G4AntiNuclElastic.cc

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// $Id: G4AntiNuclElastic.cc  - A.Galoyan 02.05.2011
// GEANT4 tag $Name: not supported by cvs2svn $
//
// Geant4 Header : G4AntiNuclElastic
//
// 
 
#include "G4AntiNuclElastic.hh"
 
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "G4IonTable.hh"
#include "Randomize.hh"
#include "G4AntiProton.hh"
#include "G4AntiNeutron.hh"
#include "G4AntiDeuteron.hh"
#include "G4AntiAlpha.hh"
#include "G4AntiTriton.hh"
#include "G4AntiHe3.hh"
#include "G4Proton.hh"
#include "G4Neutron.hh"
#include "G4Deuteron.hh"
#include "G4Alpha.hh"
#include "G4Pow.hh"
 
#include "G4NucleiProperties.hh"       
 
G4AntiNuclElastic::G4AntiNuclElastic() 
  : G4HadronElastic("AntiAElastic")
{
  //V.Ivanchenko commented out 
  //SetMinEnergy( 0.1*GeV );
  //SetMaxEnergy( 10.*TeV );
 
 
  theAProton       = G4AntiProton::AntiProton();
  theANeutron      = G4AntiNeutron::AntiNeutron();
  theADeuteron     = G4AntiDeuteron::AntiDeuteron();
  theATriton       = G4AntiTriton::AntiTriton();
  theAAlpha        = G4AntiAlpha::AntiAlpha();
  theAHe3          = G4AntiHe3::AntiHe3();
 
  theProton   = G4Proton::Proton();
  theNeutron  = G4Neutron::Neutron();
  theDeuteron = G4Deuteron::Deuteron();
  theAlpha    = G4Alpha::Alpha();
 
 
  cs = new G4ComponentAntiNuclNuclearXS();
  fParticle = 0;
  fWaveVector = 0.;
  fBeta = 0.;
  fZommerfeld = 0.;
  fAm = 0.;
  fTetaCMS = 0.;    
  fRa = 0.;
  fRef = 0.;
  fceff = 0.;
  fptot = 0.;
  fTmax = 0.;
  fThetaLab = 0.;
}
 
/////////////////////////////////////////////////////////////////////////
G4AntiNuclElastic::~G4AntiNuclElastic()
{
  delete cs;  
}
 
////////////////////////////////////////////////////////////////////////
// sample momentum transfer in the CMS system 
G4double G4AntiNuclElastic::SampleInvariantT(const G4ParticleDefinition* particle, 
                         G4double Plab,  G4int Z, G4int A)
{
  G4double T;
  G4double Mproj = particle->GetPDGMass();
  G4LorentzVector Pproj(0.,0.,Plab,std::sqrt(Plab*Plab+Mproj*Mproj));
  G4double ctet1 = GetcosTeta1(Plab, A); 
 
  G4double energy=Pproj.e()-Mproj;   
  
  const G4ParticleDefinition* theParticle = particle;
 
  G4ParticleDefinition * theDef = 0;
 
  if(Z == 1 && A == 1)       theDef = theProton;
  else if (Z == 1 && A == 2) theDef = theDeuteron;
  else if (Z == 1 && A == 3) theDef = G4Triton::Triton();
  else if (Z == 2 && A == 3) theDef = G4He3::He3();
  else if (Z == 2 && A == 4) theDef = theAlpha;
 
 
  G4double TargMass =G4NucleiProperties::GetNuclearMass(A,Z); 
 
  //transform to CMS
 
  G4LorentzVector lv(0.0,0.0,0.0,TargMass);   
  lv += Pproj;
  G4double S = lv.mag2()/GeV/GeV;
 
  G4ThreeVector bst = lv.boostVector();
  Pproj.boost(-bst);
 
  G4ThreeVector p1 = Pproj.vect();
  G4double ptot    = p1.mag();
 
  fbst = bst;
  fptot= ptot;
  fTmax = 4.0*ptot*ptot;  
 
  if(Plab/std::abs(particle->GetBaryonNumber()) < 100.*MeV)    // Uzhi 24 Nov. 2011
  {return fTmax*G4UniformRand();}                              // Uzhi 24 Nov. 2011
  
  G4double  Z1 = particle->GetPDGCharge();
  G4double  Z2 = Z;  
  
