GEANT321/gphys/gphys.doc

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:21:19  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 #if defined(CERNLIB_DOC)
  11 *CMZ :  3.21/02 29/03/94  15.41.21  by  S.Giani
  12 *-- Author :
  13 *
  14 ************************************************************************
  15 *                                                                      *
  16 *                  Introduction to the section PHYS                    *
  17 *                  --------------------------------                    *
  18 *                                                                      *
  19 *                                                                      *
  20 * THE PHYSICS PROCESSES                                                *
  21 *                                                                      *
  22 *  The processes  currently implemented in GEANT3  can be classified   *
  23 * as follows:                                                          *
  24 *                                                                      *
  25 * - Decays in flight                                                   *
  26 * - Multiple scattering (Gaussian or Moliere)                          *
  27 * - Continuous electromagnetic processes                               *
  28 * - Discrete electromagnetic processes                                 *
  29 * - Hadronic interactions                                              *
  30 * - Muon nucleus-interactions.                                         *
  31 *                                                                      *
  32 *  The  fist  two  are  controlled  by  the  routines  GDECAY  which   *
  33 * generates the decay products and  GMULTS which computes the change   *
  34 * in  the angle  due to  multiple scattering  over a  given tracking   *
  35 * step.   The  others  are  reviewed  separately  in  the  following   *
  36 * paragraphs.                                                          *
  37 *  For  convenience the  particles are  given a  'tracking type'  in   *
  38 * GEANT, depending on their interaction with matter:                   *
  39 *                                                                      *
  40 *   ITRTYP = 1  photon                                                 *
  41 *            2  electron and positron                                  *
  42 *            3  neutral particles                                      *
  43 *            4  charged hadrons                                        *
  44 *            5  muon                                                   *
  45 *            6  'Geantino'                                             *
  46 *            7  Cerenkov photon                                        *
  47 *            8  Ion                                                    *
  48 *                                                                      *
  49 *  The  paragraph  5  gives  a  summary  of  the  physics  processes   *
  50 * activated for  each type  of particle with  the momentum  range of   *
  51 * validity when relevant.  GPHYSI controls the initialisation of the   *
  52 * various processes.                                                   *
  53 *                                                                      *
  54 * CONTINUOUS ELECTROMAGNETIC PROCESSES                                 *
  55 *                                                                      *
  56 * GMOLI     Initializes Moliere scattering                             *
  57 * GPROBI    initializes material 'constants'  used for computing the   *
  58 *           probability of various interactions.                       *
  59 * GDRELA    Control routine  to fill   DE/DX tables for  energy loss   *
  60 *           due to ionisation.                                         *
  61 * GDRELP    Calculates  energy loss  due to  ionisation for  charged   *
  62 *           particles other than electrons and positrons.              *
  63 * GDRELE    Calculates energy  loss due to ionisation  for electrons   *
  64 *           and  positrons.  As  Moller  and  Bhabba scattering  are   *
  65 *           treated  as discrete  processes the  energy loss  due to   *
  66 *           ionisation is a function  of the electron kinetic energy   *
  67 *           cut-off DCUTE below which these processes are treated as   *
  68 *           a continuous energy loss [BASE 030, common /GCPHYS/].      *
  69 * GBRELA    Initializes   Bremsstrahlung  cross-section   and  fills   *
  70 *           energy  loss tables  for Bremsstrahlung.   Both formulae   *
  71 *           depend on  the photon  energy cut-off BCUTE  below which   *
  72 *           Bremsstrahlung is  treated as  a continuous  energy loss   *
  73 *           [BASE 030, common /GCPHYS/].                               *
  74 * GPRELA    Fills  DE/DX  tables  for  energy loss  by  direct  pair   *
  75 *           production  for high  energy  muons.  The  corresponding   *
  76 *           discrete process is not considered.                        *
  77 * GRANGI    Calculates    the    stopping     range    tables    for   *
  78 *           electron/positron, muon and proton.                        *
  79 * GMULOF    Calculates the tables for the maximum step allowed to to   *
  80 *           continuous processes: Bending  in magnetic field, energy   *
  81 *           loss and multiple scattering.                              *
  82 * GCOEFF    Calculates  the   interpolation  coefficients   for  the   *
