pythiaeRHIC/pythia/pyrvg2.f

0001
0002 C*********************************************************************
0003
0004 C...PYRVG2
0005 C...Integrand for L-R interference contributions
0006
0007       FUNCTION PYRVG2(X)
0008
0009       IMPLICIT NONE
0010       COMMON/PYRVPM/RM(0:3),A(2),B(2),RESM(2),RESW(2),MFLAG
0011       DOUBLE PRECISION X, RM, A, B, RESM, RESW, DELTAY, PYRVS
0012       DOUBLE PRECISION RVS,PYRVG2,E2,E3,C1,SR1,SR2
0013       LOGICAL MFLAG
0014       SAVE/PYRVPM/
0015       C1     = 2D0*SQRT(MAX(0D0,X))
0016       RVS    = PYRVS(X,X,RESM(1),RESW(1),RESM(2),RESW(2))
0017       IF (.NOT.MFLAG) THEN
0018         E2     = X/C1
0019         E3     = (RM(0)**2-X)/C1
0020         DELTAY = 4D0*E2*E3
0021         PYRVG2 = DELTAY*RVS*X*(A(1)*A(2)+B(1)*B(2))*(RM(0)**2-X)
0022       ELSE
0023         E2     = (X-RM(1)**2+RM(2)**2)/C1
0024         E3     = (RM(0)**2-X-RM(3)**2)/C1
0025         SR1    = SQRT(MAX(0D0,E2**2-RM(2)**2))
0026         SR2    = SQRT(MAX(0D0,E3**2-RM(3)**2))
0027         DELTAY = 4D0*SR1*SR2
0028         PYRVG2 = DELTAY*RVS*(X-RM(1)**2-RM(2)**2)*((A(1)*A(2)
0029      &       + B(1)*B(2))*(RM(0)**2+RM(3)**2-X)
0030      &       + 2D0*(A(1)*B(2)+A(2)*B(1))*RM(3)*RM(0))
0031       ENDIF
0032       RETURN
0033       END