CERN Program Library Long Writeup W5013 - CERNLIB ...

Geant 3.16 GEANT User’s Guide PHYS441
Origin : L.Urbán Submitted: 26.10. 84
Revision : Revised: 11.10.93
Documentation :
1 Subroutines
Simulation of discrete bremsstrahlung by muons
CALL GBREMM
GBREMM generates a photon from bremsstrahlung of a highly energetic muon as a discrete process. For the
angular distribution of the photon, is calls the function GBTETH.
Input:
Output:
via common /GCTRAK/;
via common /GCKING/.
GBREMM is called from the tracking routine GTMUON when the muon reaches its radiation point during the
tracking stage of GEANT.
VALUE = GBTETH (ENER,PARTM,EFRAC)
ENER
PARTM
EFRAC
(REAL) kinetic energy of the muon;
(REAL) mass of the radiating particle (m µ in this case);
(REAL) ratio of the energy of the radiated photon to the energy of the muon.
GBTETH calculates the angular distribution of the e − e + pair in photon pair production and of the photon in
bremsstrahlung. In case of bremsstrahlung it gives the scaled angle (η = Eθm −1 ) of the photon.
2 Method
The differential cross-section for the emission of a photon of energy k by a muon of energy E is [99, 100]:
where
dσ
dv = N v
( 4
3 − 4 3 v + v2 )
Φ(δ) (1)
Φ(δ) =
N = normalisation factor v = k E
δ = m2 µ v
e = 2.718 ...
2E 1 − v
⎧ ( ) ( √ )
189mµ 189 e
⎪⎨
ln
m e Z 1/3 − ln
m e Z 1/3 δ +1
( ) ( √ ) ( )
189mµ 189 e
2
⎪⎩ ln
m e Z 1/3 − ln
m e Z 1/3 δ +1 +ln
3 Z−1/3
v c = k c
E ≤ v ≤ (
1 − 0.75 √ e m µ
E Z1/3 )
= v max
if Z ≤ 10
if Z>10
311 PHYS441 – 1