Updates on the 2D clusterization

Clusterization

• Slight issues with extracting the correct time information for found cluster maxima in GPUChainTrackingClusterizer.cxx - Maxima are read out to file but time information is incorrect since it always saves the current local time (typically wrong by a TPC drifttime ~600 units). To be investigated
• Build local "dummy-maximizer" trying to just find maxima from the digits themselves by comparing with the surrounding digits and checking for charge ≥ neighbouring charges for all 8 neighbouring charges
• ~73% of all digit maxima (dummy-clusterizer) can be found in the ideal clusterizer -> Neural network should learn to when there is a maximum and when there is not, using the ideal clusterizer

Neural Networks

• PbPb, 50 Events @ 50kHz
• CNN trained on 11x11 windows (pad x time) with an output of 0 (no maximum in ideal clusterizer) to 1 (maximum found in ideal clusterizer).
• Using a hard cut at 50% probability by the network: Currently ~84% accuracy is reached (accuracy = (TP + TN) / all)
• As an easy-to-imagine number: 730k maxima found in digits where a corresponding maximum was found in the ideal clusterizer, then the network produces 740k cluster-maxima (so the output maxima are at least not much more than the found ideal clusters)

--> Further steps:

• Clean-up of the training data is needed
• Ideal clusterizer is sometimes one digit off from a maximum in the digits (maybe noise?) - to be investigated

--> Benefits:

• Choose cutoff probability - Tradeoff between computing resources and accuracy (setting the threshold higher will produce less maxima but also reduce the accuracy for already correctly identified maxima)