TLorentzVector M(1.0, 2.0, 3.0, 4.0);
TLorentzVector M1(1.0, 2.0, 3.0, 4.0); TLorentzVector M2(2.0, 3.0, 4.0, 5.0); TLorentzVector Msum = M1 + M2;
TCanvas *c1 = new TCanvas("c1", "c1", 500, 500); c1->cd(); M.DrawArrow(0, 0, M.Px(), M.Py());Therefore, the TLorentzVector M class is a part of the ROOT package library in C++.