
nts/
40 G
eV
-110
1
10
210
310
[GeV]T H200 300 400 500 600 700 800 900
Eve
nts/
40 G
eV
-110
1
10
210
310)-1Data (Lum = 1.1 fb
QCD DiBoson
)+jets ν W(e )+jets ν µ W()+jets ν τ W(
Z(e e)+jets )+jets µ µ Z(
)+jets τ τ Z()+jets ν ν Z(
t t
CDF Run II Preliminary
• Results from DØ based on 1 fb−1 of data
Selection Signal Efficiency (%) Data BackgroundDijet 7.05 ± 0.39+0.96
−0.88 5 7.47 ± 1.06+1.32−1.02
3–Jet 6.66 ± 0.37+1.11−1.01 6 6.10 ± 0.37+1.26
−1.16
Gluino 5.74 ± 0.35+0.81−0.72 34 33.35 ± 0.81+5.56
−4.92
• No evidence found for production of Squarks and Gluinos at Tevatron
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 26/47
Squark and Gluino Selection• Common selection for all three analyses
N 2 acoplanar jets and large E/TI 1 or 2 additional jets (3–jet, Gluino analysis)
N Reject events with electrons or muonsI Suppress W and Z events
N Veto on events where E/T is aligned with jetsI Reject events with mismeasured jets
,any jet) (degrees)TE(min
φ∆0 20 40 60 80 100 120 140 160 180
Even
ts /
5
0
50
100
150
200
250
300
0 20 40 60 80 100 120 140 160 1800
50
100
150
200
250
300
DØ PreliminaryData
+ jetsν l→W + jetsνν →Z
ttWW,WZ,ZZ
+ jets-l+ l→Zsingle-tSignal
Neutralino
Missing E
Neutralino
T
Jet Jet
⇐ Signal configuration
QCD background ⇒
Jet 1
Jet 2missing ET
reco jet pT
reco jet pT
true jet pT
true jet pT
• At the end cuts on E/T and HT are optimized for every selection
(GeV)TE0 50 100 150 200 250 300 350 400 450 500
Even
ts /
20
1
10
210
310
410
0 50 100 150 200 250 300 350 400 450 500
1
10
210
310
410DØ Preliminary
Data + jetsν l→W + jetsνν →Z
ttWW,WZ,ZZ
+ jets-l+ l→Zsingle-tSignal ⇐ E/T distribution
HT distribution ⇒
[GeV]T H200 300 400 500 600 700 800 900
Eve
nts/
40 G
eV
-110
1
10
210
310
[GeV]T H200 300 400 500 600 700 800 900
Eve
nts/
40 G
eV
-110
1
10
210
310)-1Data (Lum = 1.1 fb
QCD DiBoson
)+jets ν W(e )+jets ν µ W()+jets ν τ W(
Z(e e)+jets )+jets µ µ Z(
)+jets τ τ Z()+jets ν ν Z(
t t
CDF Run II Preliminary
• Results from DØ based on 1 fb−1 of data
Selection Signal Efficiency (%) Data BackgroundDijet 7.05 ± 0.39+0.96
−0.88 5 7.47 ± 1.06+1.32−1.02
3–Jet 6.66 ± 0.37+1.11−1.01 6 6.10 ± 0.37+1.26
−1.16
Gluino 5.74 ± 0.35+0.81−0.72 34 33.35 ± 0.81+5.56
−4.92
• No evidence found for production of Squarks and Gluinos at Tevatron
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 26/47
Event DisplaysHighest E/T events
Dijet analysis• E/T = 368 GeV• HT = 489 GeV• p
jet1
T = 282 GeV, pjet
2
T = 174 GeVp
jet3
T = 33 GeV
Gluino analysis• E/T = 321 GeV• HT = 464 GeV• p
jet1
T = 254 GeV, pjet
2
T = 77 GeV,p
jet3
T = 67 GeV, pjet
4
T = 66 GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 27/46
Results• The analyses are optimized for three benchmark scenarios
N Vary m0 and m1/2, other parameters constant: A0 = 0, µ < 0 and tan β = 3/5
Gluino Mass (GeV)0 100 200 300 400 500 600
Squa
rk M
ass
(GeV
)
0
100
200
300
400
500
600-1DØ Preliminary, 0.96 fb
<0µ=0, 0
=3, Aβtan
UA1
UA2
LEP
CDF
IB
DØ IA
DØ IB
no mSUGRA
solution
CDF
II
)2 (GeV/cg~M0 100 200 300 400 500 600
)2 (G
eV/c
q~M
0
100
200
300
400
500
600observed 95% C.L.
