  Light clusters such as alpha particles and deuterons are predicted to occur
in hot nuclear matter as encountered in intermediate-energy heavy-ion
collisions and protoneutron stars. To examine the in-medium properties of such
light clusters, we consider a much simplified system in which like an impurity,
a single alpha particle is embedded in a zero-temperature, dilute gas of
non-interacting neutrons. By adopting a non-selfconsistent ladder approximation
for the effective interaction between the impurity and the gas, which is often
used for analyses of Fermi polarons in a gas of ultracold atoms, we calculate
the quasiparticle properties of the impurity, i.e., the energy shift, effective
mass, quasiparticle residue, and damping rate.
