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Standalone Muon Seeding

Standalone Muon Seeding. Rick Wilkinson. One Problem Solved: Bad Seed Efficiency in Cracks. ORCA PTDR Standalone Muon. CMSSW. Efficiency Bug Found. Single-segment seeds in MB1 and MB2 were accidentally being removed Bug was introduced in porting from ORCA. Endcap Seed p T Resolution.

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Standalone Muon Seeding

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  1. Standalone Muon Seeding Rick Wilkinson

  2. One Problem Solved:Bad Seed Efficiency in Cracks ORCA PTDR Standalone Muon CMSSW

  3. Efficiency Bug Found Single-segment seeds in MB1 and MB2 were accidentally being removed Bug was introduced in porting from ORCA

  4. Endcap Seed pT Resolution • Endcap pT algorithm makes some strange assumptions: • Measures pT only from direction of “best” segment • Uses only local magnetic field, not field integral

  5. Estimating Endcap Muon Seed pT • Should estimate pT from the bending between stations, not slope within a station • Field integrals look reasonably linear for a given chamber type. • Try to parametrize: • pT = (c1 + c2 * h) / Df

  6. Phi Bend between stations 1 and 2

  7. Endcap Seed pT algorithm • If there are segments in stations 1 & 2, get pT from the bend between them: • pT = (c1 + c2 * h) / Df • Use 10 GeV muons for parametrization • If not, try stations 1 & 3. • If not, then what? • Use old algorithm for pT? • or assign a straight track with errors up to min pT : • q/p = 0, • s(q/p) = 1/ (3GeV)?

  8. Endcap Seed pT: Results Blue is new, red is old, for 100 GeV muons Overlap region is bad, but there should be some good barrel-only seeds there

  9. Effect on 100 GeV standalone endcap m- • Helps prevent a few catastrophic failures • But some muons are missing! Needs to be investigated.

  10. Effect on 1 TeV standalone endcap m- • Seems to help a lot! • Piotr showed a plot of bad TeV standalone reconstruction last meeting • Still too many misreconstructed. • Barrel also has a spike at low pT.

  11. To-do next • Find why some muons aren’t reconstructed • Seed errors too small? • Get others to validate what I have, and release it into 1_3_1. • Committed to CVS • Parametrize errors as well • Seed errors could have a big effect on final reconstruction • Deal with barrel-endcap overlap region

  12. Conclusion • A lot of the bad effects we’ve seen in muon reconstruction can be directly blamed on bad seeding. • The efficiency dips at |h|=0.2 were due to a seeding bug. • Endcap seed pT was wrong, and could cause bad standalone reconstruction. • Endcap seed pT can now be calculated from bend in phi between stations. • New seeding not quite ready: unexplained inefficiency • UC Riverside group is starting to rewrite the seeding, but are willing to use this pT calculation. • Still lots of work and tuning left to do.

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