Models of Particle Detection in Regions of Spacetime

We investigate two models of measuring devices designed to detect a non-relativistic free particle in a given region of spacetime. These models predict different probabilities for a free quantum particle to enter a spacetime region $R$ so that this notion is device dependent. The first model is of a von Neumann coupling which we present as a contrast to the second model. The second model is shown to be related to probabilities defined through partitions of configuration space paths in a path integral. This study thus provides insight into the physical situations to which such definitions of probabilities are appropriate.