Reference analysis of the signal + background model in counting experiments

The model representing two independent Poisson processes, labelled as “signal” and “background” and both contributing at the same time to the total number of counted events, is considered from a Bayesian point of view. This is a widely used model for the searches of rare or exotic events in presence of some background source, as for example in the searches performed by the high-energy physics experiments. In the assumption of some prior knowledge about the background yield, a reference prior is obtained for the signal alone and its properties are studied. Finally, the properties of the full solution, the marginal reference posterior, are illustrated with few examples.