Setting the SecondNucleonEmitter at run-time and enabling SRC in CC-QEL interactions by CarlosNeutrino · Pull Request #506 · GENIE-MC/Generator

CarlosNeutrino · 2026-07-07T12:31:55Z

Description

This Pull Request changes the way the SecondNucleonEmitter for SRC is configured. It adds the SecondNucleonEmitter in CC-QEL events (not configured before, as QELEventGenerator does not use FermiMover):

Before this changes, the SecondNucleonEmitter was only read from the config/ files independently from the NuclearModel.
The SecondNucleonEmitter depends strongly on the NuclearModel, and the code was using incompatible SecondNucleonEmitter algorithms for the specified global NuclearModel.
StringUtils.h → used for Split
Now, the SecondNucleonEmitter is configured at run-time depending on the global NuclearModel. In specific, the new code:
- config/FermiMover.xml and config/QELEventGenerator.xml include two new strings ("NuclearModels" and "SecondNucleonEmitters") that read the NuclearModel along with the corresponding SecondNucleonEmitter
- FermiMover.cxx and QELEventGenerator.cxx LoadConfig() reads the strings and sets the correct SecondNucleonEmitter.
- The globally configured NuclearModel is read from the GlobalParameterList.

Development

A future improvement is to create a standalone module that runs SecondEmitter independently, so we do not duplicate the code in FermiMover and QELEventGenerator

Notes for reviewers

I tried to read the NuclearModel from EventGeneratorListAssembler but there was not any simpler way of doing it (neither did I manage to make it work) John Plows and I agreed to go ahead with GlobalParameterList
I have tested that the code compiles and it runs.

…rithm is decided at run time instead of directly from the FermiMover.xml file. This avoids that the SecondNucleonEjection and NuclearModel could be incompatible

…leon emitter

Copilot

Pull request overview

This pull request makes the SRC SecondNucleonEmitter selection depend on the globally configured NuclearModel at runtime (instead of being fixed purely by per-algorithm XML), and enables SecondNucleonEmitter handling in CC-QEL event generation.

Changes:

Add runtime mapping logic in FermiMover and QELEventGenerator to choose a SecondNucleonEmissionI implementation based on the global NuclearModel.
Extend config/FermiMover.xml and config/QELEventGenerator.xml with NuclearModels / SecondNucleonEmitters string lists to define the mapping.
Invoke SecondNucleonEmissionI::ProcessEventRecord() in QELEventGenerator before creating the remnant nucleus so the remnant accounts for a possible second nucleon.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Physics/QuasiElastic/EventGen/QELEventGenerator.h	Adds SecondNucleonEmitter state and mapping container.
src/Physics/QuasiElastic/EventGen/QELEventGenerator.cxx	Selects SecondNucleonEmitter at runtime from global NuclearModel and applies it during event record processing.
src/Physics/NuclearState/FermiMover.h	Adds mapping container for NuclearModel → SecondNucleonEmitter.
src/Physics/NuclearState/FermiMover.cxx	Selects SecondNucleonEmitter at runtime from global NuclearModel (replacing fixed sub-alg selection).
config/QELEventGenerator.xml	Adds NuclearModel/SecondNucleonEmitter mapping strings for QEL generator config.
config/FermiMover.xml	Adds NuclearModel/SecondNucleonEmitter mapping strings for FermiMover config.

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kjplows · 2026-07-17T16:15:00Z

  <param_set name="Default">
-     <param type="bool"   name="KeepHitNuclOnMassShell"> false                     </param>
-     <param type="alg" name="SecondNucleonEmitter"> genie::SpectralFunction2p2h/Default </param>
+      <param type="bool"   name="KeepHitNuclOnMassShell"> false                     </param>


Extra indentation... Not the end of the world but worth pointing out.

kjplows · 2026-07-17T16:28:39Z

+
+      <!-- Possible SecondNucleonEmitters for every different NuclearModel -->
+      <param type="string" name="NuclearModels">genie::LocalFGM;genie::FGMBodekRitchie;genie::EffectiveSF</param>
+      <param type="string" name="SecondNucleonEmitters">genie::SRCNuclearRecoil/Default;genie::SRCNuclearRecoil/Default;genie::SpectralFunction2p2h/Default</param>


