# Acoustic & Radio EeV Neutrino Detection Activities

Europe/Rome
Description

## The 9th International Workshop on Acoustic and Radio EeV Neutrino Detection Activities (ARENA 2022) will be held in Hotel NH Collection Santiago de Compostela, Spain, just 5 min. walking distance to the historic part of Santiago.

The new amazing discoveries reported from high-energy neutrino, gamma-ray and gravitational wave detectors have started the exciting era of multi-messenger astronomy, opening a new window to the most extreme universe.

ARENA is the major bi-annual event for scientists to pioneer, develop and consolidate techniques for ultra-high-energy particle detection, paving the way to the future.

Registration
ARENA 2022 Registration form
Participants
• Alvarez-Muniz, Jaime
• Ammerman-Yebra, Juan
• Buitink, Stijn
• Büsken, Max
• Carvalho Jr., Washington
• Chiche, Simon
• Coleman, Alan
• Corstanje, Arthur
• de Almeida, Rogerio
• De Kockere, Simon
• de Vries, Krijn
• Decoene, Valentin
• Desmet, Mitja
• Diego-Tortosa, Dídac
• Dujmovic, Hrvoje
• Fodran, Tomáš
• Gatius Oliver, Clara
• Giaccari, Ugo Gregorio
• Glaser, Christian
• Gottowik, Marvin
• Hallmann, Steffen
• Henrichs, Jakob
• Heyer, Nils
• Huege, Tim
• Huesca Santiago, Enrique
• Hughes, Kaeli
• Hörandel, Jörg
• Jianli, Zhang
• Karastathis, Nikolaos
• Krampah, Godwin Komla
• Lahmann, Robert
• Latif, Uzair Abdul
• Lautridou, Pascal
• LE COZ, Sandra
• Lukic, Vesna
• Martineau, Olivier
• Martinelli, Sara
• Martins, Miguel
• Mulrey, Katharine
• Nelles, Anna
• Oeyen, Bob
• Pandya, Hershal
• Parente, GONZALO
• Paudel, Ek Narayan
• Pawlowsky, Jannis
• Plaisier, Ilse
• Pont, Bjarni
• Rautenberg, Julian
• riehn, felix
• Saharan, Mohit
• Schlüter, Felix
• Schoorlemmer, Harm
• Schröder, Frank
• Stanley, Rose
• Stjärnholm, Sigfrid
• Straub, Maximilian
• Toscano, Simona
• Tueros, Matias
• Turcotte-Tardif, Roxanne
• Van den Broeck, dieder
• Zas, Enrique
• Zeolla, Andrew
Jaime Alvarez-Muniz
• Tuesday, June 7
• 8:30 AM 9:00 AM
Registration 30m
• 9:00 AM 9:10 AM
Opening and welcome
• 9:10 AM 11:30 AM
• 9:10 AM

The Askaryan Radio Array (ARA) is searching for high energy neutrinos (>10 PeV) from the cosmos using clusters of antennas buried under the South Pole ice sheet at a maximum depth of 200 m. ARA is looking at the radio Cherenkov emission generated when neutrinos interact with the surrounding medium. The array consists of 5 radio stations, each of them monitoring an independent portion of the ice to maximize the detector effective volume. ARA stations use a combination of vertically polarized (VPol) and horizontally polarized (HPol) antennas, as well as calibration devices (calpulser) for antenna positioning and ice properties studies. One of the newest ARA stations has been equipped with an independent phased array detector allowing to lower the trigger threshold and consequently improve the array sensitivity at low energies. ARA has been taking data since 2012 and analysis of the full data set is ongoing. In this contribution I will present the latest results in the ARA search for cosmic neutrinos, which produced the best limit from an in-ice radio detector above 100 PeV. Additionally I will discuss calibration efforts and ongoing work in analysis and reconstruction.

Speaker: Toscano, Simona
• 9:30 AM
Results from a low-threshold ultrahigh-energy neutrino search with the Askaryan Radio Array 20m

The Askaryan Radio Array (ARA) is an in-ice radio detector at the South Pole that targets radio emission from neutrino-induced particle cascades. Designed to detect neutrinos above 10 PeV, ARA has been taking data for over ten years and includes five independent stations. The newest ARA station is equipped with a phased array trigger, which lowers the trigger threshold compared to previous ARA stations and thus increases the neutrino sensitivity. In this contribution, we discuss the newest ARA analysis results from this phased array trigger and show a corresponding improvement in analysis efficiency, rejecting thermal backgrounds and providing vertex direction in the deep ice. We will also discuss the implications of this analysis for future radio-detection experiments.

