PWGCF : Femtouniverse -- Fixing bug in dphi calculation (#5643)

* PWGCF : Femtouniverse -- Fixing bug in dphi calculation

The extra factor of 0.1 that was scaling the magnetic field is removed. 
However, after removing this factor, the asin(<arg>) function for calculating dphi was blowing up at certain (mostly higher) values of radii. This is also taken care of by only allowing abs(<arg>) < 1.0.

* PWGCF : Femtouniverse -- Fixing bug in dphi calculation

The extra factor of 0.1 that was scaling the magnetic field is removed.
However, after removing this factor, the asin() function for calculating dphi was blowing up at certain (mostly higher) values of radii. This is also taken care of by only allowing abs() < 1.0.

* Update FemtoUniverseDetaDphiStar.h

* Update FemtoUniverseDetaDphiStar.h

Author: prchakra

PWGCF/FemtoUniverse/Core/FemtoUniverseDetaDphiStar.h

@@ -13,6 +13,7 @@
 /// \brief FemtoUniverseDetaDphiStar - Checks particles for the close pair rejection.
 /// \author Laura Serksnyte, TU München, laura.serksnyte@tum.de
 /// \author Zuzanna Chochulska, WUT Warsaw & CTU Prague, zchochul@cern.ch
+/// \author Pritam Chakraborty, WUT Warsaw, pritam.chakraborty@cern.ch
 
 #ifndef PWGCF_FEMTOUNIVERSE_CORE_FEMTOUNIVERSEDETADPHISTAR_H_
 #define PWGCF_FEMTOUNIVERSE_CORE_FEMTOUNIVERSEDETADPHISTAR_H_
@@ -377,7 +378,10 @@ class FemtoUniverseDetaDphiStar
     // End: Get the charge from cutcontainer using masks
     float pt = part.pt();
     for (size_t i = 0; i < 9; i++) {
-      tmpVec.push_back(phi0 - std::asin(0.3 * charge * 0.1 * magfield * tmpRadiiTPC[i] * 0.01 / (2. * pt)));
+      double arg = 0.3 * charge * magfield * tmpRadiiTPC[i] * 0.01 / (2. * pt);
+      if (abs(arg) < 1.0) {
+        tmpVec.push_back(phi0 - std::asin(arg));
+      }
     }
   }
 
@@ -426,12 +430,15 @@ class FemtoUniverseDetaDphiStar
     float charge1 = GetCharge(part1);
     float charge2 = GetCharge(part2);
 
-    double deltaphiconstFD = 0.3 * 0.1 * 0.01 / 2;
+    double deltaphiconstFD = 0.3 / 2;
     // double deltaphiconstAF = 0.15;
     double afsi0b = deltaphiconstFD * magfield * charge1 * ChosenRadii / part1.pt();
     double afsi1b = deltaphiconstFD * magfield * charge2 * ChosenRadii / part2.pt();
+    double dphis = 0.0;
 
-    double dphis = part2.phi() - part1.phi() + TMath::ASin(afsi1b) - TMath::ASin(afsi0b);
+    if (abs(afsi0b) < 1.0 && abs(afsi0b) < 1.0) {
+      dphis = part2.phi() - part1.phi() + TMath::ASin(afsi1b) - TMath::ASin(afsi0b);
+    }
     return dphis;
   }
 };