The HELIOS experiment has measured inclusive
p
spectra of negative particles in the rapidity region 1.0
y<1.9. the="" general="" shape="" of="">
p
spectra in p +W, O+W and S+W is similar, but cannot be described by a single exponential. Compared to p+p collisions, an excess is observed for low and high
p
. This effect increases with the projectile mass. Except for very low
E
, the average transverse momentum
p
> is found to be approximately constant up to the highest accessible values of
E
.