pyrvg1.f

Go to the documentation of this file. Or view the newest version in sPHENIX GitHub for file pyrvg1.f

 
C*********************************************************************
 
C...PYRVG1
C...Integrand for resonance contributions
 
      FUNCTION pyrvg1(X)
 
      IMPLICIT NONE
      common/pyrvpm/rm(0:3),a(2),b(2),resm(2),resw(2),mflag
      DOUBLE PRECISION x, rm, a, b, resm, resw, deltay,pyrvr
      DOUBLE PRECISION rvr,pyrvg1,e2,e3,c1,sr1,sr2,a1,a2
      LOGICAL mflag
      SAVE/pyrvpm/
      rvr    = pyrvr(x,resm(1),resw(1))
      c1     = 2d0*sqrt(max(0d0,x))
      IF (.NOT.mflag) THEN
        e2     = x/c1
        e3     = (rm(0)**2-x)/c1
        deltay = 4d0*e2*e3
        pyrvg1 = deltay*rvr*x*(a(1)**2+b(1)**2)*(rm(0)**2-x)
      ELSE
        e2     = (x-rm(1)**2+rm(2)**2)/c1
        e3     = (rm(0)**2-x-rm(3)**2)/c1
        sr1    = sqrt(max(0d0,e2**2-rm(2)**2))
        sr2    = sqrt(max(0d0,e3**2-rm(3)**2))
        deltay = 4d0*sr1*sr2
        a1     = 4.*a(1)*b(1)*rm(3)*rm(0)
        a2     = (a(1)**2+b(1)**2)*(rm(0)**2+rm(3)**2-x)
        pyrvg1 = deltay*rvr*(x-rm(1)**2-rm(2)**2)*(a1+a2)
      ENDIF
      RETURN
      END