  Boost invariance and multiplicity dependence of the charge balance function
are studied in $\pi^{+}\rp$ and $\rK^{+}\rp$ collisions at 250 GeV/$c$ incident
beam momentum. Charge balance, as well as charge fluctuations, are found to be
boost invariant over the whole rapidity region, but both depend on the size of
the rapidity window. It is also found that the balance function becomes
narrower with increasing multiplicity, consistent with the narrowing of the
balance function when centrality and/or system size increase, as observed in
current relativistic heavy ion experiments.
