Jets (Cone R=0.7) No Cuts Jets reconstructed using the cone algorithm. N ----- The number of jets in the event. I see a two-peaked distribution with 2 jets most-likely and 0 jets next-most-likely. That is understandable given that QCD events tend to have at least two or more jets, balancing in Et. Other events have either two or more jets that fall below threshold (typical of MinBias) or no jets at all above threshold. There are lots of events with 3 or more jets and even a few with 10. Exchange 18-Apr-2003 Question (GB): The high multiplicity is due to fake jets, due to noise. Are quality criteria applied (see jetmet web page/certification)? Answer (HM): No quality cuts yet. Perhaps it's better to monitor "all" jets. Answer (MW): The cut Et>8GeV for these plots is extremely low. At such low Et we expect large numbers of multijet events - even with such high multiplicities. (of course, there is also some background here - but not *only* background) Et ----- The Et of jets. We don't save jets reconstructed with Et less than 8 GeV. Eta ----- Jet eta. There must be a fairly heavy trigger bias as jets are produced approximately flat in eta at a given Et. Exchange 18-Apr-2003 Question (HTD): Why does it fall at higher eta? What are the horns at |eta|=1.1? Answer (GB): It's trigger coverage. Cases where the jet deposits lots of energy on coarse hadronic (CH). The CH tends to be noisy. Answer (MW): Jets are not produced flat in eta (also not for a given Et). NLO predicts that for: Et> 50GeV the eta spectrum dies out at eta>2.7 Et>100GeV - " - eta>2.0 Et>400GeV - " - eta>1.0 I can't give a good explanation for the horns. But it looks as if jets at |eta|=1.3 are reconstructed at smaller values so their |eta| is shifted to approx 1.0 Phi ----- Jet phi. Exchange 18-Apr-2003 Question (HTD): What's with the large bump at phi=1.6 and the smaller one at phi=3.2? Answer (GB): Calorimeter problems (a warm zone, under investigation). EMF ----- The electromagnetic fraction of jets, including electrons. Exchange 02-May-2003 Question (HTD): Does this include electrons? Answer (MW): I don't know what this plot includes.... But in principle an isolated electron will be classified as a jet (until the jet selection criteria remove this background). Standard jet ID selection criterion: 0.051. F90 ----- Exchange 02-May-2003 Question (HTD): What is this? Answer (MW): The ratio of N90 and the total number of towers in the jet. The standard selection does not directly cut on this variable, but only on the combined variable f90ch, defined as: f90ch = f90 + 0.5 CHF. The cut is: CHF<0.1 or f90ch<0.8. Jet Et (PHI vs ETA) ------------------- Exchange 18-Apr-2003 Question (HTD): I'm not sure I understand this plot. What's it mean? Answer ():