LauBelleSymNR.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>
using std::cout;
using std::cerr;
using std::endl;

#include "TMath.h"

#include "LauBelleSymNR.hh"
#include "LauKinematics.hh"

ClassImp(LauBelleSymNR)


LauBelleSymNR::LauBelleSymNR(const 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),
        alpha_(0.0),
        initialised_(kFALSE),
        shapeNo_(0)
{
}

LauBelleSymNR::~LauBelleSymNR()
{
        // Destructor
}

void LauBelleSymNR::initialise(Bool_t symmetricalDP, Double_t alpha, const TString& shape)
{
        alpha_ = alpha;  
        shapeNo_ = 0;

        if (symmetricalDP == kFALSE) {
                cerr << "ERROR in LauBelleSymNR::initialise : Dalitz plot is not symmetric - this lineshape is not appropriate." << endl;
                return;
        }

        if (shape == "BelleSymNR") {
                cout << "Initialising the Belle non-resonant model with alpha = " << alpha << endl;
                shapeNo_ = 1; 
        } else if (shape == "NRTaylor") {
                cout << "Initialising the Taylor expansion non-resonant model with alpha = " << alpha << endl; 
                shapeNo_ = 2;
        } else {
                cerr << "ERROR in LauBelleSymNR::initialise : Non-resonant parameterisation not recognised." << endl;
                return;
        }

        initialised_ = kTRUE;
}

LauComplex LauBelleSymNR::amplitude(const LauKinematics* kinematics)
{
        if (initialised_ == kFALSE) {
                cerr<<"ERROR in LauBelleSymNR::amplitude : LauBelleSymNR is not initialised. Returning zero amplitude."<<endl;
                return LauComplex(0.0, 0.0);
        }

        // This function returns the complex dynamical amplitude for a Belle Non-Resonant distribution

        // Calculate for symmetric DPs, e.g. 3pi or 3K, by using shapeNo = 1 or 2
        // Have s<->t symmetry already done in Dynamics flip function.
        // For Kpipi or similar plots, one can use the separate exponentials
        // and consider them as two separate components with their own mag and phase.
        // For this shapeNo = 3 and shapeNo = 4 need to be used to create the two
        // individual amplitudes (with the same value of alpha).

        // Calculate Mandelstam variables.
        // s = m_13^2, t = m_23^2, u = m_12^2. 
        Double_t s = kinematics->getm13Sq();
        Double_t t = kinematics->getm23Sq();
        //Double_t u = kinematics->getm12Sq();

        Double_t magnitude(1.0);

        if (shapeNo_ == 1) {
                magnitude = TMath::Exp(-alpha_*s) + TMath::Exp(-alpha_*t);
        } else if (shapeNo_ == 2) {
                Double_t mParentSq = kinematics->getmParentSq();
                magnitude = alpha_*(s + t)/mParentSq + 1.0;
        }

        LauComplex resAmplitude(magnitude, 0.0);

        return resAmplitude;

}

LauComplex LauBelleSymNR::resAmp(Double_t mass, Double_t spinTerm)
{
        cerr << "ERROR in LauBelleSymNR : This method should never be called." << endl;
        cerr << "                       : Returning zero amplitude for mass = " << mass << " and spinTerm = " << spinTerm << "." << endl;
        return LauComplex(0.0, 0.0);
}