searches for supersymmetry in multileptonic signatures at...

Searches for Searches for Supersymmetry Supersymmetry ininMultileptonic Multileptonic Signatures Signatures atat thethe

TevatronTevatron

Giulia Manca, University ofLiverpool

Workshop on Collider PhysicsArgonne National Laboratory,

8-12 May 2006

8th May 2006 Giulia Manca, University of Liverpool

1 OutlineOutline

• Supersymmetry• The Tevatron and its

experiments• Searching for SUSY• Conclusions• Outlook


2

Higgs

γ

G~

νe νµ ντ

e µ τ

Standard Model Particles Susy Particles

Quarks Leptons Force particles Squarks Sleptons SusyForce particles

Higgsino

Graviton GravitinoG~G

Higgs

SupersymmetrySupersymmetryExtends the Standard Model (SM) by predicting a new symmetry:spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)


3

Higgs

γ

G~

νe νµ ντ

e µ τ



Higgsino


Higgs



4

Higgs

γ

G~

νe νµ ντ

e µ τ



Higgsino


Higgs


χ±i

χ0i

~

4 neutralinos

2 charginos

~


5

Higgs

γ

G~

νe νµ ντ

e µ τ



Higgsino


Higgs


χ±i

χ0i

~

4 neutralinos

2 charginos

~

New Quantum Number R-Parity ⇒Lightest Sparticle (LSP) stable!

2sLBp 1)(R ++

!= +1 (SM particles)-1 (Susy particles)


6

Higgs

γ

G~

νe νµ ντ

e µ τ



Higgsino


Higgs


χ±i

χ0i

~

4 neutralinos

2 charginos

~

New Quantum Number R-Parity ⇒Lightest Sparticle (LSP) stable!

2sLBp 1)(R ++

!= +1 (SM particles)-1 (Susy particles)

broken


7 Limitations of Standard ModelLimitations of Standard Model

• Stabilisation of Higgs mass at EW scale• Couplings don’t unify at one scale• Dark Matter• Dark Energy• Neutrino masses• Gravity

H Hf

f

Standard Model




H Hf

f

Standard Model

SUSYSUSY

H Hf

f~

~




H Hf

f

Standard Model

SUSYSUSY

H Hf

f~

~

SUSY




H Hf

f

Standard Model

SUSYSUSY

H Hf

f~

~

SUSY

->->LSP LSP


12

Wide range of signatures: look for SuSy specific signatures or

excess in SM ones; examples:

SupersymmetrySupersymmetry: how ?: how ?

Large Missing Energy ET

Isolated leptons

Multijets

…and many more!!

χ0 χ±mSugra:

!

˜ q ˜ g

Rp : LSP


13





Isolated leptons

Multijets

…and many more!

χ0 χ±mSugra:

!

˜ q ˜ g

Rp : LSP

10101212

1010

101044

((fbfb))

Remember : VERY SMALL cross sections !!


14





Isolated leptons

Multijets

…and many more!

χ0 χ±mSugra:

!

˜ q ˜ g

Rp : LSP

10101212

1010

101044

((fbfb))

Remember : VERY SMALL cross sections !!


15

hep-ph/9311269EWEW

scalescale

GUTGUTscalescale

HiddenHiddenSectorSector

GRAVITY

RadiativeRadiativeEWSBEWSBCorrectionsCorrections

mSugramSugra: a working model: a working model• SUSY broken through gravity• Five parameters:

M0:common scalar mass atGUT scale

M1/2:common gaugino mass atGUT scale(i.e. M1(GUT)=M2(GUT)=M3(GUT)= M1/2 )

A0: common trilinear scalarinteraction at the GUT scale(Higgs-sfermionR-sfermionL)

tanβ: ratio of Higgs vacuumexpectation values

Sign(µ), the higgsino massparameter(µ2 determined by EWSB)

• Lightest supersymmetricparticle(LSP) is the χ0

1, stable


16 mSugra mSugra Existing LimitsExisting Limits : LEP: LEP•• LSP ~ 50 GeV/cLSP ~ 50 GeV/c22

•• Chargino > 103 GeV/c Chargino > 103 GeV/c22 (heavy sneutrinos); (heavy sneutrinos); •• Sleptons > Sleptons > 90-100 GeV/c90-100 GeV/c22 fo forr M( M(χχ00

11)<M()<M(llRR)); ;


17 The The TevatronTevatron

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 athigh efficiency

Mar01-Aug05750 pb-1






Mar01-Aug05750 pb-1






Mar01-Aug05750 pb-1

design goal

base goal

Still long way to go!

