fix(layout)!: follow integration layout 2026-0.1 along the beam

src/SHiPGeometry.cpp

@@ -65,12 +65,15 @@ GeoPhysVol* SHiPGeometryBuilder::build() {
                GeoTrf::Translate3D(0.0, 0.0, 28.95 * m));
 
     // Build and place UpstreamTagger (sensitive scintillator slab)
-    // Z: 32.52 to 32.92 m → centre: 32.72 m
+    // Integration layout 2026-0.1 (EDMS 3287817 v1.1): 0.4 m slot from 32.67
+    // to 33.07 m at the entrance of the decay volume. The 160 mm tile plane is
+    // placed inside that slot with its rear face flush with the decay-volume
+    // container (32.92 m), so it cannot sit exactly on the slot mid-plane.
     SHiPUBTManager ubtManager;
     UpstreamTaggerFactory upstreamTaggerFactory(materials);
     GeoVPhysVol* upstreamTagger = upstreamTaggerFactory.build(&ubtManager);
     placeChild(world, upstreamTagger, "/SHiP/upstream_tagger", 3,
-               GeoTrf::Translate3D(0.0, 0.0, 32.72 * m));
+               GeoTrf::Translate3D(0.0, 0.0, 32.84 * m));
 
     // Build and place DecayVolume
     // Z: 32.92 to 83.32 m → centre: 58.12 m
@@ -81,25 +84,27 @@ GeoPhysVol* SHiPGeometryBuilder::build() {
 
     // Build and place Trackers (container with 4 stations).
     // The factory already handles internal positioning; place the container at
-    // its centre Z (average of station 1 and 4 centres).
+    // its centre Z (average of station 1 and 4 centres, integration layout
+    // 2026-0.1: station mid-planes at 84.22, 86.22, 93.22 and 95.22 m).
     TrackersFactory trackersFactory(materials);
     GeoPhysVol* trackers = trackersFactory.build();
-    constexpr double trackersCentreZ = (84.07 + 95.07) / 2.0 * m;
+    constexpr double trackersCentreZ = (84.22 + 95.22) / 2.0 * m;
     placeChild(world, trackers, "/SHiP/trackers", 5,
                GeoTrf::Translate3D(0.0, 0.0, trackersCentreZ));
 
     // Build and place Magnet
-    // Z: 87.07 to 92.07 m → centre: 89.57 m
+    // Integration layout 2026-0.1: 5 m slot with its mid-plane at 89.72 m.
     MagnetFactory magnetFactory(materials);
     GeoPhysVol* magnet = magnetFactory.build();
-    placeChild(world, magnet, "/SHiP/magnet", 6, GeoTrf::Translate3D(0.0, 0.0, 89.57 * m));
+    placeChild(world, magnet, "/SHiP/magnet", 6, GeoTrf::Translate3D(0.0, 0.0, 89.72 * m));
 
     // Build and place TimingDetector
-    // Z: 95.902 m (from GDML reference)
+    // Integration layout 2026-0.1: 0.46 m slot from 96.14 to 96.60 m, placed
+    // at the slot centre.
     TimingDetectorFactory timingDetectorFactory(materials);
     GeoPhysVol* timingDetector = timingDetectorFactory.build();
     placeChild(world, timingDetector, "/SHiP/timing_detector", 7,
-               GeoTrf::Translate3D(0.0, 0.0, 95.902 * m));
+               GeoTrf::Translate3D(0.0, 0.0, 96.37 * m));
 
     // Build and place Calorimeter (ECAL + HCAL).
     // The layer structure comes from CalorimeterConstants.h; the outer container

subsystems/Magnet/README.md

@@ -21,7 +21,7 @@ SHiPMagnet (Air, 6500×8600×5000 mm)
  └─ CV_4 (Aluminium)                        at (-2600, 0, +1525)
 ```
 
-Position in world: z = 89570 mm.
+Position in world: z = 89720 mm (mid-plane of the 87.22–92.22 m slot in integration layout 2026-0.1, EDMS 3287817 v1.1).
 
 ## Materials
 

subsystems/TimingDetector/README.md

@@ -14,7 +14,7 @@ Timing_Detector (Air, 5500×6500×500 mm)
      3 columns × 110 rows; z stagger = (row%2)·12 + (col%2)·90 mm
 ```
 
-Position in world: z = 95902 mm.
+Position in world: z = 96370 mm (centre of the 96.14–96.60 m slot in integration layout 2026-0.1, EDMS 3287817 v1.1).
 
