pythiaeRHIC/pythia/pytbhb.f

0001 C------------------------------------------------------------------
0002       SUBROUTINE PYTBHB(MT,MB,MHP,BR,GAMT)
0003 C  WIDTH AND BRANCHING RATIO FOR (ON-SHELL) T-> B W+, T->B H+
0004       IMPLICIT DOUBLE PRECISION(A-H, O-Z)
0005       IMPLICIT INTEGER(I-N)
0006       DOUBLE PRECISION MW2,MT,MB,MHP,MW,KFUN
0007       COMMON/PYCTBH/ ALPHA,ALPHAS,SW2,MW2,TANB,VTB,V,A
0008       SAVE /PYCTBH/
0009
0010 C   TOP WIDTH CALCULATION
0011 C       VTB  = 0.99
0012       MW=DSQRT(MW2)
0013       XB=(MB/MT)**2
0014       XW=(MW/MT)**2
0015       XH =(MHP/MT)**2
0016       GAMTBH = 0D0
0017       IF (MT .LT. (MHP+MB)) THEN
0018 C  T ->B W ONLY
0019          BETW = DSQRT(1.D0-2*(XB+XW)+(XW-XB)**2)
0020          GAMTBW = VTB**2*ALPHA/(16*SW2)*MT/XW*BETW*
0021      &        (2*(1.D0-XB-XW)-(1.D0+XB-XW)*(1.D0-XB -2*XW) )
0022          GAMT  = GAMTBW
0023       ELSE
0024 C T ->BW +T ->B H^+
0025          BETW = DSQRT(1.D0-2*(XB+XW)+(XW-XB)**2)
0026          GAMTBW = VTB**2*ALPHA/(16*SW2)*MT/XW*BETW*
0027      &        (2*(1.D0-XB-XW)-(1.D0+XB-XW)*(1.D0-XB -2*XW) )
0028 C
0029          KFUN = DSQRT( (1.D0-(MHP/MT)**2-(MB/MT)**2)**2
0030      &        -4.D0*(MHP*MB/MT**2)**2 )
0031          GAMTBH= ALPHA/SW2/8.D0*VTB**2*KFUN/MT *
0032      &        (V**2*((MT+MB)**2-MHP**2)+A**2*((MT-MB)**2-MHP**2))
0033          GAMT  = GAMTBW+GAMTBH
0034       ENDIF
0035 C THUS BR IS
0036       BR=GAMTBH/GAMT
0037       RETURN
0038       END