Make conversion accept MCParticles with helicity (#120)

* Make conversion accept MCParticles with helicity

Transparent for now

* Switch to pre-processor constant for compatility checks

* Do not include version header as it's not necessary

* Fix warning for narrowing conversion

Author: tmadlener

k4EDM4hep2LcioConv/include/k4EDM4hep2LcioConv/k4EDM4hep2LcioConv.ipp

@@ -489,7 +489,11 @@ std::unique_ptr<lcio::LCCollectionVec> convertMCParticles(const edm4hep::MCParti
       lcio_mcp->setMomentumAtEndpoint(momentumEndpoint);
       lcio_mcp->setMass(edm_mcp.getMass());
       lcio_mcp->setCharge(edm_mcp.getCharge());
+#ifdef EDM4HEP_MCPARTICLE_HAS_HELICITY
+      float spin[3] = {0, 0, static_cast<float>(edm_mcp.getHelicity())};
+#else
       float spin[3] = {edm_mcp.getSpin()[0], edm_mcp.getSpin()[1], edm_mcp.getSpin()[2]};
+#endif
       lcio_mcp->setSpin(spin);
       int colorflow[2] = {0, 0};
       lcio_mcp->setColorFlow(colorflow);

k4EDM4hep2LcioConv/include/k4EDM4hep2LcioConv/k4Lcio2EDM4hepConv.ipp

@@ -108,7 +108,11 @@ convertMCParticles(const std::string& name, EVENT::LCCollection* LCCollection, M
     lval.setCharge(rval->getCharge());
     lval.setTime(rval->getTime());
     lval.setMass(rval->getMass());
+#ifdef EDM4HEP_MCPARTICLE_HAS_HELICITY
+    lval.setHelicity(rval->getSpin()[2]);
+#else
     lval.setSpin(edm4hep::Vector3f(rval->getSpin()));
+#endif
     lval.setVertex(edm4hep::Vector3d(rval->getVertex()));
     lval.setEndpoint(edm4hep::Vector3d(rval->getEndpoint()));
     lval.setMomentum(rval->getMomentum());

tests/src/CompareEDM4hepEDM4hep.cc

@@ -58,7 +58,11 @@ bool compare(const edm4hep::MCParticleCollection& origColl, const edm4hep::MCPar
                  "momentumAtEndpoint in particle " << i);
     REQUIRE_SAME(origPart.getMass(), part.getMass(), "mass in particle " << i);
     REQUIRE_SAME(origPart.getCharge(), part.getCharge(), "charge in particle " << i);
+#ifdef EDM4HEP_MCPARTICLE_HAS_HELICITY
+    REQUIRE_SAME(origPart.getHelicity(), part.getHelicity(), "helicity in particle " << i);
+#else
     REQUIRE_SAME(origPart.getSpin(), part.getSpin(), "spin in particle " << i);
+#endif
 
     REQUIRE_SAME(origPart.isCreatedInSimulation(), part.isCreatedInSimulation(), " in particle " << i);
     REQUIRE_SAME(origPart.isBackscatter(), part.isBackscatter(), " in particle " << i);

tests/src/CompareEDM4hepLCIO.cc

@@ -4,9 +4,10 @@
 
 #include "IMPL/TrackerHitImpl.h"
 
+#include <edm4hep/VertexRecoParticleLinkCollection.h>
+
 #include <cmath>
 #include <cstdint>
-#include <edm4hep/VertexRecoParticleLinkCollection.h>
 
 #include "TMath.h"
 
@@ -110,7 +111,11 @@ bool compare(const EVENT::MCParticle* lcioElem, const edm4hep::MCParticle& edm4h
   ASSERT_COMPARE(lcioElem, edm4hepElem, getEndpoint, "endpoint in MCParticle");
   ASSERT_COMPARE(lcioElem, edm4hepElem, getMomentum, "momentum in MCParticle");
   ASSERT_COMPARE(lcioElem, edm4hepElem, getMomentumAtEndpoint, "momentumAtEndpoint in MCParticle");
+#ifdef EDM4HEP_MCPARTICLE_HAS_HELICITY
+  ASSERT_COMPARE_VALS(lcioElem->getSpin()[2], edm4hepElem.getHelicity(), "spin.z / helicity in MCParticle");
+#else
   ASSERT_COMPARE(lcioElem, edm4hepElem, getSpin, "spin in MCParticle");
+#endif
 
   ASSERT_COMPARE_RELATION(lcioElem, edm4hepElem, getDaughters, objectMaps.mcParticles, "daughters in MCParticle");
   ASSERT_COMPARE_RELATION(lcioElem, edm4hepElem, getParents, objectMaps.mcParticles, "parents in MCParticle");

tests/src/EDM4hep2LCIOUtilities.cc

@@ -52,7 +52,11 @@ edm4hep::MCParticleCollection createMCParticles(const int num_elements,
     elem.setMomentum({i * 1.f, i * 2.f, i * 3.f});
     elem.setMomentumAtEndpoint({i * 3.f, i * 2.f, i * 1.f});
     elem.setMass(125. * i);
+#ifdef EDM4HEP_MCPARTICLE_HAS_HELICITY
+    elem.setHelicity(i * 42); // avoid ever hitting the magic value of 9
+#else
     elem.setSpin({i * 0.5f, i * 0.25f, i * 0.25f});
+#endif
     elem.setCreatedInSimulation(1);
     elem.setBackscatter(0);
     elem.setVertexIsNotEndpointOfParent(1);