  We calculate cross sections for the far forward LHC detectors to be used for
luminosity measurement. A simple model, based on a parametrization of available
inclusive neutron data and the assumption that 2 arm rates in non-diffractive
events are uncorrelated, is introduced. The calculated rates are in reasonable
agreement with preliminary data from RHIC and we are now comparing with rates
at 3 LHC energies.
