#include "TChannel_Basic.h"

TChannel_Basic::TChannel_Basic(const vector<string>& locArguments) : UserAmplitude<TChannel_Basic>(locArguments)
{
	// Helicity Sum //Unused
	// string locHelicityString = locArguments[0];

	// Particle indices
	vector<int> locParticleIndexVector;
	ExtractInts_SingleUnderscore(locArguments[1], locParticleIndexVector);
	dNumParticleIndices = BuildArray(locParticleIndexVector, dParticleIndices);

	// T-Slope
	dTSlope = AmpParameter(locArguments[2]);

	// need to register any free parameters so the framework knows about them
	registerParameter(dTSlope);
}

complex<GDouble> TChannel_Basic::calcAmplitude(GDouble** locKinematics) const
{
	// Get Beam
	TLorentzVector locBeamP4 = TLorentzVector(locKinematics[0][1], locKinematics[0][2], locKinematics[0][3], locKinematics[0][0]);

	// Get/Build Product 1
	TLorentzVector locP4;
	for(int loc_i = 0; loc_i < dNumParticleIndices; ++loc_i)
	{
		int locIndex = dParticleIndices[loc_i];
		locP4 += TLorentzVector(locKinematics[locIndex][1], locKinematics[locIndex][2], locKinematics[locIndex][3], locKinematics[locIndex][0]);
	}

	double locT = locP4.M2() - 2.0*locP4.E()*locBeamP4.E() + 2.0*locP4.Vect().Dot(locBeamP4.Vect()) + locBeamP4.M2();

	return exp(-1.0*fabs(locT)*dTSlope);
}