  G4double beta = CalculateParticleBeta(particle, ptot); 
  G4double n  = CalculateZommerfeld( beta,  Z1,  Z2 );
  G4double Am = CalculateAm( ptot,  n,  Z2 );
  fWaveVector = ptot;     //   /hbarc; 
        
  G4LorentzVector Fproj(0.,0.,0.,0.);  
  G4double  XsCoulomb = sqr(n/fWaveVector)*pi*(1+ctet1)/(1.+Am)/(1.+2.*Am-ctet1); 
  XsCoulomb=XsCoulomb*0.38938e+6;
 
 
  G4double XsElastHad =cs->GetElasticElementCrossSection(particle, energy, Z, (G4double)A);
  G4double XstotalHad =cs->GetTotalElementCrossSection(particle, energy, Z, (G4double)A);
 
 
  XsElastHad/=millibarn; XstotalHad/=millibarn;
 
 
  G4double CoulombProb =  XsCoulomb/(XsCoulomb+XsElastHad);
 
// G4cout<<" XselastHadron " << XsElastHad << "  XsCol "<< XsCoulomb <<G4endl; 
// G4cout <<"  XsTotal" << XstotalHad <<G4endl;  
// G4cout<<"XsInel"<< XstotalHad-XsElastHad<<G4endl;        
 
  if(G4UniformRand() < CoulombProb)
  {  // Simulation of Coulomb scattering
 
   G4double phi = twopi * G4UniformRand();
   G4double Ksi =  G4UniformRand();
 
   G4double par1 = 2.*(1.+Am)/(1.+ctet1);
 
// ////sample ThetaCMS in Coulomb part
 
   G4double cosThetaCMS = (par1*ctet1- Ksi*(1.+2.*Am))/(par1-Ksi);
 
   G4double PtZ=ptot*cosThetaCMS;
   Fproj.setPz(PtZ);
   G4double PtProjCMS = ptot*std::sqrt(1.0 - cosThetaCMS*cosThetaCMS);
   G4double PtX= PtProjCMS * std::cos(phi);
   G4double PtY= PtProjCMS * std::sin(phi);
   Fproj.setPx(PtX);     
   Fproj.setPy(PtY);
   Fproj.setE(std::sqrt(PtX*PtX+PtY*PtY+PtZ*PtZ+Mproj*Mproj));    
   T =  -(Pproj-Fproj).mag2();      
  } else
 
  {  
///////Simulation of strong interaction scattering////////////////////////////
 
//   G4double Qmax = 2.*ptot*197.33;    // in fm^-1
   G4double Qmax = 2.*3.0*197.33;    // in fm^-1
   G4double Amag = 70*70;          //  A1 in Magora funct:A1*exp(-q*A2)
   G4double SlopeMag = 2.*3.0;    // A2 in Magora funct:A1*exp(-q*A2)
 
   G4double sig_pbarp= cs->GetAntiHadronNucleonTotCrSc(particle,energy); 
   
   fRa = 1.113*G4Pow::GetInstance()->Z13(A) -                     
         0.227/G4Pow::GetInstance()->Z13(A);                      
   if(A == 3) fRa=1.81;
   if(A == 4) fRa=1.37;
 
   if((A>=12.) && (A<27) ) fRa=fRa*0.85;
   if((A>=27.) && (A<48) ) fRa=fRa*0.90;
   if((A>=48.) && (A<65) ) fRa=fRa*0.95;
 
   G4double Ref2 = 0;
   G4double ceff2 =0;
   G4double rho = 0;
   if  ((theParticle == theAProton) || (theParticle == theANeutron))  
   {
    if(theDef == theProton)
    { 
//   G4double Mp2=sqr(theDef->GetPDGMass()/GeV ); 
 
// change 30 October
  
     if(Plab < 610.) 
     { rho = 1.3347-10.342*Plab/1000.+22.277*Plab/1000.*Plab/1000.-
      13.634*Plab/1000.*Plab/1000.*Plab/1000. ;}
     if((Plab < 5500.)&&(Plab >= 610.) )
     { rho = 0.22; }
     if((Plab >= 5500.)&&(Plab < 12300.) )
     { rho = -0.32; }
     if( Plab >= 12300.)
     { rho = 0.135-2.26/(std::sqrt(S)) ;}
 
