protection against xPDFmotherOld == 0

diff --git a/PYTHIA8/pythia8175/src/SpaceShower.cxx b/PYTHIA8/pythia8175/src/SpaceShower.cxx
index 00005a7154c56d6a04716afef950f8f59e0d320f..52707afd6b015587d18a8b129d5c6eb094e6fa4c 100644 (file)
--- a/PYTHIA8/pythia8175/src/SpaceShower.cxx
+++ b/PYTHIA8/pythia8175/src/SpaceShower.cxx
@@ -785,6 +785,11 @@ void SpaceShower::pT2nearQCDthreshold( BeamParticle& beam,
   double logM2Lambda2  = log( m2Massive / Lambda2 );
   double xPDFmotherOld = beam.xfISR(iSysNow, 21, xDaughter, 
     factorMultFac * m2Threshold);
+  if (xPDFmotherOld == 0) {
+    infoPtr->errorMsg("Error in SpaceShower::pT2nearQCDthreshold: "
+      "xPDFmotherOld is 0"); 
+    return; 
+  }
 
   // Variables used inside evolution loop. (Mainly dummy start values.)
   int    loop    = 0;