text: Real Function ppk0(srt)
    Real xarray(7), earray(7)
    Save
    Data xarray/0.030, 0.025, 0.025, 0.026, 0.02, 0.014, 0.06/
    Data earray/3.67, 4.95, 5.52, 6.05, 6.92, 7.87, 10./
    pmass = 0.9383
    ppk0 = 0
    If (srt<=2.63) Return
    If (srt>4.54) Then
       ppk0 = 0.037
       Return
    End If
    plab = sqrt(((srt**2-2.*pmass**2)/(2.*pmass))**2-pmass**2)
    If (plab<earray(1)) Then
       ppk0 = xarray(1)
       Return
    End If
    Do ie = 1, 7
       If (earray(ie)==plab) Then
          ppk0 = xarray(ie)
          Goto 10
       Else If (earray(ie)>plab) Then
          ymin = alog(xarray(ie-1))
          ymax = alog(xarray(ie))
          xmin = alog(earray(ie-1))
          xmax = alog(earray(ie))
          ppk0 = exp(ymin+(alog(plab)-xmin)*(ymax-ymin)/(xmax-xmin))
          Goto 10
       End If
    End Do
  10 Continue
    Return
  End Function ppk0
  