σobserved +/-1obs. ISR/FSR syst. incl.expected 95% C.L.
no mSUGRAsolution
)10
χ∼) < m(q~m(LEP 1 + 2
UA1
UA2
FNAL Run I
g~
= Mq~M
CDF Run II Preliminary -1L=1.1 fb
3-jets inclusive<0µ=5, β=0, tan0A
)2 (GeV/cg~M0 100 200 300 400 500 600
)2 (G
eV/c
q~M
0
100
200
300
400
500
600
• Mass limitsN Squarks: 391 (375) GeV Gluinos: 309 (289) GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 28/46
Search for long lived particles
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 29/46
Search for CHAMPS• Search for long lived Charged Massive Particles
N Particles do not decay inside the detectorN Highly ionizing and penetrating
• Signature in the detector: “slow muon”N Particle penetrates cal and muon systemN Use time–of–flight system to measure β
• Signal expected at high massN Background sits at low mass
)2 (GeV/cTOF
βMass from track momentum and 0 50 100 150 200 250 300
Even
ts /
10 G
eV
-110
1
10
210
)-1CDF Run II Preliminary (1.0 fb
> 40 GeVT
, pµCentral
Background Prediction Stop2220 GeV/c
)2Stop Mass (GeV/c100 120 140 160 180 200 220 240 260
Cros
s se
ctio
n (p
b)
-210
-110
1
10 Stop Production cross section (NLO)µCross section limit from central
-1 = 1.03 fbL dt ∫
CDF Run II Preliminary • Main background componentsN Cosmic muons and instrumental
background• Interpreted in SUSY models with one
compactified extra dimensionN In these models Stop is the LSP
• Mass limit: mt > 250 GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 30/46
Search for Long lived Gluinos• Long lived Gluinos are predicted in several models
N For example split SUSY• Gluinos can stop inside the detector
N Can decay at random times ⇒ Not related to any beam crossingN Decay can also occur if no beam is in the machine
• Very hard to model trigger for these events• Need a good model for the alive time of the
detector
Gluino Mass (GeV)150 200 250 300 350 400 450 500 550 600
Cros
s Se
ctio
n Li
mit
(pb)
-110
1
-1, L=410 pbOD
100 hours18 hours<3 hours
• No evidence for stopped Gluinos
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 31/46
Indirect searches
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 33/47
Search for Bs → µµ
• New physics can also be observed indirectly• The decay Bs → µµ is a very good candidate
N Decay is a flavor changing neutral currentI In the SM it is forbidden at tree level
⇒ Small branching fraction:BR(Bs → µµ) = (3.4 ± 0.4) · 10−9
N Enhancement in SUSY models: ∼ (tan β)6
−W −µ
+µ+W
s
b
t υ l
−µ
+µ
dHs
b
• Blind analysis ⇒ Predict events in signal region from sidebandsN Good agreement between number of events predicted and observedN No observation ⇒ Upper limits on the branching fraction
]2) [GeV/c-µ +µInvariant mass (4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4
)2Ev
ents/
5 (M
eV/c
0
0.5
1
1.5
2
2.5Signal regionSideband 1
DØ Run IIb PreliminarySideband 2
• Current limitsN DØ (2 fb−1): BR(Bs → µµ) < 9.3 · 10−8
N CDF (0.78 fb−1): BR(Bs → µµ) < 1.0 · 10−7
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 33/46
Conclusion• Summary
N Tevatron, CDF and DØ are performing wellI Already collected more than 2.7 fb−1 of dataI Nearly factor three more than the data used in the results presented here
N SUSY searches probing new regions in phase spaceI New mass limits beyond LEP2 limits
• Tevatron will further probe Supersymmetry in so far uncovered territory
O. Buchmueller et al.,arXiv:0707.3447v1
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 35/47
– p. 2/2
– p. 3/2
BACKUP SLIDES
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 36/47
Search for Stop Quarks• Due to mixing in third generation, Stop can be light
