Clusterer will prioritize labels with lower trackIndex - #15782
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The HIP may produce a large number of delta electrons (e.g. a magnetic monopole typically produces a few 10K deltas in the barrel). Since we limit the number of saved MC labels per ITS/MFT cluster to `Clusterer::MaxLabels` (=10), in a large cluster receiving contributions from both the HIP and its delta rays, the HIP label might not be saved if MaxLabels delta electrons contributing to the same cluster have already been accounted for (the order is quasi-random). To minimize the chance of such label loss, assuming that the track ID of the HIP is smaller than those of its delta rays, when there is no free slot left in the label buffer, the new label (e.g. that of the HIP) will replace the label with the largest track ID already present in the buffer.
shahor02
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f3sch,
fprino,
mconcas and
mcoquet642
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September 9, 2026 22:46
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The HIP may produce a large number of delta electrons (e.g. a magnetic monopole typically produces a few 10K deltas in the barrel). Since we limit the number of saved MC labels per ITS/MFT cluster to
Clusterer::MaxLabels(=10), in a large cluster receiving contributions from both the HIP and its delta rays, the HIP label might not be saved if MaxLabels delta electrons contributing to the same cluster have already been accounted for (the order is quasi-random).To minimize the chance of such label loss, assuming that the track ID of the HIP is smaller than those of its delta rays, when there is no free slot left in the label buffer, the new label (e.g. that of the HIP) will replace the label with the largest track ID already present in the buffer.