TPC SCD: add clampTgSlp to keep residuals beyond MaxTgSlp - #15839
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The |tan(phi)| < param::MaxTgSlp condition on a TPC cluster residual is evaluated on the REFERENCE track's direction. For ITS-TPC tracks that direction carries the ITS curvature error, so dropping the cluster selects on that error (over-curved references reach the limit first), a one-sided selection that grows with radius for pt below ~0.3 GeV. With clampTgSlp=true the cluster is kept and tgSlp is stored saturated at +-MaxTgSlp (tgSlp == +-0x7fff, UnbinnedResid::isTgSlpClamped()); dy, dz, y, z are unchanged. Default false = unchanged behaviour and file content; the format is not changed. With clampTgSlp the saturated tgSlp is not the track's angle, and the voxel fit extracts dX from dY vs tan(phi) (also used by the map-correction check in staticMapCreator.C). ResidualsContainer::fill and staticMapCreator.C therefore skip UnbinnedResid::isTgSlpClamped() residuals when binning; they stay in the unbinned output. The vDrift estimate (dz vs z only) still uses them. No effect unless clampTgSlp is on. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
matthias-kleiner
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shahor02 and
wiechula
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September 24, 2026 16:19
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shahor02
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Sep 24, 2026
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The |tan(phi)| < param::MaxTgSlp condition on a TPC cluster residual is evaluated on the REFERENCE track's direction. For ITS-TPC tracks that direction carries the ITS curvature error, so dropping the cluster selects on that error (over-curved references reach the limit first), a one-sided selection that grows with radius for pt below ~0.3 GeV. With clampTgSlp=true the cluster is kept and tgSlp is stored saturated at +-MaxTgSlp (tgSlp == +-0x7fff, UnbinnedResid::isTgSlpClamped()); dy, dz, y, z are unchanged. Default false = unchanged behaviour and file content; the format is not changed.
With clampTgSlp the saturated tgSlp is not the track's angle, and the voxel fit extracts dX from dY vs tan(phi) (also used by the map-correction check in staticMapCreator.C). ResidualsContainer::fill and staticMapCreator.C therefore skip UnbinnedResid::isTgSlpClamped() residuals when binning; they stay in the unbinned output. The vDrift estimate (dz vs z only) still uses them. No effect unless clampTgSlp is on.
Example of rejected fraction of clusters from no dist MC:
MC_noDist.pdf