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RICH: make local Z the radial axis for radiator and photosensor tiles #15503

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RICH: make local Z the radial axis for radiator and photosensor tiles #15503

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RICH: make local Z the radial axis for radiator and photosensor tiles
Jun 9, 2026
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RICH: make local Z the radial axis for radiator and photosensor tiles…
Jun 9, 2026
599f0d5
RICH: make local Z the radial axis for radiator and photosensor tiles…
Jun 9, 2026
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45 changes: 25 additions & 20 deletions Detectors/Upgrades/ALICE3/RICH/simulation/src/RICHRing.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -67,22 +67,26 @@ Ring::Ring(int rPosId,
int radTileCount{0}, photTileCount{0}, argSectorsCount{0};
// Radiator tiles
for (auto& radiatorTile : radiatorTiles) {
radiatorTile = new TGeoArb8(radZ / 2);
radiatorTile->SetVertex(0, -radThick / 2, -radYmin / 2);
radiatorTile->SetVertex(1, -radThick / 2, radYmin / 2);
radiatorTile->SetVertex(2, radThick / 2, radYmin / 2);
radiatorTile->SetVertex(3, radThick / 2, -radYmin / 2);
radiatorTile->SetVertex(4, -radThick / 2, -radYmax / 2);
radiatorTile->SetVertex(5, -radThick / 2, radYmax / 2);
radiatorTile->SetVertex(6, radThick / 2, radYmax / 2);
radiatorTile->SetVertex(7, radThick / 2, -radYmax / 2);
// Local Z is the thin (radial) dimension, looking outward from the IP
// (previously this was local X, while for running with ACTS we need local Z).
// The placement rotation below is adjusted by +90 deg about Y
// to keep the tile in the same physical position.
radiatorTile = new TGeoArb8(radThick / 2);
radiatorTile->SetVertex(0, radZ / 2, -radYmin / 2);
radiatorTile->SetVertex(1, -radZ / 2, -radYmax / 2);
radiatorTile->SetVertex(2, -radZ / 2, radYmax / 2);
radiatorTile->SetVertex(3, radZ / 2, radYmin / 2);
radiatorTile->SetVertex(4, radZ / 2, -radYmin / 2);
radiatorTile->SetVertex(5, -radZ / 2, -radYmax / 2);
radiatorTile->SetVertex(6, -radZ / 2, radYmax / 2);
radiatorTile->SetVertex(7, radZ / 2, radYmin / 2);

TGeoVolume* radiatorTileVol = new TGeoVolume(Form("radTile_%d_%d", rPosId, radTileCount), radiatorTile, medAerogel);
radiatorTileVol->SetLineColor(kOrange - 8);
radiatorTileVol->SetLineWidth(1);

auto* rotRadiator = new TGeoRotation(Form("radTileRotation_%d_%d", radTileCount, rPosId));
rotRadiator->RotateY(-thetaBDeg);
rotRadiator->RotateY(90.0 - thetaBDeg); // +90 compensates the X->Z swap of the tile's local axes
rotRadiator->RotateZ(radTileCount * deltaPhiDeg);

auto* rotTransRadiator = new TGeoCombiTrans(radRad0 * TMath::Cos(radTileCount * TMath::Pi() / (nTilesPhi / 2)),
Expand All @@ -96,22 +100,23 @@ Ring::Ring(int rPosId,

// Photosensor tiles
for (auto& photoTile : photoTiles) {
photoTile = new TGeoArb8(photZ / 2);
photoTile->SetVertex(0, -photThick / 2, -photYmin / 2);
photoTile->SetVertex(1, -photThick / 2, photYmin / 2);
photoTile->SetVertex(2, photThick / 2, photYmin / 2);
photoTile->SetVertex(3, photThick / 2, -photYmin / 2);
photoTile->SetVertex(4, -photThick / 2, -photYmax / 2);
photoTile->SetVertex(5, -photThick / 2, photYmax / 2);
photoTile->SetVertex(6, photThick / 2, photYmax / 2);
photoTile->SetVertex(7, photThick / 2, -photYmax / 2);
// Local Z is the thin (radial) dimension, looking outward from the IP
photoTile = new TGeoArb8(photThick / 2);
photoTile->SetVertex(0, photZ / 2, -photYmin / 2);
photoTile->SetVertex(1, -photZ / 2, -photYmax / 2);
photoTile->SetVertex(2, -photZ / 2, photYmax / 2);
photoTile->SetVertex(3, photZ / 2, photYmin / 2);
photoTile->SetVertex(4, photZ / 2, -photYmin / 2);
photoTile->SetVertex(5, -photZ / 2, -photYmax / 2);
photoTile->SetVertex(6, -photZ / 2, photYmax / 2);
photoTile->SetVertex(7, photZ / 2, photYmin / 2);

TGeoVolume* photoTileVol = new TGeoVolume(Form("%s_%d_%d", GeometryTGeo::getRICHSensorPattern(), rPosId, photTileCount), photoTile, medSi);
photoTileVol->SetLineColor(kOrange - 8);
photoTileVol->SetLineWidth(1);

auto* rotPhoto = new TGeoRotation(Form("photoTileRotation_%d_%d", photTileCount, rPosId));
rotPhoto->RotateY(-thetaBDeg);
rotPhoto->RotateY(90.0 - thetaBDeg); // +90 compensates the X->Z swap of the tile's local axes
rotPhoto->RotateZ(photTileCount * deltaPhiDeg);
auto* rotTransPhoto = new TGeoCombiTrans(photR0 * TMath::Cos(photTileCount * TMath::Pi() / (nTilesPhi / 2)),
photR0 * TMath::Sin(photTileCount * TMath::Pi() / (nTilesPhi / 2)),
Expand Down