Calculations will be performed to improve the theoretical predictions for underground and accelerator experiments detecting high energy elementary particle interactions. Consequently, experimental results can be better interpreted whether as tests of aspects of the standard model of strong nuclear, weak and electromagnetic forces or as signals of new physics. Large underground detectors act as neutrino telescopes by detecting the conversions of neutrinos to muons in the water, rock or ice surrounding the detector. Neutrinos produced by galactic or extra-galactic sources travel undeviated to the earth, bringing information about the astrophysical processes that cannot be inferred from studying electomagnetic radiation. Muons and neutrinos are also produced by cosmic ray interactions with air nuclei in the earth's atmosphere. At high energies, charmed particle production and decay in the atmosphere is the dominant terrestrial source of fluxes of muons and neutrinos. A new calculation of the fluxes of muon and neutrinos from the decays of charmed particles that are produced in the atmosphere will be performed using a range of inputs consistent with laboratory measurements of charm production, extrapolated to higher energy. In addition, calculations related to the interpretation of electron neutrino and muon neutrino conversions to charged particles in underground detectors will be refined. The improvements to existing calculations may have an impact on the allowed regions of parameter space in models with neutrino oscillations. A `Monte Carlo` simulation of neutrino production of charm quarks in quantum chromodynamics (QCD) will be developed. QCD is the theoretical description of the strong nuclear force. The Monte Carlo will be used by experimental groups to help them determine strange quark content of the proton.
