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PHOTONUC

activates gamma interactions with nuclei

See also EMF, MUPHOTON

For all SDUM's except MUMUPAIR/MUMUPRIM:

     WHAT(1) : flag to switch on nuclear interactions of photons:
              =< -1.0 : reset to default (no photonuclear interactions)
              =   0.0 : ignored
              =   1.0 : photonuclear interactions are activated at all
                        energies
              =   2.0 : photonuclear interactions are activated only in
                        the high energy range (above 0.7 GeV)
              =   3.0 : photonuclear interactions are activated only in
                        the region of the Delta resonance
              =   4.0 : only quasi-deuteron interactions are activated
              =   5.0 : only Giant Dipole Resonance interactions are
                        activated
              >= 10.0 : interpreted as ih + id * 10 + iq * 100 + ig * 1000
                        where ih = 1 to activate High-energy interactions
                              id = 1 to activate Delta Resonance
                              iq = 1 to activate Quasi-deuteron
                              ig = 1 to activate Giant Resonance
                        and each is = 0.0 otherwise

             Default = 0.0 (no photonuclear interaction)

     WHAT(2), WHAT(3) : not used

     WHAT(4) = lower index bound of materials where the indicated
               photonuclear interactions are activated
               ("From material WHAT(4)..."
               Default = 3.0

     WHAT(5) = upper index bound of materials where the indicated
               photonuclear interactions are activated
               ("...To  material WHAT(5)..."
               Default = WHAT(4)

     WHAT(6) = step length in assigning indices ("...in steps of
               WHAT(6)").
               Default = 1.0.

For SDUM = MUMUPAIR/MUMUPRIM:

     WHAT(1) : flag to switch on muon pair production by photons:
             = -1: resets to default (no muon pair production)
             =  0: ignored
             >  0: interpreted as ich + iqe * 10 + iin * 100 + ids * 1000
          where ich = 1 to activate muon pair coherent production
                iqe = 1 to activate muon pair incoherent quasielastic production
                iin = 1 to activate muon pair incoherent inelastic production
                ids = 1 to activate muon pair deep inelastic production
                and each is = 0.0 otherwise
               Default: no muon pair production by photons

     WHAT(2) = interaction length biasing factor
             = 0: ignored
             0 < |WHAT(2)| < 1: the interaction length of the photon is reduced
               by a factor |WHAT(2)|
             1 =< |WHAT (2)|: a possible previous biasing factor is reset to the
               default value (no biasing)
             0< WHAT(2) < 1: the primary particle always survives with reduced
               weight
             -1 < WHAT(2) < 0: Russian Roulette is played to decide if the
               primary particle will be killed, or survive with its original
               weight
             Default: no biasing

     WHAT(3) : not used

     WHAT(4) = lower index bound of materials where the indicated
               photomuon production mechanisms are activated
               ("From material WHAT(4)..."
               Default = 3.0

     WHAT(5) = upper index bound of materials where the indicated
               photomuon production mechanisms are activated
               ("...To  material WHAT(5)..."
               Default = WHAT(4)

     WHAT(6) = step length in assigning indices ("...in steps of
               WHAT(6)").
               Default = 1.0.

        SDUM = MUMUPRIM: photomuon production biasing applied to primaries only

     Default (option PHOTONUC not given): photon interactions with
            nuclei as well as photomuon production are not simulated

Notes:

• 1) Muon photonuclear interactions (via virtual photons) are not handled by PHOTONUC but by MUPHOTON.

• 2) Because photonuclear cross sections are much smaller than photon cross sections for electromagnetic interactions with atoms and electrons, analogue simulations of photonuclear interactions are very inefficient. Generally, it is recommended to use PHOTONUC in combination with LAM-BIAS to increase artificially the frequency of photonuclear interactions. See the Notes
• 9) and
• 10) to option LAM-BIAS for more details.

• 3) High-energy photonuclear interactions are also activated by WHAT(1) and WHAT(4) in option EMF. However, this is a duplicate that eventually will be removed.

Example 1:

 * Giant Resonance and Quasideuteron photonuclear interactions are requested
 * in material 18. The photon hadronic interaction length is artificially
 * shortened by a factor 0.02 in order to improve statistics
 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
 PHOTONUC      1100.0       0.0       0.0      18.0       0.0       0.0
 LAM-BIAS         0.0      0.02      18.0       7.0       0.0       0.0

Example 2:

 * Photonuclear interactions are requested at all energies in materials
 * 3, 7, 11 and 15. The photon hadronic interaction length is shortened
 * by a factor 0.025
 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
 PHOTONUC         1.0       0.0       0.0       3.0      15.0       4.0
 LAM-BIAS         0.0     0.025       0.0       7.0       0.0       0.0