feat: configurable weight factor for longitudinal impact parameter in seed weight

Core/include/Acts/Seeding/SeedFilter.ipp

@@ -159,7 +159,8 @@ void SeedFilter<external_spacepoint_t>::filterSeeds_2SpFixed(
       }
 
       // term on the weight that depends on the value of zOrigin
-      weight += -std::abs(zOrigin) + m_cfg.compatSeedWeight;
+      weight += -(std::abs(zOrigin) * m_cfg.zOriginWeightFactor) +
+                m_cfg.compatSeedWeight;
 
       // skip a bad quality seed if any of its constituents has a weight larger
       // than the seed weight

Core/include/Acts/Seeding/SeedFilterConfig.hpp

@@ -19,9 +19,12 @@ struct SeedFilterConfig {
   // the allowed delta between two inverted seed radii for them to be considered
   // compatible.
   float deltaInvHelixDiameter = 0.00003 * 1. / Acts::UnitConstants::mm;
-  // the impact parameters (d0) is multiplied by this factor and subtracted from
-  // weight
+  // the transverse impact parameters (d0) is multiplied by this factor and
+  // subtracted from weight
   float impactWeightFactor = 1.;
+  // the logitudinal impact parameters (z0) is multiplied by this factor and
+  // subtracted from weight
+  float zOriginWeightFactor = 1.;
   // seed weight increased by this value if a compatible seed has been found.
   float compatSeedWeight = 200.;
   // minimum distance between compatible seeds to be considered for weight boost

Examples/Python/python/acts/examples/itk.py

@@ -328,6 +328,7 @@ def itkSeedingAlgConfig(inputSpacePointsType):
         seedConfMaxZOrigin=150.0 * u.mm,
         minImpactSeedConf=1.0 * u.mm,
     )
+    zOriginWeightFactor = 1
     compatSeedWeight = 100
     curvatureSortingInFilter = True
     phiMin = 0
@@ -487,6 +488,7 @@ def itkSeedingAlgConfig(inputSpacePointsType):
     )
     seedFilterConfigArg = SeedFilterConfigArg(
         impactWeightFactor=impactWeightFactor,
+        zOriginWeightFactor=zOriginWeightFactor,
         compatSeedWeight=compatSeedWeight,
         compatSeedLimit=compatSeedLimit,
         numSeedIncrement=numSeedIncrement,

Examples/Python/python/acts/examples/reconstruction.py

@@ -65,6 +65,7 @@
     "SeedFilterConfig",
     [
         "impactWeightFactor",
+        "zOriginWeightFactor",
         "compatSeedWeight",
         "compatSeedLimit",
         "numSeedIncrement",
@@ -76,7 +77,7 @@
         "useDeltaRorTopRadius",
         "deltaRMin",
     ],
-    defaults=[None] * 11,
+    defaults=[None] * 12,
 )
 
 SpacePointGridConfigArg = namedtuple(
@@ -364,6 +365,7 @@ def addSeeding(
                         else seedFilterConfigArg.deltaRMin
                     ),
                     impactWeightFactor=seedFilterConfigArg.impactWeightFactor,
+                    zOriginWeightFactor=seedFilterConfigArg.zOriginWeightFactor,
                     compatSeedWeight=seedFilterConfigArg.compatSeedWeight,
                     compatSeedLimit=seedFilterConfigArg.compatSeedLimit,
                     numSeedIncrement=seedFilterConfigArg.numSeedIncrement,
@@ -486,6 +488,7 @@ def addSeeding(
                         else seedFilterConfigArg.deltaRMin
                     ),
                     impactWeightFactor=seedFilterConfigArg.impactWeightFactor,
+                    zOriginWeightFactor=seedFilterConfigArg.zOriginWeightFactor,
                     compatSeedWeight=seedFilterConfigArg.compatSeedWeight,
                     compatSeedLimit=seedFilterConfigArg.compatSeedLimit,
                     numSeedIncrement=seedFilterConfigArg.numSeedIncrement,

Examples/Python/src/TrackFinding.cpp

@@ -43,6 +43,7 @@ void addTrackFinding(Context& ctx) {
     ACTS_PYTHON_STRUCT_BEGIN(c, Config);
     ACTS_PYTHON_MEMBER(deltaInvHelixDiameter);
     ACTS_PYTHON_MEMBER(impactWeightFactor);
+    ACTS_PYTHON_MEMBER(zOriginWeightFactor);
     ACTS_PYTHON_MEMBER(compatSeedWeight);
     ACTS_PYTHON_MEMBER(deltaRMin);
     ACTS_PYTHON_MEMBER(maxSeedsPerSpM);

docs/core/seeding.md

@@ -209,10 +209,6 @@ likely to stem from a particle than another seed using the same middle SP with
 smaller impact parameters. The number of compatible seeds ($N_t$) is used to increase the weight, as a higher number of measurements 
 will lead to higher quality tracks.  Finally, the weight can also be affected by optional detector-specific cuts.
 
-:::{note} 
-The $z_0$ term in the weight is not yet fully configurable, but this will change soon.
-:::
-
 The {func}`SeedFilter::filterSeeds_2SpFixed` function also includes a configurable {class}`Acts::SeedConfirmationRangeConfig` seed confirmation step that, when enabled,
 classifies higher quality seeds as "quality confined" seeds if they fall within a predefined range of parameters ($d_0$, $z_0$ and $N_t$) that also
 depends on the region of the detector (i.e., forward or central region). If the seed is not