Do not change the PDG code of beam remnants

Author: pzhristov

Generators/src/GeneratorPythia8.cxx

@@ -654,14 +654,6 @@ Bool_t
     // first particle is system
     auto particle = event[iparticle];
     auto pdg = particle.id();
-    // Select nuclei (A PDG id code for nuclei is on the form 100ZZZAAAI)
-    if (std::abs(pdg) > 1000000000) {
-      // Ignore isospin if equal to 9
-      auto pdgNoI = (pdg / 10) * 10;
-      if (std::abs(pdg - pdgNoI) == 9) {
-        pdg = pdgNoI;
-      }
-    }
     auto st = o2::mcgenstatus::MCGenStatusEncoding(particle.statusHepMC(), //
                                                    particle.status())      //
                 .fullEncoding;