pythiaeRHIC/pythia/pyrvsb.f

0001
0002 C*********************************************************************
0003
0004 C...PYRVSB
0005 C...Auxiliary function to PYRVSF for calculating R-Violating
0006 C...sfermion widths. Though the decay products are most often treated
0007 C...as massless in the calculation, the kinematical boundary of phase
0008 C...space is tested using the true masses.
0009 C...MODE = 1: All decay products massive
0010 C...MODE = 2: Decay product 1 massless
0011 C...MODE = 3: Decay product 2 massless
0012 C...MODE = 4: All decay products  massless
0013
0014       FUNCTION PYRVSB(KFIN,ID1,ID2,RM2,MODE)
0015
0016       IMPLICIT DOUBLE PRECISION (A-H,O-Z)
0017       IMPLICIT INTEGER (I-N)
0018       COMMON/PYDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
0019       COMMON/PYDAT2/KCHG(500,4),PMAS(500,4),PARF(2000),VCKM(4,4)
0020       SAVE /PYDAT1/,/PYDAT2/
0021       DOUBLE PRECISION SM(3)
0022       INTEGER PYCOMP, KC(3)
0023       KC(1)=PYCOMP(KFIN)
0024       KC(2)=PYCOMP(ID1)
0025       KC(3)=PYCOMP(ID2)
0026       SM(1)=PMAS(KC(1),1)**2
0027       SM(2)=PMAS(KC(2),1)**2
0028       SM(3)=PMAS(KC(3),1)**2
0029 C...Kinematics check
0030       IF ((SM(1)-(PMAS(KC(2),1)+PMAS(KC(3),1))**2).LE.0D0) THEN
0031         PYRVSB=0D0
0032         RETURN
0033       ENDIF
0034 C...CM momenta squared
0035       IF (MODE.EQ.1) THEN
0036         P2CM=1./(4*SM(1))*(SM(1)-(PMAS(KC(2),1)+PMAS(KC(3),1))**2)
0037      &       * (SM(1)-(PMAS(KC(2),1)-PMAS(KC(3),1))**2)
0038       ELSE IF (MODE.EQ.2) THEN
0039         P2CM=1./(4*SM(1))*(SM(1)-(PMAS(KC(3),1))**2)**2
0040       ELSE IF (MODE.EQ.3) THEN
0041         P2CM=1./(4*SM(1))*(SM(1)-(PMAS(KC(2),1))**2)**2
0042       ELSE
0043         P2CM=SM(1)/4.
0044       ENDIF
0045 C...Calculate Width
0046       PYRVSB=RM2*SQRT(MAX(0D0,P2CM))/(8*PARU(1)*SM(1))
0047       RETURN
0048       END