CERN Program Library Long Writeup W5013 - CERNLIB ...

DEEMAX
The formula used by GEANT is the following:
DEEMAX =
⎧
⎪⎨
⎪⎩
0.25 if ISVOL =0 and X 0 < 2 cm
0.25 − √ 0.2 if ISVOL =0 and X 0 ≥ 2 cm
X0
0.2
√ if ISVOL ≠0
X0
STMIN
TMAXFD
STEMAX
ISVOL > 0 defines a sensitive detector, while ISVOL ≤ 0 is a non-sensitive detector (see [HITS]).
The default value corresponds to a stopping range of 200 keV above CUTELE.
The default value corresponds to 20 ◦ if the input value to GSTMED is ≤ 0 or > 20 ◦ , otherwise the
input value is taken.
The default value is 10 10 (BIG variable in common /GCONST/).
These values have been tuned empirically on a variety of setups and users are invited to start with automatic
computation. The values of the parameters can be checked with a call to GPRINT(’TMED’,0) after GPHYSI
has been called. Use of AUTO mode is strongly recommended because it makes GEANT a predictive tool. In
this way all parameters are automatically computed by the system as opposed to tuning data and MonteCarlo
via the tracking parameters.
8 Energy loss
8.1 Energy loss tables
In previous versions of GEANT (up to version 3.13) the energy lost by a charged particle travelling through
matter was calculated by the formula:
∆E = dE
dx × step
The quantity dE/dx was calculated and tabulated for e ± , µ ± and protons and the value for a particle of a
given energy E 0 was calculated interpolating linearly the tables:
dE
dx ∣ = dE
E=E0 dx ∣ +
E ( 0 − E i dE
E=Ei E i+1 − E i dx ∣ − dE
)
E=Ei+1 dx ∣ (7)
E=Ei
= GEKRT1 × dE
dx ∣ + GEKRAT × dE
E=Ei dx ∣ (E i