Refactoring the sTGC cluster builder tools
The Caruana cluster builder tool uses a Gaussian fitting algorithm to reconstruct clusters having at least three strips and relies on a weighted average to reconstruct strip clusters with multiplicity less than three strips. This merge request eliminates the duplicated methods implemented both in the SimpleClusterBuilderTool and CaruanaClusterBuilderTool. The common methods are moved to a new class STgcClusterBuilderCommon.
The main changes are listed below:
- Do not allow empty strip in clusters. Now strip cluster is formed only of strips that have some amount of charge. sTGC is 3.2-mm wide, so it is unnecessary to allow one empty strip. Also this change has negligible impact as shown in the following plot. The data sample used for the comparison is one lumiblock of run 439519.
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The clustering methods are modified to skip strip with negative charge. Eventually, the current protection in the RDO->PRD converter, which discards channels having negative charge, might be dropped to allow building clusters with more robust methods ro to avoid trimming data. The methods will still run fine in such case.
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The Caruana method has been modified to run more stably by reversing to the weighted average for some type of clusters. The method uses a Gaussian fitting algorithm to reconstruct clusters that have at least three strips and reverses to the weighted average for other clusters. In particular, the method reverses to the weighted average if
- clusters have less than three strips
- clusters have the staircase shape
- reconstructed position of the cluster is not on top of any strips of the cluster
- error on the mean position of the cluster is too large
Below are some plots of the clusters reconstructed with the Caruana method. The data sample is one lumiblock of run 439519. The MC sample has 5000 particleGun dimuons.
Comparison, in data, between the Caruana and weighted average is shown below.
Note: To make all the plots above, we select muons reconstructed with muAuthor = 1 or muAuthor = 5 and pT(muon) > 15 GeV.
The bug fix from !59809 (closed) are included, so changes in the STGC PRDs are expected.