Update HistogramsLibrary.cxx (#8050)

Filling a 2D plot between Mass and VNContribReal

Author: debadatta333

PWGDQ/Core/HistogramsLibrary.cxx

@@ -837,6 +837,7 @@ void o2::aod::dqhistograms::DefineHistograms(HistogramManager* hm, const char* h
       }
       if (subGroupStr.Contains("mult")) {
         hm->AddHistogram(histClass, "Mass_Pt_MultFV0A", "", false, 200, 0.0, 5.0, VarManager::kMass, 40, 0.0, 40.0, VarManager::kPt, 100, 0.0, 25000.0, VarManager::kMultFV0A);
+        hm->AddHistogram(histClass, "Mass_VtxNcontribReal", "Mass vs VtxNcontribReal", false, 200, 0.0, 5.0, VarManager::kMass, 200, 0, 200.0, VarManager::kVtxNcontribReal);
       }
       if (subGroupStr.Contains("polarization")) {
         hm->AddHistogram(histClass, "cosThetaHE", "", false, 100, -1., 1., VarManager::kCosThetaHE);