Status of Fast Tracking Algorithm MdcHough Guowei YU 8 th March 2006

Outline Introduction MdcHough Algorithm Results and Discussions Summary

Introduction  Algorithm Developments in MDC Reconstruction  Presented by W.D.Li,Migrated from ATLAS DeveloperOffline AlgorithmEvents filter Algorithm S.L.ZangMdc Tracking Y.ZhangMdcPatRec X.M.ZhangMdcFastTrk G.W.YUMdcHough

 Purpose  Efficient track finding  Nice transverse momentum resolution  High efficiency of track finding at high noise level

MdcHough Algorithm 43 layers,19 axial type |cos  |<0.93 Cell is near square ~8.1mm Interaction point Cosθ=0.83 Cosθ=0.93

Flow of MdcHough HitsPTPT Initial track finding Local maximum finding Track selection and Merging Track fitting MdcHough

 Initial track finding ( use a LUT-base Hough Transform)  (R,  )  ( ,1/p T ) [  (0~2  ) p T (400MeV~  )] qC T R=sin (  –  0 ) C T = 0.3/p T  Build a wire-ordered look-up table (   1/p T = 300  100). wire n+1 wire n active wire n-1 wire.. Bin 1Bin 2…Bin 100 Bin 1Bin 2…Bin 100 Bin 1Bin 2…Bin 100. wire-ordered LUT Flow of MdcHough

 Local maximum finding (select good track candidates by wired- oreded LUT)  Track selection and Merging  N hit > 15  Merge some tracks sharing more than 9 hits Flow of MdcHough

 Track fitting  Obtain hits from Bin-ordered LUT  Fitting track to get P T by using lpav tool. bin n+1 bin n bin bin n-1 number.. wire 1wire 2…wire 19 wire 1wire 2…wire 19 wire 1wire 2…wire 19. bin-ordered LUT Flow of MdcHough

Results and Discussion  Track Reconstruction CPU Time ~ 1ms/1 track  Resolution of P T (1.0GeV  )  Generate  (P T :1GeV) by Fixpt  Efficiency of Reconstruction (  ) VS cos  (polar angular)  p=8.0 MeV

 Efficiency of Reconstruction VS P T (  e  p)  Momentum resolution VS P T (μ,e,π,p) Double Gauss Fit

Noise level type 0: = C type 1:  1/r type 2:  1/r 2 (P T :1.0GeV  )  Efficiency vs noise  Resolution VS noise

Summary It costs about 1ms to reconstruct 1 track Efficiency of reconstruction(  ) :   >99% (P T >300MeV) for single track   >99% when noise level are 5%,10%,15% and 20%   decrease quickly when polar angular more than 0.8 Resolution of momentum(  p):  P T < 1.0GeV  p of proton is more than others  P T > 1.0GeV  p keeps about same value for all particles   p turns bad at noise level is more than 10% in type “0” Same results by adding wires shift;  Further work is to enhance  near polar angular and test the Algorithm in adjusted magnetic field

Thank!