 ## Materials
 

subsystems/Trackers/README.md

@@ -32,18 +32,18 @@ The spectrometer dipole between stations 2 and 3 is a separate subsystem
  └─ /SHiP/trackers/tracker_magnet (Air, inert marker box)
 ```
 
-Station Z positions (centres): 84070, 86070, 93070, 95070 mm.
-Position in world: centred at z = 89570 mm (average of stations 1 and 4).
+Station Z positions (centres): 84220, 86220, 93220, 95220 mm.
+Position in world: centred at z = 89720 mm (average of stations 1 and 4).
 Stations 1-2 are upstream of the magnet, stations 3-4 downstream.
 
 ## Tracker magnet
 
 `/SHiP/trackers/tracker_magnet` is an inert, air-filled marker volume for
-the tracker magnet, centred at z = 86820 mm with a 460 mm Z extent.
+the tracker magnet, centred at z = 86970 mm with a 460 mm Z extent.
 
 It is **not** a physically-scaled dipole. The spectrometer dipole proper is
-the separate `Magnet` subsystem (iron yoke + coils) occupying z = 87.07 to
-92.07 m. The only space inside the trackers container that is clear of both
+the separate `Magnet` subsystem (iron yoke + coils) occupying z = 87.22 to
+92.22 m. The only space inside the trackers container that is clear of both
 the straw stations and that yoke is the ~0.5 m gap between station 2 and the
 yoke, so the marker is sized and placed to fit there without overlap.
 

subsystems/Trackers/include/Trackers/TrackersFactory.h

@@ -19,10 +19,11 @@ class SHiPMaterials;
  *
  * Builds 4 straw tracking stations for the SHiP spectrometer. Station
  * envelopes and z-positions follow the GDML reference / subsystem_envelopes.csv:
- * - Station 1: Z 83.57-84.57 m → centre 84.07 m
- * - Station 2: Z 85.57-86.57 m → centre 86.07 m
- * - Station 3: Z 92.57-93.57 m → centre 93.07 m
- * - Station 4: Z 94.57-95.57 m → centre 95.07 m
+ * - Station 1: Z 83.72-84.72 m → centre 84.22 m
+ * - Station 2: Z 85.72-86.72 m → centre 86.22 m
+ * - Station 3: Z 92.72-93.72 m → centre 93.22 m
+ * - Station 4: Z 94.72-95.72 m → centre 95.22 m
+ *   (integration layout 2026-0.1, EDMS 3287817 v1.1)
  * Station envelope (GDML statbox): half 3000 × 3430 × 500 mm.
  *
  * Each station envelope is filled with 4 stereo views. A view is a material
@@ -78,12 +79,12 @@ class TrackersFactory {
     //
     // NOTE: this is NOT a physically-scaled dipole. The spectrometer dipole
     // proper is the separate Magnet subsystem (iron yoke + coils) occupying
-    // z = 87.07-92.07 m. The only free space inside the trackers container
+    // z = 87.22-92.22 m. The only free space inside the trackers container
     // and clear of that yoke is a ~0.5 m gap, so this marker is sized to fit
     // there. It exists so the tracker magnet has a named placeholder in the
     // geometry; simulation/field code can locate it by the name
     // "/SHiP/trackers/tracker_magnet".
-    static constexpr double s_trackerMagnetZ = 86820.0 * mm;    ///< centre
+    static constexpr double s_trackerMagnetZ = 86970.0 * mm;    ///< centre
     static constexpr double s_trackerMagnetHalfZ = 230.0 * mm;  ///< half-depth
 
    private:
@@ -98,10 +99,10 @@ class TrackersFactory {
     static constexpr double s_halfZ = 500.0 * mm;   // 50 cm
 
     // Station Z positions (centres, from origin).
-    static constexpr double s_station1Z = 84070.0 * mm;  // 84.07 m
-    static constexpr double s_station2Z = 86070.0 * mm;  // 86.07 m
-    static constexpr double s_station3Z = 93070.0 * mm;  // 93.07 m
-    static constexpr double s_station4Z = 95070.0 * mm;  // 95.07 m
