void QCDvertex()
{
   //
   // Draws the feynman diagram for the basic QED vertex.
   //
   TCanvas *c1 = new TCanvas("c1", "A canvas", 10, 10, 900, 300);
   c1->Range(0, 0, 150, 50);
   Int_t linsav = gStyle->GetLineWidth();
   gStyle->SetLineWidth(3);
   TLatex t;
   t.SetTextAlign(22);
   t.SetTextSize(0.1);
   TLine * l;
   //
   // The ee --> ee diagram
   //
   l = new TLine(30, 25, 50, 10); l->Draw();
   l = new TLine(30, 25, 50, 40); l->Draw();
   g = new TCurlyLine(10, 25, 30, 25, 0.09, 0.04); g->Draw();
   //   g = new TCurlyArc(10, 25, 30, 25, 0.05, 0.02); g->Draw();
   t.DrawLatex(55,10,"Q_{i}");
   t.DrawLatex(55,40,"#bar{Q}_{i}");
   t.DrawLatex(7,25,"g");
   // 
   // The three gluon diagram
   //
   g = new TCurlyLine(80, 25, 100, 25, 0.09, 0.04); g->Draw();
   g = new TCurlyLine(100, 25, 120, 10, 0.09, 0.04); g->Draw();
   g = new TCurlyLine(100, 25, 120, 40, 0.09, 0.04); g->Draw();
   t.DrawLatex(77,25,"g");
   t.DrawLatex(125,10,"g");
   t.DrawLatex(125,40,"g");
   
   c1->Update();
   gStyle->SetLineWidth(linsav);
}