Analytic Forms of Cosmic Ray Spectra Suitable for Muon Tomography

Performance characteristics of different approaches to muon tomography depend critically on the nature of the targets to be imaged and the flux of cosmic ray muons available at the site to be studied. To a reasonable approximation, the zenith angle θ and muon energy or momentum pμ dependences of the flux are similar at all potential tomography sites but the total muon flux does depend on site elevation. Accurate models of the θ and pμ dependence of the cosmic ray muon flux are important for planning and assessing tomography projects. This note summarizes models for muon spectra used by the groups participating in the Japan Society for the Promotion of Science (JSPS) workshop on muon tomography held in Washington, D.C. on Feb. 15-16, 2012; its purpose is to provide a common basis for future discussions of possible options for applying muon tomography at the Fukushima nuclear power plant.