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feat: Add GSF momentum cut v2 #4903

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28f6bb7
add cut
benjaminhuth Dec 10, 2025
d17996a
do it
benjaminhuth Dec 11, 2025
5c30342
Merge remote-tracking branch 'upstream/main' into fix/gsf-efficiency
benjaminhuth Dec 11, 2025
9859961
restore
benjaminhuth Dec 11, 2025
79fdb4c
fix
benjaminhuth Dec 11, 2025
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2 changes: 2 additions & 0 deletions Core/include/Acts/TrackFitting/GsfOptions.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,8 @@ struct GsfOptions {

double weightCutoff = 1.e-4;

double transverseMomentumCut = 0.0; // GeV, no cut by default

bool abortOnError = false;

bool disableAllMaterialHandling = false;
Expand Down
44 changes: 38 additions & 6 deletions Core/include/Acts/TrackFitting/detail/GsfActor.hpp
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Expand Up @@ -97,6 +97,9 @@ struct GsfActor {
/// When to discard components
double weightCutoff = 1.0e-4;

/// Minimum transverse momentum (in GeV) for components
double transverseMomentumCut = 0.0; // GeV, no cut by default

/// When this option is enabled, material information on all surfaces is
/// ignored. This disables the component convolution as well as the handling
/// of energy. This may be useful for debugging.
Expand Down Expand Up @@ -271,6 +274,13 @@ struct GsfActor {
return;
}

// Check if all components were removed by momentum cut
if (tmpStates.tips.empty()) {
ACTS_VERBOSE("All components removed by transverse momentum cut");
stepper.clearComponents(state.stepping);
return;
}

updateStepper(state, stepper, tmpStates);
}
// We have material, we thus need a component cache since we will
Expand Down Expand Up @@ -301,11 +311,9 @@ struct GsfActor {
result);

if (componentCache.empty()) {
ACTS_WARNING(
"No components left after applying energy loss. "
"Is the weight cutoff "
<< m_cfg.weightCutoff << " too high?");
ACTS_WARNING("Return to propagator without applying energy loss");
ACTS_VERBOSE(
"All components removed by cuts (weight or momentum cutoff)");
stepper.clearComponents(state.stepping);
return;
}

Expand All @@ -328,7 +336,7 @@ struct GsfActor {

template <typename propagator_state_t, typename stepper_t,
typename navigator_t>
bool checkAbort(propagator_state_t& /*state*/, const stepper_t& /*stepper*/,
bool checkAbort(propagator_state_t& state, const stepper_t& stepper,
const navigator_t& /*navigator*/, const result_type& result,
const Logger& /*logger*/) const {
if (m_cfg.numberMeasurements &&
Expand All @@ -337,6 +345,13 @@ struct GsfActor {
return true;
}

// Stop if all components have been removed
if (stepper.numberComponents(state.stepping) == 0) {
ACTS_VERBOSE(
"Stop navigation because all components were removed by cuts");
return true;
}

return false;
}

Expand Down Expand Up @@ -434,6 +449,14 @@ struct GsfActor {
}();

assert(p_prev + delta_p > 0. && "new momentum must be > 0");

// Apply pT cut here to avoid const of expansion and merging later
const auto pT = (p_prev + delta_p) * std::sin(new_pars[eBoundTheta]);
if (pT < m_cfg.transverseMomentumCut) {
ACTS_VERBOSE("Skip new component with pT=" << pT << " GeV");
continue;
}

new_pars[eBoundQOverP] =
particleHypothesis.qOverP(p_prev + delta_p, old_bound.charge());

Expand Down Expand Up @@ -583,6 +606,14 @@ struct GsfActor {

const auto& trackStateProxy = *trackStateProxyRes;

const auto &params = trackStateProxy.parameters();
const auto p = stepper.particleHypothesis(state.stepping).extractMomentum(params[eBoundQOverP]);
const auto pT = p * std::sin(params[eBoundTheta]);
if (pT < m_cfg.transverseMomentumCut) {
ACTS_VERBOSE("Skip component with pT=" << pT << " after Kalman update");
continue;
}

// If at least one component is no outlier, we consider the whole thing
// as a measurementState
if (trackStateProxy.typeFlags().test(TrackStateFlag::MeasurementFlag)) {
Expand Down Expand Up @@ -801,6 +832,7 @@ struct GsfActor {
m_cfg.abortOnError = options.abortOnError;
m_cfg.disableAllMaterialHandling = options.disableAllMaterialHandling;
m_cfg.weightCutoff = options.weightCutoff;
m_cfg.transverseMomentumCut = options.transverseMomentumCut;
m_cfg.mergeMethod = options.componentMergeMethod;
m_cfg.calibrationContext = &options.calibrationContext.get();
}
Expand Down
3 changes: 3 additions & 0 deletions Examples/Algorithms/TrackFitting/include/ActsExamples/TrackFitting/TrackFitterFunction.hpp
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Expand Up @@ -93,6 +93,8 @@ enum class MixtureReductionAlgorithm { weightCut, KLDistance };
/// @param betheHeitlerApprox The object that encapsulates the approximation.
/// @param maxComponents number of maximum components in the track state
/// @param weightCutoff when to drop components
/// @param transverseMomentumCut minimum transverse momentum (in GeV) for
/// components
/// @param componentMergeMethod How to merge a mixture to a single set of
/// parameters and covariance
/// @param mixtureReductionAlgorithm How to reduce the number of components
Expand All @@ -105,6 +107,7 @@ std::shared_ptr<TrackFitterFunction> makeGsfFitterFunction(
std::shared_ptr<const Acts::MagneticFieldProvider> magneticField,
const std::shared_ptr<const Acts::BetheHeitlerApprox>& betheHeitlerApprox,
std::size_t maxComponents, double weightCutoff,
double transverseMomentumCut,
Acts::ComponentMergeMethod componentMergeMethod,
MixtureReductionAlgorithm mixtureReductionAlgorithm,
double reverseFilteringCovarianceScaling, const Acts::Logger& logger);
Expand Down
6 changes: 5 additions & 1 deletion Examples/Algorithms/TrackFitting/src/GsfFitterFunction.cpp
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Expand Up @@ -60,7 +60,8 @@ struct GsfFitterFunctionImpl final : public ActsExamples::TrackFitterFunction {

