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CERN Program Library Long Writeup W5013 - CERNLIB ...

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Geant 3.16 GEANT User’s Guide PHYS325<br />

Origin : M.S. Dixit Submitted: 17.06.85<br />

Revision : G.Lynch Revised: 16.12.93<br />

Documentation : F.Carminati<br />

1 Subroutines<br />

1.1 Initialisation<br />

Molière scattering<br />

CALL GMULOF<br />

GMULOF calculates the table of maximum steps corresponding to the energies in the array ELOW for electrons<br />

and muons. It is called during initialisation by GPHYSI. For hadrons and ions the computation is performed<br />

during tracking in the routines GTHADR and GTHION.<br />

CALL GMOLI<br />

(AC,ZC,WMAT,NLM,DENS,OMC*,CHC*)<br />

AC REAL array of dimenstion NLM containing the mass numbers;<br />

ZC REAL array of dimenstion NLM containing the atomic numbers;<br />

WMAT REAL array containing the proportions by weight of the component of a mixture/compound. 1<br />

in case of a single component;<br />

NLM INTEGER number of the elements in the mixture/compound;<br />

DENS REAL density in g cm −3 ;<br />

OMC REAL b c constant of Molière theory;<br />

CHC REAL χ cc constant of Molière theory.<br />

GMOLI calculates the two material-dependent constants (OMC and CHC). These are needed during initialisation<br />

by GMULOF and during tracking to sample the scattering angle, as explained below. It is called at initialisation<br />

time by the routine GPROBI which initialises some material constants and computes the probabilities for<br />

various processes.<br />

1.2 Sampling of the multiple scattering angle<br />

CALL GMULTS<br />

GMULTS is the steering routine for the sampling of the multiple scattering angle when the variable IMULTS in<br />

common /GCPHYS/ is 1 or 2. This variable can be controlled by the MULT data record. The routine decides<br />

if the material-dependent constant OMC computed by GMOLI during initialisation has to be corrected due to<br />

its dependence on β and Z inc , and selects Molière theory (GMOLIE) or single Coulomb scattering (GMCOUL).<br />

It updates the direction of the particle in the array VECT (COMMON GCTRAK). It is called by the tracking<br />

routines GTELEC, GTHADR, GTHION and GTMUON.<br />

CALL GMOLIO<br />

(AC,ZC,WMAT,NLM,DENS,BETA2,CHARG2,OMC*)<br />

BETA2<br />

CHARG2<br />

REAL β 2 of the particle;<br />

REAL charge squared of the particle in electron charge unit (Zinc 2 in the following).<br />

All the other arguments are routine GMOLI. GMOLIO re-evaluates the material-dependent constant OMC. Itis<br />

called by GMULTS, if needed.<br />

242 PHYS325 – 1

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