[ALICE3] IOTOF: Adjust layer radius calculations for stave tilt and chip thickness (#15220)

* [ALICE3] IOTOF: Adjust layer radius calculations for stave tilt

* Refactor iTOF and oTOF layer initialization logic

* Update README.md

* Update IOTOFBaseParam.h default thickness

* Updated stave tilt angle for segmented iTOF configuration.

Author: njacazio

Detectors/Upgrades/ALICE3/IOTOF/README.md

@@ -23,7 +23,7 @@ Configurables for various sub-detectors are presented in the following Table:
 | `IOTOFBase.segmentedInnerTOF` | `false` (default), `true`                                        | Use segmented geometry for inner TOF           |
 | `IOTOFBase.segmentedOuterTOF` | `false` (default), `true`                                        | Use segmented geometry for outer TOF           |
 | `IOTOFBase.detectorPattern`   | ` ` (default), `v3b`, `v3b1a`, `v3b1b`, `v3b2a`, `v3b2b`, `v3b3` | Optional layout pattern                        |
-| `IOTOFBase.x2x0`              | `0.02` (default)                                                 | Chip thickness in fractions of the rad. lenght |
+| `IOTOFBase.x2x0`              | `0.000527` (default)                                             | Chip thickness in fractions of the rad. lenght |
 
 
 For example, a geometry with fully cylindrical tracker barrel (for all layers in VD, ML and OT) can be obtained by

Detectors/Upgrades/ALICE3/IOTOF/base/include/IOTOFBase/IOTOFBaseParam.h

@@ -28,12 +28,12 @@ struct IOTOFBaseParam : public o2::conf::ConfigurableParamHelper<IOTOFBaseParam>
   std::string detectorPattern = ""; // Layouts of the detector
   bool segmentedInnerTOF = false;   // If the inner TOF layer is segmented
   bool segmentedOuterTOF = false;   // If the outer TOF layer is segmented
-  float x2x0 = 0.02f;               // thickness expressed in radiation length, for all layers for the moment
+  float x2x0 = 0.000527f;           // thickness expressed in radiation length, for all layers for the moment
 
   O2ParamDef(IOTOFBaseParam, "IOTOFBase");
 };
 
 } // namespace iotof
 } // end namespace o2
 
-#endif
+#endif

Detectors/Upgrades/ALICE3/IOTOF/simulation/src/Detector.cxx

@@ -96,10 +96,10 @@ void Detector::configLayers(bool itof, bool otof, bool ftof, bool btof, std::str
   }
   if (itof) { // iTOF
     const std::string name = GeometryTGeo::getITOFLayerPattern();
-    const int nStaves = itofSegmented ? 24 : 0;               // number of staves in segmented case
-    const double staveWidth = itofSegmented ? 5.42 : 0.0;     // cm
-    const double staveTiltAngle = itofSegmented ? 10.0 : 0.0; // degrees
-    const int modulesPerStave = itofSegmented ? 10 : 0;       // number of modules per stave in segmented case
+    const int nStaves = itofSegmented ? 24 : 0;              // number of staves in segmented case
+    const double staveWidth = itofSegmented ? 5.42 : 0.0;    // cm
+    const double staveTiltAngle = itofSegmented ? 3.0 : 0.0; // degrees
+    const int modulesPerStave = itofSegmented ? 10 : 0;      // number of modules per stave in segmented case
     mITOFLayer = ITOFLayer(name,
                            dInnerTof.first, 0.f, dInnerTof.second, 0.f, x2x0, itofSegmented ? ITOFLayer::kBarrelSegmented : ITOFLayer::kBarrel,
                            nStaves, staveWidth, staveTiltAngle, modulesPerStave);