     Ref2 = 0.35 + 0.9/std::sqrt(std::sqrt(S-4.*0.88))+0.04*std::log(S) ;
     ceff2 = 0.375 - 2./S + 0.44/(sqr(S-4.)+1.5) ;
 
/*   
   Ref2=0.8/std::sqrt(std::sqrt(S-4.*Mp2)) + 0.55; 
   if(S>1000.) Ref2=0.62+0.02*std::log(S) ;
   ceff2 = 0.035/(sqr(S-4.3)+0.4) + 0.085 * std::log(S) ;
   if(S>1000.) ceff2 = 0.005 * std::log(S) + 0.29;
*/
 
     Ref2=Ref2*Ref2;
     ceff2 = ceff2*ceff2;
 
     SlopeMag = 0.5;        // Uzhi
     Amag= 1.;              // Uzhi
    }
 
    if(Z>2) 
    {  Ref2 = fRa*fRa +2.48*0.01*sig_pbarp*fRa - 2.23e-6*sig_pbarp*sig_pbarp*fRa*fRa; 
       ceff2 = 0.16+3.3e-4*sig_pbarp+0.35*std::exp(-0.03*sig_pbarp);
    }
    if( (Z==2)&&(A==4) )
    {  Ref2 = fRa*fRa -0.46 +0.03*sig_pbarp - 2.98e-6*sig_pbarp*sig_pbarp;
       ceff2= 0.078 + 6.657e-4*sig_pbarp + 0.3359*std::exp(-0.03*sig_pbarp);
    }
    if( (Z==1)&&(A==3) )
    {  Ref2 = fRa*fRa - 1.36 + 0.025 * sig_pbarp - 3.69e-7 * sig_pbarp*sig_pbarp;
       ceff2 = 0.149 + 7.091e-04*sig_pbarp + 0.3743*std::exp(-0.03*sig_pbarp);
    }
    if( (Z==2)&&(A==3) )
    {  Ref2 = fRa*fRa - 1.36 + 0.025 * sig_pbarp - 3.69e-7 * sig_pbarp*sig_pbarp;
       ceff2 = 0.149 + 7.091e-04*sig_pbarp + 0.3743*std::exp(-0.03*sig_pbarp);
    }  
    if( (Z==1)&&(A==2) )
    {
       Ref2 = fRa*fRa - 0.28 + 0.019 * sig_pbarp + 2.06e-6 * sig_pbarp*sig_pbarp;  
       ceff2 = 0.297 + 7.853e-04*sig_pbarp + 0.2899*std::exp(-0.03*sig_pbarp);
    }
   }
 
   if (theParticle == theADeuteron)
   {
    sig_pbarp= cs->GetAntiHadronNucleonTotCrSc(particle,energy/2.); 
    Ref2 = XstotalHad/10./2./pi ;
    if(Z>2)
    {
     ceff2 = 0.38 + 2.0e-4 *sig_pbarp + 0.5 * std::exp(-0.03*sig_pbarp);
    }
    if(theDef == theProton)
    { 
     ceff2 = 0.297 + 7.853e-04*sig_pbarp + 0.2899*std::exp(-0.03*sig_pbarp);
    }
    if(theDef == theDeuteron)
    { 
     ceff2 = 0.65 + 3.0e-4*sig_pbarp + 0.55 * std::exp(-0.03*sig_pbarp);
    }
    if( (theDef == G4Triton::Triton()) || (theDef == G4He3::He3() ) )
    {
     ceff2 = 0.57 + 2.5e-4*sig_pbarp + 0.65 * std::exp(-0.02*sig_pbarp);
    }
    if(theDef == theAlpha)
    {
     ceff2 = 0.40 + 3.5e-4 *sig_pbarp + 0.45 * std::exp(-0.02*sig_pbarp);
    }
   }
 