Speaker: Hughes, Kaeli (University of Chicago)
• 9:50 AM
Results from the ARIANNA high-energy neutrino detector 20m

The ARIANNA in-ice radio detector explores the detection of UHE neutrinos with shallow detector stations on the Ross Ice Shelf and the South Pole. I will present recent results that lay the foundation for future large-scale experiments. I will show a limit on the UHE neutrino flux derived from ARIANNA data, measurements of the more abundant air showers, results from in-situ measurement campaigns, a study of a potential background from internal reflection layers, and give an outlook of future detector improvements.

Speaker: Glaser, Christian (Uppsala University)
• 10:10 AM
The Payload for Ultrahigh Energy Observations (PUEO) 20m

PUEO is a long duration balloon experiment which will launch in 2024 from Antarctica that builds on the successes of the previous flights of the ANITA experiment in order to probe the cosmic neutrino flux above EeV energies. PUEO, like ANITA, seeks to measure coherent radio emission in the form of Askaryan emission from neutrino interactions inside the Antarctic ice sheet and both geomagnetic and Askaryan emission from i) decays of Earth-emergent $\tau$-leptons in the atmosphere sourced from cosmic $\tau$ neutrinos ii) downward going cosmic rays reflected off the ice and iii) direct cosmic rays arriving above the Earth horizon.

Over the course of 4 flights, the ANITA experiment set the most stringent constrains on the diffuse flux of neutrinos with energies above 30EeV, in addition to measuring: 64 reflected cosmic ray candidates, 7 direct cosmic ray candidates, and an excess of candidates with non-inverted polarity from below the horizon that require further observation and analysis. PUEO improves upon the sensitivity of ANITA by over an order of magnitude below energies of 30EeV, thereby increasing the number of expected events from all event classes and allowing for stronger statistics, better constraints on physical models, and access to new energy regimes. These improvements are made primarily by i) more then doubling the number of antennas flown ii) including both dedicated low and high frequency drop-down instruments and iii) including an interferometric phased array trigger, thereby allowing for a decreased energy threshold via beamforming. PUEO also has significantly improved pointing resolution and ability to filter anthropogenic noise at the trigger level, allowing for better analysis efficiency and source classification. Using these improvements, over the course of a 30 day flight, PUEO will either make the first significant measurement of or set the strongest constraints to date on the diffuse flux of cosmic neutrinos above energies of 1EeV, in addition to following up the anomalous near-horizon events observed by ANITA and searching for transient sources.

Speaker: Cummings, Austin Lee (Pennsylvania State University)
• 10:30 AM
The Radio Neutrino Observatory Greenland (RNO-G): Status Update 20m

In 2021, the first three stations of the Radio Neutrino Observatory in Greenland (RNO-G) have been installed and started data-taking. The deployment of additional stations is currently ongoing. RNO-G is an in-ice detector with the prospect to the first detection of a neutrino shower beyond $\sim$10 PeV via the Askaryan emission. With a projected 90% CL upper limit below $E^2\Phi\sim\, 10^{-8}$ GeV/cm$^2$/s/sr, RNO-G will be the first detector reaching realistic predicted GZK and astrophysical neutrino fluxes.

In this talk, we present the current status of the instrument and give an overview of the efforts towards calibration and analysis of the data recorded so far.

Speaker: Hallmann, Steffen (DESY)
• 10:50 AM
Triboelectric events in RNO-G 15m

The Radio Neutrino Observatory Greenland (RNO-G) has the scientific purpose to observe ultra-high energy cosmogenic neutrinos through in-ice radio detection. The remoteness of polar experiments makes sure that anthropogenic sources of background are naturally lowered. However, other sources of noise are present and have to be studied in order to reach rejection rates necessary to unambiguously identify such rare neutrino events. Triboelectric effects can generate radio signals that represent a possible source of background in such detectors. In polar environments, triboelectic events can be produced by wind blowing over the granular surface of snow, which generates a force that displaces surface charge and induces an electrostatic potential difference, with subsequent coronal discharge. Discharges over timescales of nanoseconds can then lead to radio-frequency emissions at characteristic MHz – GHz frequencies. For RNO-G, as for other radio detectors, this was observed more intensely above a wind speed value of O(10 m/s). Here we present an analysis on the first year RNO-G data that show the possible correlation of high-wind periods and increasing noise.

