Searches for double partons

1. Searches for double partons Lee Pondrom April 16, 2012

2. Jet20 Data Stntuple gjt1bk & gjt1bj 3E6 events • Require only one vertex • Require at least two jets with |η|<1. ET1>20 GeV. Other jet ET>5 GeV • Apply level 5 jet energy corrections • Events • Jet1&2 Jet3 Jet4 Lum(live) • 110203 61769 21174 151694/nb • 56% 19% • Prescaled σ ≈ 0.7 nb; unprescaled σ≈1.2b

3. Jet20 data Jet ET

4. Jet20 data Δφ distributions

5. Following Rick Field, define the transverse region relative to jet1φ • Look at charged tracks with |η|<1, pT>.5 GeV, and with /3<Δφ<2/3, where Δφ is the azimuthal angle between the track and the highest ET (trigger) jet. • These tracks are sensitive to the underlying event, and hence at least in part depend on multiparton interactions.

6. Jet20 data properties of the transverse tracks

7. Jet20 transverse track pT cut • Based on the idea that the transverse region has some sensitivity to what is going on in the event other than the two primary jets, we make a cut on the scalar sum of track pT>15 GeV. • This cut leaves 1611events – 1.5% of all dijets. The fraction increases with jet energy. • The cut moves jet3 into the Δφ region of the tracks.

8. Effect of the ∑transtrackpT>15GeV on the jet φ distributions

9. Effect of the ∑transtrack pT>15 GeV cut on jet φ • Of the 1611events, 1495, or 93%, have jet3ET >5 GeV, and these jets are clustered around /2 relative to the trigger jet. • 15 GeV is too high relative to the main jet activity, so the correlation Δφ12 is strongly perturbed.

10. Δφ34 and the high pT transverse tracks • The idea is that jets 3 and 4 could be result of independent scattering of two other partons. • If that is true, a good place to look is in the Δφ region of the underlying event. • The ∑transtrack pT>15 GeV serves as a ‘trigger’. • Δφ34 should peak near .

11. Δφ34 and jet3ET before and after track∑pT>15 GeV cut

12. Enhancement near Δφ=? • Normalizing the two distributions to Δφ<1.5 gives a difference 2.4<Δφ<3.2 of • -8±17 events. • Transverse jet energies for jets3 and 4 are increased by the track pT cut

13. Look at jet100 data 1E6 events gjt4bk & Pythia bt0stb • Same requirements: only one good vertex, trigger jet ET>100 GeV, level5 jetECorr • Yields for 1E6 events • Jet1&2 jet3 jet4 pT>15GeV Lum • 170710 101231 35034 10247 126342/nb • Jet3 and jet4 fractions same as jet20 • pT>15 GeV fraction 4x larger than jet20 • σ ≈ 1.3 nb no prescale

14. Jet100 data and Pythia ET

15. Jet100 & Pythia transtrack pT and Δφ12

16. Jet100 data effect of the transverse tracks on Δφ12 and Δφ13

17. Jet100 effect of transverse tracks on jetET3 and Δφ34

18. Jet100 & Pythia effect of ∑pT>15 GeV cut on transverse tracks

19. Jet100 effect of transverse tracks Jet100 similar to jet20. Pythia & data agree. Perturbation of Δφ12 considerably less than for jet20. Δφ13 shifts so that jet3 is /2 away from jet1 Jet3 ET shifts to larger values

20. Compare jet100 and Pythia Δφ34 before and after ∑pT>15GeV cut

21. Jet100 data and Pythia Δφ34 • The data and Pythia agree qualitatively in the shapes of the Δφ34 angular distributions before and after the ∑pT>15 GeV cut on the scalar sum of transverse tracks. • Near Δφ34≈ Pythia has a smaller excess than the data.

22. Now compare Δφ34 before and after ∑pT>15 GeV cut

23. Excess near Δφ34≈ • Normalize the plots to .5<Δφ34<1.5 • Subtract (after cut)-(before cut) 2.4<Δφ34<3.2. • Jet100 data difference = 295±50 events • Pythia difference = 54±30 events

24. Does this excess mean anything? • There are 170710 jet100 good dijet events • So the excess 2.4<Δφ34<3.2 is 0.0017±0.0003. • Pythia excess is smaller: 0.0007±0.0004. • If the number of MPI’s per hard scatter is 5, which comes from Field’s analysis of Drell Yan (PRD?), the probability of a second hard scatter is 0.00034±0.00005, or about 3.5E-4 for the jet100 data.

