wideResonanceCrossSection.cpp

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//
//    Copyright 2010
//
//    This file is part of starlight.
//
//    starlight is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    starlight is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with starlight. If not, see <http://www.gnu.org/licenses/>.
//
//
// File and Version Information:
// $Rev:: 264                         $: revision of last commit
// $Author:: jseger                   $: author of last commit
// $Date:: 2016-06-06 21:05:12 +0100 #$: date of last commit
//
// Description:
//
//
//


#include <iostream>
#include <fstream>
#include <cmath>

#include "starlightconstants.h"
#include "wideResonanceCrossSection.h"


using namespace std;
using namespace starlightConstants;


//______________________________________________________________________________
wideResonanceCrossSection::wideResonanceCrossSection(const inputParameters& inputParametersInstance, const beamBeamSystem&  bbsystem)
  : photonNucleusCrossSection(inputParametersInstance, bbsystem)//hrm
{
  _wideWmax = _wMax;
  _wideWmin = _wMin;
  _wideYmax = _yMax;
  _wideYmin = -1.0 * _wideYmax;
  _Ep       = inputParametersInstance.protonEnergy();
}


//______________________________________________________________________________
wideResonanceCrossSection::~wideResonanceCrossSection()
{

}


//______________________________________________________________________________
void
wideResonanceCrossSection::crossSectionCalculation(const double bwnormsave)
{
  //     This subroutine calculates the cross-section assuming a wide
  //     (Breit-Wigner) resonance.

  double W,dW,dY;
  double y1,y2,y12,ega1,ega2,ega12;
  double csgA1,csgA2,csgA12,int_r,dR;
  double Eth;
  int    I,J,NW,NY,beam;

  double bwnorm = bwnormsave; //used to transfer the bwnorm from the luminosity tables

  //gamma+nucleon threshold.
  Eth=0.5*(((_wideWmin+protonMass)*(_wideWmin+protonMass)
            -protonMass*protonMass)/(_Ep+sqrt(_Ep*_Ep-protonMass*protonMass)));
                   
  NW   = 100;
  dW   = (_wideWmax-_wideWmin)/double(NW);
  
  NY   =  1200;
  dY   = (_wideYmax-_wideYmin)/double(NY);
  
  if (getBNORM()  ==  0.){
    cout<<" Using Breit-Wigner Resonance Profile."<<endl;
  }
  else{
    cout<<" Using Breit-Wigner plus direct pi+pi- profile."<<endl;
  }
  
  cout<<" Integrating over W from "<<_wideWmin<<" to "<<_wideWmax<<endl;

        int A_1 = getbbs().electronBeam().A(); 
        int A_2 = getbbs().targetBeam().A();

  int_r=0.;
 
        // Do this first for the case when the first beam is the photon emitter 
        // Treat pA separately with defined beams 
        // The variable beam (=1,2) defines which nucleus is the target 
  for(I=0;I<=NW-1;I++){
    
    W = _wideWmin + double(I)*dW + 0.5*dW;
    
    for(J=0;J<=NY-1;J++){
      
      y1  = _wideYmin + double(J)*dY;
      y2  = _wideYmin + double(J+1)*dY;
      y12 = 0.5*(y1+y2);

                        if( A_2 == 1 && A_1 != 1 ){
                          // pA, first beam is the nucleus and is in this case the target  
                          // Egamma = 0.5*W*exp(-Y); 
                          ega1  = 0.5*W*exp(-y1);
                          ega2  = 0.5*W*exp(-y2);
                          ega12 = 0.5*W*exp(-y12);
                          beam = 1; 
                        } else if( A_1 ==1 && A_2 != 1){
                          // pA, second beam is the nucleus and is in this case the target 
                          ega1  = 0.5*W*exp(y1);
                          ega2  = 0.5*W*exp(y2);
                          ega12 = 0.5*W*exp(y12);
                          beam = 2; 
                        } else {
                          ega1  = 0.5*W*exp(y1);
                          ega2  = 0.5*W*exp(y2);
                          ega12 = 0.5*W*exp(y12);
                          beam = 2; 
                        }
      
      
      if(ega1 < Eth || ega2 < Eth) continue;
      if(ega2 > maxPhotonEnergy()) continue;
          
      csgA1=getcsgA(ega1,W,beam);

