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Hadronic jets in Z->ee

Hadronic jets in Z->ee. Lee Pondrom 25 February 2013. High p T muon and electron Stntuples. Filesets runs Z->ee Z->  bhelbd 138425-186598 8947 12898 bhelbh 190697-203799 7403 12750 bhelbi 203819-233111 12968 17721

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Hadronic jets in Z->ee

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  1. Hadronic jets in Z->ee Lee Pondrom 25 February 2013

  2. High pT muon and electron Stntuples • Filesets runs Z->ee Z-> • bhelbd 138425-186598 8947 12898 • bhelbh 190697-203799 7403 12750 • bhelbi 203819-233111 12968 17721 • bhelbj 233133-246231 9150 23090 • bhelbk 252836-261005 6263 12314 • bhelap 261119-312510 53054 136199 • Six muon filesets are bhmu– runs in same order • Total e’s 834E6, total ’s 313E6 all runs

  3. Stntuple electron filesets • Typical electron fileset has 3X as many events as a typical muon fileset. • Use of the CAF is essential for the e’s • Total number of Z->ee events ~100000, less than 1/2 the total Z->mumu ~215000 • Z->ee average yield per event ~0.0001. • Z-> average yield per event ~0.0007

  4. Electron quality cuts • Electromagnetic shower in the CEM plus matching charged track in the COT. • (z,φ) coordinates at radius of CES gives shower location. • ET>25 GeV (both electrons) • At least one high pT electron must satisfy: • Had/Em < 0.055+0.00045*E • Isolation variable: (ET in CEM+CHA in cone of 0.4 around the electron shower, minus the ET of the electron shower)/eleET<0.1

  5. Electron quality cuts, highest pT electron • Cluster ET/track match pT<2.0 if pT<50GeV • Track pT is generally lower due to radiation • Lshr < 0.2. Lshare is a variable used by CDF since antiquity. It checks that the transverse shower development in the CEM is consistent with that expected from electromagnetic radiation. • Thus Had/Em is a longitudinal, and Lshr is a transverse shower shape variable.

  6. (n-1) cuts for the highest pT e.

  7. (n-1) cuts for the highest pT e.Not applied to the second e

  8. Jets in the Z->ee data • Electron shower clusters are included in the jet block. • Because of the high electron ET>25GeV, and the ordering in jet ET, the electrons tend to be jet1 and jet2. • To remove the electrons from the jet block, all jets within ΔR<0.1 of either electron are eliminated, where ΔR=(Δ2+Δφ2)1/2 • There are fewer multijet Z->ee events than • Z->

  9. φ distributions jet1-ele1/ele2

  10. φ distributions jet2 ele1/ele2

  11.  Distributions jet1 ele1/ele2

  12.  Distributions jet2 ele1/ele2

  13. ΔR for electron 1

  14. ΔR for electron 2

  15. Φ and  matches for jets 1 and 2 • Jets and electrons are ordered in ET • About 90% of the time jet1=electron1 and jet2=electron2. • ET’s are not identical, and sometimes the order is reversed. • ΔR<.1 gives a jet-electron match • Both electrons must have a match.

  16. Φ and  distributions for jet3

  17. Φ and  distributions for jet4

  18. Jets 3 and 4 • Jets 3 and 4 depopulated in φ near the e’s • Sometimes jet3 is identified as ele2 • Jet4 seems to be free to be a gluon • Two electrons are required, ET>25GeV, ||<1, opposite charge (no mass or pTZ cuts). • 97776 events.(full data sample) • 80<mass<100 & pTZ>10GeV • 35879 events • 20849 at least one jet ET>5 GeV • 7015 at least two jets ET>5GeV • 1295 at least three jets ET>5GeV

  19. Z->ee plus jets data and Pythia • Remove the electrons from the jet block • ‘cuts’ 80<mee<100GeV, and pTZ>10GeV • DATA • e+e- pair jet1 jet2 jet3 • 35897 20849 7015 1295 • Pythia • 10400 5461 1485 232 • Fewer jets 2&3 in Pythia

  20. Z->ee and Z-> data ~9fb-1

  21. Z->ee and Z-> full data samples • Muon data normalized x 0.44 to compare to electron data. Less than ½ as many e’s. • Mass peaks coincide. Muon resolution sharper. • Distributions of pTZ are not the same. • Z->ee is softer. May be related to loss of jets.

  22. Z->ee and Z->

  23. Z->ee and Z->

  24. Z->ee and Z->

  25. Z->ee and Z->

  26. Jet yields Z->ee and Z-> • ratios jets/(80<mee<100GeV,pTZ>10GeV) • jet1=0.54; jet2=0.20; jet3=0.036. • Ratios jets/(80<m<100GeV,pTZ>10GeV) • jet1=0.52; jet2=0.37; jet3=0.18. • Jet1, the recoil, is the same, but jets 2 and 3 are much rarer in the Z->ee data.

  27. Further checks on missing jets • Does the presence of the electrons hide some jets? Electron Iso ET(R=0.4)/ET<0.1 would tend to take out neighboring jets • Analogous muon cut Iso E < 5 GeV, with tower energies MaxEEm=2 GeV, MaxEHad=6 GeV, which would also tend to take out neighboring jets.

  28. Apply electron-jet match cuts to the muons • Normal electron-jet match cut is ΔR<.1, but ΔR<.2 gives the same result, since the distributions are very sharp. (slides 7&8) • Muon-jet ΔR match peaks are broader. • Most of the width comes from Δφ for unknown reasons.

  29. Muon-jet match ΔR plots

  30. Electron cuts on the jets in Z-> • Eliminate all jets within ΔR<0.2 of either muon, where ΔR=(Δ2 + Δφ2)1/2 • Ratios (after ΔR cut)/(before ΔR cut) • Jet1=0.92 • Jet2=0.75 • Jet3=0.60 • So jet3 loses about 40%. Not enough to explain the discrepancy.

  31. Compare Δφ distributions for e-jet and -jet after ΔR cut • Eliminate all jets within ΔR<.2 of either lepton. • This removes electrons from the jet bank, and also removes those jets which are close to either muon. • Done on only a subset of the data, so relative normalization is different. • (Z->ee pTZ>10GeV)/ • (Z-> pTZ>10GeV)=0.54

  32. Δφ jet1-leptons 1or 2 for Z->ee and Z->

  33. Δφ jet2 - leptons

  34. Δφ jet3 - leptons

  35. Δφ exercise • Normalized jet1 yields are the same, although Δφ distributions are different. • For each jet, the regions near either electron are depopulated relative to the same regions near the muons. • For jet3, the loss in the electron sample is across all Δφ.

  36. Num of e jets and num of  jets

  37. Where do the jets go? • It looks like they are not there in the first place-the ‘five jet’ list is already depleted. • Removal of the electrons does not change the numbers of extra jets- the distribution just moves over two bins. • Z-> and Z->ee have the same number of recoil jet #1, but Z-> has more multijet events.

  38. Electron quality cuts • Applied to at least one electron candidate: • Had/Em<0.055+0.00045*ET (longitudinal) • Lshr <0.2 (transverse) • ET/pT<2.0 (or pT>50 GeV) • Iso<0.1 ET(R=0.4)/ET • Applied to both electron candidates gives 2/3 the data, but no relative change in # of jets.

  39. Electron quality cuts • Z->ee sample is ~10-4 of the high pT electron triggers, so it is not possible to relax the quality cuts on the data. • Pythia Z->ee sample is ~100%, so the cuts can be relaxed in the MC. • This was done, and the Z yield from the Pythia file increased by 3%! Of course no change in the # of jets.

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