SUSY Searches at theTevatron Peter Ratoff Lancaster University

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SUSY Searches at theTevatronPeter
RatoffLancaster University

• CDF, DØ and Tevatron Status
• New Run I SUSY Results
• First Glimpse of Run II Data

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The Fermilab Tevatron Collider
Chicago ?
p
?p
1.96 TeV
Booster
CDF
p
CDF
DØ
Tevatron
?p
?p source
Main Injector Recycler
DØ
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The Tevatron Run 2

• Tevatron upgrade
• Increased energy
• 1.8 TeV ? 1.96 TeV
• Increased luminosity
• 0.1 fb-1 ? 2 fb-1 ? 15 fb-1

• Detector upgrades
• Higher event rates and backgrounds (electronics,
  DAQ, trigger)
• Considerable expansion of the physics capabilities

• Physics opportunities
• Top
• Higgs
• New Phenomena
• Electroweak
• Beauty
• QCD

(Run 2a)
(Run 2b)
(Run 1)
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Run 2 in 2001/2002

• Considerable fraction (25) of collected
  luminosity devoted to detector commissioning.
• Significant progress in identification of
  physics objects e, m, jets, electromagnetic
  and jet energy scales, etc.

• Currently
• Finishing detector commissioning
• Completing triggers and improve DAQ
• Debugging, calibration, alignment
• Refining reconstruction algorithms
• Also looking forward to more
  integrated luminosity!!!

2002 Projected Integrated Luminosity
Integrated Luminosity (pb-1)
date
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The Upgraded DØ Detector

• Builds on the strengths of DØ
• Excellent calorimetry with faster readout
• Upgraded muon system for better m-ID

• Augments its tracker and trigger capabilities
• Inner tracking (silicon tracker, fiber tracker)
  with 2T superconducting solenoid
• Preshowers
• Pipelined 3-level trigger

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SUSY models

• SUSY is the best motivated scenario today for
  physics beyond the Standard Model
• doesnt contradict precise Electroweak data
• predicts light Higgs
• unification of gauge couplings at GUT scale
• essential element of String Theories
• provides explanation of Cold Dark Matter in the
  Universe!
• SUSY must be broken symmetry (otherwise MSUSY
  MSM)
• variety of models proposed - differ mainly in the
  nature of the messenger interactions
• most experimental results obtained in the context
  of the SUGRA and GMSB models

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SUSY Phenomenology at Hadron Colliders

• Physics environment and expected SUSY
  phenomenology are quite different at ee- and
  Hadron collider machines
• production expected to
  dominate
• squarks and gluinos are quite heavy ? decay via
  multi-step cascades

? many high PT jets and leptons plus large
missing transverse energy
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SUGRA models

• SUSY breaking is communicated to the physical
  sector by gravitational interactions
• GUT scale parameters RGEs ? low-scale
  phenomenology

M0 common scalar mass M1/2 common gaugino
mass A0 common trilinear coupling value tanb
ratio of the V.E.V. of the two Higgs
doublets sign of m Higgsino mass parameter
Highly constrained minimal SUGRA
? LSP is lightest neutralino - a neutral WIMP ?
excellent CDM candidate
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Single Electron Channel
Bckg Wjets, qcd multijet, tt Cuts Ete gt20
GeV,Etj gt14 GeV (? 4), no isolated
muons, MET gt 25 GeV L 92.7 pb-1
Sensitive to moderate m0 Complements dilepton and
JetsMET channels
Observed events 72 Expected background 80 10
DØ
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Single Electron Channel
A0 0, ? lt 0 , tan? 3
DØ
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Stop Search
Mixing between SUSY partners of tL and tR
is proportional to mtop ? large mixing ?lighter
SUSY state experimentally accessible
Assume sneutrino is LSP...
Final state 2 leptonsjetsMET
Drell-Yan, heavy quark pair prod., QCD fakes,
diboson production
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Stop Search (II)
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R-parity and its violation

• Discrete quantum number
• R (-1)3B2SL is 1 for SM particle,-1
  for sparticles
• R-parity violation can be introduced by
• WDL1 (1/2)lijkLiLjekl' ijkLiQjdkm'
  iLiHu
• WDB1 (1/2)l'' ijkuidjdk

Decay of the LSP Signatures maybe very
different Single sparticle production
possible Whither dark matter candidate
mSUGRA with RPV One RPV coupling dominates If
coupling large enough, resonant prod. Otherwise
pair production
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Decays of Stop Pair
Bilinear RPV (BRPV) stop ? ? b
Assuming RPV only in 3rd gen.
ttX tl b th b X Final state lepton
hadronic t 2 jets
Bckg W/Z jets, multijet, diboson Cuts
pTlepton gt10 GeV,th clustergt15,
MT(lepton,Met)lt35GeV/c2,HTgt70, ? 2jets
(ET gt15 GeV) L 106 pb-1
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Decays of Stop Pair
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Pair Production di-muon channel
LSP
Final state 2m 4jets
No missing ET

• Bckg Drell-Yan, tt, Z?mmjets, Z?tt?mm
• Cuts ptm gt15(10) GeV,ptjets gt15 GeV,
• St gt 150 GeV,Mmm gt5 GeV,Acoplanaritygt0.03
• Run1 L 77.5 4 pb-1

Events observed 0 Expected bckg. 0.18 0.03
0.02
DØ
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Pair Production di-muon channel
Run IIa projection
2 fb-1
DØ
? lt 0 , A0 0 , tan? 2
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Resonant Productiondi-muon channel
Large RPV coupling
_

?1o

u
? u d
Resonant prod. and decay of LSP via RPV Final
state 2m 2jets
?L
_
_
d
?
? u d
l -
d
W -
?l
Bckg tt, Z2jets, WWjets Cuts pTm gt20 GeV,
pTjets gt20 GeV, ST gt50 GeV, DR(m-jet) gt
0.5 L 94 5 pb-1
?
Observed events 5 Expected bckg 5.34 0.07
D?
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Resonant Productiondi-muon channel
Run IIa projection
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GMSB models

• Messenger sector couples to source of
  SUSY-breaking and physical sector of MSSM
  (through gauge interactions)
• The identity of the NLSP and its lifetime
  determine the phenomenology

c?
neutralino ???G
slepton l?lG
NLSP
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Light Gravitino Search
qq ? GGg qg ? GGq gg ? GGg
Final state METjet
Bckg mismeasured multi-jets W/Z
jets, tt, diboson Cuts MET gt50 GeV, removal of
events w/ isolated tracks, Df(MET,jet) gt90o,
Etlead-jet gt80 GeV, 0.1 lt EMFlead-jet lt 0.95 L
87 pb-1
CDF
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Light Gravitino Search (II)
For MET gt175 GeV Events observed 19 Expected
bckg 21.6
s(PTGG gt100GeV) lt 3.1pb ?F gt 217 GeV mG gt 1.1 x
10-5 eV/c2
CDF
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Di-photon Channel
Publ. 1998
Neutralino pair production
Final state 2 photons MET
Bckg multijet, direct photons,Wg,
Wjets, Z?ee Cuts ETg1 gt20 GeV,ETg2 gt12 GeV,
recon. Vertex, METgt25 GeV L 106.3 5.6
pb-1
D?
Events observed 2 Expected bckg 2.3 0.9
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Di-photon Channel (II)
D?
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Di-photon Channel (III)
Run II
D? Run II preliminary
10 pb-1
MET
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Summary

• Comprehensive searches for SUSY have been carried
  out at the Tevatron exploiting the Run I data to
  the fullest.
• A new era is beginning ...
• First preliminary Run II Results