  83 *           energy/Range relation  to be used in  the calculation of   *
  84 *           the energy loss.                                           *
  85 *                                                                      *
  86 * DISCRETE ELECTROMAGNETIC PROCESSES                                   *
  87 *                                                                      *
  88 *   For the simulation of each  given discrete physics process three   *
  89 * tasks have to be performed:                                          *
  90 *                                                                      *
  91 * - The evaluation  of the step  length.  This is computed  from the   *
  92 *   updated  probability for  the  occurrence of  the process.   The   *
  93 *   corresponding code  has been  inserted directly in  the tracking   *
  94 *   routines for each tracking type as appropriate.                    *
  95 * - After transport  of the  particle, the  generation of  the final   *
  96 *   state particles (GEANT routines GPHOT, GCOMP, etc.)                *
  97 * - If the  particle survives  after the interaction,  recompute the   *
  98 *   probability.                                                       *
  99 *                                                                      *
 100 *   It should be outlined that the  evaluation of the step length is   *
 101 * made independently  for each  process which  can occur,  the final   *
 102 * step  size  being the  minimum  of  all  and the  process  finally   *
 103 * considered being the corresponding one.                              *
 104 *                                                                      *
 105 * GPHOTI    Tabulates  cross-section  for photo-electric  effect  at   *
 106 *           initialisation time                                        *
 107 * GPHOT     Simulates photo-electric mechanism                         *
 108 * GCOMPI    Tabulates  cross-section  for  Compton  intersection  at   *
 109 *           initialisation time                                        *
 110 * GCOMP     Simulates Compton scattering                               *
 111 * GPRSGA    Tabulates   cross-section   for   pair   production   at   *
 112 *           initialisation time                                        *
 113 * GPAIRG    Simulates electron pair production by photons              *
 114 * GBRSGA    Tabulates    cross-section    for   Bremsstrahlung    at   *
 115 *           initialisation time                                        *
 116 * GBREME    Simulates  hard  Bremsstrahlung   by  electrons.  -  see   *
 117 *           cut-off BCUTE in routine GBRELA above                      *
 118 * GDRSGA    Tabulates cross-section for  delta-ray at initialisation   *
 119 *           time                                                       *
 120 * GDRAY     Simulates delta rays (Moller or Bhabba scattering) - see   *
 121 *           cut-off DCUTE in routine GDRELE above                      *
 122 * GANNII    Tabulates  cross-section  for positron  annihilation  at   *
 123 *           initialisation time                                        *
 124 * GANNI     Simulates positron annihilation in flight                  *
 125 * GANNIR    Simulates positron annihilation at rest.                   *
 126 * GPFISI    Tabulates cross-section for photo-fission                  *
 127 * GPFIS     Simulates photo-fission                                    *
 128 *                                                                      *
 129 * HADRONIC PROCESSES                                                   *
 130 *                                                                      *
 131 *   For GHEISHA:                                                       *
 132 * GPGHEI    returns the hadronic cross section                         *
 133 * GHEISH    Simulates  hadronic  interactions, program  GHEISHA  (H.   *
 134 *           Fesefeldt) in GEANH file.                                  *
 135 *                                                                      *
 136 *   For FLUKA:                                                         *
 137 * FLDIST    returns the hadronic cross section                         *
 138 * FLUFIN    Simulates    hadronic   interactions,    program   FLUKA   *
 139 *           (A.Ferrari et al.) in GEANH file.                          *
 140 *                                                                      *
 141 * MUON INTERACTION                                                     *
 142 *                                                                      *
 143 * GBRELM    Tabulates energy loss by soft Bremsstrahlung               *
 144 * GBRSGM    Tabulates cross-section for hard Bremsstrahlung            *
 145 * GBREMM    Generates hard Bremsstrahlung                              *
 146 * GPAIRI    Tabulates cross-section for direct pair production         *
 147 * GPAIRM    Generate direct pair production                            *
 148 * GMUNUI    Tabulates cross-section for nuclear interaction            *
 149 * GMUNU     Generates nuclear interaction                              *
 150 * GDRELM    Tabulates energy loss by soft delta rays                   *
 151 * GDRSGA    Tabulates cross-section for hard delta rays                *
 152 * GDRAY     Generates delta rays                                       *
 153 *                                                                      *
 154 ************************************************************************
 155 #endif