pyrvg3.f

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C*********************************************************************
 
C...PYRVG3
C...Function to do Y integration over true interference contributions
 
      FUNCTION pyrvg3(X)
 
      IMPLICIT NONE
      common/pyrvpm/rm(0:3),a(2),b(2),resm(2),resw(2),mflag
C...Second Dalitz variable for PYRVG4
      common/pyg2dx/x1
      DOUBLE PRECISION rm, a, b, resm, resw, x, x1
      DOUBLE PRECISION e2, e3, c1, sq1, sr1, sr2, ymin, ymax
      DOUBLE PRECISION pyrvg3, pyrvg4, pygau2
      LOGICAL mflag
      EXTERNAL pygau2,pyrvg4
      SAVE/pyrvpm/,/pyg2dx/
      pyrvg3=0d0
      c1=2d0*sqrt(max(1d-9,x))
      x1=x
      IF (.NOT.mflag) THEN
        e2    = x/c1
        e3    = (rm(0)**2-x)/c1
        ymin  = 0d0
        ymax  = 4d0*e2*e3
      ELSE
        e2    = (x-rm(1)**2+rm(2)**2)/c1
        e3    = (rm(0)**2-x-rm(3)**2)/c1
        sq1   = (e2+e3)**2
        sr1   = sqrt(max(0d0,e2**2-rm(2)**2))
        sr2   = sqrt(max(0d0,e3**2-rm(3)**2))
        ymin  = sq1-(sr1+sr2)**2
        ymax  = sq1-(sr1-sr2)**2
      ENDIF
      pyrvg3 = pygau2(pyrvg4,ymin,ymax,1d-3)
      RETURN
      END