[PWGLF] Add configurable for old covariance matrix calculation (#17884)

Author: romainschotter

PWGLF/Utils/strangenessBuilderHelper.h

@@ -253,6 +253,7 @@ class strangenessBuilderHelper
     fitter.setMaxChi2(1e9);
     fitter.setUseAbsDCA(true);
     fitter.setWeightedFinalPCA(false);
+    fitter.setOldMode(true); // enable old convariance matrix calculation until this has been fully tested
 
     v0selections.minCrossedRows = -1;
     v0selections.dcanegtopv = -1.0f;

PWGLF/Utils/strangenessBuilderModule.h

@@ -334,6 +334,9 @@ struct coreConfigurables : o2::framework::ConfigurableGroup {
 
   // test the possibility of refitting with material corrections (DCA Fitter option)
   o2::framework::Configurable<bool> refitWithMaterialCorrection{"refitWithMaterialCorrection", false, "do refit after material corrections were applied"};
+
+  // enable old convariance matrix calculation until this has been fully tested
+  o2::framework::Configurable<bool> useOldModeDCAFitter{"useOldModeDCAFitter", true, "Use old mode for DCA fitter?"};
 };
 
 // strangenessBuilder: V0 building options
@@ -824,6 +827,9 @@ class BuilderModule
     // Set option to refit with material corrections
     straHelper.fitter.setRefitWithMatCorr(baseOpts.refitWithMaterialCorrection.value);
 
+    // set option to enabled the old mode
+    straHelper.fitter.setOldMode(baseOpts.useOldModeDCAFitter.value);
+
     // Initialise the RCTFlagsChecker
     if (eventSelectOpts.cfgApplyRCTrequirement) {
       rctFlagsChecker.init(eventSelectOpts.cfgRCTLabel.value, eventSelectOpts.cfgCheckZDC, eventSelectOpts.cfgTreatLimitedAcceptanceAsBad);