1. Jet/Met meeting 11/21/2002 Jet studies 2. Fake jets in p13.02.00 and p11.13.00 3. Effect of coarse hadronic layers and negative cells on jets 1. Jet chunk certification in p13.02.00 Emmanuel Busato

2. JetChunk certification in p13.02.00 Comparison between JetChunk in p13.02.00 TMB and jet branches in p13.02.00 root-tuple (created from DSTs) (algo=JCCB)

3. n90 Root-tuple TMBTMB- root tuple

4. E Root-tuple TMBTMB- root tuple

5. Pt Root-tuple TMBTMB- root tuple

6. EMF Root-tuple TMBTMB-root tuple

7. Phi Root-tuple TMBTMB-root tuple

8. Eta Root-tuple TMBTMB-root tuple

9. JetChunk certification summary - For floats, difference TMB root- tuple  10**- 3 - An exception is variable EMF where difference is  5.10**- 3 - Problem with n90 ?

10. Fake jets in p13.02.00 and p11.13.00 Lot of fake jets in p11.13.00 => new quality cut : f90<- 0.5CHF + 0.8 What is the situation in p13.02.00 (where ZS : 2.5  ? - Criterion : f90 if high =>fake jet if low => good jet

11. in p11.13.00 data CHF Cone R=0.7 Cone R=0.5 N1 good jets N2 fake jets N2/N1  33  N2/N1  60  N1 N2

12. in p13.02.00 data N2/N1  16  Cone R=0.5 Cone R=0.7 N2/N1  30  N2 N1

13. The number of fake jets is reduced by a factor of  2 in p13.02.00, where we have 2.5  of zero suppression (instead of 2.1 in p11.13.00) Fake jets in p13.02.00 and p11.13.00 summary

14. Current status of the algorithms : Jets are constructed with a list of positive energy towers. These towers are made of positive and negative energy cells. What happens if we remove corresponding layers (15, 16, 17) ? (input of the algorithm : calorimeter towers without CH layers) Not consistent with Met calculation, which is done with towers > 200MeV or cells > 100MeV Coarse Hadronic may be responsible for fake jets What happens if we keep only positive cells in jets ? Effect of coarse hadronic layers and negative cells on jets

15. Cone R=0.5 N2/N1  7.5  N2/N1  16  N1 N2 N1 N2 N1 N2/N1  7.5  Current algo Without CH layers and neg cells Without CH layers Cone R=0.7 N2 N1 N2 N1 N2 N1 N2/N1  14  N2/N1  30  N2/N1  14  Current algo Without CH layers and neg cells Without CH layers

16. Summary => reconstruction without CH layers reduces the number of fake jets by a factor of  2