  We study the feasibility of performing a $\nu_\mu$ disappearance
long-baseline experiment using a neutrino beam coming from muon decays. The
advantage of such a technique with respect to the production of neutrino beams
from pions is that in a muon decay both muon and electron neutrinos are
produced in the same quantity. In case of $\nu_\mu\to\nu_{\tau,s}$
oscillations, the $\nu_e$ charged current (CC) events can be used as a control
sample, to predict in situ the $\nu_\mu$ rates, thus reducing the systematics
due to the knowledge of the neutrino flux, which is the main source of
uncertainties for disappearance experiments. We consider as our neutrino
target, the ICARUS detector in its final mass configuration of 4.8 kton.
