SUSY2001

1
Squark Gluino searches at D0

• 
  SUSY2001
• Andrei Nomerotski
  Fermilab/D0
• Squarks Gluinos in SUSY
• Run I results
• - jets MET
• - dileptons
• - stop sector
• New results
• Run 2 prospects

2
Squaks and Gluinos in SUSY

• Squarks are are scalar partners of quarks
• Gluinos are fermionic partners of gluons

3
Squaks and Gluinos in SUSY

• Squarks gluinos will be copiously
• produced at Tevatron if they are light
• Production x-sections does not depend
• on SUSY parameters

• Decays are strong function of SUSY
• parameter space
• Assume R parity conservation

4
Stop and sbottom quarks in SUSY

• Stop can be light because top is so heavy
  
• gt large and negative radiation
  corrections
• gt large splitting between
• Sbottom can be light if is large
  

consider decays
Goes via loop if
Is closed.
Or 4 body decay
5
Experimental signatures

• squarks gluinos
• classic MET 3 or more jets
• MET dileptons
• MET single lepton jets
• for Gauge Mediated SUSY
• MET photon jets
• MET photon bottom
• 3rd generation squarks
• MET 2 charm jets
• MET 2 bottom
• MET dileptons
• MET lepton bottom

6
D0 stop search
3 body decay
Signature electron muon MET Low
background, good sensitivity
7
Data Selection

• Preselection
• Electron Candidate Muon Candidate
• ETEM gt10 GeV, ?lt 3.3, Isolt0.3, pTgt7 GeV, ?lt
  2 ?2 lt 300
• Triggers
• Run 1 mu_ele_XXX, ele_jet_XXX, mu_jet_XXX
• Luminosity
• Run 1A 13.9 pb-1, Run 1B 94.4pb-1
• Total Luminosity for this run/triggers
  combination 108.3?5.7 pb-1

8
Backgrounds

• Standard Processes
• tt? e? X 0.40 pb
• Z0? ??- ? e? X 26.6 pb
• WW ? e? X 0.69 pb
• D-Y ? ?? - ? e? X 5.5 pb
• Fakes (jets passing the electron or muon ID cuts)
• f(jet ? ?) lt 10 -4 (neglected)
• Fake rate for electrons 2-3 10 -4
• estimated from Data (92-93 Top paper)

9
Data/Background/Signal
For signal simulated at mstop 120 GeV m n
60 GeV
With E_Te gt 15 GeV E_Tmu
gt 15 GeV E_Tmiss gt 15 GeV

• Expected sTop 18.5 evts
• SM background 28.5 evts
• Data 30 evts
• for 108 pb-1
• Good agreement data/MC
• No signal
• S/B 1/2 gt more cuts

10
Event Selection

• 1 electron (ET(e)gt15 GeV with ?lt2.5 (1.1-1.5
  excluded) )
• 1 muon (pT(?)gt15 GeV avec ?lt1.7)
• ET gt15 GeV

11
Data/Bckgd/Signal after All Cuts
mstop 120 GeV m snu 60 GeV
E_Te, mu gt 15 GeV E_Te, mu gt 15 GeV E_Tmiss gt
15 GeV he hm lt 2 15lt Dfem lt 165

• sTop 13.9 evt
• bkg 13.4 evt
• data 11 evt
• S/B 1

12
Signal Efficiency

• 1) Number of expected Signal events
• 2) Signal Efficiency
• Ex at 120,60 Gev for m_stop,m_snu
• N_gene e-mu
  e-mu-Etmiss cuts BR(2/9) MC corr.
• of events 18956 5309
  4842 3585
• partial eff. 100 28
  91.2 74 22.2 66
• total eff. 100 28
  25.5 19 4.2 2.8
• 1)
• 2)

13
Systematic Errors
Signal
Production cross-section renormalisation /
factorisation scale
7.5
PDFs uncertainties
5
Gluon radiation
(ISR,FSR) 3, 3 MC
correction

11.5 Event Selection

6
Total

16.6
Background
Error on the inclusive e - mu E_Tmiss
sample
7.4 From acceptance
corrections, multiple interaction, trigger/id
errors, uncertainties on the production
cross-section
Event Selection

6 Total


9.5
Luminosity

5.3
14
CDF/D0 Results Comparison

• CDF analysis
• 1 electron or 1 muon
• (E_T gt 10 GeV)
• 2 jets (gt12 and 8 GeV)
• E_Tmiss (gt 25 GeV)
• Eff 5.7 81 evts seen,
• 87.3 /-8.8 expected
• DO analysis
• 1 electron 1 muon
• (E_T gt 15 GeV)
• No Jet requirements
• E_Tmiss (gt 15 GeV)
• Eff 3.4 11 evts seen,
• 13.4 /-1.5 expected
• Signal eff. given at m_stop, m_snu 120, 40
  GeV

15
3 Body Cross-Section Limits
16
Exclusion Contour (3 Body)
Excluded Region, for m-sTop Up to 140 GeV
for m-snu 43 GeV Up to 130 GeV for m-snu 85 GeV
17
Scalar top quark
Mass reach in various stop search channels
for Run II
18
Conclusions

• Excellent Run I results continue to come
• Impressive reach in SUSY in Run II