Update from the Photons + MET Group

1. Update from the Photons + MET Group Bruce Schumm UC Santa Cruz / SCIPP 11 March 2010

2. Background Info Since the SUSY/ETMiss Kick-Off, group has expanded a bit • Photon(s) + leptons (U. Michigan) • Constraining MET with data (U. Victoria) Plus prior Photons + MET (GMSB) group • DESY • Liverpool • Santa Cruz

3. 100 pb-1 Analyses Plan to have two baseline analyses, both GMSB-inspired, but concerned about model indpendence • Photon(s) plus MET • Subject of this presentation • Photons(s) plus leptons plus MET • Subject of later presentation by U Michigan

4. Photons plus MET Analysis We’ve been asked to think about • Baseline analysis • Possible hard/medium/soft scenario • What we can do with 10 pb-1 for summer conferences • Should support progress towards baseline 100 fb-1 analysis

5. Prior Studies 10 TeV / 200 pb-1 analysis with • Two photons and hard (160 GeV) MET cut (SCIPP) • Two photons and NJET cut; soft MET cut (DESY) e.g. Two Photon plus MET Result

6. New Thinking I: Production and Decay Scales Very roughly, two scales in problem • Production scale; heavier mass SUSY partner sets overall Pt scale of event • Decay scale: NLSP (0) sets scale for MET So: use two independent discriminating variables: • MET • HT (sum of ET of all objects in event, excluding MET) (But how independent are these really?) Production Decay

7. Baseline Analysis Proposal for Baseline Analysis • Require two photons (powerful background suppression) • Optimize cuts on MET and HT based on SPS8 trajectory (“analytic continuation” of GMSB1 to higher neutralino mass) Is underway and should be available soon.

8. Further Thinking II: Strong vs. Electroweak Production Initial production can be “strong” (two squarks/gluinos), “electroweak” (two gaugino), or mixed (one of each) • Still two photons from final decay, but signature quite different otherwise • Electroweak production dominates at 2 TeV (Tevatron)

9. Relative Percentages of the Types • Breakdowns for 10k points • Key: • Bin 0 = Weak • Bin 1 = Mixed • Bin 2 = Strong • About ~30% for Λ=90 TeV and ~10% Λ=120 TeV • Total production cross sections: • Λ=90 TeV : 0.51pb • Λ=100 TeV : 0.29 pb • Λ=110 TeV : 0.17 pb • Λ=120 TeV : 0.11 pb • Strong production has effective x-section of ~11 fb for Λ=120 7 TeV SPS8 rates Weak Strong

10. HT (sum of all ET except MET) vs. MET for full GMSB Sample

11. Optimal cut from MET analysis HT (sum of all ET except MET) vs. MET for “Strong” GMSB Sample

12. Optimal cut from MET analysis HT (sum of all ET except MET) vs. MET for “Weak” GMSB Sample

13. HT vs. MET for ttbar (e  background; require one SL decay)

14. HT vs. MET for QCD (JF17, 7 TeV MC09)

15. Baseline Analysis and Strong vs. Electroweak Producion Possibility: “Hard” analysis selects strong component with low backgrounds; “Soft” analysis sensitive to weak component but with higher backgrounds Note that production was almost exclusively weak at Tevatron But: weak-sensitive is more sophisticated analysis, perhaps not for first pass…? Proposal is to start with single, “hard” analysis.

16. 10 pb-1 Plans Unlikely to set new limits or discover GMSB SUSY (although strong channel is turning on, with clear signature)

17. Can we

18. Three Categories of Events • Seems to be three main categories of events classified by the sparticles coming out of the hard scatter • Weak production • Events with two: neutralinos, charginos, sleptons • Strong production • Events with two: sqaurks or gluinos • Mixed • Take one particle each from the two other categories • All three types of events have different characteristics • The ‘mixed’ type are basically intermediary of the two • Used 7 TeV SPS8 atlfastII sample

19. Effect of Photon Selection • Using the normal selection cuts for photons from past analysis (pt, isolation, etc) • Looking at weak versus strong, the weak production events seem to have greater proportion of events with 2 photons • Photons being lost because the strong prod. events are busier? • This plus all remaining plots are using Λ=90TeV

20. Photon PT Spectrum • Pt spectrum seems to have longer tail for the strong prod events • Seems to be a lot of the tail (plot needs better zoom) • Though current pt cuts (or slightly higher even) shouldn’t bias us against one or the other prod mechanism

21. Missing Et Spectrum • Definitely different shapes as we thought • Strong production is most of the tail • MET > 160 GeV cut - definitely cut out most of the weak production as was speculated

22. Number of Jets • Jets (sorta random): • Et > 20 GeV • Eta < 2.5 • Removed overlap with photons + electrons (deltaR cut) • Strong and weak production fairly different in terms of number of jets • Mixed typed are intermediary

23. “Meff” – no Missing Et • Sum of the et of the four highest et selected jets (that weren’t removed by overlap) • Double structure indeed comes from what we though it did • Strong production peak is already pretty small at Λ=90 for 7 TeV

24. “Meff” – w/ Missing Et • Shifts spectrum to the right • Strong production peak moves further – though that’s expected from the met distributions

25. HT • Everything added together – nothing surprising here

26. Summary • The strong and weak production mechanisms contribute as we had come to suspect • There is a third intermediary type of events, but its cross section is very small • Strong production component is already pretty small at Λ=90 for 7 TeV and drops off quite quickly from there • No real revelations here but at least it conforms what we had suspected was going on