GPU: Fix incorrect sign of b field in GetPropagatedXYZ, and treat neg…

…ative cosPhi correctly
AliceO2Group · Feb 15, 2023 · 976334a · 976334a
1 parent bd597e8
commit 976334a
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Showing 2 changed files with 11 additions and 4 deletions.
diff --git a/GPU/GPUTracking/Merger/GPUTPCGMPropagator.cxx b/GPU/GPUTracking/Merger/GPUTPCGMPropagator.cxx
@@ -566,15 +566,17 @@ GPUd() int GPUTPCGMPropagator::GetPropagatedYZ(float x, float& GPUrestrict() pro
   float bz = GetBz(mT->X(), mT->Y(), mT->Z());
   float k = mT0.QPt() * bz;
   float dx = x - mT->X();
-  float kdx = k * dx;
   float ex = mT0.CosPhi();
   float ey = mT0.SinPhi();
-  float ey1 = kdx + ey;
+  float ey1 = ey - k * dx;
   if (CAMath::Abs(ey1) > GPUCA_MAX_SIN_PHI) {
     return 1;
   }
   float ss = ey + ey1;
   float ex1 = CAMath::Sqrt(1.f - ey1 * ey1);
+  if (ex < 0) {
+    ex1 = -ex1;
+  }
   float cc = ex + ex1;
   float dxcci = dx / cc;
   float dy = dxcci * ss;

diff --git a/GPU/GPUTracking/SliceTracker/GPUTPCTrackParam.cxx b/GPU/GPUTracking/SliceTracker/GPUTPCTrackParam.cxx
@@ -806,15 +806,20 @@ GPUd() int MEM_LG(GPUTPCTrackParam)::GetPropagatedYZ(float bz, float x, float& p
 {
   float k = mParam.mP[4] * bz;
   float dx = x - mParam.mX;
-  float kdx = k * dx;
   float ey = mParam.mP[2];
   float ex = CAMath::Sqrt(1 - ey * ey);
-  float ey1 = kdx + ey;
+  if (SignCosPhi() < 0) {
+    ex = -ex;
+  }
+  float ey1 = ey - k * dx;
   if (CAMath::Abs(ey1) > GPUCA_MAX_SIN_PHI) {
     return 0;
   }
   float ss = ey + ey1;
   float ex1 = CAMath::Sqrt(1.f - ey1 * ey1);
+  if (SignCosPhi() < 0) {
+    ex1 = -ex1;
+  }
   float cc = ex + ex1;
   float dxcci = dx / cc;
   float dy = dxcci * ss;