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Reconstructing Neutrino Interactions in Liquid Argon TPCs Ben Newell Steve Dennis. Outline. LAr-TPCs Automation desirable Algorithmic recognition. Cellular Automata. Conway's 'Game of Life' Local rules Cell states update simultaneously. CATS – The Cellular Automaton at HERA-B.
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Reconstructing Neutrino Interactions in Liquid Argon TPCs Ben Newell Steve Dennis
Outline • LAr-TPCs • Automation desirable • Algorithmic recognition
Cellular Automata • Conway's 'Game of Life' • Local rules • Cell states update simultaneously
CATS – The Cellular Automaton at HERA-B • HERA-B experiment uses eight 'superlayers' • Create 'track segments' between layers • Cellular automaton on track segments
Cellular Automata for Track Reconstruction • Cells have an index – initially 1 • Local – only neighbours • Common endpoint • 'Breaking angle' • Principal Direction
The CA Algorithm – Forward Pass • For each cell: • Look for leftward neighbours • Check if any have same index • Mark index to update • Update all indices • Repeat
The CA Algorithm – Reverse Pass • Start at highest index cell • Run to cell of index 1 using steps of 1 • Mark cells used • Repeat with unused cells • Build all possible paths • Result: List of track candidates
CARLA – A Cellular Automaton for Reconstruction in Liquid Argon • Implemented in Python • Extra steps required to suit our needs
Clustering the Data • LAr-TPC resolution ~mm • Thousands of voxels in principal direction • Performance problems • Clustering • Voxel size • Clustering orthogonal to principal direction • Reject 'lone' points
Post-Processing • Problems: • Breaking • Kinks • Clones • Filtering by shared points • Track cleaning • Breaker • Merger
Generalisation to 3D • Simple to work in higher dimensions • Directionality • May miss tracks • Solution: permute the axes and run on each • Recombine the results
Parameters for reconstruction • Voxel size • Clustering radius • Cell tolerance • Filtering tolerance • Breaking Angle • Merger • Direction Tolerance • Distance Tolerance • Breaker • Correlation Tolerance • Segment length
Future Developments • Improvements to filtering • Documentation • User Interface