Adding in filter for 3D model of cathode for systematics

[jzennamo]

Description

Please provide a detailed description of the changes this pull request introduces.

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$${\color{blue}\bf{\textrm{IMPORTANT UPDATE Feb 2nd 2026:}}}$$ If you are making a PR which is intended as a patch for the CURRENT production for gen 2 SBND analyses, you must make two PRs: one for develop and one for the production/sbnd-gen2 branch.

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Checklist

• Added at least 1 label from available labels.
• Assigned at least 1 reviewer under Reviewers,
• Assigned all contributers including yourself under Assignees
• Linked any relevant issues under Developement
• Does this PR affect CAF data format? If so, please assign a CAF maintainer (PetrilloAtWork or JosiePaton) as additional reviewer.
• Does this affect the standard workflow?
• Is this PR a patch for the ongoing production? If so, separate PR must also be made for production/v10_06_00 branch!

Relevant PR links (optional)

Does this PR require merging another PR in a different repository (such as sbnanobj/sbnobj etc.)?

Link(s) to docdb describing changes (optional)

Is there a docdb describing the issue this solves or the feature added?

[jzennamo]

OK, so, using cosmic data I created a 3D representation of the cathode, I integrated that into SBNDCode and tried to create a version of the gdml that removes the cathode. This was validated using cosmic MC and is ready to be merged and used to generate a systematic variation.

[tbwester]

Overall implementation looks good. Personally I prefer a larsoft service with centralized, sbnd-level cathode config file instead of configuring within the filter fhicl. I can't comment on the GDML nor jsonnet files.

[tbwester]

Did you consider making this a larsoft service? Then this could be used elsewhere with unified experiment-defined configuration (not just set in the filter configuration fhicl)

[jzennamo]

I did not

[jzennamo]

This PR also requires this PR in sbnd_data:
http://github.com/SBNSoftware/sbnd_data/pull/11

[tomjunk]

Looks fine to me. sbnd_cathode_v8.txt has 62 nans in it -- they tend to be at the ends of lines, or in batches near the edges. The policy is "outside" which I guess is conservative. Maybe extrapolate to fill these in?

[tomjunk]

Looks okay, except for all those nans in sbnd_cathode_v8.txt