Charm Production and High Energy Atmospheric Muon and Neutrino Fluxes

TL;DR

This work computes atmospheric muon and neutrino fluxes from cosmic-ray interactions using both Monte Carlo cascade simulations and analytic Z-moment methods, with special focus on charm induced prompt fluxes. Charm production is modeled predominantly with perturbative QCD, while intrinsic charm is explored as a non-perturbative alternative. The main finding is that the prompt fluxes are significantly lower than many earlier estimates, reducing the atmospheric background for high-energy neutrino observations. The paper also analyzes non-scaling effects and provides a framework for evaluating charm production at ultra-high energies, informing neutrino telescope prospects and background modeling.

Abstract

Production of muons and neutrinos in cosmic ray interactions with the atmosphere has been investigated with Monte Carlo models for hadronic interactions. The resulting conventional muon and neutrino fluxes (from $π$ and $K$ decays) agree well with earlier calculations, whereas our prompt fluxes from charm decays are significantly lower than earlier estimates. Charm production is mainly considered as a well defined perturbative QCD process, but we also investigate a hypothetical non-perturbative intrinsic charm component in the proton. The lower charm rate implies better prospects for detecting very high energy neutrinos from cosmic sources.

Figures (13)

• Figure 1: Distribution of the altitude for the primary interactions as obtained in the cascade simulations.
• Figure 2: The $E^3$-weighted flux of muons ($\mu^+ +\mu^-$), muon-neutrinos ($\nu_{\mu} + \bar{\nu}_{\mu}$) and electron-neutrinos ($\nu_e + \bar{\nu}_e$) from decays of the specified particles. The error bars indicate the statistical precision of the Monte Carlo simulation.
• Figure 3: The $E^3$-weighted vertical flux of muons, muon-neutrinos and electron-neutrinos from conventional ($\pi , K$ decays) and prompt (charm decays) sources and their sum ('total'). The solid lines are from the cascade simulation (section 3) and the dashed lines are from the analytic $Z$-moment method (section 4).
• Figure 4: Energy-dependence of production $Z_{kh}$-moments, Eq. (\ref{['eq:zmom']}), for incoming particle $k$ producing hadron $h$. Solid lines are the results of our model using the initial spectrum with a 'knee', Eq. (\ref{['eq:primary']}), whereas the dotted lines are obtained with a constant spectral index $\gamma=1.7$. Dashed lines show the values of Lipari93 based on Feynman scaling.
• Figure 5: Illustration of charm production in pQCD. The leading order processes (a,b,c) and an important next-to-leading order process (d).