• 11:05 AM
Searching for air showers with RNO-G 15m

The Radio Neutrino Observatory – Greenland (RNO-G) is an in-ice
neutrino detector, using the detection of radio emission to target the first
measurement of neutrinos beyond PeV energies. In total 35 stations are
planned for the detector, resulting in a detection volume of around 100
km${}^3$. Each of these stations is equipped with deep antennas embedded $\sim$100 m into the ice and downward-pointing LPDA buried $\sim$3 m into the
snow. At each station three additional LPDA are pointing towards the
sky and thus can be used to look for air showers.
In this contribution, we will give an insight into the air shower analysis
of RNO-G, showing the expected number of air showers per station and
presenting the status of the template search for air showers.

Speaker: Henrichs, Jakob (DESY)
• 11:30 AM 12:00 PM
Coffee and tea 30m
• 12:00 PM 1:30 PM
• 12:00 PM
Angular Resolution for the Radio Neutrino Observatory Greenland (RNO-G). 15m

In the ultra-high energy regime, the low predicted neutrino fluxes are out of reach for currently running neutrino detectors. Larger instrumented volumes are needed to probe these low fluxes. The Radio Neutrino Observatory Greenland (RNO-G) detects radio waves emitted by neutrino induced particle showers in the Greenlandic ice sheet. Radio waves have a large attenuation length in ice (O(1km)) and therefore RNO-G implements a sparse instrumentation to cover an unprecedented volume. The first three RNO-G stations have been deployed last summer and deployment will be ongoing in the next three years.
This contribution discusses the angular resolution of RNO-G. We use a method that uses a parametrization for the emitted electric field which is forward folded through the detector and matched with the voltage traces as obtained in the antennas of an RNO-G station. We obtain a median angular resolution of 3 degrees for an optimized event set (50 %), and a median of 1.3 degrees for the subset of events which have significant signal strength in two antennas measuring perpendicular electric-field components, such that a good measurement of the polarization can be obtained.

Speaker: Plaisier, Ilse
• 12:15 PM

The SLAC T-576 beam test has shown the radar echo detection method as a feasible technique to probe high-energy-particle-initiated cascades in dense media, such as ice. Furthermore, particle-level simulations show that the radar echo method has a very promising sensitivity to investigate the flux of cosmic neutrinos at energies greater than 1 PeV. Detecting these cosmic neutrinos is the aim of the Radar Echo Telescope for Neutrinos (RET-N). To show the in-nature viability of the radar echo method, we present the Radar Echo Telescope for Cosmic Rays (RET-CR). RET-CR will provide the proof of principle necessary for the construction of RET-N by detecting, using radar, the in-ice continuation of cosmic-ray induced air showers impinging on the high altitude Antarctic ice sheet. The energy and arrival direction of the original air shower will be reconstructed using a surface cosmic ray detector, complimenting the reconstruction that is possible using the in-ice radar setup. We present our current simulation efforts for RET-CR, which provides an estimate of the expected event rate, as well as the detector layout optimization. This work is then placed in context of the final RET-N detector.

Speaker: Stanley, Rose (Vrije Universiteit Brussel - IIHE)
• 12:35 PM
From signal properties toward reconstruction for the Radar Echo Telescope for neutrinos 20m

Speaker: Lukic, Vesna (VUB)
• 12:55 PM
The NuMoon Experiment: Preliminary results and upper limits on UHE particles 20m

Ultra-high energy (UHE) particles interacting with the Moon produce particle showers in the regolith. Due to charge asymmetry in the shower front, a short broadband coherent burst of radio emission is produced - via a phenomenon referred to as the Askaryan effect. With ground based radio telescopes, such pulses can be searched for. The LOw Frequency ARray (LOFAR) - a radio observatory located in the Netherlands - is currently the largest radio array operating at frequencies between $110 - 190$~MHz; an optimum frequency range for Lunar signal search. A pulse search on the near-surface of the Moon is carried out. This requires a proper understanding of the background noise and other factors (like the ionosphere) that could have an adverse effect on the signal. In this contribution, we discuss results from first Lunar observations with LOFAR and the development of a trigger algorithm for future observations. Results from a detailed Monte-Carlo (MC) simulation of the effective lunar aperture for UHE particles and the expected sensitivity to the UHE particle flux are shown.

