1. Standalone Muon Seeding Rick Wilkinson

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

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

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

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

6. 6 Phi Bend between stations 1 and 2

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

8. 8 Endcap Seed p T : 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. 9 Effect on 100 GeV standalone endcap  - Helps prevent a few catastrophic failures But some muons are missing! Needs to be investigated.

10. 10 Effect on 1 TeV standalone endcap  - 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 p T.

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

12. 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 |  |=0.2 were due to a seeding bug. Endcap seed p T was wrong, and could cause bad standalone reconstruction. Endcap seed p T 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 p T calculation. Still lots of work and tuning left to do.