We arehere

Trileptons Trileptons at the at the TevatronTevatron


21

Higgsinos andgauginos mix

CHARGINOSNEUTRALINOS

pp

~

1

±!

~

0

2!

~

0

1!

~

0

1!

l

l

l

!

Low background Easy to trigger

LOW MODEL DEPENDENCE

Striking signature at Hadron Collider,THREE LEPTONS

In mSUGRA Rp conserved scenario,LARGE MISSING TRANSVERSEENERGY from the stable LSP+ν

The The trilepton trilepton signalsignal

GOLDEN SIGNAL AT THE TEVATRON !!


22 Chargino-Neutralino Chargino-Neutralino productionproduction……

~

0

2!

~

1

±!

W*

q

q

t-channelinterferes

destructively

q

'q

~

q

~

0

2!

~

1

±!

Low cross section (weakly produced)

100 150 200 250 300 350 400 450 50010-3

1

10-2

10-1

10 SUSY σ(pb) vs sparticlemass(GeV/c2) for√ s=1.96 TeV

T. Plehn, PROSPINO

χ02 χ±1

Tevatron sensitive to the BULKregion in WMAP data


23 ……and decayand decay

~

0

1!

~

0

2!

Z*l

l

~

0

2!

l

l~

l ~

0

1!

~

1

±!

!

l~

l ~

0

1!

~

1

±!

l

!~

! ~

0

1!

~

0

1!

~

1

±!

W*!

l

Leptons of 1st, 2nd

generation are preferredLeptons of 3rd generation

are preferred

Best reach Tevatronfor mass sleptons~mass

chargino

Char

gino

Dec

ayNeu

tralino

Dec

ay

Leading lepton

Next-To-Leading lepton

Third lepton


24

Missing Transverse Energy(MET)

e µ

µ

Finding SUSY at CDFFinding SUSY at CDFCENTRAL REGION

µ

Had Calorimeter

Muon system

Drift chamber

EmCalorimeter

η=0η=1

Recover loss inacceptance dueto cracks in thedetector if weaccept muonswith no hits in

the MuonChamber

Real MET Particles escaping detection (n)

Fake METMuon pT or jet ET mismeasurementAdditional interactionsCosmic ray muonsMismeasurement of the vertex


25 DO detectorDO detector

η=1.0η=0

η=2.0

η=3.0η=1.0

η=3.6

•Coverage to muons up to eta~2


26 The SM Control SamplesThe SM Control Samples

Lepton ID efficienciesTrigger efficienciesCalibrationLepton E and P ScaleLuminosity

Fake rates Jet Energy Scale


27 The tuning of the detector responseThe tuning of the detector response

Generatorlevel MEt

Raw Met afterreconstruction

Corrected Met

WithoutMinimum

bias

The final plot!

MC Z/γ∗−>ττ


28 Learning from Data: Z Learning from Data: Z ppTT

Events in the tailbackground toSUSY events!

Tune for parton KT and QCDscale in MC Generators

Trileptons Trileptons at CDFat CDF


30 How to investigate How to investigate thethe different scenarios? different scenarios?

Low tanβregion

High tanβregion

sensitiveto leptonic τ

decay

sensitiveto all τdecaysHigh pT Single Lepton710e±e±,e±µ±, µ±µ±

High pT Single LeptonOngoingeµ + e/µ

Low pT Dilepton312µµ + e/µ

Low pT DileptonOngoingeµ/µe + track

610

Ongoing

350

750

LUM

Low pT Dilepton

Low pT Dilepton

High pT Single Lepton


TRIGGER PATH

eµ + e/µ

ee + track

ee + e/µ

µl + e/µ

CHANNEL

Low tanβ scenario tanβ=5 , 38%

High tanβ scenario tanβ=20, 100%

Full acceptance

coverageHigh pT data-sample benchmark

to understand low pT data-sample


31 How to investigate How to investigate thethe different scenarios ? different scenarios ?

Low tanβregion

High tanβregion

sensitiveto leptonic τ

decay

sensitiveto all τdecaysHigh pT Single Lepton705e±e±,e±µ±, µ±µ±

High pT Single LeptonOngoingeµ + e/µ

Low pT Dilepton310µµ + e/µ

Low pT DileptonOngoingeµ/µe + track

610

Ongoing

350

750

LUM

Low pT Dilepton

Low pT Dilepton



TRIGGER PATH

eµ + e/µ

ee + track

ee + e/µ

µl + e/µ

CHANNEL

Low tanβ scenario tanβ=5 , 38%

High tanβ scenario tanβ=20, 100%

Full acceptance

coverageHigh pT data-sample benchmark

to understand low pT data-sample


32 Analysis StrategyAnalysis StrategyCOUNTING EXPERIMENTCOUNTING EXPERIMENT• Optimise selection criteria for best

signal/background value;• Apply selection criteria to the data

• Define the signal region and keep itblind

•Test agreement observed vs.expected number of events inorthogonal regions (“controlregions”)

