Constructors and Accessors

• HepLorentzVector( )
• HepLorentzVector( x, y, z, t )
• HepLorentzVector( v, t )
• HepLorentzVector( t, v )
• HepLorentzVector( t )
• HepLorentzVector( x, y, z )
• HepLorentzVector( v )

The following accessor methods are used to obtain the named coordinate components, as in double s = p.t();.

• x( ) y( ) z( ) t( )
• px( ) py( ) pz( ) e( )
• getX( ) getY( ) getZ( ) getT( )
• v( ) or getV( ) or vect( )

The Cartesian components may also be accessed by the index syntax, using either square braces or parentheses. In either case, the meaning of the index is 0-based, with the time component last. An enum is nested in the HepLorentzVector class to help clarify this: X=0, Y=1, Z=2, T=3.

The spatial components can also be accessed in spherical coordinates:

• HepDouble theta() const;
• HepDouble cosTheta() const;
• HepDouble phi() const;
• HepDouble rho() const;

There is a family of methods of the form set Component () which may be used to set one component in Cartesian or spherical coordinates, or the $\rho$ cylindrical coordinate, keeping the other components in that system constant.

• setX(HepDouble); setPx(HepDouble);
• setY(HepDouble); setPy(HepDouble);
• setZ(HepDouble); setPz(HepDouble);
• setT(HepDouble); setE(HepDouble);
• setTheta(HepDouble); $\triangleright$ see eqn. 
• setPhi(HepDouble); $\triangleright$ see eqn. 
• setRho(HepDouble); setPerp(HepDouble); $\triangleright$ see eqn. 

The entire spatial component can be set at once, keeping the time component constant.

• setVect(HepDouble); setV(HepDouble);

And there is a family of set() methods, corresponding to the constructors, that may be used to update all four of a HepLorentzVector's coordinates at once.

• set (x, y, z, t);
• set (v, t);
• set (t, x);

Assignment from a Hep3Vector is supported, as in p = v;.

Finally, there are conversion operators to const and non-const Hep3Vector; these were present in the original CLHEP classes. They ignore the time component.