LauNRAmplitude.cc

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// Copyright University of Warwick 2004 - 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 <iostream>

#include "LauKinematics.hh"
#include "LauNRAmplitude.hh"

ClassImp(LauNRAmplitude)

LauNRAmplitude::LauNRAmplitude(TString resName, Double_t resMass, Double_t resWidth, Int_t resSpin,
                Int_t resCharge, Int_t resPairAmpInt, const LauDaughters* daughters) :
        LauAbsResonance(resName, resMass, resWidth, resSpin, resCharge, resPairAmpInt, daughters),
        d_(1.3232e-3),
        c1_(0.65),
        c2_(0.55),
        p1_(18.0),
        p2_(15.0)
{
}

LauNRAmplitude::~LauNRAmplitude()
{
}

void LauNRAmplitude::initialise()
{
}

LauComplex LauNRAmplitude::amplitude(const LauKinematics* kinematics)
{
        // Get the information from the kinematics object
        Double_t m13Sq = kinematics->getm13Sq();
        Double_t m23Sq = kinematics->getm23Sq();
        Double_t m13 = kinematics->getm13();
        Double_t m23 = kinematics->getm23();

        // Calculate the magnitude
        Double_t magnitude = TMath::Sqrt( m13 * m23 *
                                          this->f(m23Sq, c1_, p1_) * 
                                          this->f(m13Sq, c2_, p2_) * 
                                          TMath::Exp( -1.0 * d_ * m13Sq*m13Sq * m23Sq*m23Sq )
                                        );

        // return the amplitude
        LauComplex resAmplitude(magnitude, 0.0);
        return resAmplitude;
}

LauComplex LauNRAmplitude::resAmp(Double_t mass, Double_t spinTerm)
{
        std::cerr << "ERROR in LauNRAmplitude::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);
}

Double_t LauNRAmplitude::f(Double_t s, Double_t c, Double_t p) const
{
        return 1.0 / (1.0 + TMath::Exp( c * (s-p) ));
}