Directivity function of muon detector

We introduce a new concept of directivity function (DF) to describe directional sensitivity of a particle detector. DF is а 3D function, describing the sensitivity of a detector to asymptotic directions of primary protons. It defines the contribution of primary protons, arriving from different asymptotic directions to the count rate of the detector. We develop the approach for computing the DF and derive it in particular case of SEVAN muon detector, located at mount Aragats, Armenia. Obtained data enable one to outline the region of solid angles, inside of which the arriving protons contribute a given percentage of count rate. In general, the DF can have the multi peak shape. It provides the most detailed and accurate description of directional sensitivity of a particle detector and we suggest that it is used in space research based on neutron and muon detectors.