chigen::models Namespace Reference

Classes
class	chi_1
class	chi_1_0
class	chi_1_1
class	chi_2
class	chi_2_0
class	chi_2_1
class	chi_2_2
class	ColorSingletPartonicModel
class	x3872
class	x3872_0
class	x3872_1

Functions
EvtSpinDensity	createSpinDensity (int spin, int projection)

Function Documentation

EvtSpinDensity chigen::models::createSpinDensity	(	int	spin,
		int	projection
	)

Returns momentum density corresponding to particle with total spin

spin 

and spin projection

projection 

.

Parameters

spin	total spin of particle
projection	absolute value of spin projection onto particle momentum and -1 for unpolarized particle

Definition at line 11 of file ColorSingletModels.cxx.

References chigen::ensure_chigen_is_initialized().

                                                                       {
    assert(spin == 1 || spin == 2);
    assert(-1 <= projection);
    assert(2 >= projection);

    chigen::ensure_chigen_is_initialized();
    
    //state = 9   -> unpolarized
    //state = 10  -> (1,0)
    //state = 11  -> (1,1)
    //state = 20  -> (2,0)
    //state = 21  -> (2,1)
    //state = 22  -> (2,2)
    //state = 19  -> unpolarized
    
    const int state = 10 * spin + projection;
    EvtSpinDensity matrix;
    switch (state) {
        case 9:
            matrix.setDiag(3);
            return matrix;
        case 10:
            matrix.setDim(3);
            matrix.set(2, 2, EvtComplex(1.0, 0.0));
            return matrix;
        case 11:
            matrix.setDim(3);
            matrix.set(0, 0, EvtComplex(1.0, 0.0));
            matrix.set(1, 1, EvtComplex(1.0, 0.0));
            return matrix;
        case 19:
            matrix.setDiag(5);
            return matrix;
        case 20:
            matrix.setDim(5);
            matrix.set(4, 4, EvtComplex(1.0, 0.0));
            return matrix;
        case 21:
            matrix.setDim(5);
            matrix.set(2, 2, EvtComplex(1.0, 0.0));
            matrix.set(3, 3, EvtComplex(1.0, 0.0));
            return matrix;
        case 22:
            matrix.setDim(5);
            matrix.set(0, 0, EvtComplex(1.0, 0.0));
            matrix.set(1, 1, EvtComplex(1.0, 0.0));
            return matrix;
        default:
            throw std::runtime_error("Not a valid polarization.");
    }
}