Change FF LGAD resolution from 8ns to 30ps - #2938
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🟢 Approval recommended
The changes are a consistent, unit-explicit parameter update (30 * dd4hep::picosecond) in the relevant detector plugins and align with existing code expectations that timing resolutions are expressed in ns-equivalent DD4hep units.
Pull request overview
This PR updates the configured timing resolution for far-forward LGAD-based tracker subsystems from the long-standing default of 8 ns to 30 ps, aligning the digitization/reconstruction smearing with the expected sensor performance and reducing unintended coincidence-time smearing in downstream analyses.
Changes:
- Set
SiliconTrackerDigi_factorytimeResolutionto30 * dd4hep::picosecondfor RPOTS, FOFFMTRK, and B0TRK. - Set
TrackerHitReconstruction_factorytimeResolutionto30 * dd4hep::picosecondfor the same detectors to propagate the improved timing to reconstructed hits.
File summaries
| File | Description |
|---|---|
| src/detectors/RPOTS/RPOTS.cc | Updates Roman Pot digitization and rechit timing resolution to 30 ps. |
| src/detectors/FOFFMTRK/FOFFMTRK.cc | Updates Forward Off-Momentum tracker digitization and rechit timing resolution to 30 ps. |
| src/detectors/B0TRK/B0TRK.cc | Updates B0 tracker digitization and rechit timing resolution to 30 ps. |
Review details
- Files reviewed: 3/3 changed files
- Comments generated: 0
- Review effort level: Lite
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Capybara summary for PR 2938
Last updated 2026-09-02T19:25-04:00 5788c1b |
Thanks @ajentsch |
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🟡 Changes recommended
The new edm4eic::unit::ps expressions are likely double and are used to initialize a float config via aggregate initialization, which can cause a narrowing-conversion compile error unless cast to float.
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Review details
- Files reviewed: 3/3 changed files
- Comments generated: 3
- Review effort level: Lite
Briefly, what does this PR introduce? Please link to any relevant presentations or discussions.
Updates the FF tracker timing resolution from 8ns which was the default for all detectors when introduced to the 30ps expected by the sensor (referenced from the now quite old digitization spreadsheet https://docs.google.com/spreadsheets/d/1s8oXj36SqIh7TJeHFH89gQ_ayU1_SVEpWQNkx6sETKs/edit?gid=238482234#gid=238482234)
Studies by @Garypenman highlighted looking for coincidences between the FF protons and FB electrons was being smeared out significantly more than anticipated. @ajentsch
A more detailed digitization approach and the correctness of the resolution value of other detectors are not being considered in this PR
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