Search for SUGRA at
Silke DuensingSUSY 2003, June 10 th
Interactions
p p
~1 TeV ~1 TeVu
d
u
u
u
d
SUGRA@Tevatron
p p
~1 TeV ~1 TeVu
d
u
u
u
d
Sparticles are produced in pairs
R-parity conservation: decay into the “partner” +LSP
LSP->missing energy, mET at Tevatron
Squark/gluino pair production
Jets + Missing ET is generic signature for squark/gluino production in SUGRA
Typical cross-sections (pb)
m [GeV]
Jets + Missing ET
Typical cross-sections (pb)
m [GeV]
– Offline: • leading jet has pT > 100 GeV , leading two jets are central
– insures full efficiency of trigger
• mET calculated by adding all calorimeter towers with E>200 MeV
– Used are (the first) ~ 4 pb-1
• Selection : >=2 jets + mET – Trigger:
• >=1 jet with pT > 65 GeV
Jets + Missing ET
• Selection : >=2 jets + mET – Background (I) - Physics:
• PYTHIA-generated and fully simulated samples for physics backgrounds (real mET)
– Background (II) - Instrumental: • Ensure good quality of data• Require ||(mET, jet1,2)>0.15
– reject events where mET results from mismeasured Jet pT
• fit to low mET region to estimate QCD background
– mismeasured mET
g~
Fit interval 40-65 GeV
mET
(GeV)
QCD Bkg.
Total Bkg
Data 95%CL (pb)
≥ 70 17.48.4 18.48.4 7 4.2
≥ 80 8.55.3 9.5 5.3 6 3.8
≥ 90 4.23.2 5.1 3.2 4 3.1
≥ 100 2.01.8 2.7 1.8 3 2.7
Jets + Missing ET
Fit interval 40-65 GeV
• Error is sum of:– Statistical error of QCD bkg
• From error of fit parameters
– Systematic error of QCD bkg• From different fit ranges
– (much smaller) statistics of MC sample of physics background
• Neutralinos/charginos– trilepton channel
• Electron-muon channel– Low SM background
WW, ttbar, Z/WW, ttbar, Z/** -> ->
– gain compared to Run I for DØ:improved particle identification
pp ˜ i˜ j
, ˜ i0 ˜ j
, ˜ i0 ˜ j
0
Final States with Leptons
– Provides model independent limit on NP cross section
• require pT >15 GeV for both leptons (e/)
• physics background from Monte Carlo
• Instrumental background (fake rates) from data
• Quote cross-section limits as function of mET
Njet
mET
PT
einclusive search
e inclusive
~30 pb-1
Process Size
ZeWW ett e jj
5.6 ± 0.4
1.0 ± 0.1
0.02 ± 0.01
QCD + W+jets
3.01 ± 2.7
All 9.6 ± 2.7
Data 13
No jets ET > 15 GeVNo missing ET cut
Ø
mET DATA TOT BKG
> 0 13 9.6 2.7
> 5 10 7.4 2.2
> 10 7 4.6 1.6
> 15 6 3.0 1.3
> 20 3 2.3 1.1
> 25 3 1.9 1.0
> 30 2 1.6 0.8
> 40 0 1.4 0.7
> 45 0 1.1 0.5
100 fb
e - Limits on New Physics
Z dominates
Instrumental + WW
A(WWe
Chargino-Neutralino production
Tri-Lepton signature
Look at lee
Typical cross-sections (pb)
pp ˜ i˜ j
l1, 2, 3 ET X
2 points in Minimal2 points in Minimal
SUGRASUGRA
mm ≈≈2m2m
2m 2m ≈≈ 90 and 125 GeV90 and 125 GeV
~
01
~
01
~
Tri-lepton eel - pre-selection
1) At least 2 electrons (leading e p1) At least 2 electrons (leading e pTT>15 GeV >15 GeV 22ndnd e p e pTT>10 GeV) >10 GeV)
• Start from di-electron sample– understand trigger,
reconstruction, simulation
– verify determination of QCD fake background
• from data with inverted identification cuts
L = 42.0 pb-1
Tri-lepton eel-event selection
1) At least 2 electrons (leading e p1) At least 2 electrons (leading e pTT>15 GeV >15 GeV 22ndnd e p e pTT>10 GeV)>10 GeV)2)2) 10<Mee<70 GeV10<Mee<70 GeV
3) M3) MTT(e,mE(e,mETT)>15 GeV)>15 GeV
Tri-lepton eel- cross section limit
1) At least 2 electrons (leading e p1) At least 2 electrons (leading e pTT>15 GeV >15 GeV 22ndnd e p e pTT>10 GeV)>10 GeV)2) 10<Mee<70 GeV2) 10<Mee<70 GeV3) M3) MTT(e,mET)>15 GeV(e,mET)>15 GeV4) A third isolated track P4) A third isolated track PTT>5 GeV,|>5 GeV,||<3.0|<3.05) mET>15 GeV5) mET>15 GeV
typical selection efficiency for SUGRA 2-4%
Tri-lepton eel- cross section limit
1) At least 2 electrons (leading e p1) At least 2 electrons (leading e pTT>15 GeV >15 GeV 22ndnd e p e pTT>10 GeV)>10 GeV)2) 10<Mee<70 GeV2) 10<Mee<70 GeV3) M3) MTT(e,mET)>15 GeV(e,mET)>15 GeV4) A third isolated track P4) A third isolated track PTT>5 GeV,|>5 GeV,||<3.0|<3.05) mET>15 GeV5) mET>15 GeV
Cuts Sum Bkg Data
1) 3216 43 3132
2) 660 19 721
3) 96 8 123
4) 3.2 2.3 3
5) 0.0 1.4 0
x BR(3lepton) < 3.5 pb (95% CL)
……sensitivity still about factor of 7 away from extending excluded area in the parameter space
work in progress more data
Trilepton - eee mET event
Summary
• The Run II Era for searches has begun at DØ…– with a search for squarks/gluinos in Jet mET
– with a look at the e final state– with a trilepton - search containing electrons– So far - nothing beyond SM … but:
• all this will be updated with improved analyses, more channels and
more luminosity
-, PT = 45 GeV
e+, PT = 21 GeV
Missing ET = 33.5 GeV
Highest mET e event