Atmospheric leptons, the search for a prompt component

TL;DR

The paper analyzes atmospheric leptons with a focus on the prompt component from charmed hadrons, highlighting its significance as a background to astrophysical neutrinos. It combines analytic cascade formalisms with charm-production models (TIG, ERS, RQPM) and discusses knee effects in the primary spectrum via energy-dependent Z-factors, producing predictions for muon and neutrino fluxes and expected rates in a km^3 detector. The study finds that prompt fluxes can become significant around 100 TeV and can exceed conventional fluxes depending on charm model; the results underscore the need for improved charm data and integrated Monte Carlo treatments to interpret IceCube observations. The work also provides practical estimates of event rates for neutrino-induced muons and electron neutrino cascades, informing background assessments for high-energy neutrino astronomy.

Abstract

The flux of high-energy (>GeV) neutrinos consists primarily of those produced by cosmic-ray interactions in the atmosphere. The contribution from extraterrestrial sources is still unknown. Current limits suggest that the observed spectrum is dominated by atmospheric neutrinos up to at least 100 TeV. The contribution of charmed hadrons to the flux of atmospheric neutrinos is important in the context of the search for astrophysical neutrinos because the spectrum of such "prompt" neutrinos is harder than that of "conventional" neutrinos from decay of pions and kaons. The prompt component therefore becomes increasingly important as energy increases. This paper reviews the status of the search for prompt muons and neutrinos with emphasis on the complementary aspects of muons, electron neutrinos and muon neutrinos.

Figures (6)

• Figure 1: Left: All-particle spectrum from Ref. Gaisser2012 where references to the data are given. Right: Spectrum of nucleons for several assumptions (see text for explanation).
• Figure 2: Predictions of three models for the flux of prompt muons. See text for discussion of the rescaled plots.
• Figure 3: Muon spectra including prompt contribution. Left: prompt component from ERS model (rescaled); Right: prompt component from RQPM model (rescaled).
• Figure 4: Neutrino spectra including the prompt contribution. Left: $\nu_\mu+\bar{\nu}_\mu$; Right: $\nu_e+\bar{\nu}_e$.
• Figure 5: Integral muon rate. Left: with rescaled ERS model for prompt muons; Right: with rescaled RQPM model for charm.