diff --git a/Phys/DecayTreeFitter/python/DecayTreeFitter/DecayTreeFitter.py b/Phys/DecayTreeFitter/python/DecayTreeFitter/DecayTreeFitter.py
index 966f477a1dfd01f600a134f0d21a00fb91ef9363..5f327d94a55deba5e7ba45f27694b0dde327e5b7 100644
--- a/Phys/DecayTreeFitter/python/DecayTreeFitter/DecayTreeFitter.py
+++ b/Phys/DecayTreeFitter/python/DecayTreeFitter/DecayTreeFitter.py
@@ -1,5 +1,5 @@
 ###############################################################################
-# (c) Copyright 2022-2023 CERN for the benefit of the LHCb Collaboration      #
+# (c) Copyright 2022-2024 CERN for the benefit of the LHCb Collaboration      #
 #                                                                             #
 # This software is distributed under the terms of the GNU General Public      #
 # Licence version 3 (GPL Version 3), copied verbatim in the file "COPYING".   #
@@ -157,17 +157,17 @@ class DecayTreeFitter:
         self.PERR = self.__call__(
             functor=F.MATH_ERROR @ F.MATH_SCALAR_MOMENTUM @ F.FOURMOMENTUM,
             apply_to_particle_params=True)
-        self.TAU = self.__call__(
+        self.CTAU = self.__call__(
             functor=F.MATH_VALUE @ F.PARTICLE_PARAMS_CTAU,
             apply_to_particle_params=True)
-        self.TAUERR = self.__call__(
+        self.CTAUERR = self.__call__(
             functor=F.MATH_ERROR @ F.PARTICLE_PARAMS_CTAU,
             apply_to_particle_params=True)
         self.FD = self.__call__(
-            functor=F.MATH_VALUE @ F.PARTICLE_PARAMS_DECAY_LENGTH,
+            functor=F.MATH_VALUE @ F.PARTICLE_PARAMS_FLIGHT_DISTANCE,
             apply_to_particle_params=True)
         self.FDERR = self.__call__(
-            functor=F.MATH_ERROR @ F.PARTICLE_PARAMS_DECAY_LENGTH,
+            functor=F.MATH_ERROR @ F.PARTICLE_PARAMS_FLIGHT_DISTANCE,
             apply_to_particle_params=True)
 
     def _apply_functor(self, functor: BoundFunctor, relation: DataHandle):
diff --git a/Phys/FunctorCore/include/Functors/LHCbMath.h b/Phys/FunctorCore/include/Functors/LHCbMath.h
index 3f784ec0f2ff1f5bd30e470a8d95057d059a825b..6299f88a4aa125a873da6dedb4ef1074b18160be 100644
--- a/Phys/FunctorCore/include/Functors/LHCbMath.h
+++ b/Phys/FunctorCore/include/Functors/LHCbMath.h
@@ -120,13 +120,13 @@ namespace Functors::LHCbMath {
 
   namespace ParticleParams {
     /**
-     * @brief decayLength, access the decay length of Gaudi::Math::ParticleParams
+     * @brief flightDistance, access the decay length of Gaudi::Math::ParticleParams
      */
-    struct decayLength : public Function {
+    struct flightDistance : public Function {
 
-      constexpr auto name() const { return "ParticleParams::decayLength"; }
+      constexpr auto name() const { return "ParticleParams::flightDistance"; }
 
-      auto operator()( const Gaudi::Math::ParticleParams& input ) const { return input.decayLength(); }
+      auto operator()( const Gaudi::Math::ParticleParams& input ) const { return input.flightDistance(); }
 
       template <typename T>
       auto operator()( const T& p ) const -> decltype( Functors::Optional{( *this )( *p )} ) {
@@ -136,7 +136,7 @@ namespace Functors::LHCbMath {
       template <typename... Data>
       auto operator()( Data... ) const {
         static_assert( detail::always_false<Data...>::value,
-                       "The fucntor Functors::LHCbMath::ParticleParams::decayLength can only apply to "
+                       "The fucntor Functors::LHCbMath::ParticleParams::flightDistance can only apply to "
                        "Gaudi::Math::ParticleParams" );
       }
     };
diff --git a/Phys/FunctorCore/python/Functors/__init__.py b/Phys/FunctorCore/python/Functors/__init__.py
index 19e7120eb2487ffa9ce6cbc7a13c8a8d753428e3..f4c5d847b6303c1cb75a7bb875d1f05adfcf1b22 100644
--- a/Phys/FunctorCore/python/Functors/__init__.py
+++ b/Phys/FunctorCore/python/Functors/__init__.py
@@ -278,9 +278,10 @@ MATH_INVARIANT_MASS = Functor(
     'MATH_INVARIANT_MASS', 'LHCbMath::invariantMass',
     'Returns the scalar momentum by input.invariantMass()')
 # ParticleParams
-PARTICLE_PARAMS_DECAY_LENGTH = Functor(
-    'PARTICLE_PARAMS_DECAY_LENGTH', 'LHCbMath::ParticleParams::decayLength',
-    'Returns the decay length of Gaudi::Math::ParticleParams')
+PARTICLE_PARAMS_FLIGHT_DISTANCE = Functor(
+    'PARTICLE_PARAMS_FLIGHT_DISTANCE',
+    'LHCbMath::ParticleParams::flightDistance',
+    'Returns the flight distance of Gaudi::Math::ParticleParams')
 PARTICLE_PARAMS_CTAU = Functor(
     'PARTICLE_PARAMS_CTAU', 'LHCbMath::ParticleParams::ctau',
     'Returns the c*tau of Gaudi::Math::ParticleParams')
diff --git a/Phys/FunctorCore/tests/src/TestFunctors.cpp b/Phys/FunctorCore/tests/src/TestFunctors.cpp
index 0c74a2ae647b86cf06778758e72d3928f513b543..216cff44ec3aa4cc0446f4f6d5a4983e1ab78c64 100644
--- a/Phys/FunctorCore/tests/src/TestFunctors.cpp
+++ b/Phys/FunctorCore/tests/src/TestFunctors.cpp
@@ -3035,13 +3035,13 @@ BOOST_AUTO_TEST_CASE( test_lhcb_math_functors ) {
   pos_mom( 2, 2 ) = 0.01;
   Gaudi::Math::ParticleParams params{pos, P4, decay_length, pos_mom, len_pos, len_mom};
 
-  Functors::LHCbMath::ParticleParams::ctau        CTAU;
-  Functors::LHCbMath::ParticleParams::decayLength DECAY_LENGTH;
-  Functors::LHCbMath::ParticleParams::lenPosCov   LEN_POS_COV;
-  Functors::LHCbMath::ParticleParams::lenMomCov   LEN_MOM_COV;
+  Functors::LHCbMath::ParticleParams::ctau           CTAU;
+  Functors::LHCbMath::ParticleParams::flightDistance FLIGHT_DISTANCE;
+  Functors::LHCbMath::ParticleParams::lenPosCov      LEN_POS_COV;
+  Functors::LHCbMath::ParticleParams::lenMomCov      LEN_MOM_COV;
 
   BOOST_CHECK_EQUAL( CTAU( params ), params.ctau() );
-  BOOST_CHECK_EQUAL( DECAY_LENGTH( params ), params.decayLength() );
+  BOOST_CHECK_EQUAL( FLIGHT_DISTANCE( params ), params.flightDistance() );
   BOOST_CHECK_EQUAL( LEN_POS_COV( params ), params.lenPosCov() );
   BOOST_CHECK_EQUAL( LEN_MOM_COV( params ), params.lenMomCov() );
 }