More volume overlaps corrected
[u/mrichter/AliRoot.git] / ISAJET / code / ssgt.F
CommitLineData
0795afa3 1#include "isajet/pilot.h"
2 REAL FUNCTION SSGT(S,AMSQ,Z,I,J)
3C-----------------------------------------------------------------------
4C Function for Sig(qqbar->z_i + z_j
5C-----------------------------------------------------------------------
6#if defined(CERNLIB_IMPNONE)
7 IMPLICIT NONE
8#endif
9#include "isajet/sssm.inc"
10#include "isajet/sspar.inc"
11 REAL S,AMSQ,K,Z,MZI,MZJ,RS,TPP,TPM,BTP,BTM
12 INTEGER I,J,ITHI,ITHJ
13C
14 MZI=ABS(AMZISS(I))
15 MZJ=ABS(AMZISS(J))
16 IF (AMZISS(I).LT.0.) THEN
17 ITHI=1
18 ELSE
19 ITHI=0
20 END IF
21 IF (AMZISS(J).LT.0.) THEN
22 ITHJ=1
23 ELSE
24 ITHJ=0
25 END IF
26 RS=SQRT(S)
27 K=SQRT(S*S+(MZI**2-MZJ**2)**2-2*S*(MZI**2+MZJ**2))/
28 $ 2./RS
29 TPP=S*S-(MZI**2-MZJ**2)**2-4*K*S**1.5*Z+4*K*K*S*Z*Z
30 TPM=S*S-(MZI**2-MZJ**2)**2+4*K*S**1.5*Z+4*K*K*S*Z*Z
31 BTP=(S-MZI**2-MZJ**2)/2.-RS*K*Z+AMSQ**2
32 BTM=(S-MZI**2-MZJ**2)/2.+RS*K*Z+AMSQ**2
33 SSGT=(TPP/BTP**2+TPM/BTM**2-8*(-1.)**(ITHI+ITHJ)*
34 $ MZI*MZJ*S/BTM/BTP)/16.
35 RETURN
36 END