1. Alan Barr Claire Gwenlan
Early SUSY discovery
Alan Barr Claire Gwenlan
How to best use early data
poor knowledge of multi-jet backgrounds
incomplete measurement of other backgrounds
limited detector understanding
We wont be able to find SUSY quickly in the “16 jets + 4 leptons” channel!
UK SUSY/Exotics
29th February 2007

2. Robust topologies LSP q squark q _ q _ q (and similar) LSP
BACKGROUND topology
(QCD)
SIGNAL topology

3. Small Njets + ET Select a small number of high PT jets
Large signal cross-section
Large control statistics
Relatively well known SM backgrounds
Relatively model independent
Does not rely on leptonic cascades
Does not rely on hadronic cascades
Use kinematics rather than “busyness of event” to pick out SUSY

4. Selection Keep it simple Two jets
ET (J1,2) > 150 GeV; |η1,2| < 2.5
Plot MT2
N.B. MT2 → 0 if:
ET → 0
ET parallel to either jet
Jet ET → 0
J.Phys.G29: ,2003,
Phys.Lett.B463:99-103,1999
Characteristics of backgrounds

5. Sample discrimination
1 fb-1 !
Full sim CSC AODs

6. Requirements Need: Do not need:
Some understanding of ET and energy scale
Degree needs to be determined
Some lepton ID
Estimate Z→νν from Z→ μμ
Some idea of ttbar background
Do not need:
B-tagging
Detailed understanding of jet resolution tails
Missing ET tails from multi-jets
To know much about loss of energy in cracks etc

7. Summary & next steps Idea Next:
Use simple topology for rapid discovery of light sparticles
2 jets + missing energy
Kinematic plot of MT2 gives good discrimination
Backgrounds under control
Excellent prospects if SUSY is light
Next:
QCD background from Alpgen (rather than Pythia)
Trigger
Backgrounds from control regions

8. Backups

9. Samples CSC 11.0.x AODs (Full Simulation)
SUSY (SU3): herwig (+jimmy)
Jets (J1-J8): >5017 pythia
ttbar (no all-hadronic): 5200 (+jimmy)
ttbar (only all-hadronic): 5204 (+jimmy)
Zee :
Zmumu:
Wenu: herwig (+jimmy)
More to add when R12 AODs available…