  A phenomenological model of the time evolution of a particle wavepacket is
presented that is subject to scattering event with small momentum transfer. It
is suited for three dimensions and allows for an additional potential. For a
random value of a phase parameter, it is equivalent to the decoherence by
scattering off plane wave field states. Imposing some condition on the same
phase parameter, the model delivers definite outcomes in a local pointer base.
Common sense notions about the quantum-classical transition are readily
obtained: Decoherent free particle solutions are localized constant-width
wavepackets, quantum barrier scattering results in random reflection and
transmission. The scattering process assumed in the phenomenological model is
realized by scattering of a particle pair interacting by a force-distance law
with small momentum transfer. Particles are localized not by decoherence but by
a classical lensing effect. Schmidt paths in the Schmidt representation of the
multiparticle state are products of single-particle wavepackets. Therefore the
model has a natural 'Many Worlds' interpretation, identifying each Schmidt path
with a classical branch. Different runs of the phenomenological model map the
state of the same particular particle within different branches.