•Look in the signal region andcount number of SUSY events !!Or set limit on the model


33

e

µ

µ

νµ

pp

BackgroundsBackgrounds

• HEAVY FLAVOUR PRODUCTION

Leptons mainly have low pT

Leptons are not isolated

MET due to neutrinos

• DRELL YAN PRODUCTION +additional lepton

Leptons have mainly high pT

Small MET

Low jet activity

• DIBOSON (WZ,ZZ) PRODUCTION

Leptons have high pT

Leptons are isolated and separated

MET due to neutrinos

irreducible backgrounde

e

µ

µ

γpp

The third leptonoriginates from γ

conversion

µ

µpp

π0The third lepton isa fake lepton

e

e

Backgrounds: Backgrounds: how to reduce themhow to reduce them??


34 Selection criteria:Selection criteria: Mass Mass

Dimuon events

Mll<76 GeV & Mll >106 GeV

Mll> 15 (20,25) GeV

min Mll < 60 GeV

(dielectron+track analysis)

Rejection of J/Ψ, Υ and Z

Dimuon Mass(GeV/c2)

SUSY

SUSY

SUSY

SUSY


35 ΔΦΔΦ( ( l,l ) , Jet Veto,) , Jet Veto, Missing EnergyMissing Energy

HT=∑jetETj

Jet ET > 20GeV

KinematicVariable

n. Jets <2

Trileptonanalyses

HT < 80GeV

Dielectron+ track

analysis

Kinematic Cut

Analysis

Rejection of DY and high jetmultiplicity processes

SUSY


36 Understanding of the DataUnderstanding of the DataEach 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

Invariant Mass 15 76 106

10

1

5

??

Z + fakeDY + γ

Diboson

M

ET

SIGNALREGION

Very good agreement between SM prediction and observed data

µµ-like signL=704 pb-1

L=704 pb-1

EWK low DY Zmass


37 Systematic uncertaintySystematic uncertainty

Major systematic uncertainties affecting themeasured number of events

ee+lepton (high-pt)

Signal

Lepton ID 5%

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%

Z->ee MC


38 Results !Results !Look at the “SIGNAL” region

01.01±0.070.78±0.15 µe +e/µ

11.61±0.220.64±0.18 µµ +e/µ

00.49±0.060.17±0.05ee + e/µ

00.17±0.040.13±0.03 µµ +e/µ (low-

pT)

0.36±0.27

3.18±0.33

ExampleSUSY

Signal

10.48±0.07ee+track

96.80±1.00e±e±,e±µ±, µ±µ±

Obs-erveddata

Totalpredicted

backgroundAnalysis


39 HighestHighest lepton-pt eventlepton-pt event

220 GeV/c2Mass OS1

12 GeV/c2Mass OS2

In the ee like-sign analysis, we observe one interesting event

e- : 103 GeV

MET : 25 GeV

γ : 15 GeV

e- : 107 GeVe+ : 5 GeV


40 LimitLimitNo SUSY :(•Combined all analyses toobtain a limit on the massof the chargino in mSugra-like scenariowith no slepton mixingslepton masses ~ neutralinomasses• Observed limit:

M(χ±1) ~ 127 GeV/c2

σxBR ~ 0.25 pb

• Sensitive up to massesM(χ±

1) ~ 140 GeV/c 2 σxBR ~ 0.2 pb

Better than LEP andTevatron Run I


41 LimitLimit

But : we are modeldependent !

In “standard” mSugraSensitive to charginomasses of ~ 116 GeV/c2

Not able to exclude thisparticular region ofparameter space withthese results …

Trileptons Trileptons at DOat DO


43 Chargino Chargino and and Neutralino Neutralino in 3in 3ll+E+ETT

In mSUGRA:3 leptons+ET

Luminosity ~350 pb-1

Use tau leptons

43.85±0.75SUM

10.64±0.38µ±µ±

00.58±0.14eτ+t

10.36±0.13µτ+t

21.75±0.57µµ+t

00.31±0.13eµ+t

00.21±0.12ee+t

OBSERVEDSM expectedSelection

M(eτ) (GeV/c2)

PRL 95,151805 (2005)

6 analyses:-2l(l=e,µ,τ)+isolated track or µ±µ±

− ET and topological cuts (Mll,Δφ, MT)


