Prompt atmospheric neutrinos and muons: NLO vs LO QCD predictions
Graciela Gelmini, Paolo Gondolo, Gabriele Varieschi
TL;DR
The study evaluates atmospheric muon and neutrino fluxes from charm decays by comparing LO and NLO QCD predictions using the MNR framework, coupled with a full atmospheric cascade simulation via PYTHIA. It finds that the full NLO lepton fluxes can be well approximated by Born-level fluxes scaled by a factor of about 2.2–2.4, with the exact value mildly PDF-dependent, validating a practical scaling approach. A major sensitivity arises from the small-$x$ behavior of the gluon PDF, explaining discrepancies with earlier, lower flux estimates. These results refine prompt flux predictions relevant for high-energy neutrino telescopes and clarify the role of PDF extrapolations in cosmic-ray–induced lepton production.
Abstract
We compare the leading and next-to-leading order QCD predictions for the flux of atmospheric muons and neutrinos from decays of charmed particles. We find that the full NLO lepton fluxes can be approximated to within 10% by the Born--level fluxes multiplied by an overall factor of 2.2-2.4, which depends slightly on the PDF. This supports the approach in Thunman, Ingelman, Gondolo (1996). We also find that their very low lepton fluxes are due to the mild slope they used for the gluon distribution function at small momentum fractions, and that substantially larger lepton fluxes result when the slope of the gluon distribution function at small momentum fractions is larger.