Speaker: Mr Krampah, Godwin Komla (Vrije University of Brussels)
• 1:30 PM 3:00 PM
Lunch 1h 30m
• 3:00 PM 4:30 PM
Ice Data Analysis & Tools 1
• 3:00 PM
Using NuRadioMC to study the performance of UHE radio neutrino detectors 15m

NuRadioMC is an open-source, Python-based simulation and reconstruction
framework for radio detectors of Ultra-High-Energy (UHE) neutrinos and
cosmic rays. Its modular design makes NuRadioMC suitable for use with a
range of past, current and future detectors. In addition, the recent
deployment of a complete documentation as well as a pip release make
NuRadioMC relatively easy to learn and use. This talk will outline the
features currently available and under development in NuRadioMC, with a
focus on its usage to simulate and study in-ice radio neutrino
detectors, such as the planned IceCube-Gen2 Radio extension.

Speaker: Bouma, Sjoerd
• 3:20 PM
NuLeptonSim: A practical use of a neutrino propagation code as an event generator 20m

To calculate the sensitivity of current and future telescopes to astrophysical neutrinos, it is necessary to understand the key properties (energy, flavor, and probability weight) of both these primary neutrinos and their secondary particles after propagation through the Earth. The properties of these particles are strongly influenced by the various interactions that both neutrinos and their secondaries are subject to, and a full treatment of the propagation is required. Many different computation schemes exist to treat this problem (NuTauSim, TauRunner, and NuPyProp being just a few examples).

In this work, we detail NuLeptonSim, an update to the NuTauSim Monte Carlo neutrino propagation code for high energy tau neutrinos. The improvements included in NuLeptonSim include i) all flavor neutrino modeling ii) Glashow Resonance interactions and iii) compatibility with detector frameworks (arbitrary definitions of detector geometry and particle trajectory, including downwards trajectories). We demonstrate the results from including these effects on the Earth emergence probability of various charged leptons and their corresponding energy distributions. Using NuLeptonSim to model propagation, we calculate the sensitivity of the Askaryan Radio Array (ARA) experiment to cosmic neutrinos. Following this calculation, we also include secondary particle interactions (radiative losses from muons and $\tau$-leptons) to improve the estimate of the sensitivity.

Speaker: Cummings, Austin Lee (Pennsylvania State University)
• 3:40 PM
Simulation of the propagation of cosmic ray air shower cores in ice 20m

We present the results of simulation studies of the propagation of cosmic ray air shower cores through high-altitude polar ice sheets, using both the COSIKA Monte Carlo code and the Geant4 simulation toolkit. We discuss the general features of the in-ice particle cascade, covering the deposited energy density, the longitudinal development of the shower, and a general parameterization of the radial charge distribution of the cascade front in function of Xmax. We present preliminary calculations of the Askaryan radio emission of the in-ice particle cascades. We find that the core of the air shower dominates the emission during the propagation in the ice, which may mimic an in-ice neutrino-induced particle cascade. Finally, we discuss the feasibility of using RADAR echo techniques to detect the plasma created in the ice by the particle cascade.

Speaker: Mr De Kockere, Simon (VUB-IIHE)
• 4:00 PM
Propagating Air Shower Radio Signals to In-ice Antennas 20m

Radio emissions from cosmic ray showers serve as an essential background signal for in-ice radio detectors in the polar regions. Furthermore, cosmic ray showers can also serve as calibration sources for in-ice radio detectors due to their relatively large flux. Thus, we have adapted CoREAS for simulating their radio signals in in-ice antennas. We present a novel way to upgrade CoREAS such that it takes into account curved ray paths caused by the exponential refractive index profiles of air and ice, which enables propagating signals from air to antennas located inside the ice sheets. Analytic raytracing expressions are used to calculate the relevant parameters for the curved ray paths between the air shower particles and the in-ice antennas. Although analytic raytracing takes around 0.05 to 0.1 ms per call, it is still too slow to do it for all the particles in the air shower. Therefore we have developed an interpolation scheme that calculates ray parameters using pre-tabulated raytraced values and takes around 200 ns per call. In this work, we will show some simulations of air-shower signals as observed by in-ice antennas.

