  Recent measurements by the BRAHMS collaboration of high-pT hadron production
at forward rapidities at RHIC found the relative production rate(d-Au)/(p-p) to
be suppressed, rather than enhanced. Examining other known reactions (forward
production of light hadrons, the Drell-Yan process, heavy flavor production,
etc.), one notes that all of these display a similar property, namely, their
cross sections in nuclei are suppressed at large xF. Since this is the region
where x2 is minimal, it is tempting to interpret this as a manifestation of
coherence, or of a color glass condensate, whereas it is actually a simple
consequence of energy conservation and takes place even at low energies. We
demonstrate that in all these reactions there is a common suppression mechanism
that can be viewed, alternatively, as a consequence of a reduced survival
probability for large rapidity gap processes in nuclei, Sudakov suppression, an
enhanced resolution of higher Fock states by nuclei, or an effective energy
loss that rises linearly with energy. Our calculations agree with data.