   if( (theParticle ==theAHe3) || (theParticle ==theATriton) )
   {
    sig_pbarp = cs->GetAntiHadronNucleonTotCrSc(particle,energy/3.);
    Ref2 = XstotalHad/10./2./pi ;
    if(Z>2)
    {
     ceff2 = 0.26 + 2.2e-4*sig_pbarp + 0.33*std::exp(-0.03*sig_pbarp);
    }  
    if(theDef == theProton)
    {
     ceff2 = 0.149 + 7.091e-04*sig_pbarp + 0.3743*std::exp(-0.03*sig_pbarp);         
    }
    if(theDef == theDeuteron)
    {
     ceff2 = 0.57 + 2.5e-4*sig_pbarp + 0.65 * std::exp(-0.02*sig_pbarp);
    }
    if( (theDef == G4Triton::Triton()) || (theDef == G4He3::He3() ) )
    {
     ceff2 = 0.39 + 2.7e-4*sig_pbarp + 0.7 * std::exp(-0.02*sig_pbarp);
    }
    if(theDef == theAlpha)
    {
     ceff2 = 0.24 + 3.5e-4*sig_pbarp + 0.75 * std::exp(-0.03*sig_pbarp);
    }
   }
 
 
   if (theParticle == theAAlpha)
   {
    sig_pbarp = cs->GetAntiHadronNucleonTotCrSc(particle,energy/3.);
    Ref2 = XstotalHad/10./2./pi ;
    if(Z>2)
    {
     ceff2 = 0.22 + 2.0e-4*sig_pbarp + 0.2 * std::exp(-0.03*sig_pbarp);
    }
    if(theDef == theProton)
    {
     ceff2= 0.078 + 6.657e-4*sig_pbarp + 0.3359*std::exp(-0.03*sig_pbarp);   
    }
    if(theDef == theDeuteron)  
    {
     ceff2 = 0.40 + 3.5e-4 *sig_pbarp + 0.45 * std::exp(-0.02*sig_pbarp);
    }   
    if( (theDef == G4Triton::Triton()) || (theDef == G4He3::He3() ) )
    {
     ceff2 = 0.24 + 3.5e-4*sig_pbarp + 0.75 * std::exp(-0.03*sig_pbarp);   
    }
    if(theDef == theAlpha)   
    {
     ceff2 = 0.17 + 3.5e-4*sig_pbarp + 0.45 * std::exp(-0.03*sig_pbarp);
    }
   }
 
   fRef=std::sqrt(Ref2);
   fceff = std::sqrt(ceff2);     
// G4cout<<" Ref  "<<fRef<<" c_eff "<<fceff<< " rho "<< rho<<G4endl; 
 
 
   G4double Q = 0.0 ;
   G4double BracFunct;
   do 
   {
    Q = -std::log(1.-(1.- std::exp(-SlopeMag * Qmax))* G4UniformRand() )/SlopeMag;
    G4double x = fRef * Q;
    BracFunct = ( ( sqr(BesselOneByArg(x))+sqr(rho/2. * BesselJzero(x)) )
*   sqr(DampFactor(pi*fceff*Q))) /(Amag*std::exp(-SlopeMag*Q));
 
    BracFunct = BracFunct * Q * sqr(sqr(fRef));   
   } 
   while (G4UniformRand()>BracFunct);
 
   T= sqr(Q); 
   T*=3.893913e+4;                // fm -> MeV^2
   }
 
   G4double cosTet=1.0-T/(2.*ptot*ptot);
   if(cosTet >  1.0 ) cosTet= 1.;          // Uzhi 30 Nov. 
   if(cosTet < -1.0 ) cosTet=-1.;          // Uzhi 30 Nov. 
   fTetaCMS=std::acos(cosTet);
 
   return T;
}
 
/////////////////////////////////////////////////////////////////////
//  Sample of Theta in CMS
 G4double G4AntiNuclElastic::SampleThetaCMS(const G4ParticleDefinition* p, G4double plab,
                                                                         G4int Z, G4int A)
{ 
  G4double T;
  T =  SampleInvariantT( p, plab,  Z,  A);
 
   // NaN finder
  if(!(T < 0.0 || T >= 0.0))
  {
    if (verboseLevel > 0)
    {
      G4cout << "G4DiffuseElastic:WARNING: A = " << A
             << " mom(GeV)= " << plab/GeV
             << " S-wave will be sampled"
             << G4endl;
    }
    T = G4UniformRand()*fTmax;
 
