2 C.----------------------------------------------------------------------
4 C. PHOTOS: PHOton radiation in decays control FACtor
6 C. Purpose: This is the control function for the photon spectrum and
7 C. final weighting. It is called from PHOENE for genera-
8 C. ting the raw photon energy spectrum (MODE=0) and in PHO-
9 C. COR to scale the final weight (MODE=1). The factor con-
10 C. sists of 3 terms. Addition of the factor FF which mul-
11 C. tiplies PHOFAC for MODE=0 and divides PHOFAC for MODE=1,
12 C. does not affect the results for the MC generation. An
13 C. appropriate choice for FF can speed up the calculation.
14 C. Note that a too small value of FF may cause weight over-
15 C. flow in PHOCOR and will generate a warning, halting the
16 C. execution. PRX should be included for repeated calls
17 C. for the same event, allowing more particles to radiate
18 C. photons. At the first call IREP=0, for more than 1
19 C. charged decay products, IREP >= 1. Thus, PRSOFT (no
20 C. photon radiation probability in the previous calls)
21 C. appropriately scales the strength of the bremsstrahlung.
23 C. Input Parameters: MODE, PROBH, XF
25 C. Output Parameter: Function value
27 C. Author(s): S. Jadach, Z. Was Created at: 01/01/89
28 C. B. van Eijk Last Update: 13/02/90
30 C.----------------------------------------------------------------------
36 COMMON/PHOPRO/PROBH,CORWT,XF,IREP
38 DATA PRX,FF/ 0.D0, 0.D0/
40 IF (IREP.EQ.0) PRX=1.D0
44 C-- Following options are not considered for the time being...
45 C-- (1) Good choice, but does not save very much time:
46 C-- FF=(1.0D0-SQRT(XF)/2.0D0)/(1.0+SQRT(XF)/2.0D0)
47 C-- (2) Taken from the blue, but works without weight overflows...
48 C-- FF=(1.D0-XF/(1-(1-SQRT(XF))**2))*(1+(1-SQRT(XF))/SQRT(1-XF))/2