std::size_t maxComponents = 0;
double weightCutoff = 0;
const double momentumCutoff = 0; // 500_MeV;
double transverseMomentumCut = 0.0; // GeV, no cut by default
const double momentumCutoff = 0; // 500_MeV;
bool abortOnError = false;
bool disableAllMaterialHandling = false;
MixtureReductionAlgorithm reductionAlg =
Expand Down Expand Up @@ -93,6 +94,7 @@ struct GsfFitterFunctionImpl final : public ActsExamples::TrackFitterFunction {
gsfOptions.referenceSurface = options.referenceSurface;
gsfOptions.maxComponents = maxComponents;
gsfOptions.weightCutoff = weightCutoff;
gsfOptions.transverseMomentumCut = transverseMomentumCut;
gsfOptions.abortOnError = abortOnError;
gsfOptions.disableAllMaterialHandling = disableAllMaterialHandling;
gsfOptions.componentMergeMethod = mergeMethod;
Expand Down Expand Up @@ -177,6 +179,7 @@ std::shared_ptr<TrackFitterFunction> ActsExamples::makeGsfFitterFunction(
std::shared_ptr<const Acts::MagneticFieldProvider> magneticField,
const std::shared_ptr<const Acts::BetheHeitlerApprox>& betheHeitlerApprox,
std::size_t maxComponents, double weightCutoff,
double transverseMomentumCut,
Acts::ComponentMergeMethod componentMergeMethod,
MixtureReductionAlgorithm mixtureReductionAlgorithm,
double reverseFilteringCovarianceScaling, const Acts::Logger& logger) {
Expand Down Expand Up @@ -210,6 +213,7 @@ std::shared_ptr<TrackFitterFunction> ActsExamples::makeGsfFitterFunction(
std::move(trackFitter), std::move(directTrackFitter), geo);
fitterFunction->maxComponents = maxComponents;
fitterFunction->weightCutoff = weightCutoff;
fitterFunction->transverseMomentumCut = transverseMomentumCut;
fitterFunction->mergeMethod = componentMergeMethod;
fitterFunction->reductionAlg = mixtureReductionAlgorithm;
fitterFunction->reverseFilteringCovarianceScaling =
Expand Down
2 changes: 2 additions & 0 deletions Python/Examples/python/reconstruction.py
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Expand Up @@ -1643,6 +1643,7 @@ def addTruthTrackingGsf(
trackingGeometry: acts.TrackingGeometry,
field: acts.MagneticFieldProvider,
inputProtoTracks: str = "truth_particle_tracks",
transverseMomentumCut: float = 0.5,
logLevel: Optional[acts.logging.Level] = None,
) -> None:
customLogLevel = acts.examples.defaultLogging(s, logLevel)
Expand All @@ -1658,6 +1659,7 @@ def addTruthTrackingGsf(
"componentMergeMethod": acts.examples.ComponentMergeMethod.maxWeight,
"mixtureReductionAlgorithm": acts.examples.MixtureReductionAlgorithm.KLDistance,
"weightCutoff": 1.0e-4,
"transverseMomentumCut": transverseMomentumCut,
"reverseFilteringCovarianceScaling": 100.0,
"level": customLogLevel(),
}
Expand Down
11 changes: 6 additions & 5 deletions Python/Examples/src/TrackFitting.cpp
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Expand Up @@ -112,20 +112,21 @@ void addTrackFitting(py::module& mex) {
std::shared_ptr<const MagneticFieldProvider> magneticField,
const std::shared_ptr<const BetheHeitlerApprox>& betheHeitlerApprox,
std::size_t maxComponents, double weightCutoff,
double transverseMomentumCut,
ComponentMergeMethod componentMergeMethod,
MixtureReductionAlgorithm mixtureReductionAlgorithm,
double reverseFilteringCovarianceScaling, Logging::Level level) {
return makeGsfFitterFunction(
std::move(trackingGeometry), std::move(magneticField),
betheHeitlerApprox, maxComponents, weightCutoff,
componentMergeMethod, mixtureReductionAlgorithm,
reverseFilteringCovarianceScaling,
transverseMomentumCut, componentMergeMethod,
mixtureReductionAlgorithm, reverseFilteringCovarianceScaling,
*getDefaultLogger("GSFFunc", level));
},
"trackingGeometry"_a, "magneticField"_a, "betheHeitlerApprox"_a,
"maxComponents"_a, "weightCutoff"_a, "componentMergeMethod"_a,
"mixtureReductionAlgorithm"_a, "reverseFilteringCovarianceScaling"_a,
"level"_a);
"maxComponents"_a, "weightCutoff"_a, "transverseMomentumCut"_a,
"componentMergeMethod"_a, "mixtureReductionAlgorithm"_a,
"reverseFilteringCovarianceScaling"_a, "level"_a);

mex.def(
"makeGlobalChiSquareFitterFunction",
Expand Down
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