C program for neutron efficiency

#include <iostream>
#include <cmath>
using namespace std;

double crossSectionHydrogenFunction();
double numberCarbonFunction(double thickness, 
                            const double CUBICCENTIMETERCARBON);
double numberHydrogenFunction(double thickness, 
                              const double CUBICCENTIMETERHYDROGEN);
double crossSectionCarbonFunction();
void efficiencyFunction(double numberHydrogen, double numberCarbon, 
                        double crossSectionHydrogen, double crossSectionCarbon, 
                        double thickness);

/************************************************************************
* This program is to find the
* efficiency of a neutron detector.
************************************************************************/
double  main()
{
  double neutronEnergy;
  double numberHydrogen;
  double numberCarbon;
  double crossSectionHydrogen;
  double crossSectionCarbon;
  double thickness;
  const double CUBICCENTIMETERCARBON = 5.23e22;
  const double CUBICCENTIMETERHYDROGEN = 4.74e22;

  cout << endl;
  cout << "Enter thickness of detector (in centimeters): ";
  cin >> thickness;

  crossSectionHydrogen = crossSectionHydrogenFunction();
  numberCarbon = numberCarbonFunction(thickness,
                                      CUBICCENTIMETERCARBON);
  numberHydrogen = numberHydrogenFunction(thickness,
                                          CUBICCENTIMETERHYDROGEN);
  crossSectionCarbon = crossSectionCarbonFunction();

  efficiencyFunction(numberHydrogen, numberCarbon,
                     crossSectionHydrogen, crossSectionCarbon,
                     thickness);
}

/**********************************************************************
 * Equation for cross section of hydrogen according to
 * equation 15-9 from Radiation Detection and Measurement
 *                                   by Glenn Knoll
 *********************************************************************/
 double crossSectionHydrogenFunction()
 {
   double neutronEnergy;
   double crossSectionHydrogen;

   cout << endl;
   cout << "Enter neutron energy (in MeV): ";
   cin >> neutronEnergy;

   crossSectionHydrogen = ((4.83e-24 / sqrt(neutronEnergy))
                             - .578e-24);

   return crossSectionHydrogen;
 }

/**********************************************************************
 * Equation for calculating the number of Carbons in
 * the problem per cubic centimeter, dependent on what
 * the user put in for the thickness of the detector.
 *********************************************************************/
 double numberCarbonFunction(double thickness, const
                             double CUBICCENTIMETERCARBON)
 {
   double numberCarbon;

   numberCarbon = CUBICCENTIMETERCARBON;
   return numberCarbon;
 } 

/*********************************************************************
 * Equation for calculating the number of Hydrogens in
 * the problem per cubic centimeter, dependent on what
 *  the user put in for the thickness of the detector.
 ********************************************************************/
 double numberHydrogenFunction(double thickness, const
                               double CUBICCENTIMETERHYDROGEN)
 {
   double numberHydrogen;

   numberHydrogen = CUBICCENTIMETERHYDROGEN;
   return numberHydrogen;
 }

/*********************************************************************
 * Requesting the cross section from the Knoll book, and
 * then calculating it from barns to centimeters.
 ********************************************************************/
 double crossSectionCarbonFunction()
 {
   double crossSectionCarbon;

   cout << endl;
   cout << "Enter the cross section of Carbon by "
        << "looking in Radiation" << endl
        << "Detection and Measurement by Glenn Knoll, on"
        << " page 535, " << endl
        << "Figure 15-15b (in barns): ";
   cin >> crossSectionCarbon;
   crosSectionCarbon = crossSectionCarbon * 1e-24;

   return crossSectionCarbon;
 }

/*******************************************************************
 * Equation for efficiency according to equation 15-8b
 * from Radiation Detection and Measurement
 *                            by Glenn Knoll
 ******************************************************************/
 void efficiencyFunction(double numberHydrogen, double
                         numberCarbon, double crossSectionHydrogen,
                         double crossSectionCarbon, double
                         thickness)
 {
   double efficiency;
   double nHcH = numberHydrogen * crossSectionHydrogen;
   double nCcC = numberCarbon * crossSectionCarbon;

   efficiency = (((nHcH) / (nHcH + nCcC)) * (1-exp(-(nHcH
                                                  + nCcC)
                                            * thickness)));
   if(efficiency <= 0)
   {
     efficiency = 0;
   }
   cout.precision(4);
   cout << endl;
   cout << "Therefore, the efficiency of our "
        << "system is: " << efficiency *100 << "%" << endl;
   cout << endl;
   return;
 }