Confirming L1 decision Use: DaVinci v7r4 field 043 Idea (Teubert’s) : Most of min.bias L1 possitive trigger are due to missmeasurements of Pt (P) How mutch Tracker information (from ST, OT) we need to recover from these mistakes? Extra handles or interesting particles-tracks to consider? (track with larger Pt 95% comes from b) Secondary verteces few particles to try “Mass” window Jose A. Hernando, 26/05/02, weekly trigger meeting Status: using a simple estrapolator-momentum estimator using L1OTClusters (Niels) working in a simple pattern recognition to find the hits from the L1 track candidates not easy, especially for OT... adapting HLT long track finder algorithm into a tool to do the pattern recognition as HLT does (with Nicolas) As the L1 candidates are a bias simple (large P, Pt) maybe wihtout a perfect pattern, it could work. runing the simple pattern (and the HLT) on the stripped mim.bias sample and signal (ie DsK) to compute efficiency and rejection

confirming L1:: estrapolator & pattern Simple estrapolator-momentum estimator: Assumption: 1.Consider that a track leaves a “straight line” segment in the detectors (TT,OT,IT) 2.Using MC, parameter the change of slope and offset at the middle of the detector as funcion of 1/pp 3.Going reverse from a delta of slope of offset from a segment in one detector one gets a estimation of 1/pp Very naive assumption: works ok TT, kind off IT >7 GeV, and somehow for OT > 10 GeV But the estimation p is “acceptable” (22-2-5%) os sigma_p/p for (TT,IT,OT) segments Pattern recognition: combinatorial approach: create clusters of hits (tripplets) in each stations and combine them to make segments Each cluster can be in several segments The good combination should be there, but how to pick it up? direct approach: (a la Kalman) Use initial seed (pp estimate from TT (mc)) Eatch hit goes into one segment, otherwise it starts a new segment. There is always a favoured segment. The good combination could not be there, but it is faster search.

Confirming L1 :: simple direct pattern A simple direct pattern: use a initial estimation of momentum (from TT, MC) the simple estrapolator gives a position and direction at a given plane and detector: a tube!. open a 3 sigmas (on p) window around the extrapolated point, ordered hit according to the distance to that point. “extrapolated” segments to that planes. Open a search window for each segments (minimum window + 3 sigma (from p) on delta slope * delta z) a hit goes to the segment close in distance and inside segment window. Otherwise it starts a new segment. the segment is updated (if hits are x only): new offset and slope of the segment the are 2 control variables of the segment: chi2 of the fit (well... this is not a straight line) overp consistency: (overp estimated from offset are in sigmas with the one estimated with change on slope?) (“loose” cut to accept a hit into a segment) segments ordered by size (number of clusters) and for equal size favour the one close to the extrapolated (offset) seed

Confirming L1 :: efficiency of pattern, using pmc as seed Reconstructible: All tracks TT matched pmc>3GeV, 2 x hits in different stations (a good x segment) Efficiency vs 1/p and 1/pt p_seed = MC!! highly efficienct! Problems TT (suspect: confidency cut) TT IT OT

Confirming L1 :: purity of pattern, using pmc as seed Purity of the best segment: Hits of the segments associated to MC particle / all hits of the segment Purity vs 1/p and 1/pt p_seed = MC!! The 1st segment is almost always the good one It his high pure for TT,IT (95%) and pure for OT (80%) Purity decreases at lower p for OT TT IT OT

Confirming L1 :: efficiency of pattern, using pTT as seed Reconstructible: All tracks TT matched pmc>3GeV, 2 x hits in different stations Efficiency vs 1/p and 1/pt p_seed = p_Mariusz_TT!! Efficienct (>90%)! Problems at high P! investigating: suspects: small window or consistency cut TT IT OT

Confirming L1 :: purity of pattern, using pTT as seed  Purity vs 1/p and 1/pt p_seed = p_Mariusz_TT!! Well. As least TT is pure! They are pure ~80% at very high P and Pt for IT and OT Hope?: Maybe it is no so bad :( for our bias sample of L1 candiates... if it was a wrong TT pt assigment we will not cached it if it was good some, there are some chances of piching it up! TT IT OT

Confirm L1 :: conclusions and more Conclusions: Estimating p from the clusters at OT and IT with 4% sigma_p/p, it is easy. Finding the hits associated to the VeloTT track is an elaborate patient (art) task. (could we be patient in the trigger?) The simple direct approach of the pattern recognition, maybe works..! Next Steps: Cuantify L1 efficiency and rejection instead of eff/purity. Use HLT long track finder algorithms. Code it as a Tool (with Nicolas) Technicalities: The trigger L1-HLT tracking does: convert clusters to hits, create segments and tracks (MW,OC,NA,BH,JAH) We should define interfaces: (easy to agree on interfaces than in concrete classes) and make tools (estrapolator, track_finder,..) with these interfaces. It will help us to share code. I will try to prepare a proposal for these interfaces.