Merge pull request #5819 from bendavid/py8200final_72x

Backport of interface changes for final pythia 8.200 release (72x)

GeneratorInterface/Pythia8Interface/plugins/LHAupLesHouches.cc

@@ -65,6 +65,8 @@ bool LHAupLesHouches::setEvent(int inProcId, double mRecalculate)
 
   const std::vector<float> &scales = event->scales();
 
+  bool doRecalculate = (mRecalculate > 0.);
+
   unsigned int iscale = 0;
   for(int i = 0; i < hepeup.NUP; i++) {
     //retrieve scale corresponding to each particle
@@ -81,12 +83,25 @@ bool LHAupLesHouches::setEvent(int inProcId, double mRecalculate)
       scalein = scales[iscale];
       ++iscale;
     }
+
+    double energy = hepeup.PUP[i][3];
+    double mass = hepeup.PUP[i][4];
+
+    // Optionally recalculate mass from four-momentum.
+    if (doRecalculate && mass > mRecalculate) {
+      mass = sqrtpos( energy*energy - hepeup.PUP[i][0]*hepeup.PUP[i][0] - hepeup.PUP[i][1]*hepeup.PUP[i][1] - hepeup.PUP[i][2]*hepeup.PUP[i][2]);
+    }
+    // If not, recalculate energy from three-momentum and mass.
+    else {
+      energy = sqrt( hepeup.PUP[i][0]*hepeup.PUP[i][0] + hepeup.PUP[i][1]*hepeup.PUP[i][1] + hepeup.PUP[i][2]*hepeup.PUP[i][2] + mass*mass);
+    }
+
     addParticle(hepeup.IDUP[i], hepeup.ISTUP[i],
                 hepeup.MOTHUP[i].first, hepeup.MOTHUP[i].second,
                 hepeup.ICOLUP[i].first, hepeup.ICOLUP[i].second,
                 hepeup.PUP[i][0], hepeup.PUP[i][1],
-                hepeup.PUP[i][2], hepeup.PUP[i][3],
-                hepeup.PUP[i][4], hepeup.VTIMUP[i],
+                hepeup.PUP[i][2], energy,
+                mass, hepeup.VTIMUP[i],
                 hepeup.SPINUP[i],scalein);
   }