On the Accuracy of Underground Muon Intensity Calculations

Abstract

Cosmic-ray muons detected by deep underground and underwater detectors have served as an information source on the high-energy cosmic-ray spectrum and hadronic interactions in air showers for almost a century. The theoretical interest in underground muons has nearly faded away because space-borne experiments probe the cosmic-ray spectrum more directly, and accelerators provide precise measurements of hadron yields. However, underground muons probe unique hadron interaction energies and phase space, which are still inaccessible to present accelerator experiments. The cosmic-ray nucleon energies reach the hundred-TeV and PeV ranges, which are barely accessible with space-borne experiments. Our new calculation combines two modern computational tools: mceq for surface muon fluxes and proposal for underground transport. We demonstrate excellent agreement with measurements of cosmic-ray muon intensities underground within estimated errors. Beyond that, the precision of historical data turns out to be significantly smaller than our error estimates. This result shows that the sources of high-energy atmospheric lepton flux uncertainties at the surface or underground can be significantly constrained without taking more data or building new detectors. The reduction of uncertainties can be expected to impact data analyses at large-volume neutrino telescopes and be used for the design of future ton-scale direct dark matter detectors.

daemonflux: Data-Driven Muon-Calibrated Neutrino Flux

“…In future iterations, we will employ the code mute [20,21] to further constrain the its parameters using a selection of muon measurements underground. In the contribution [21], we present that the underground data is well described by the present daemonflux.…”

Challenges and Opportunities for Predicting Muons in Underground and Underwater Labs Using MUTE

“…The computational scheme of mute (v1.0.1) used for labs under flat overburdens is described in [1]. In this follow-up work, we introduce mute v2 [3], capable of calculating muon observables for laboratories beneath mountains.1 For the case of a flat overburden, symmetry in the azimuthal angle is assumed across all calculations, and there is a direct correspondence between slant depth, 𝑋, and zenith angle, 𝜃, for a given vertical depth ℎ:…”

“…mute (MUon inTensity codE) is a Python program that combines two state-of-the-art codes, mceq and proposal, to predict muon intensities and spectra in underground and underwater laboratories. Our previous work [1] has demonstrated the accuracy of mute in reproducing the measured vertical equivalent muon intensities within the models' uncertainties. Moreover, we have shown that the experimental uncertainties are smaller than the theoretical uncertainties, making the vertical-equivalent data an effective calibration source for high-energy neutrino flux calculations.…”

“…The unique opportunity to study high-energy muons without the technical challenges or costs associated with surface-based spectrometers, capable of resolving multi-hundred TeV range energies, is provided by large-volume detectors situated underground. In our previous work, we concentrated on the development of the mute code [1], a method designed for the efficient calculation of underground muon fluxes and other related observables. As a result, we deduced that a subset of underground muon measurements could serve as a "calibration source" for certain unconstrained model uncertainties, such as those recently incorporated by daemonflux [2].…”