BEACH 04J. Piedra1 SiSA Tracking Silicon stand alone (SiSA) tracking optimization SiSA validation Matthew Herndon University of Wisconsin Joint Physics Meeting May 14th, 2008

2 The Problem M. Herndon ProductionExe execution times for high luminosity are large 15 minutes for some events Time dominated by tracking code Primarily SiSA and COT tracking Slightly larger contribution from SiSA Tracking code execution time appears to have a luminosity to the 4th power dependence Silicon tracking optimization New version developed for generation 7 Faster to make forward tracking algorithm possible SiSA tracking is substantially faster for nearly the same efficiency Work now focused on validation rather than any code development Joint Physics Meeting

3 SiSA Optimizations M. Herndon Large number of optimizations SiSA uses two 3D silicon Hits and a primary vertex as a seed Silicon Hits Remove all hits with charge below 20 ADC counts Tighten clustering requirements and do not use bad hits as track seeds Increase 20 ADC count threshold as a function of path length through the sensor Use only high pt vertices as seed Highest pt vertex and any vertex above sum pT 10 GeV This is the source of a slight inefficiency - may want tune, tcl switch installed Only allow 51% missed hits during search 4/7 Several stages, final cut is tighter Improve search strategy Search for r-phi hit when 3D hit not found immediately - in another loop before Only one loop - three loops before - didn’t add any efficiency Joint Physics Meeting

4 SiSA Optimizations M. Herndon Fix bugs Counters of found hits and traversed layers were incorrectly done Very loose hit requirements were made to make up for this Require only one missed hit for final candidates Speeds up down stream algorithms such as IO tracking and non tracking modules This results in most of the efficiency loss - allowing two missed hits doubles the track collection size and most of the tracks are fake. Remove duplicate tracks SiSA re-searches the seed after making the full track. If two similar seeds resulted in the same hits in the inner part of the detector the re-search can result in an exact duplicate Also speeds up down stream modules Result is a much faster algorithm with similar efficiency and less fake tracks Joint Physics Meeting

5 Performance M. Herndon Tested on high luminosity jet stream data Luminosities ~ e30 Execution times on 3Hz machine Built vs c patch f. Current ProductionExe configuration Joint Physics Meeting ModuleOld(sec)New(sec SiSA IO COT OI Total Production SiSA 10 times faster ProductcionExe twice as fast

6 Validation M. Herndon Central tracking should not be effected. Test forward tracking efficiency Tracking efficiency using Z  ee events Tight central electron Standard joint physics tight cuts Forward calorimeter cluster with Et > 10GeV Joint Physics Meeting Z mass from calorimeter Et and direction Background subtraction from far high sideband

7 Z  ee: Efficiency M. Herndon Silicon efficiency relative to calorimeter Joint Physics Meeting 5% less overall efficiency in some bins 3% less tracks with COT hits in some bins

8 Plans and Conclusions M. Herndon Substantial gain made in speed for small efficiency loss Plans Validate efficiency at very high luminosity This is critical since the high pt vertex cut may effect efficiency Need access to stripped production output sample of Z->ee events Does this exist? Will be slow if I have to strip it. Programs not used for 2 years. Validate that central tracking not effected Central tracking code was not modified. However, dozens of files were changed and testing is good. Will test on J/Psi->mumu events Test on pathological 15 minute events Need to validate final release from Production group. Fast once above things are set up. A few days of work. Joint Physics Meeting