Muon Seeding 1

The Various Seeders Three general purpose seeders – ancientMuonSeed – MuonSeed – SET – Not just a seeder: can do its own fitting, too. – standAloneMuonSeeds Merges results of two or more seeders Plus some special purpose algorithms – CosmicMuonSeed – mcMuonSeed – RPCSeedFinder – Histogramming method for TeV (not committed) ~10000 lines of code 2

What Seeders Do Find patterns (vectors of RecHits) Associate a p T – Bending in  between inner stations for seeds with more than one segment –  direction for single segment seeds Find a position and direction – Usually from a single segment – SET uses  2 fit Assign errors to position and direction Final cleaning 3

Optimizing Our Seeding We have three complete general purpose seeders Maybe we can see which components do which tasks best – Which does pattern recognition best, or error estimation best. Trying to engineer the software to conform to standard interfaces. – So we can swap components in and out – Not easy. Limited success merging ancient and SET. – Only code sharing done now is p T estimation. 4

Judging Seeders Need a quick way to judge the seeders See if changes help or hurt Validate releases See if problems are confined to one seeder 100 GeV muon RelVals are a good test case – Lower energies are too easy! We should be looking at the resulting Standalone muons Maybe don’t need to look at STA pT resolution first Driven by STA refit, anyway? 5

Judging Seeders (II) I’d argue we need to look first at “pathologies” – Efficiency of STA – Can see where another seeder finds muons where yours misses – Ghost rate of STA See if you need more aggressive seed cleaning – Rate of “collapse” of STA, where STA pT < 10% of input pT Often due to bad seed direction. Be more careful in picking primary segment Compare events where one seeder gets it right, and another doesn’t. Can run all three seed+standalone+analyzer sequences in one job 6

Preliminary Judgments 100 GeV pT RelVal, |  |<2.5 Efficiency Ghosting Collapse SeederEFFGHOSTCOLLAPSE ancient88.7%0.005%2.1% MuonSeed92.6%0.04%6.8% SET91.1%0.07%3.1% 7

Preliminary Judgments 100 GeV pT RelVal, |  |<2.5 8 SeederEFFGHOSTCOLLAPSE ancient91.1%0.07%3.1% MuonSeed92.6%0.04%6.8% SET88.7%0.005%2.1% SET+custom STA 89.8%0.07%2.7%

Conclusion Seeding is crucial to muon reconstruction – Drives efficiency – Picking a bad segment, p T, or errors can be disastrous. Easy to get started – Look at events that fail in one seeder, succeed in another. Effort here very likely to improve muons for everyone 9