Speaker: Dr Latif, Uzair Abdul (Vrije Universiteit Brussel)
• 4:30 PM 5:05 PM
Coffee and tea 35m
• 5:05 PM 6:45 PM
Ice Data Analysis & Tools 2
• 5:05 PM
A macroscopic model of radar detection for the Radar Echo Telescope 20m

We introduce a new macroscopic model to simulate in-ice radar detection of high-energy particle cascades. Ultra-high-energy cosmic events can reach the polar ice as a cosmic-ray extensive air shower or as a single neutrino. In both cases, the interaction with the ice media produces a high-energy particle cascade, which leaves a short-lived plasma trail composed of ionized ice electrons. Unlike direct radio detection methods, the RET experiment aims to use radar technique to detect the particle cascade via the reflection of radio waves off this plasma.

Starting with well-known parametrizations of the cascade's charge distribution, the model is based on a macroscopic physical optics approach, and therefore employs well-understood ideas such as skin-depth, reflectivity and opacity in a novel description of the radar scatter of particle cascades. We show that this new description is built from first-principles from the single-electron approach used in other Monte-Carlo models. The model includes all the known relevant physics that will affect the radar signal, such as the free charge collisional damping, electron lifetime, and relativistic effects due to the cascade propagation.

Speaker: Huesca Santiago, Enrique (IIHE-VUB)
• 5:25 PM
Deep Learning for the Classification and Recovery of Cosmic-Ray Radio Signals Against Background Measured at the South Pole 20m

A major hurdle in radio detection of cosmic-ray air showers is the continuous background that contaminates the signals. In this work, we use deep learning techniques to mitigate the effect of background by training two convolutional neural networks (CNNs). One network is used to distinguish the radio traces containing air-shower signals from those traces containing only background. The other network is trained to extract the underlying radio signals by removing the noise from the contaminated traces. In order to produce the required dataset for the CNNs training, we used CoREAS for the geomagnetic field and observation height of the South Pole to simulate radio signals. As noise samples, we used generated radio background as well as radio background recorded by SKALA antennas of a prototype station of the IceCube-Gen2 surface array at the South Pole. The frequency band used in the analysis ranges from 100 MHz to 350 MHz. These networks can improve, on the one hand, the detection threshold of externally triggered radio array and, on the other hand, improve the accuracy of the pulse parameters, such as the arrival direction and amplitude of the radio pulses, which are subsequently used to reconstruct the properties of cosmic-ray air showers.

Speaker: Coleman, Alan
• 5:45 PM
Deep-learning based event reconstruction for shallow in-ice UHE neutrino detectors 20m

We present an end-to-end reconstruction of the neutrino energy, direction and flavor from shallow in-ice radio detector data using deep neural networks (DNNs). For the first time, we were able to determine the neutrino direction with a few degrees resolution also for the complicated event class of electron neutrino charged-current interactions where the shower development is impacted by the LPM effect. This result highlights the advantages of DNNs to model the complex correlations in radio detector data. We will present an outlook of extending the model to predict the complex probability distribution of the neutrino direction using Normalizing Flows. Furthermore, we discuss how this work can be used for real-time alerts and an end-to-end detector optimization of, e.g., IceCube-Gen2 radio.

Speaker: Stjärnholm, Sigfrid (Uppsala University)
• 6:05 PM
Radio propagation in non-uniform media 20m

It has been established that, in naturally occurring ice, exotic propagation
modes exist for radio signals. An interesting consequence of this is that it
seems possible for signal to propagate to the receiver from an area which
lies in the expected shadow zone. We present a ray tracing script based
on Fermat’s principle that has been developed with the aim to model
and understand these propagation modes. The results of this script have
been found in agreement with an earlier prediction that over-densities
are able to guide the ray paths. In addition to the in-ice problem of
propagation modes we use this approach to evaluate approximations made
in air-shower radio emission simulations and verify if the approximations
break down for certain geometries.

Speaker: Van den Broeck, Dieder
• 6:25 PM
First-principle calculation of birefringence effects for in-ice radio detection of neutrinos 20m

The detection of high-energy neutrinos in the EeV range requires new detection techniques to cope with the small expected flux. The radio detection method, utilizing Askaryan emission, can be used to detect these neutrinos in polar ice. The propagation of the radio pulses has to be modeled carefully to reconstruct the energy, direction, and flavor of the neutrino from the detected radio flashes. Here, we study the effect of birefringence in ice, which splits up the radio pulse in two orthogonal polarization components with slightly different propagation speeds. This provides useful signatures to determine the neutrino energy and is potentially important to determine the neutrino direction to degree precision. We calculated the effect of birefringence from first principles where the only free parameter is the dielectric tensor as a function of position. Our code can propagate full RF waveforms which for the first times allows to take interference due to changing polarization eigenvectors during propagation into account. The model is available open-source through the NuRadioMC framework. We compare our results to in-situ calibration data from the ARA and ARIANNA experiments and find good agreement for the available time delay measurements, improving the predictions significantly compared to previous studies. Finally the implications and opportunities for neutrino detection are discussed.