44 Chargino Neutralino Chargino Neutralino LimitsLimitsmSUGRA: M(χ±)≈M(χ0

2) ≈2M(χ01)

“3l-max”• M( l ) > M(χ0

2)• No slepton mixing

Limits : σxBR < 0.2 pb M(χ±

1)>116 GeV/c2

“Heavy Squarks”• M(χ±)≈M(χ0

2)≠3M(q)σxBR < 0.2 pbM(χ±

1)>128 GeV/c2

“Large m0”• M(l)>>M(χ02 ,χ±)

No sensitivity

~~

Analyses being updated with 1 fb-1

A0=0

~~ ~

~

~ ~ ~

~

~ ~~

~mSugra

optimisticscenario


45 Chargino Neutralino Chargino Neutralino LimitsLimitsmSUGRA: M(χ±)≈M(χ0

2) ≈2M(χ01)

“3l-max”• M( l ) > M(χ0

2)• No slepton mixing

Limits : σxBR < 0.2 pb M(χ±

1)>116 GeV/c2

“Heavy Squarks”• M(χ±)≈M(χ0

2)≠3M(q)σxBR < 0.2 pbM(χ±

1)>128 GeV/c2

“Large m0”• M(l)>>M(χ02 ,χ±)

No sensitivity

~~ A0=0

~~ ~

~

~ ~ ~

~

~ ~~

~mSugra

optimisticscenario

M(slep)>>M(neutralino)=> 2Bodies decay

region

3rd lepton too softOnly LS

analysessensitive

Neutralino decay invisible to neutrinos

3 Bodiesdecay region


46 Summary and Outlook:Summary and Outlook:Chargino Chargino and and Neutralino Neutralino in in mSugramSugra

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 Charginomasses up to ~250 GeV and σxBR ~ 0.05-0.01 pb !!

Ellis, Heinemeyer, Olive, Weiglein,

hep-ph\0411216

Favouredby EW

precisiondata

nownow


47 Susy Susy at the LHC !at the LHC !• Will generally be found

fast!• But SUSY comes in very

many flavours• Hints from the Tevatron

would help on searchpriorities, e.g. tanβ large:

3rd generationimportant(τ’s, b’s)

R-parity is violated No ET

GMSB models: Photons important

Split-SUSY: Stable charged

hadrons

Can setup triggersaccordingly

up to 2 TeV

up to 2.3 TeV

up to 2.8 TeV

Inclusive searchSTATISTICAL

reach only


48 Susy Susy at the LHC !at the LHC !• Will generally be found

fast!• But SUSY comes in very

many flavours• Hints from the Tevatron

would help on searchpriorities, e.g. tanβ large:

3rd generationimportant(τ’s, b’s)

R-parity is violated No ET

GMSB models: Photons important

Split-SUSY: Stable charged

hadrons

Can setup triggersaccordingly

up to 2 TeV

up to 2.3 TeV

up to 2.8 TeV

Inclusive searchSTATISTICAL

reach only


49 Production Cross-sections at the LHCProduction Cross-sections at the LHC

• In mSugra: squark-gluino

dominate (jets+metchannel)

• Direct productioncross-sections small But could be the only

way to observe SUSY ifquark-gluinos areheavy ! (“focus point”)

• In other regionstrileptons signalenhanced from squark-gluino cascade

χ02 χ±1

∼ ∼

T. Plehn, PROSPINO

σ(pb)

mass(GeV/c2)

3,000eventsin 3fb-1

300keventsin 3fb-1

SUSY σ(pb) vs sparticlemass(GeV/c2) for √ s=14 TeV

But also : 6x106 Zs, 2.4x106 t-antitop and

150,000 WZ !


50

Depends on:Observable:

Mass measurement at the LHCMass measurement at the LHC• Mass constraints• Invariant masses in

pairs Missing energy Kinematic edges

Limits depend on angles betweensparticle decays


51 Building on leptonsBuilding on leptons……

• Other possibilities with leptonsignatures in mSugra:Jets+MET+leptons -> mass of the

sparticles in the cascadeLike-sign dileptons -> still sensitive to

chargino-neutralino but also on gluino pairproduction ! (no jet veto)

R-parity violating scenarios


52 ConclusionsConclusions

• Chargino-neutralino are the goldendiscovery model at the Tevatron !

• Hints from the Tevatron can givedirections to the LHC

• At the LHC, chargino-neutralinoproduction crucial in study the propertiesof the new sparticles as their masses (butonly mSugra considered)

•• Exciting times to comeExciting times to come !!

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