25. Look at Jet50 data and Pythia • Jet20 data are too low ET relative to the ∑transtrackpT>15 GeV cut. • Jet50 data are higher, and the Pythia file bt0srb has 4.5E6 events, while bt0stb (jet100) has only 1E6 events, so we have better statistics for the monte carlo. • Same procedure as jet20 and jet100

26. Jet transverse energies after level5 jet energy corrections

27. Jet-jet Δφ correlations jet50 and Pythia

28. Jet50 data and Pythia

29. Jet50 data and Pythia after ∑transtrackpT>15 GeV cut

30. Jet50 data and Pythia after ∑transtrackpT>15 GeV cut

31. Δφ34 for jet50 data and Pythia w/wo ∑transtrackpT>15 GeV

32. Jet50 data and Pythia agree well • The excess near Δφ34 =  when the transverse track ‘trigger’ is applied now appears in both the data and Pythia. • The excess normalized to the number of events is: • jet50 jet100 • Data 0.0016±0.0002 0.0017±0.0003 • Pythia 0.0009±0.0002 0.0007±0.0004

33. So what?

34. Look at the second vertex • Jet100 data gjt4bk and gjt4bm 12E6 events • Exactly two vertices in the event, separated by at least 10 cm. • Jets 1 and 2 are on vertex number 1. • At least 3 tracks with |η|<1 and pT>0.5 GeV are on vertex number 2 • Cross section for a vertex defined by these track cuts is about 6 mb.

35. Tracks on the second vertex

36. Jet ET on 2nd vertex with ∑trackpT>15 GeV ‘trigger’

37. JetET on 2nd vertex • The transverse track scalar ∑pT>15GeV ‘trigger’ selects events on the second vertex which are softer than Jet20, the lowest transverse energy jet trigger in the data.

38. Effect of the second vertex ∑pT>15 GeV on jet Δφ

39. Effect of second vertex tracks on jets3 and 4

40. Add first and second vertex Δφ34 distributions

41. Δφ34 correlation • The peak near Δφ= corresponds to: • 2.4<Δφ34<3.2 = 141±12 events • This is 3.7E-4 of all two vertex events. • This fraction is in agreement with the excess observed in jet100 data, provided that there are 5 multiparton interactions per hard collision. • The Pythia effect is about 3σ smaller than the data. More Pythia MC would be useful

42. Extend the study to Drell-Yan  pairs • Use high pT muon trigger stntuples • 5E8 events total available. • 1E6 events takes about 4 hours to analyze • So 5E8 would take 3 months of steady computing, unless I can speed things up. • 5E7, or 10%, analyzed so far

43. ± pair yields from high pT muon trigger Stntuples • Require two muons opposite charge |η|<1. • Eliminate events with cosmic rays • Require at least one CMU*CMP muon • Require at least one jet ET>5 GeV • 48894 events 30GeV<m<130GeV • 40567 events 80GeV<m<100 GeV • 28811 events Z pair pT>10 GeV

44. D-Y mass and pT plots

45. D-Y mass and pT • Gauss fit to peak at 90.8 GeV, width 3.8 GeV • Pair pT compared to recoil jet ET with level5 jet energy corrections is much harder than jet20 ET spectrum

46. Compare to Pythia D-Y

47. Δφ and ΔET for track pair and recoil jets

48. Data compared to Pythia D-Y

49. Δφ and ΔET for track pair and recoil jets Pair pT>10GeV. Central Δφ peak consistent with jet-jet Δφ12 for jet20 data. Δφ=|(recoil jetsφ) – tracksφ| -  is asymmetric, with a tail towards negative values, ie jets and tracks in the same quadrant. ΔET is nearly symmetric, with a shift such that jet ET is about 4 GeV low relative to the tracks, even with level5 jetEcorr. Pythia agrees with both plots.

50. Scalar sum pT for transverse tracks Z data, jet20data, and Pythia