Matthew Reid 1 st Year PhD University of Warwick 1
Interested in pattern recognition for pixel detectors New techniques that could be applicable to the upgrade Aim– Increase the reconstruction efficiency of tracks in the Timepix test beam Any questions just interrupt me! 2
3 Reference cluster Cluster in detector i
Tree structure of the kNN algorithm 4
5 SEED HIT Candidate hits after 1 st iteration Candidate hits after 2 nd iteration
Example for k=3, projections in both xz- plane and yz-plane: (Note degeneracy) xz-plane yz-plane 6 z z y x SEED HIT Candidate hits 1 st iter Candidate hits 2 nd iter
Kalman Filter gives best estimates for a linear system (see backup slides for detail) Allows you to take into account multiple scattering based on Moliere formula for thick material to find better track fit Measurement uncertainty based on pitch of pixel ~ 55µm 7
Example taken using: bin/tpanal –c cond/Alignment507.dat –z /afs/cern.ch/lhcb/group/vertex/vol7/Timepix/ZSData/Run507.root –n 9 MAX number of tracks with current algorithm is the plane with the lowest number of clusters? ? WRONG!! Detector PlaneNumber of Clusters C03W K05W D09W M06W I02W E05W DUT D04W0015 Bias the data set so ignore 8
The maximum number of clusters depends on the alignment of detectors Since the alignment is not perfect we are required to look in area shown in graph Hence not all clusters can be used in the reconstruction. 9
10 Detector PlaneNumber of ClustersNumber of Aligned Clusters C03W K05W D09W M06W I02W E05W TOTAL676571
Original AlgorithmNew Algorithm Number of Tracks5175 Number of rejected tracks-16 Efficiency54%79% ?? ( ) Projection of Tracks in xz 11 z x z x y
Residuals are of a comparable order to the original code giving ~6µm, over all planes (unfortunately) 12
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