void arrow (Double_t x1, Double_t y1, Double_t x2, Double_t y2, Int_t ls)
{
TArrow *arr = new TArrow(x1,y1,x2,y2,0.025,"|>");
arr->SetFillColor(1);
arr->SetFillStyle(1001);
arr->SetLineStyle(ls);
arr->SetAngle(19);
arr->Draw();
}
void
HHV4Vector::Draw(Int_t color, Int_t style) const
{ // draw particle for event display in x-y view
TArrow *Ar = new TArrow(0, 0, Px(), Py(), 0.001, "|>");
Ar->SetLineColor(color);
Ar->SetFillColor(color);
Ar->SetLineWidth(3);
Ar->SetLineStyle(style);
Ar->Draw();
}