  }
 
  if(fptot > 0.)                             // Uzhi 24 Nov. 2011
  {
   G4double cosTet=1.0-T/(2.*fptot*fptot);
   if(cosTet >  1.0 ) cosTet= 1.;          // Uzhi 30 Nov. 
   if(cosTet < -1.0 ) cosTet=-1.;          // Uzhi 30 Nov. 
   fTetaCMS=std::acos(cosTet); 
   return fTetaCMS;
  } else                                    // Uzhi 24 Nov. 2011
  {                                         // Uzhi 24 Nov. 2011
   return 2.*G4UniformRand()-1.;            // Uzhi 24 Nov. 2011
  }                                         // Uzhi 24 Nov. 2011
}  
 
 
/////////////////////////////////////////////////////////////////////
//  Sample of Theta in Lab System
 G4double G4AntiNuclElastic::SampleThetaLab(const G4ParticleDefinition* p, G4double plab,
                                                                         G4int Z, G4int A)
{ 
  G4double T; 
  T = SampleInvariantT( p, plab,  Z,  A);
 
 // NaN finder
  if(!(T < 0.0 || T >= 0.0))
  {
    if (verboseLevel > 0)               
    {
      G4cout << "G4DiffuseElastic:WARNING: A = " << A
             << " mom(GeV)= " << plab/GeV
             << " S-wave will be sampled"
             << G4endl;
    }
    T = G4UniformRand()*fTmax;
  }
 
  G4double phi  = G4UniformRand()*twopi;
 
  G4double cost(1.);
  if(fTmax > 0.) {cost = 1. - 2.0*T/fTmax;}             // Uzhi 24 Nov. 2011
 
  G4double sint;
  if( cost >= 1.0 )
  {
    cost = 1.0;
    sint = 0.0;
  }
  else if( cost <= -1.0)
  {
    cost = -1.0;
    sint =  0.0;
  }
  else
  {
    sint = std::sqrt((1.0-cost)*(1.0+cost));
  }
 
  G4double m1 = p->GetPDGMass();
  G4ThreeVector v(sint*std::cos(phi),sint*std::sin(phi),cost);
  v *= fptot;
  G4LorentzVector nlv(v.x(),v.y(),v.z(),std::sqrt(fptot*fptot + m1*m1));
   
  nlv.boost(fbst);
   
  G4ThreeVector np = nlv.vect();
  G4double theta = np.theta();
  fThetaLab = theta; 
 
  return theta;
}
 
////////////////////////////////////////////////////////////////////
//   Calculation of Damp factor
 G4double G4AntiNuclElastic::DampFactor(G4double x)
{
   G4double df;
   G4double  f3 = 6.; // first factorials
 
 if( std::fabs(x) < 0.01 )
  { 
      df=1./(1.+x*x/f3); 
 }
  else
  {
    df = x/std::sinh(x); 
  }
  return df;
}
 
 
/////////////////////////////////////////////////////////////////////////////////
//  Calculation of particle velocity Beta
 
 G4double G4AntiNuclElastic::CalculateParticleBeta( const G4ParticleDefinition* particle, 
                                    G4double momentum    )
{
  G4double mass = particle->GetPDGMass();
  G4double a    = momentum/mass;
  fBeta         = a/std::sqrt(1+a*a);
 
  return fBeta; 
}
 
 
///////////////////////////////////////////////////////////////////////////////////
//   Calculation of parameter Zommerfeld
 
 G4double G4AntiNuclElastic::CalculateZommerfeld( G4double beta, G4double Z1, G4double Z2 )
{
  fZommerfeld = fine_structure_const*Z1*Z2/beta;
 
  return fZommerfeld; 
}
 
////////////////////////////////////////////////////////////////////////////////////
//  
G4double G4AntiNuclElastic::CalculateAm( G4double momentum, G4double n, G4double Z)
{
  G4double k   = momentum/hbarc;
  G4double ch  = 1.13 + 3.76*n*n;
  G4double zn  = 1.77*k/G4Pow::GetInstance()->A13(Z)*Bohr_radius; 
  G4double zn2 = zn*zn;
  fAm          = ch/zn2;
 
  return fAm;
}
 
/////////////////////////////////////////////////////////////
//
// Bessel J0 function based on rational approximation from
// J.F. Hart, Computer Approximations, New York, Willey 1968, p. 141
   
