1. A measurement of the Ratio of Three over Two Jet Cross Sections with CMS at 7TeV 70 nb -1 P.Kokkas, I.Papadopoulos, C.Fountas, I.Evangelou, N.Manthos University of Ioannina, Greece Senior Editor for PAS : James Rohlf Boston University, USA

2. Data Analysis Data Samples (Runs 135149-135575) : /MinimumBias/Commissioning10-SD_JetMETTau-Jun14thSkim_v1/RECO (Runs 136066-137028) : /JetMETTau/Run2010A-Jun14thReReco_v2/RECO (Runs 138564-139790) : /JetMETTau/Run2010A-PromptReco-v4/RECO CMS official JSON files: Cert_132440-137028_7TeV_June14thReReco_Collisions10_JSON.txt Cert_132440-139790_7TeV_StreamExpress_Collisions10_JSON.txt Total Integ.Lumi = 76 nb -1 (Evaluated from crab) MC Samples PYTHIA: QCDDiJet_Ptxxtoxx/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO Madgraph: QCD_Ptxxtoxx-madgraph/Spring10-START3X_V26_S09-v1/GEN-SIM-RECO 2 On line Selection: Require BPTX Technical bit 0, to select events with consistent timing with LHC bunch crossing Select events with HLT Jet30U P.Kokkas, Univ. of Ioannina

3. Trigger Studies P.Kokkas, Univ. of Ioannina3 Runs 135149-137028 Runs 138564-139790 HLT Jet TriggerL1 PrerequisitePrescaled HLT Jet15UL1 SingleJet6UYes (for Runs>138564 ) HLT Jet30UL1 SingleJet20Uno HLT Jet50UL1 SingleJet30Uno Main HLT Jet Triggers HLT Jet TriggerTurn on points (GeV) Leading Jet HLT Jet30U62 HLT Jet50U87 Trigger efficiencies: Complete agreement of new sample (Runs>138564) with the old sample (Runs<137028)

4. Trigger HT2 P.Kokkas, Univ. of Ioannina4 Runs 135149-137028 Runs 138564-139790 Runs 135149-137028 Runs 138564-139790 HLT Jet Trigger H T nJets≥2 (GeV) H T nJets≥3 (GeV) HLT Jet30U120170 HLT Jet50U230 Since we plot R 32 above 200 GeV trigger HLT Jet30U is fully efficient.

5. Data Stability 5 nJets≥2 Plot does not take into account error of Luminocity. Runs 135528, 138750, 139020, 139365, 139368 and 139459 are some sigmas away. Correspond to 9.5 nb -1.

6. Data Stability P.Kokkas, Univ. of Ioannina6 nJets≥3

7. Data Stability P.Kokkas, Univ. of Ioannina7

8. Data Stability Good runs P.Kokkas, Univ. of Ioannina8 nJets≥2

9. Data Stability Good runs P.Kokkas, Univ. of Ioannina9 nJets≥3

10. Data Stability Good runs P.Kokkas, Univ. of Ioannina10

11. Off Line selection P.Kokkas, Univ. of Ioannina11 Off line Selection: Primary Vertex: |PVz| 4 Jet selection: p T ≥ 50 GeV and |y|≤2.5 “Loose” Jet ID : EMF > 0.01 OR |η|>2.6, n90Hits > 1, FHPD < 0.98 SelectionEvents 76nb -1 Events 66.5nb -1 AfterTrigger, Data quality &PV p T ≥50GeV, |y|≤2.5 & ‘’Loose” JetID At least 2 jets182565156417 At least 3 jets106369171

12. 76nb -1 P.Kokkas, Univ. of Ioannina12 76 nb -1

13. Data over PYTHIA : All Jets 13

14. Data over PYTHIA : Leading Jets 14 PYTHIA MC normalized to the total number of inclusive DiJet events.

15. Data over Madgraph : All Jets 15

16. Data over Madgraph : Leading Jets 16 Madgraph MC normalized to the total number of inclusive DiJet events.

17. NJets P.Kokkas, Univ. of Ioannina17 PYTHIA and Madgraph MC normalized to the total number of inclusive DiJet events.

18. Data over MC 18

19. R 32 at calo Level P.Kokkas, Univ. of Ioannina19 AxB Pythia

20. 66.5 nb -1 P.Kokkas, Univ. of Ioannina20 66.5 nb -1

21. Data over PYTHIA : All Jets 21

22. Data over PYTHIA : Leading Jets 22 PYTHIA MC normalized to the total number of inclusive DiJet events.

23. Data over Madgraph : All Jets 23

24. Data over Madgraph : Leading Jets 24 Madgraph MC normalized to the total number of inclusive DiJet events.

25. Njets 25 PYTHIA and Madgraph MC normalized to the total number of inclusive DiJet events.

26. Data over MC 26

27. R 32 at calo Level P.Kokkas, Univ. of Ioannina27 AxB Pythia

28. Final Result P.Kokkas, Univ. of Ioannina28 Final Result

29. R32 at Hadron Level 76nb P.Kokkas, Univ. of Ioannina29

30. R 32 at Hadron Level 66.5 nb -1 P.Kokkas, Univ. of Ioannina30

31. Spare P.Kokkas, Univ. of Ioannina31

32. Data Stability statistics 32

33. Data Stability statistics 33

34. R32 P.Kokkas, Univ. of Ioannina34

35. PT Ratios old-new P.Kokkas, Univ. of Ioannina35

36. P.Kokkas, Univ. of Ioannina36

37. Data over PYTHIA : all Jets HT>200 37

38. Data over PYTHIA : Leading Jets HT>200 38

39. Data over Madgraph : all Jets HT>200 39

40. Data over PYTHIA : Leading Jets HT>200 40

41. nJets HT>200 P.Kokkas, Univ. of Ioannina41