  Initial results on particle yields obtained by the HARP experiment are
presented. The measurements correspond to proton--nucleus collisions at beam
energies of 12.9 $GeV/c$ and for a thin Al target of 5% interacion legth. The
angular range considered is between 10 and 250 $mrad$. This results are the
first step in the upcoming measurement of the forward production cross-section
for the same target and beam energy, relevant for the calculation of the
far--to--near ratio of the K2K experiment.