N Can be pair produced at the Tevatron• If Stop is light enough it can only decay into cχ0
1
N The decays tχ01 and bχ±
1 are forbidden• Major background contributions are
N W+jets, Z+jets and multijet production• Selection strategy
N Select events with acoplanar dijetsN Reject events with isolated electrons, muons
or tracksN Require large E/T and H/T
N Apply heavy flavor tagging to reduce lightjet contributions from background
• Optimize selection for different mass points
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 37/47
Search for Stop Quarks (2)• Main background after final selection
N W(→ `ν) = jets and Z(→ νν) + jetsN Background varies between 57 and 82 events depending on Stop mass
• Signal efficienciesN Range from 0.1% to 5% depending on Stop and Neutralinos mass
• Data is in agreement with the SM expectation
• Mass limitsN Stop: mt > 160 GeVN Neutralino: mχ0
1> 75 GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 38/47
Search for GMSB
• In Gauge Mediated SUSY Breaking (GMSB) models the Gravitino G is the LSPN If the Chargino χ0
1 is the NLSP it decays to Gravitinos: χ01 → γG
N Final state consists of two photons and E/T due to escaping Gravitinos• Search for inclusive γγ+E/T events with 1.1 fb−1 of data
(GeV)T
Missing E0 20 40 60 80 100 120 140 160 180 200
N / 3
GeV
-110
1
10
210
310 dataγγ
γγW/Z+electron mis-IDjet mis-ID
=75 TeVΛSM + signal =90 TeVΛSM + signal
(GeV)T
Missing E0 20 40 60 80 100 120 140 160 180 200
N / 3
GeV
-110
1
10
210
310 -1 Preliminary 1.1 fb∅D• Major background components
N Events with true E/T
I W+jets/γ, tt
N Events with instrumental E/T
I Multijets and direct γγproduction, Z → ee
• Diphoton selection yields 2341 events
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 39/47
Search for GMSB (2)• Search for the signal in the high E/T region (for different energy scales Λ)
E/T Background Data Signal(GeV) true E/T fake E/T Total Λ = 75 TeV Λ = 90 TeV> 30 1.16 ± 0.14 9.62 ± 1.12 10.8 ± 1.1 16 28.3 ± 1.0 8.7 ± 0.3> 60 0.19 ± 0.07 1.44 ± 0.43 1.6 ± 0.4 3 18.1 ± 0.8 6.4 ± 0.3
(TeV)Λ70 75 80 85 90 95 100 105 110
(fb)
σ
10
210
[GeV]10χm
100 120 140
[GeV]1+χm
180 200 220 240 260
-1 Preliminary 1.1 fb∅D LO cross-sectionNLO cross-sectionexpected limit
observed limit • No evidence for a signal• Energy scale and mass limits
N Λ > 92 TeVN mχ±
1
> 231 GeV, mχ0
1> 126 GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 40/47
Search for GMSB (3)• Search for long lived Neutralinos
N In GMSB models pair production of Gauginos is dominantN Gauginos decay into the lightest Neutralino
I Final states consists of a delayed photon, jets and E/T
• Main selection criteriaN Select events with time delayed photonN Require large E/T
• Mass limit (depending on lifetime)N mχ0
1> 101 GeV for τ = 5 ns
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 41/47
Search for Stops in the Dilepton Channel• Search for scalar top quarks in final states with two leptons and two b–quarks
N t decays dominantly into b`ν if t → bχ±1 and t → bχ0
1 are forbidden• Main selection criteria
N Two isolated leptonsN At least two jets, highest pT jet must be tagged as b–jet (only µµ channel)N Significant E/T
N Other kinematic variables: invariant mass, scalar sum of all pT
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 42/47
Search for Stops in the Dilepton Channel (2)
Background Data Signaltt Diboson Total Point A Point B
ee 7.4 20.2 31.7 ± 2.7 34 26.0 ± 1.5 17.3 ± 0.6eµ 2.3 0 2.9 ± 0.4 1 3.1 ± 0.2 3.3 ± 0.4
• Good agreement of data and SM prediction
• Mass limits in mt–mν planeN Largest mt limit: mt > 186 GeV