Speaker: Heyer, Nils (Uppsala University)
• 6:45 PM 10:00 PM
• Wednesday, June 8
• 9:00 AM 11:30 AM
• 9:00 AM
GRAND: The Giant Radio Array for Neutrino Detection 20m

The Giant Radio Array for Neutrino detection (GRAND) is a proposed next-generation observatory of ultra-high-energy particles of cosmic origin: neutrinos, cosmic rays, and gamma-rays) at energies above 10^17eV. GRAND will consist of a network of ~20 large surface arrays of radio antennas (10000 km² each) deployed at favorable locations around the world, and scheduled to start operations in the early 2030s .

We will present the staged construction approach designed to achieve this ambitious plan. In particular, we will show how GRANDProto300 (GP300), a 300-antenna pathfinder setup to be deployed over 200 km², will validate the detection strategy of GRAND. We will also discuss the present status of the project: in 2022, the first GP300 antennas will deployed in a remote valley of the Gobi desert in China, four antennas will be deployed in the Nançay observatory in France as a testbench for advanced trigger methods and we will explore plans for deployment of a ten-antenna test array at the Auger site.

Speaker: Martineau-Huynh, Olivier
• 9:20 AM
The Beamforming Elevated Array for COsmic Neutrinos (BEACON): A Radio Detector for Earth-Skimming Tau Neutrinos 20m

When ultrahigh energy tau neutrinos skim the Earth, they can generate tau leptons that then decay in the atmosphere, forming upgoing extensive air showers. The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a novel detector concept that utilizes a mountaintop radio interferometer to search for the radio emission due to these extensive air showers. The prototype, located at the White Mountain Research Station in California, consists of 4 custom crossed-dipole antennas operating in the 30-80 MHz range and uses a directional interferometric trigger to achieve reduced thresholds and background rejection. The prototype will first be used to detect extensive air showers from down-going cosmic rays to validate the detector model. In this talk, we give an overview of the BEACON concept and the status of its prototype. We also discuss the ongoing cosmic ray search which utilizes both data analysis and simulation.

Speaker: Zeolla, Andrew
• 9:40 AM
Prospects for radio cosmic-ray measurements with SKA-Low 20m

Following the experience with LOFAR measurements, we explore some of the interesting possibilities that would be offered by the SKA-Low telescope.
The low-frequency part of the Square Kilometre Array, to be built in Australia, features an enormous antenna density of about 50,000 antennas in the inner core region of radius 500 m, with a frequency band from 50 to 350 MHz. This allows to resolve the shower footprints to smaller length scales compared to LOFAR.
From CoREAS simulations, a SKA-Low antenna model plus noise contributions, and adapted LOFAR analysis scripts, we obtain a resolution in the shower maximum Xmax and energy that is considerably better than at LOFAR.
Furthermore, we explore the possibilities of measuring the longitudinal profile of the air shower beyond $X_{\rm max}$, for individual air showers. This would improve mass composition analysis by measuring an additional composition-dependent quantity. Moreover, it would offer an opportunity to discriminate between the different predictions of hadronic interaction models, hence contributing to hadronic physics at energy levels beyond man-made accelerators.

Speaker: Corstanje, Arthur
• 10:00 AM
Cosmic-rays with LOFAR: Overview and Upgrades 20m

The LOFAR radio telescope measures the radio emission from extensive air showers generated by cosmic rays in the energy range of $10^{16}$ to $10^{18}$ eV. Measurements of the emission in the 30-80 MHz range allows for the reconstruction of the cosmic ray energy, arrival direction, and most importantly the shower maximum, Xmax, with an average precision below 20 g/cm$^2$. The detector consists of a densely instrumented antenna array and a triggering scintillator array which has been recently extended to double its previous size. In this contribution, we present the overview of the detector, on-going analyses, and plans for improved cosmic ray detection with the upcoming LOFAR 2.0 upgrade.

