SigmaFactor is excluded from fittable parameters, see Feature #1763.

Core/Particle/ParticleDistribution.cpp

@@ -33,6 +33,7 @@ ParticleDistribution::ParticleDistribution(const IParticle& prototype,
     mP_particle->registerAbundance(false);
     if(auto dist = m_par_distribution.getDistribution())
         registerChild(dist);
+    registerParameter(BornAgain::Abundance, &m_abundance);
 }
 
 ParticleDistribution* ParticleDistribution::clone() const

GUI/coregui/Models/DistributionItems.cpp

@@ -21,7 +21,7 @@
 #include <cmath>
 
 const QString DistributionItem::P_NUMBER_OF_SAMPLES = "Number of samples";
-const QString DistributionItem::P_SIGMA_FACTOR = "Sigma factor";
+const QString DistributionItem::P_SIGMA_FACTOR = Constants::DistributionSigmaFactor;
 const QString DistributionItem::P_IS_INITIALIZED = "is initialized";
 
 DistributionItem::DistributionItem(const QString name) : SessionItem(name)

GUI/coregui/Models/ModelPath.cpp

@@ -246,6 +246,8 @@ bool ModelPath::isTranslatable(const SessionItem *item, const QString &par_name)
     Q_UNUSED(item);
     if(par_name.contains(Constants::DetectorType))
         return false;
+    if(par_name.contains(Constants::DistributionSigmaFactor))
+        return false;
     return true;
 }
 

GUI/coregui/Models/item_constants.h

@@ -232,6 +232,8 @@ const ModelType FITPAR_LOWERLIMITED = "lower limited";
 const ModelType FITPAR_UPPERLIMITED = "upper limited";
 const ModelType FITPAR_FREE = "free";
 
+const ModelType DistributionSigmaFactor = "Sigma factor";
+
 // --- Custom variants ----------------------------------------------------------
 
 const ModelType ScientificDoublePropertyType = "ScientificDoubleProperty";