CDF

D0

Supersymmetry at the Tevatron

R. DeminaUniversity of Rochester

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20 years of SUSY

And still, no one is prettier…“We like the way she walks, We like the way

she talks” but…God damn it, where is she?

Supersymmetry:Fermion-Boson symmetry.

If R-parity is conserved the lightest neutralino

is stable – an excellent dark matter candidate.

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Outline

• Data sets• Tri-leptons• Jets and missing energy

– Straight up– With heavy flavor

• Gauge Mediated SUSY Breaking – photons with missing energy

• Long-lived particles• Conclusions

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Run II data taking

Presented analyses are based on pre-shutdown data<200pb-1

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SUSY production at Tevatron

• 200 pb-1

– 1013collisions– 80 chargino/ neutralino

(3l) events produced– 800 squark/gluino events

produced

• To control backgrounds searches based on “signatures”: 3 or more physics objects

TEl 3~~1

02

TEjetsqqgg ~~,~~

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Tri-leptons

• Chargino/neutralino production – three leptons and missing energy signature

• Main challenge - weak production low cross sections– LEP limits are very restrictive

• Need extremely well controlled backgrounds

3e 2e

3 2e

ee(l) e(l)

• Leptonic branching are enhanced if sleptons are lighter than gauginos

(l ) – isolated track = e,

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ee+lepton

2 Electrons: EM cluster+track match• PT>12 (8) GeV• ||<1.1 (3.0)

1. Anti-Z– 15<Mee<60 GeV (ee)<2.8

2. Anti-W(e)+– >=1hit in silicon or tighter

electron likelihood

3. Anti tt– Veto jets with ET>80GeV

4. Anti-Drell Yan– Missing ET>20GeV (eMET)>0.4

Potential signal

175pb-1

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ee+lepton

5. Lepton = isolated track:– PT>3GeV

6. Etmiss x PT(track)>250GeV

(signal)=2-3%

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Tri-leptons

• Summary after all cuts:

Channel

Data Total SM background

e e l 1 0.270.42 0.02

e 1 2.490.37 0.18

e l 0 0.540.24 0.04

1 0.130.06 0.02

Add isolated track with PT>3 GeV

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Combined tri-leptons

• Run 1 cross section limit much improved• Soon will reach MSugra prediction (in the best scenario

with low slepton masses)

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Jets and missing energy

• Squarks and gluions: • Strong production

– larger cross section, – but really large instrumental

backgrounds (2 orders of magnitude over SM processes)

•4 events left 2.67 expected from SM sources (Z/W production)•17.1 event expected for M0=25,M1/2=100GeV

85 pb-1

2 jets ET>60 (50) GeV30<(jet,MET)<165o

Final cuts:Missing ET>175 GeV

HT>275 GeV

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Squarks and gluinos

• M0=25GeV; A0=0; tan=3; <0

M(gluino)>333GeVRun 1 – 310 GeV

M(squark)>292GeV

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B-jets and missing energy

• High tan() scenario under study: sbottom is lighter than other squarks and gluino

•4b-jets+missing energy

•>=3jets (ET>10 GeV)•Missing ET>35 GeV

•1 b-tag– 5.6+-1.4 events SM predicted - 4 observed

•2 b-tags –0.5+-0.1 events SM predicted - 1 observed

01~~

;~~~~ bbbbbbgg

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Met

• Gauge mediated SUSY breaking at scale

• Gravitino – LSP• NLSP (neutralino) LSP• Dominant SUSY mode:

185 pb-1

Signature – 2 photons, missing energyPT(photon)>20 GeV in ||<1.1

1 event survived 2.5±0.5 expected from SM

Missing ET>40 GeV

GeVm

GeVm

TeV

180)(

105)(

8.78

1

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Long Live Particles!

• LSP – charged particle, or• NLSP – charged particle (e.g. stop) with long decay time• Signature – isolated track of a rather slow particle• Use TOF system (CDF)• BG prediction of 2.9 +/- 0.7 (stat) +/- 3.1 (sys), with 7 observed

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Conclusions

• Tevatron detectors produce solid physics results based on datasets of up to 185 pb-1

• SUSY limits extended beyond run 1:– In trilepton signature – Missing energy and jets– Missing energy and b-jets– GMSB in diphoton final state

• New system (TOF) used to search for long lived particles

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Personal remarks1

• By now the mass limits for SUSY partners of all particles with the exception of top quark exceed the masses of their SM partners

• This means that SUSY is badly broken everywhere with possible exception of top-sector

• In run 2 (with 2fb-1) Tevatron experiments will be able to probe stop masses all the way to top mass and above– Stop production xsection =~10% (top xsection) for the same mass

• Tevatron experiments will be able – Either discover SUSY– Or verify if SUSY is broken for all SM particles

1Not necessarily representing the views of CDF and DØ collaborations