  Unfolding is a well-established tool in particle physics. However, a naive
application of the standard regularization techniques to unfold the momentum
spectrum of protons ejected in the process of negative muon nuclear capture led
to a result exhibiting unphysical artifacts. A finite data sample limited the
range in which unfolding can be performed, thus introducing a cutoff. A sharply
falling "true" distribution led to low data statistics near the cutoff, which
exacerbated the regularization bias and produced an unphysical spike in the
resulting spectrum. An improved approach has been developed to address these
issues and is illustrated using a toy model. The approach uses full Poisson
likelihood of data, and produces a continuous, physically plausible, unfolded
distribution. The new technique has a broad applicability since spectra with
similar features, such as sharply falling spectra, are common.
