JPhysicsToolkit.hh

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#ifndef __JPHYSICS_JPHYSICSTOOLKIT__
#define __JPHYSICS_JPHYSICSTOOLKIT__

#include "JTools/JConstants.hh"


/**
 * \author mdejong
 */

namespace JPHYSICS {}
namespace JPP { using namespace JPHYSICS; }

/**
 * Auxiliary classes and methods for calculation of PDF and muon energy loss.
 */
namespace JPHYSICS {
  
  /**
   * Get multiple Coulomb scattering angle.
   * 
   * The formula is taken from reference:
   * Particle Data Book, formula 27.14.
   *
   * \param  E          Energy           [GeV]
   * \param  x          distance         [m]
   * \param  X0         radiation length [m]
   * \param  M          mass             [GeV]
   * \param  Q          charge           [unit]
   * \return            angle            [rad]
   */
  inline double getThetaMCS(const double E,
                            const double x,
                            const double X0,
                            const double M,
                            const double Q)
  {
    using JTOOLS::THETA_MCS;
    
    if (E > M) {

      const double p    = sqrt((E + M) * (E - M));
      const double beta = p / E;
      
      return THETA_MCS * Q * sqrt(x/X0) * (1.0 + 0.038*log(x/X0)) / (beta*p);
    }

    return 0.0;
  }

  
  /**
   * Get multiple Coulomb scattering angle.
   *
   * \param  E          Energy [GeV]
   * \param  x          distance [m]
   * \return            angle [rad]
   */
  inline double getThetaMCS(const double E, const double x)
  {
    using namespace JTOOLS;

    return getThetaMCS(E, x, X0_WATER_M, MASS_MUON, 1.0);
  }
}

#endif