      //         >> Middle Point                      =====>>>
      csgA12=getcsgA(ega12,W,beam);         

      //         >> Second Point                      =====>>>
      csgA2=getcsgA(ega2,W,beam);
      
      //>> Sum the contribution for this W,Y. The 2 accounts for the 2 beams
      dR  = ega1*photonFlux(ega1,beam)*csgA1;
      dR  = dR + 4.*ega12*photonFlux(ega12,beam)*csgA12;
      dR  = dR + ega2*photonFlux(ega2,beam)*csgA2;
      dR  = dR*(dY/6.)*breitWigner(W,bwnorm)*dW;
      
      //For identical beams, we double.  Either may emit photon/scatter
      //For large differences in Z, we approx, that only electronBeam emits photon
      //and targetBeam scatters, eg d-Au where electronBeam=au and targetBeam=d
      //if(getbbs().electronBeam().A()==getbbs().targetBeam().A()){
      //  dR  = 2.*dR;
      //}
      int_r = int_r+dR;  
    }
  }

        // Repeat the loop for the case when the second beam is the photon emitter. 
        // Don't repeat for pA
        if( !( (A_2 == 1 && A_1 != 1) || (A_1 == 1 && A_2 != 1) ) ){ 
    for(I=0;I<=NW-1;I++){
    
    W = _wideWmin + double(I)*dW + 0.5*dW;
    
    for(J=0;J<=NY-1;J++){
      
      y1  = _wideYmin + double(J)*dY;
      y2  = _wideYmin + double(J+1)*dY;
      y12 = 0.5*(y1+y2);
      
                        beam = 1; 
      ega1  = 0.5*W*exp(-y1);
      ega2  = 0.5*W*exp(-y2);
      ega12 = 0.5*W*exp(-y12);
      
      if(ega1< Eth || ega2 < Eth) continue;
      if(ega1 > maxPhotonEnergy()) continue;
          
      csgA1=getcsgA(ega1,W,beam);

      //         >> Middle Point                      =====>>>
      csgA12=getcsgA(ega12,W,beam);         

      //         >> Second Point                      =====>>>
      csgA2=getcsgA(ega2,W,beam);
      
      //>> Sum the contribution for this W,Y. The 2 accounts for the 2 beams
      dR  = ega1*photonFlux(ega1,beam)*csgA1;
      dR  = dR + 4.*ega12*photonFlux(ega12,beam)*csgA12;
      dR  = dR + ega2*photonFlux(ega2,beam)*csgA2;
      dR  = dR*(dY/6.)*breitWigner(W,bwnorm)*dW;
      
      //For identical beams, we double.  Either may emit photon/scatter
      //For large differences in Z, we approx, that only electronBeam emits photon
      //and targetBeam scatters, eg d-Au where electronBeam=au and targetBeam=d
      // if(getbbs().electronBeam().A()==getbbs().targetBeam().A()){
      //  dR  = 2.*dR;
      // }
      int_r = int_r+dR;  
    }
    }
        }

  cout<<endl;
  if (0.01*int_r > 1.){
    cout<< " Total cross section: "<<0.01*int_r<<" barn."<<endl;
  } else if (10.*int_r > 1.){
    cout<< " Total cross section: " <<10.*int_r<<" mb."<<endl;
        } else if (10000.*int_r > 1.){
    cout<< " Total cross section: " <<10000.*int_r<<" microb."<<endl;
        } else if (10000000.*int_r > 1.){
    cout<< " Total cross section: " <<10000000.*int_r<<" nanob."<<endl;
        } else if (1.E10*int_r > 1.){
    cout<< " Total cross section: "<<1.E10*int_r<<" picob."<<endl;
        } else {
    cout<< " Total cross section: " <<1.E13*int_r<<" femtob."<<endl;
        }
  cout<<endl;
  setPhotonNucleusSigma(0.01*int_r);

}