G4double G4AntiNuclElastic::BesselJzero(G4double value)
{  
  G4double modvalue, value2, fact1, fact2, arg, shift, bessel;
 
  modvalue = std::fabs(value);
 
  if ( value < 8.0 && value > -8.0 )
  {
    value2 = value*value;
                 
    fact1  = 57568490574.0 + value2*(-13362590354.0
                           + value2*( 651619640.7  
                           + value2*(-11214424.18
                           + value2*( 77392.33017
                           + value2*(-184.9052456   ) ) ) ) );
                              
    fact2  = 57568490411.0 + value2*( 1029532985.0
                           + value2*( 9494680.718
                           + value2*(59272.64853
                           + value2*(267.8532712
                           + value2*1.0               ) ) ) );
 
    bessel = fact1/fact2;
  }
  else
  {
    arg    = 8.0/modvalue;
 
    value2 = arg*arg;
 
    shift  = modvalue-0.785398164;
 
    fact1  = 1.0 + value2*(-0.1098628627e-2
                 + value2*(0.2734510407e-4
                 + value2*(-0.2073370639e-5
                 + value2*0.2093887211e-6    ) ) );
  fact2  = -0.1562499995e-1 + value2*(0.1430488765e-3
                              + value2*(-0.6911147651e-5
                              + value2*(0.7621095161e-6
                              - value2*0.934945152e-7    ) ) );
 
    bessel = std::sqrt(0.636619772/modvalue)*(std::cos(shift)*fact1 - arg*std::sin(shift)*fact2);
  }
  return bessel;
}
 
 
//////////////////////////////////////////////////////////////////////////////
// Bessel J1 function based on rational approximation from
// J.F. Hart, Computer Approximations, New York, Willey 1968, p. 141
    
 G4double G4AntiNuclElastic::BesselJone(G4double value)
{
  G4double modvalue, value2, fact1, fact2, arg, shift, bessel;
                          
  modvalue = std::fabs(value);
                 
  if ( modvalue < 8.0 )
  {
    value2 = value*value;
    fact1  = value*(72362614232.0 + value2*(-7895059235.0
                                  + value2*( 242396853.1
                                  + value2*(-2972611.439
                                  + value2*( 15704.48260
                                  + value2*(-30.16036606  ) ) ) ) ) );
    
    fact2  = 144725228442.0 + value2*(2300535178.0
                            + value2*(18583304.74
                            + value2*(99447.43394
                            + value2*(376.9991397
                            + value2*1.0             ) ) ) );
    bessel = fact1/fact2;
  }
  else
  {
    arg    = 8.0/modvalue;  
  value2 = arg*arg;
 
    shift  = modvalue - 2.356194491;
 
    fact1  = 1.0 + value2*( 0.183105e-2
                 + value2*(-0.3516396496e-4
                 + value2*(0.2457520174e-5
                 + value2*(-0.240337019e-6          ) ) ) );
 
    fact2 = 0.04687499995 + value2*(-0.2002690873e-3
                          + value2*( 0.8449199096e-5
                          + value2*(-0.88228987e-6
                          + value2*0.105787412e-6       ) ) );
 
    bessel = std::sqrt( 0.636619772/modvalue)*(std::cos(shift)*fact1 - arg*std::sin(shift)*fact2);
    if (value < 0.0) bessel = -bessel;
  }
  return bessel;
}
 
////////////////////////////////////////////////////////////////////////////////
// return J1(x)/x with special case for small x 
G4double G4AntiNuclElastic::BesselOneByArg(G4double x)
{
  G4double x2, result;
 
  if( std::fabs(x) < 0.01 )
  {
   x  *= 0.5;
   x2 = x*x;
   result = (2.- x2 + x2*x2/6.)/4.;
  }
  else
  {
    result = BesselJone(x)/x;
  }
  return result;
} 
 
/////////////////////////////////////////////////////////////////////////////////
// return  angle from which Coulomb scattering is calculated 
G4double G4AntiNuclElastic::GetcosTeta1(G4double plab, G4int A)
{
 
// G4double p0 =G4LossTableManager::Instance()->FactorForAngleLimit()*CLHEP::hbarc/CLHEP::fermi;
  G4double p0 = 1.*hbarc/fermi;
//G4double cteta1 = 1.0 - p0*p0/2.0 * pow(A,2./3.)/(plab*plab);
  G4double cteta1 = 1.0 - p0*p0/2.0 * G4Pow::GetInstance()->Z23(A)/(plab*plab);
//////////////////
  if(cteta1 < -1.) cteta1 = -1.0;
  return cteta1;
}