+    static constexpr double s_station1Z = 84220.0 * mm;  // 84.22 m
+    static constexpr double s_station2Z = 86220.0 * mm;  // 86.22 m
+    static constexpr double s_station3Z = 93220.0 * mm;  // 93.22 m
+    static constexpr double s_station4Z = 95220.0 * mm;  // 95.22 m
 
     // Container dimensions (spans all stations).
     static constexpr double s_containerHalfZ = (s_station4Z - s_station1Z) / 2.0 + s_halfZ;

subsystems/Trackers/test_trackers.cpp

@@ -95,10 +95,10 @@ TEST_CASE("TrackersHasTrackerMagnet", "[trackers]") {
     REQUIRE(tm != nullptr);
     auto* box = dynamic_cast<const GeoBox*>(tm->getLogVol()->getShape());
     REQUIRE(box != nullptr);
-    // Span must stay clear of station 2 (ends 86570 mm) and the Magnet yoke
-    // (starts 87070 mm): 86570 <= centre ± halfZ <= 87070.
+    // Span must stay clear of station 2 (ends 86720 mm) and the Magnet slot
+    // (starts 87220 mm): 86720 <= centre ± halfZ <= 87220.
     const double centre = TrackersFactory::s_trackerMagnetZ;
     const double halfZ = box->getZHalfLength();
-    CHECK(centre - halfZ >= 86570.0);
-    CHECK(centre + halfZ <= 87070.0);
+    CHECK(centre - halfZ >= 86720.0);
+    CHECK(centre + halfZ <= 87220.0);
 }

subsystems/UpstreamTagger/README.md

@@ -59,7 +59,7 @@ registered with `SHiPUBTManager`.
 Tile totals: fine 2 × 400 + 2 × 19 200 = 39 200; coarse 300 + 2 × 3 750 = 7 800;
 **47 000 tiles** in total.
 
-Position in world: z = 32 720 mm (centre of the 32.52–32.92 m envelope).
+Position in world: z = 32 840 mm (inside the 32.67–33.07 m slot of integration layout 2026-0.1, EDMS 3287817 v1.1, with the rear face flush with the decay-volume container at 32.92 m).
 
 ## Materials
 

subsystems/UpstreamTagger/include/UpstreamTagger/UpstreamTaggerFactory.h

@@ -45,9 +45,9 @@ class SHiPUBTManager;
  * "/SHiP/upstream_tagger/..." names, mirroring the calorimeter bar layers;
  * sensitive-detector assignment is performed downstream by name pattern.
  *
- * The container envelope (half 2200 × 3200 × 80 mm, centre Z = 32 720 mm)
- * is unchanged from the previous monolithic slab so the placement in
- * SHiPGeometry and the subsystem-envelope consistency checks still hold.
+ * The container envelope (half 2200 × 3200 × 80 mm) has the same dimensions
+ * as the previous monolithic slab, so the subsystem-envelope consistency
+ * checks still hold. SHiPGeometry places it at centre Z = 32 840 mm.
  */
 class UpstreamTaggerFactory {
    public:

tests/test_consistency.cpp

@@ -177,16 +177,18 @@
         double tolerance;  // mm
     };
 
-    // Centres as placed in SHiPGeometryBuilder::build()
+    // Centres as placed in SHiPGeometryBuilder::build(). The subsystems moved for
+    // integration layout 2026-0.1 use a 50 mm tolerance, below the smallest of
+    // those shifts (120 mm), so the old positions would fail the check.
     std::vector<Expected> expected = {
         {"/SHiP/target", 432.5, 500.0},
         {"/SHiP/muon_shield", 16763.3, 500.0},
         {"/SHiP/neutrino_detector", 28950.0, 500.0},
-        {"/SHiP/upstream_tagger", 32720.0, 500.0},
+        {"/SHiP/upstream_tagger", 32840.0, 50.0},
         {"/SHiP/decay_volume", 58120.0, 500.0},
-        {"/SHiP/trackers", 89570.0, 500.0},
-        {"/SHiP/magnet", 89570.0, 500.0},
-        {"/SHiP/timing_detector", 95902.0, 500.0},
+        {"/SHiP/trackers", 89720.0, 50.0},
+        {"/SHiP/magnet", 89720.0, 50.0},
+        {"/SHiP/timing_detector", 96370.0, 50.0},
         {"/SHiP/calorimeter", 98320.0, 500.0},
     };