Speaker: Pandya, Hershal (Vrije Universiteit Brussel)
• 10:20 AM
Status and prospects of the Auger Radio Detector 20m

To find and understand the sources of ultra-high-energy cosmic rays necessitates measuring the properties of these particles with high precision. The objective of the upgrade of the Pierre Auger Observatory is to increase, in particular, the mass sensitivity of the observatory, aiming at an event-by-event identification of the particle type with unprecedented precision. Part of this upgrade is the Radio Detector (RD): radio antennas sensitive in the frequency band from 30 to 80 MHz will be added to each Surface Detector station of the observatory, thus, forming a 3000 km2 radio detector with 1660 detector stations. Each station is equipped with two loop antennas, one oriented parallel to the Earth’s magnetic field and the other perpendicular to it. An engineering array with ten stations was installed in November 2019. Results from the engineering array will be presented. Mass production of the components for the full array is ongoing. We will present an overview of the systems’ layout and the activities’ status together with an outlook on the installation and commissioning process for the world’s largest radio array for cosmic rays.

Speaker: Rautenberg, Julian (Bergische Universität Wuppertal)
• 10:40 AM
Expected performance of the AugerPrime Radio Detector 20m

The AugerPrime Radio Detector (RD) will increase the sky coverage and overall aperture for mass-sensitive measurements of ultra-high energy cosmic rays with the Pierre Auger Observatory. The installation of over 1600 dual-polarized short aperiodic loaded loop antennas on an area of about 3000$\,$km$^2$ will enable the detection of the electromagnetic radiation in the 30-80 MHz band from highly inclined air showers in coincidence with the Auger water-Cherenkov detector (WCD). The combination of complementary information from the RD regarding the electromagnetic shower component and the WCD regarding the muonic shower component yields a strong sensitivity to the mass composition of cosmic rays.

We will present the expected performance of the RD to detect and reconstruct inclined air showers. This study features comprehensive sets of Monte-Carlo generated air showers, utilizes a complete description of the instrumental response of the radio antennas, and in-situ recorded background. The estimation of an energy- and direction-dependent aperture yields an expectation of about 3900 events with energies above $10^{19}\,$eV being detected during 10 years of operation. From a full event reconstruction, we quantify the achievable energy resolution to be better than 10% at and beyond $10^{19}\,$eV. With this at hand, the potential to measure the number of muons and discriminate between different cosmic-ray primaries in combination with the WCD using inclined air showers is presented. The discrimination between proton- and iron-induced air showers is described with a figure-of-merit of 1.6.

Speaker: Schlüter, Felix (Karlsruhe Institute of Technology - Institute for Astroparticlephysics)
• 11:00 AM
Towards a Standard Definition of the Signal-to-Noise Ratio for Radio Signals of ultra-high-energy Particles 20m

Identifying and measuring radio signals of ultra-high-energy particles is a common challenge in all kind of astroparticle radio detectors, be it air-shower detection, the search for neutrino signals in the ice, or radio observatories looking for particle-induced radio pulses from the moon. Although the challenge is common, the community uses a large variety of definitions of the signal-to-noise ratio. These are either defined as amplitude ratios, which for coherent radio emission is roughly proportional to the energy of the primary particle, or as power ratios, scaling quadratically with the primary energy. Power ratios expressed in dB are common in engineering, however, signals in radio communication are usually much longer than a few wavelengths, not comparable to the short pulses induced by ultra-high-energy particles. Another complication is that different experiments measure signal in different ways, and often noise is measured in another way than the signal is. This typically leads to values larger than one when determining the signal-to-noise ratio of pure noise, instead of the naive expectation of one (or zero in cases when the noise is subtracted from the signal). However, that scaling factor of the signal-to-noise ratio of pure noise differs drastically between experiments. This makes signal-to-noise ratios incomparable between experiments and has led to misunderstandings between people from different collaborations. The purpose of this talk is to stimulate a discussion to fix this situation. Ideally, the community can agree on a common method to calculate signal-to-noise ratios, even though this implies that most if not all collaborations need to break with their traditions for the benefit of having a smoother communication and mobility between experiments.

