LauBreitWignerRes.cc

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// Copyright University of Warwick 2004 - 2014.
// 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 "LauBreitWignerRes.hh"

ClassImp(LauBreitWignerRes)


LauBreitWignerRes::LauBreitWignerRes(LauResonanceInfo* resInfo, const Int_t resPairAmpInt, const LauDaughters* daughters) :
        LauAbsResonance(resInfo, resPairAmpInt, daughters)
{
}

LauBreitWignerRes::~LauBreitWignerRes()
{
}

void LauBreitWignerRes::initialise()
{
}

LauComplex LauBreitWignerRes::resAmp(Double_t mass, Double_t spinTerm)
{
        // This function returns the complex dynamical amplitude for a Breit-Wigner resonance,
        // given the invariant mass and cos(helicity) values.

        Double_t resMass = this->getMass();
        Double_t deltaM = mass - resMass;

        Double_t resWidthO2 = 0.5 * this->getWidth();
        Double_t resWidthO2Sq = resWidthO2*resWidthO2;

        LauComplex resAmplitude(deltaM, resWidthO2);

        resAmplitude.rescale(spinTerm/(deltaM*deltaM + resWidthO2Sq));

        return resAmplitude;
}

const std::vector<LauParameter*>& LauBreitWignerRes::getFloatingParameters()
{
        this->clearFloatingParameters();

        if ( ! this->fixMass() ) {
                this->addFloatingParameter( this->getMassPar() );
        }
        if ( ! this->fixWidth() ) {
                this->addFloatingParameter( this->getWidthPar() );
        }

        return this->getParameters();
}