fix: Robust perigee propagation in HelicalTrackLinearizer (acts-pro…

…ject#2930) This fixes another case where the overstepping tolerance bites us from behind. Perigee surfaces are prone to the issue of bad path length estimation so we need a special treatment. discovered in acts-project#2917
asalzburger · May 21, 2024 · bf4f665 · bf4f665
1 parent 66d6d19
commit bf4f665
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Showing 6 changed files with 32 additions and 5 deletions.
diff --git a/CI/physmon/reference/performance_ivf_orthogonal_hist.root b/CI/physmon/reference/performance_ivf_orthogonal_hist.root
diff --git a/CI/physmon/reference/performance_ivf_seeded_hist.root b/CI/physmon/reference/performance_ivf_seeded_hist.root
diff --git a/CI/physmon/reference/performance_ivf_truth_estimated_hist.root b/CI/physmon/reference/performance_ivf_truth_estimated_hist.root
diff --git a/CI/physmon/reference/performance_ivf_truth_smeared_hist.root b/CI/physmon/reference/performance_ivf_truth_smeared_hist.root
diff --git a/Core/include/Acts/Propagator/Propagator.ipp b/Core/include/Acts/Propagator/Propagator.ipp
@@ -7,8 +7,10 @@
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 #include "Acts/EventData/TrackParametersConcept.hpp"
+#include "Acts/Propagator/ActionList.hpp"
 #include "Acts/Propagator/ConstrainedStep.hpp"
 #include "Acts/Propagator/PropagatorError.hpp"
+#include "Acts/Propagator/StandardAborters.hpp"
 #include "Acts/Propagator/detail/LoopProtection.hpp"
 
 #include <type_traits>
@@ -327,13 +329,30 @@ Acts::Result<Acts::BoundTrackParameters>
 Acts::detail::BasePropagatorHelper<derived_t>::propagateToSurface(
     const BoundTrackParameters& start, const Surface& target,
     const Options& options) const {
-  auto res = static_cast<const derived_t*>(this)
-                 ->template propagate<BoundTrackParameters, PropagatorOptions<>,
-                                      SurfaceReached, PathLimitReached>(
-                     start, target, options);
+  using ResultType = Result<typename derived_t::template action_list_t_result_t<
+      BoundTrackParameters, ActionList<>>>;
+
+  // dummy initialization
+  ResultType res = ResultType::failure(PropagatorError::Failure);
+
+  // Due to the geometry of the perigee surface the overstepping tolerance
+  // is sometimes not met.
+  if (target.type() == Surface::SurfaceType::Perigee) {
+    res = static_cast<const derived_t*>(this)
+              ->template propagate<BoundTrackParameters, PropagatorOptions<>,
+                                   ForcedSurfaceReached, PathLimitReached>(
+                  start, target, options);
+  } else {
+    res = static_cast<const derived_t*>(this)
+              ->template propagate<BoundTrackParameters, PropagatorOptions<>,
+                                   SurfaceReached, PathLimitReached>(
+                  start, target, options);
+  }
 
   if (res.ok()) {
-    // @TODO: Return optional?
+    // Without errors we can expect a valid endParameters when propagating to a
+    // target surface
+    assert((*res).endParameters);
     return std::move((*res).endParameters.value());
   } else {
     return res.error();

diff --git a/Core/include/Acts/Propagator/StandardAborters.hpp b/Core/include/Acts/Propagator/StandardAborters.hpp
@@ -155,6 +155,14 @@ struct SurfaceReached {
   }
 };
 
+/// Similar to SurfaceReached, but with an infinite overstep limit.
+///
+/// This can be used to force the propagation to the target surface.
+struct ForcedSurfaceReached : SurfaceReached {
+  ForcedSurfaceReached()
+      : SurfaceReached(std::numeric_limits<double>::lowest()) {}
+};
+
 /// This is the condition that the end of World has been reached
 /// it then triggers an propagation abort
 struct EndOfWorldReached {