(for mν = 71 GeV)N Largest mν limit: mν > 107 GeV
(for mt = 145 GeV)
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 43/47
Search for Sbottom Quarks• For high tan β the b–mass eigenstates have large separation
N Sbottom quarks might be light enough to be pair produced at the TevatronN Assume 100% branching fraction of b into bχ0
1
• Final state consists of two b–jets and E/T
• Event selectionN At least two high pT jets, one jet must be tagged as b–jetN Require significant E/TN Veto on isolated leptons
(GeV)T1st Leading Jet E0 50 100 150 200 250 300 350 400
Even
ts/1
0 G
eV
0
2
4
6
8
10
12
14
16
18
20
22
(GeV)T1st Leading Jet E0 50 100 150 200 250 300 350 400
Even
ts/1
0 G
eV
0
2
4
6
8
10
12
14
16
18
20
22
DataMis-TagQCD (HF)EWK+TopSignal
,2)=120 GeV/c1t~(M(
)2)=50 GeV/c10
χ∼M(
-1CDF Run II Preliminary, 295 pb
(GeV)TMissing E0 50 100 150 200 250
Even
ts/5
GeV
0
1
2
3
4
5
6
(GeV)TMissing E0 50 100 150 200 250
Even
ts/5
GeV
0
1
2
3
4
5
6
DataMis-TagQCD (HF)EWK+TopSignal
,2)=160 GeV/c1b~(M()2)=80 GeV/c1
0χ∼M(
-1CDF Run II Preliminary, 295 pb
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 44/47
Search for Sbottom Quarks (2)• Data is well described from SM prediction
Sbottom Mass (GeV)0 50 100 150 200
Sbottom Mass (GeV)0 50 100 150 200
Neut
ralin
o M
ass
(GeV
)
0
50
100expectedobserved
CDF Run I-188 pb
DØ Run II-1L = 310 pb
LEP=208 GeVs
)10χ
) = M
(b) +
M(
b~M(
)2) (GeV/c1b~M(0 20 40 60 80 100 120 140 160 180 200 220
)2) (
GeV
/c10 χ∼
M(
0
20
40
60
80
100
120ObservedExpected limit
Run 2∅DCDF Run 1LEP )10
χ∼
)=M(
b)+M
(
1b~M(
)-1CDF Run II Preliminary (295 pb
CDF Run2 : Theoretical uncertaintyincl. PDF, and renormalizationand factorization scale
Run2 : Theoretical uncertainty∅Dincl. renormalization andfactorization scale
• Mass limitsN DØ (310 pb−1): mb > 222 GeVN CDF (290 pb−1): mb > 195 GeV
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 45/47
Search for Stop Quarks• Search for scalar top admixture in tt events in the lepton+jets channel
N Stop quarks are pair producedN Decay channels
I t1 → bχ+1 → bWχ0
1
I t1 → bχ+1 → cχ0
1
N σ(t1t1) ≈ 0.1×σ(tt) for masses of 175 GeV• Start from a selection that is similar
to tt selectionN Main backgrounds for tt measure–
ments are W+jet and multijet eventsN tt events are of course the major
(irreducible) background for stopsearchI Use Likelihood to discriminate
top decays
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 46/47
Search for Stop Quarks (2)• Combine up to five variables in the Likelihood
mass[GeV]0 50 100 150 200 250 300
# of
ent
ries
00.020.040.060.08
0.10.120.140.160.18
0.2Hitfit reconstructed top 1 mass
StopTopW+jets
DØ PreliminaryHitfit reconstructed top 1 mass
top mass [GeV]0 50 100 150 200 250 300
# of
ent
ries
0
5
10
15
20
25
Hitfit reconstructed top 1 mass
top mass [GeV]0 50 100 150 200 250 300
# of
ent
ries
0
5
10
15
20
25
datastop x10(175/135)ttbarWbbWccWlpZ+jetssingletopdibosonQCD
-1871 pb
PreliminaryOD
Hitfit reconstructed top 1 mass
Likelihood0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
# of
ent
ries
0
5
10
15
20
25
30
35
40
Likelihood for stop 175/135
Likelihood0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
# of
ent
ries
0
5
10
15
20
25
30
35
40
datastop x10(175/135)ttbarWbbWccWlpZ+jetssingletopdibosonQCD
-1871 pb
PreliminaryOD
Likelihood for stop 175/135
• Events observed consistent with SM prediction• No evidence for stop quark admixture• Upper limits on stop quark production
N σ(t1t1) < 5.7–12.8 pb (at 95% CL)N Factor 7–12 above the MSSM prediction
SLAC Summer Institute, 08/02/2007 Marc Hohlfeld – p. 47/47