bethe_bloch.h

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#ifndef BETHE_H
#define BETHE_H
 
namespace Heed {
 
/// Ordinary Bethe-Bloch formula with various modifications.
/// Based on K. Kleinknecht, "Detectors for particle radiation".
/// 1998 - 2002,  I. Smirnov
 
double Bethe_Bloch_energy_loss(const double ratio_Z_to_A, const double I_eff,
                               const double beta, const double z);
 
/// Safer version, using gamma - 1 instead of beta.
double Bethe_Bloch_energy_loss_gamma_1(const double ratio_Z_to_A,
                                       const double I_eff, const double gamma_1,
                                       const double z);
 
double Bethe_Bloch_restricted_energy_loss_gamma_1(
    const double ratio_Z_to_A, const double I_eff, const double m,
    const double gamma_1, const double ecut, const double z);
 
// ratio_Z_to_A: 1.0/(weight/mole), weight in internal units
 
// z*e - the charge of ionizing particle
// sign is not important, z is squared inside the function.
// returns the positive value in units
// [energy] / ([density][length])=[energy]*[length]^2 / [weight]
// (internal units of CLHEP/Units/PhysicalConstants.h)
// It means the energy transfer per unit density and per unit length passed.
// To convert it to real values it need to multiply it by real density and
// by real length.
//
//       Averaging of ratio_Z_to_A by many atoms:
//       ---------------------------------------
// In 1 gram of matter there are Avogadro/A particles.
// If there are mixture of n atoms.
// If Wi - weight by weights (sum(Wi) = 1),
// in 1 gram of matter we should have
// sum(Wi * Avogadro/Ai) = Avogadro * mean(1/Ai) particles,
// and sum(Wi * Avogadro* Zi/Ai) = Avogadro * mean(Zi/Ai) electrons.
// Here the notation mean(something) means sum(Wi*something).
// If Wi - weight by atom numbers (sum(Wi) = 1),
// in 1 gram of matter we should have sum(Ki * Avogadro/Ai) particles,
// and sum(Ki * Avogadro* Zi/Ai) electrons;
// K1*Avogadro/A1  :  K2*Avogadro/A2 : ...  =
// W1              : W2              : ... .
// Then
// Ki = Ai * Wi / sum( Ai * Wi ).
// Therefore the number of particles is Avogadro / mean(Ai)
// and the number of electrons is Avogadro * mean(Zi) / mean(Ai)
// Interesting relations!
}
 
#endif