NuRadioMC: Simulating the radio emission of neutrinos from interaction to detector

TL;DR

NuRadioMC provides a modular, end-to-end Monte Carlo framework for simulating radio-detection of ultra-high energy neutrinos, spanning from neutrino interactions to detector readout. The four pillars—Event generation, Signal generation, Signal propagation, and Detector simulation—are complemented by utilities for cross-sections, Earth models, FFT handling, and unit management, all built around a Python-based, flexible architecture. The framework offers multiple signal models, including fast frequency-domain parameterizations and a detailed time-domain ARZ approach that captures LPM elongation and shower fluctuations, alongside an analytic ray-tracing propagation scheme with focusing corrections and optional numerical propagation in complex media. Three comprehensive examples illustrate sensitivity calculations, direct-vs-reflected path detection, and station-spacing optimization, demonstrating NuRadioMC’s utility for detector design, performance assessment, and reconstruction development. Publicly available on GitHub, NuRadioMC stands to accelerate design studies and data-driven reconstruction for next-generation radio neutrino experiments such as RNO, ARIANNA, GRAND, and ARA.

Abstract

NuRadioMC is a Monte Carlo framework designed to simulate ultra-high energy neutrino detectors that rely on the radio detection method. This method exploits the radio emission generated in the electromagnetic component of a particle shower following a neutrino interaction. NuRadioMC simulates everything from the neutrino interaction in a medium, the subsequent Askaryan radio emission, the propagation of the radio signal to the detector and finally the detector response. NuRadioMC is designed as a modern, modular Python-based framework, combining flexibility in detector design with user-friendliness. It includes a state-of-the-art event generator, an improved modelling of the radio emission, a revisited approach to signal propagation and increased flexibility and precision in the detector simulation. This paper focuses on the implemented physics processes and their implications for detector design. A variety of models and parameterizations for the radio emission of neutrino-induced showers are compared and reviewed. Comprehensive examples are used to discuss the capabilities of the code and different aspects of instrumental design decisions.

Figures (21)

• Figure 1: Sketch of the coordinate system used by Nu-Radio-MC and typical dimensions in the radio detection of neutrino interactions. The coordinate origin is at the ice surface. A quantity of particular interest is the viewing angle $\theta$, i.e., the angle at which the in-ice shower is observed. Due to the longitudinal extent of the shower, the viewing angle is not uniquely defined. By default, we measure the angle with respect to the neutrino interaction vertex, but sometimes it is appropriate to measure the angle with respect to the maximum of the charge-excess profile, which we denote with $\theta_\mathrm{Xmax}$. It should be noted that this is just one typical set-up, other choices of geometry are supported.
• Figure 2: Feynman diagrams of a charged current and neutral current neutrino interaction.
• Figure 3: Sketch of the geometry and the concept of a fiducial volume of the event generator. Neutrinos tracks are generated in a full simulation volume, but only the radio emission of primary or secondary interactions are considered, when they take place in a fiducial volume encompassing the detector.
• Figure 4: Top: Tau decay length as a function of the tau energy. Bottom: Tau decay energy as a function of the initial tau energy. Due to the one-tailed nature of the exponential decay function, we show the decay length for the mean proper decay time with photonuclear losses (solid line) and without any losses (dashed line). The shaded band represents the area spanning from the $10\%$ proper decay time quantile to the $90\%$ quantile ($80\%$ of total probability). This implementation matches what has been shown previously in PhysRevD.63.094020.
• Figure 5: Electric field amplitude $\varepsilon^{1m}$, $\unit[1]{m}$ from the neutrino interaction vertex (Eq. \ref{['eqn:ShelfMCConeAngle']}) for hadronic (left) and electromagnetic (right) showers with $E_{sh} = \unit[10^{18}]{eV}$ using the parameterization Alvarez2000. Note that as the viewing angle shifts away from the Cherenkov cone angle, high frequency components fall off. For the EM showers, the cone width $\sigma_\theta$ is reduced due to the LPM effect.