cdf d0 supersymmetry at the tevatron r. demina university of rochester
Post on 19-Dec-2015
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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?
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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
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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
01
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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
d
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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