fix definition of generated decay time

Author: lubynets

PWGHF/D2H/Tasks/taskLc.cxx

@@ -63,6 +63,7 @@ using namespace o2::framework::expressions;
 using namespace o2::hf_centrality;
 using namespace o2::hf_occupancy;
 using namespace o2::hf_evsel;
+using namespace o2::constants::physics;
 
 /// Λc± → p± K∓ π± analysis task
 struct HfTaskLc {
@@ -522,10 +523,18 @@ struct HfTaskLc {
           occ = o2::hf_occupancy::getOccupancyGenColl(recoCollsPerMcColl, occEstimator);
         }
 
-        const auto& mcDaughter0 = particle.template daughters_as<soa::Join<aod::McParticles, aod::HfCand3ProngMcGen>>().begin();
-        const float p2m = particle.p() / o2::constants::physics::MassLambdaCPlus;
-        const float gamma = std::sqrt(1 + p2m * p2m);                        // mother's particle Lorentz factor
-        const float properDecayTime = mcDaughter0.vt() * NanoToPico / gamma; // from ns to ps * from lab time to proper time
+        const auto mcDaughter0 = particle.template daughters_as<soa::Join<aod::McParticles, aod::HfCand3ProngMcGen>>().begin();
+        const auto mcCollision = particle.template mcCollision_as<aod::McCollisions>();
+        const auto p = particle.p();
+        const float pvX = mcCollision.posX();
+        const float pvY = mcCollision.posY();
+        const float pvZ = mcCollision.posZ();
+        const float svX = mcDaughter0.vx();
+        const float svY = mcDaughter0.vy();
+        const float svZ = mcDaughter0.vz();
+
+        const float decayLength = static_cast<float>(RecoDecay::distance(std::array<float, 3>{svX, svY, svZ}, std::array<float, 3>{pvX, pvY, pvZ}));
+        const float properDecayTime = decayLength * static_cast<float>(MassLambdaCPlus) / LightSpeedCm2PS / p;
 
         fillHistogramsGen<Signal>(particle);
 

PWGHF/TableProducer/treeCreatorLcToPKPi.cxx

@@ -412,7 +412,6 @@ struct HfTreeCreatorLcToPKPi {
 
   constexpr static float UndefValueFloat = -999.f;
   constexpr static int UndefValueInt = -999;
-  constexpr static float NanoToPico = 1000.f;
 
   using TracksWPid = soa::Join<aod::Tracks, aod::TracksPidPi, aod::PidTpcTofFullPi, aod::TracksPidKa, aod::PidTpcTofFullKa, aod::TracksPidPr, aod::PidTpcTofFullPr>;
   using Cents = soa::Join<aod::CentFV0As, aod::CentFT0Ms, aod::CentFT0As, aod::CentFT0Cs, aod::CentFDDMs>;
@@ -1002,16 +1001,14 @@ struct HfTreeCreatorLcToPKPi {
               const auto mcCollision = particleMother.template mcCollision_as<aod::McCollisions>();
               p = particleMother.p();
               pt = particleMother.pt();
-              const float p2m = p / static_cast<float>(MassLambdaCPlus);
-              const float gamma = std::sqrt(1 + p2m * p2m); // mother's particle Lorentz factor
               pvX = mcCollision.posX();
               pvY = mcCollision.posY();
               pvZ = mcCollision.posZ();
               svX = mcParticleProng0.vx();
               svY = mcParticleProng0.vy();
               svZ = mcParticleProng0.vz();
               decayLength = static_cast<float>(RecoDecay::distance(std::array<float, 3>{svX, svY, svZ}, std::array<float, 3>{pvX, pvY, pvZ}));
-              decayTime = mcParticleProng0.vt() * NanoToPico / gamma; // from ns to ps * from lab time to proper time
+              decayTime = decayLength * static_cast<float>(MassLambdaCPlus) / LightSpeedCm2PS / p;
             }
             rowCandidateMC(
               p, pt,
@@ -1032,16 +1029,14 @@ struct HfTreeCreatorLcToPKPi {
         const auto mcDaughter0 = particle.template daughters_as<soa::Join<aod::McParticles, aod::HfCand3ProngMcGen>>().begin();
         const auto mcCollision = particle.template mcCollision_as<aod::McCollisions>();
         const auto p = particle.p();
-        const float p2m = p / static_cast<float>(MassLambdaCPlus);
-        const float gamma = std::sqrt(1 + p2m * p2m); // mother's particle Lorentz factor
         const float pvX = mcCollision.posX();
         const float pvY = mcCollision.posY();
         const float pvZ = mcCollision.posZ();
         const float svX = mcDaughter0.vx();
         const float svY = mcDaughter0.vy();
         const float svZ = mcDaughter0.vz();
         const float l = static_cast<float>(RecoDecay::distance(std::array<float, 3>{svX, svY, svZ}, std::array<float, 3>{pvX, pvY, pvZ}));
-        const float t = mcDaughter0.vt() * NanoToPico / gamma; // from ns to ps * from lab time to proper time
+        const float t = l * static_cast<float>(MassLambdaCPlus) / LightSpeedCm2PS / p;
         rowCandidateFullParticles(
           particle.pt(),
           particle.eta(),