Lost Jet Update

1
Lost Jet Update

• John Krane
• Iowa State University
• jet/MET Meeting 8/29/02

• reminder of problem
• performance metric
• parameter choice

2
Problem unclustered event energy
CDF Physics groups are not using Run II algorithm

• CDF Matthais Toennesmann
• DØ me, Vishnu Z., Bob H.
• Cones can iteratate
• away from small
• Energy clusters
• The Run I algorithm did this too...

3
Modified Cone Algorithm

• CDFs search cones
• Use a small cone to find jets and iterate
  locations
• Expand cone size to full 0.7 and save
• Find midpoints found a phi-wrap bug using
  pT-weight not 4vec?
• Iterate 0.7 size midpoint jets

4
Results on selected sample (45 evts)
I never found a lost jet, but they must exist...

• Seed tracking
• Plot shown in
• OK workshop
• Symmetric in y-f,
• so just use R...

Each point was a seed
p11
Abs f drift
Abs y drift
5
Drift distance for 0.7 cones, pTgt15 GeV

• If a seed is too close (R/2) to existing jet,
  ignore it
• Standard cones can drift very long distances!
• Search cone R/2 limits drift to R...

6
R0.5 Cones

• Same comments apply...

7
R0.3 cones

• Again...

8
Normalize drift distances by R

• R0.5 cones,scaled distance

9
x-axes have suppressed zero
10
Conclusions

• Cones can drift quite far from the seed, even for
  reasonably high-pT Jets gt15 GeV
• This doesnt mean a jet is lost every time this
  happens (I have yet to find a lost jet)
• Search cones can limit drift as much as we like
• R/2 works well (almost perfectly) " R

11
Suggestions for Future Work

• Implement my rcp-driven code (but not necessarily
  a search cone setting just yet)
• Search_Factor1.0 means no search cone
• Search_Factor0.5 eventually...
• Run full Reco tests for CPU time and consistency
• Consult CDF and try to converge on a parameter
• Informally, Joey Huston thinks R/2 works well
• Would like permission to show this talk externally

12
Files altered for Search Cone mod

• energycluster/ILConeAlgorithm.hpp(Constructor
  allows search_cone argument,midpoint calculation
  fixed for phi-wrap,is_stable() need not
  iterate,min jet pT reduced during search phase)
• calreco/CalClusterReco.cpp(Read and pass
  Search_Factor from rcp)
• calreco/rcp/CalILCone07.rcp
• calreco/rcp/CalPreSCILCone07.rcp
• calreco/rcp/CalPreSCILCone05.rcp
• calreco/rcp/CalPreSCILCone03.rcp