LauKMatrixProdPole.cc

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// Copyright University of Warwick 2008 - 2013.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

// Authors:
// Thomas Latham
// John Back
// Paul Harrison

#include "LauKMatrixProdPole.hh"
#include "LauKMatrixPropagator.hh"

#include <iostream>

ClassImp(LauKMatrixProdPole)

LauKMatrixProdPole::LauKMatrixProdPole(const TString& poleName, Int_t poleIndex, Int_t resPairAmpInt,
                                       LauKMatrixPropagator* propagator, const LauDaughters* daughters) : 
        LauAbsResonance(poleName, 0.0, 0.0, 0, 0, resPairAmpInt, daughters),
        thePropagator_(propagator),
        poleIndex_(poleIndex - 1) // poleIndex goes from 1 to nPoles
{
}

LauKMatrixProdPole::~LauKMatrixProdPole() 
{
}

LauComplex LauKMatrixProdPole::resAmp(Double_t mass, Double_t spinTerm)
{
        std::cerr << "ERROR in LauKMatrixProdPole::resAmp : This method shouldn't get called." << std::endl;
        std::cerr << "                                      Returning zero amplitude for mass = " << mass << " and spinTerm = " << spinTerm << "." << std::endl;
        return LauComplex(0.0, 0.0);
}

LauComplex LauKMatrixProdPole::amplitude(const LauKinematics* kinematics)
{

        // Calculate the amplitude for the K-matrix production pole.
        // First, make sure the K-matrix propagator is up-to-date for 
        // the given centre-of-mass squared value ("s") from the kinematics.
        LauComplex amp(0.0, 0.0);

        if (thePropagator_ == 0) {
                std::cerr << "ERROR in LauKMatrixProdPole::amplitude : The propagator is null" << std::endl;
                return amp;
        }

        thePropagator_->updatePropagator(kinematics);

        // Sum the pole denominator terms over all channels j, multiplying by
        // the propagator terms. Note that we do not sum over poles, since we
        // only want one of the production pole terms.
        Int_t nChannels = thePropagator_->getNChannels();
        Int_t jChannel;

        for (jChannel = 0; jChannel < nChannels; jChannel++) {

                Double_t gj = thePropagator_->getCouplingConstant(poleIndex_, jChannel);
                LauComplex prodTerm = thePropagator_->getPropTerm(jChannel);

                prodTerm.rescale(gj);

                amp += prodTerm;

        }

        Double_t poleDenom = thePropagator_->getPoleDenomTerm(poleIndex_);
        amp.rescale(poleDenom);

        return amp;

}