Detectors/Upgrades/ALICE3/IOTOF/simulation/src/Layer.cxx

@@ -155,11 +155,13 @@ void ITOFLayer::createLayer(TGeoVolume* motherVolume)
     case kBarrelSegmented: {
       // First we create the volume for the whole layer, which will be used as mother volume for the segments
       const double avgRadius = 0.5 * (mInnerRadius + mOuterRadius);
-      const double staveSizeX = mStaves.second;                                                                                                          // cm
-      const double staveSizeY = mOuterRadius - mInnerRadius;                                                                                             // cm
-      const double staveSizeZ = mZLength;                                                                                                                // cm
-      const double deltaForTilt = 0.5 * (std::sin(TMath::DegToRad() * mTiltAngle) * staveSizeX + std::cos(TMath::DegToRad() * mTiltAngle) * staveSizeY); // we increase the size of the layer to account for the tilt of the staves
-      TGeoTube* layer = new TGeoTube(mInnerRadius - deltaForTilt, mOuterRadius + deltaForTilt, mZLength / 2);
+      const double staveSizeX = mStaves.second;                                                                                                                    // cm
+      const double staveSizeY = mOuterRadius - mInnerRadius;                                                                                                       // cm
+      const double staveSizeZ = mZLength;                                                                                                                          // cm
+      const double deltaForTilt = 0.5 * (std::sin(TMath::DegToRad() * mTiltAngle) * staveSizeX + std::cos(TMath::DegToRad() * mTiltAngle) * staveSizeY);           // we increase the size of the layer to account for the tilt of the staves
+      const double radiusMax = std::sqrt(avgRadius * avgRadius + 0.25 * staveSizeX * staveSizeX + 0.25 * staveSizeY * staveSizeY + avgRadius * 2. * deltaForTilt); // we increase the outer radius to account for the tilt of the staves
+      const double radiusMin = std::sqrt(avgRadius * avgRadius + 0.25 * staveSizeX * staveSizeX + 0.25 * staveSizeY * staveSizeY - avgRadius * 2. * deltaForTilt); // we decrease the inner radius to account for the tilt of the staves
+      TGeoTube* layer = new TGeoTube(radiusMin, radiusMax, mZLength / 2);
       TGeoVolume* layerVol = new TGeoVolume(mLayerName.c_str(), layer, medAir);
       setLayerStyle(layerVol);
 
@@ -287,11 +289,13 @@ void OTOFLayer::createLayer(TGeoVolume* motherVolume)
     case kBarrelSegmented: {
       // First we create the volume for the whole layer, which will be used as mother volume for the segments
       const double avgRadius = 0.5 * (mInnerRadius + mOuterRadius);
-      const double staveSizeX = mStaves.second;                                                                                                          // cm
-      const double staveSizeY = mOuterRadius - mInnerRadius;                                                                                             // cm
-      const double staveSizeZ = mZLength;                                                                                                                // cm
-      const double deltaForTilt = 0.5 * (std::sin(TMath::DegToRad() * mTiltAngle) * staveSizeX + std::cos(TMath::DegToRad() * mTiltAngle) * staveSizeY); // we increase the size of the layer to account for the tilt of the staves
-      TGeoTube* layer = new TGeoTube(mInnerRadius - deltaForTilt, mOuterRadius + deltaForTilt, mZLength / 2);
+      const double staveSizeX = mStaves.second;                                                                                                                    // cm
+      const double staveSizeY = mOuterRadius - mInnerRadius;                                                                                                       // cm
+      const double staveSizeZ = mZLength;                                                                                                                          // cm
+      const double deltaForTilt = 0.5 * (std::sin(TMath::DegToRad() * mTiltAngle) * staveSizeX + std::cos(TMath::DegToRad() * mTiltAngle) * staveSizeY);           // we increase the size of the layer to account for the tilt of the staves
+      const double radiusMax = std::sqrt(avgRadius * avgRadius + 0.25 * staveSizeX * staveSizeX + 0.25 * staveSizeY * staveSizeY + avgRadius * 2. * deltaForTilt); // we increase the outer radius to account for the tilt of the staves
+      const double radiusMin = std::sqrt(avgRadius * avgRadius + 0.25 * staveSizeX * staveSizeX + 0.25 * staveSizeY * staveSizeY - avgRadius * 2. * deltaForTilt); // we decrease the inner radius to account for the tilt of the staves
+      TGeoTube* layer = new TGeoTube(radiusMin, radiusMax, mZLength / 2);
       TGeoVolume* layerVol = new TGeoVolume(mLayerName.c_str(), layer, medAir);
       setLayerStyle(layerVol);