Just to point out some GENIE functionality here: you can use <param type="vec-string" name="SecondNuclearEmitters" delim=";"> and access the values as a std::vector using Algorithm::GetParamVect - see config/QELEventGeneratorSM.xml and src/Physics/QuasiElastic/EventGen/QELEventGeneratorSM.cxx::LoadConfig()

kjplows

Overall looks good, thank you @CarlosNeutrino ! Requesting changes for the following:

GetParamVect and vec-string where possible
We should discuss making the silent continue statement on second-nucleon-emission load a proper Exception.

kjplows · 2026-07-17T16:30:33Z

-  assert(fSecondEmitter);
+  // Build nuclear-model algorithm name -> SecondNucleonEmitter algorithm,
+  std::string nucl_model_names_str, fermi_mover_algids_str;
+  this->GetParam("NuclearModels",         nucl_model_names_str);


See comment on the config about loading these directly into std::vector<std::string> 🙂
(also saves you from including StringUtils.h)

kjplows · 2026-07-17T16:33:47Z

+    const SecondNucleonEmissionI * emitter =
+      dynamic_cast<const SecondNucleonEmissionI *>(alg);
+    if (!emitter) {
+    LOG("FermiMover", pWARN)


I would argue making this an exception, rather than a silent continue. If this statement triggers it's either a misconfiguration or a bad runtime load, both should trigger warnings and interrupt execution. Happy to defer to @sjgardiner or @nusense on this.

kjplows · 2026-07-17T16:37:35Z

+    this->GetParam("NuclearModels",         nucl_model_names_str);
+    this->GetParam("SecondNucleonEmitters", fermi_mover_algids_str);
+
+    std::vector<std::string> nucl_model_names  = genie::utils::str::Split(nucl_model_names_str, ";");


Same comment as above, you can avoid this with GetParamVect

kjplows · 2026-07-17T16:39:17Z

+        LOG("QELEvent", pWARN)
+        << "No SecondNucleonEmitter for nuclear model "
+        << nucl_model_name << " -- SRC recoil disabled";
+    } 


(This is not so much directed at this PR but applies anyway) - not a huge fan of duplicating code, but given QELEventGenerator contains duplicate code anyway, this is at least consistent. Maintenance caveat: any PRs targeting SecondNucleonEmitter have to be done in two locations in code.

Carlos Martin Morales and others added 8 commits May 28, 2026 03:47

Fixed conflict in LocalFGM.cxx

27e4d7d

Eliminated SRCFlag (unused)

e0ba7b8

Changed the config and src code so that the SeconNucleonEjection algo…

2e8bc3c

…rithm is decided at run time instead of directly from the FermiMover.xml file. This avoids that the SecondNucleonEjection and NuclearModel could be incompatible

Eliminated single cout that was left

c907a85

Eliminated two cout that was left

21bdc09

config/ files determine explicitely the nuclear model <--> second nuc…

36e1924

…leon emitter

Deleted ._* files accidentally commmited

65e0e59

Cleanup

65126f9

CarlosNeutrino marked this pull request as ready for review July 7, 2026 14:28

Copilot AI review requested due to automatic review settings July 7, 2026 14:28

Copilot started reviewing on behalf of CarlosNeutrino July 7, 2026 14:29 View session

CarlosNeutrino marked this pull request as draft July 7, 2026 14:31

Copilot AI reviewed Jul 7, 2026

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Fixed LOG message

72672cc

CarlosNeutrino changed the title ~~Setting the SecondNucleonEmitter at run-time~~ Setting the SecondNucleonEmitter at run-time and enabling SRC in CC-QEL interactions Jul 7, 2026

CarlosNeutrino marked this pull request as ready for review July 7, 2026 15:28

CarlosNeutrino marked this pull request as draft July 7, 2026 15:28

Added changes suggested by copilot

b760f0d

CarlosNeutrino force-pushed the cmorales/SRC_fix_AR23 branch from 8028184 to b760f0d Compare July 7, 2026 16:00

CarlosNeutrino marked this pull request as ready for review July 8, 2026 09:15

kjplows reviewed Jul 17, 2026

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kjplows requested changes Jul 17, 2026

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Setting the SecondNucleonEmitter at run-time and enabling SRC in CC-QEL interactions#506

Setting the SecondNucleonEmitter at run-time and enabling SRC in CC-QEL interactions#506
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CarlosNeutrino:cmorales/SRC_fix_AR23

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CarlosNeutrino commented Jul 7, 2026

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