PWGEM/Dilepton: fix DCA calculation

Author: dsekihat

PWGEM/Dilepton/Tasks/matchingMFT.cxx

@@ -273,8 +273,8 @@ struct matchingMFT {
     float dcaXY = std::sqrt(dcaX * dcaX + dcaY * dcaY);
     float dcaZ = -dcaXY * std::sinh(eta);
 
-    float dFdx = 2.f * dcaX / dcaXY;
-    float dFdy = 2.f * dcaY / dcaXY;
+    float dFdx = dcaX / dcaXY;
+    float dFdy = dcaY / dcaXY;
     float sigma_dcaXY = std::sqrt(cXXatDCA * dFdx * dFdx + cYYatDCA * dFdy * dFdy + 2.f * cXYatDCA * dFdx * dFdy);
 
     o2::dataformats::GlobalFwdTrack propmuonAtPV_Matched = propagateMuon(mchtrack, collision, propagationPoint::kToVertex);

PWGEM/Dilepton/Utils/EMTrackUtilities.h

@@ -33,8 +33,8 @@ float sigmaDca3D(T const& track)
   float dcaXY = track.dcaXY();                          // in cm
   float dcaZ = track.dcaZ();                            // in cm
   float dca3d = std::sqrt(dcaXY * dcaXY + dcaZ * dcaZ); // in cm
-  float dFdxy = 2.f * dcaXY / dca3d;
-  float dFdz = 2.f * dcaZ / dca3d;
+  float dFdxy = dcaXY / dca3d;
+  float dFdz = dcaZ / dca3d;
   return std::sqrt(cYY * dFdxy * dFdxy + cZZ * dFdz * dFdz + 2.f * cZY * dFdxy * dFdz);
 }
 //_______________________________________________________________________
@@ -78,8 +78,8 @@ float sigmaFwdDcaXY(T const& track)
   float dcaX = track.fwdDcaX();                       // in cm
   float dcaY = track.fwdDcaY();                       // in cm
   float dcaXY = std::sqrt(dcaX * dcaX + dcaY * dcaY); // in cm
-  float dFdx = 2.f * dcaX / dcaXY;
-  float dFdy = 2.f * dcaY / dcaXY;
+  float dFdx = dcaX / dcaXY;
+  float dFdy = dcaY / dcaXY;
   return std::sqrt(cXX * dFdx * dFdx + cYY * dFdy * dFdy + 2.f * cXY * dFdx * dFdy);
 }
 //_______________________________________________________________________