Speaker: Schröder, Frank G. (Bartol Research Institute, Departement of Physics and Astronomy, University of Delaware; and Institute for Astroparticle Physics, Karlsruhe Institute of Technology)
• 11:30 AM 12:00 PM
Coffee and tea 30m
• 12:00 PM 1:30 PM
• 12:00 PM
A continuously-operating standalone radio cosmic ray detection system at the OVRO-LWA 20m

The new cosmic ray detection system at the Owens Valley Radio Observatory Long Wavelength array expands on methods introduced in a previous demonstration to use radio signals alone to trigger data capture, reject radio frequency interference, and reconstruct the air shower properties: energy, arrival direction, and Xmax. The Owens Valley Radio Observatory- Long Wavelength Array (OVRO-LWA) in Eastern California is currently completing an expansion to 352 dual-polarization antennas and new signal processing infrastructure. The upgraded array will operate a full-duty-cycle cosmic ray detector simultaneously with a variety of radio astronomy observations. In order to detect cosmic rays in the presence of radio frequency interference, initial event classification and RFI rejection is performed on Field Programmable Gate Array boards which each process a sampled voltage timeseries from both polarizations of a subarray of thirty-two antennas. Each board uses dedicated RFI veto antennas outside the air shower radio footprint to reject RFI events. I will present the trigger design, RFI flagging strategy, and a progress update from early commissioning. When fully commissioned, the OVRO-LWA will offer a new estimate of cosmic ray composition at the upper energy limit of Galactic accelerators by observing thousands of cosmic rays per year at energies 10^17–10^18 eV and reconstructing air showers with a typical Xmax precision better than 20g/cm^2 per air shower.

Speaker: Plant, Kathryn
• 12:20 PM
Radio measurements of air-showers with an IceCube Surface Array station 20m

The surface array of the IceCube Neutrino Observatory currently consists of 162 ice Cherenkov tanks and is used both as a veto for the in-ice neutrino observations and as a capable cosmic-ray detector. In order to further enhance the science case of the IceCube surface array, the existing detectors will be complemented by an array of scintillation panels and radio antennas. The scintillation detectors will lower the energy threshold and, especially for inclined showers at higher energies, the radio antennas will significantly improve the energy and Xmax reconstruction performance. The radio-quiet environment at the South Pole allows us to measure air-shower radio emission in the novel higher frequency band between 70-350 MHz which gives us a better signal-to-noise ratio and a lower shower detection threshold compared to traditional sparse cosmic-ray radio arrays. A prototype station consisting of 8 scintillation panels and 3 radio antennas has been deployed at the South Pole in January 2020 and has been collecting data since then. Detection and successful reconstruction of air showers using this single station has proven the viability of the hardware and informs further optimizations of the detector design and shower analysis techniques that will be applied to the full array when deployed in a few years. It has also been confirmed that we can indeed measure the radio emission from air showers with energies of a few 10s PeV. This talk will explain how the triggering, data acquisition and event selection of the IceCube Surface Array Enhancement works and show the radio air shower events detected so far.

Speaker: Dujmovic, Hrvoje
• 12:40 PM
Cross-calibrating the energy scales of cosmic-ray experiments using a portable radio array 20m

We can understand cosmic-ray sources by measuring the energy of these particles and building models that describe the energy spectrum. However, at the highest end of the spectrum, energy scales between experiments are inconsistent. Comparing energy scales of different experiments has proven to be difficult, given that uncertainties on energy measurements depend on the location, technique, and equipment used.  In this contribution we discuss a radio-based technique which will be used to build a universal cosmic-ray energy scale.  A portable array of broadband antennas will be used to measure the radiation energy in air showers, which scales quadratically with the electromagnetic energy, yielding a complete, calorimetric energy reconstruction. Once the local magnetic field strength is accounted for, radiation energy can be directly compared at different locations.The array will be deployed at different experiments, measuring radiation energy contemporaneously with the experiments’ existing methods. The energy measured by each experiment can then be directly compared using the universal radiation energy measurements as a standard candle.  Using radiation energy to compare the energy scales eliminates uncertainties due to different measurement techniques and locations, and using the same detection system at each experiment eliminates the uncertainties associated with the equipment and calibration. The result will be a cross-calibration of the energy scales of different experiments with minimal uncertainty. Here we present the technique, prospects for event reconstruction, and plans for implementation.

• 1:00 PM
Study of the Uncertainties of the Galactic Radio Background as a Calibration Source for Radio Arrays 20m

The indirect detection of cosmic rays via the radio signal of extensive air showers is gaining a lot of ground. Many new arrays of radio antennas are under construction or in the phase of development. Calibrating these arrays is important for the reconstruction of observed events and for the comparability between observatories. Using reference antennas in calibration campaigns is not ideal because of large uncertainties on their signal output strength. In a different approach the arrays can be calibrated against the Galactic radio emission as the dominant source of background.
This so-called Galactic Calibration relies on predictions of the diffuse Galactic radio emission, for which models are publicly available. We present a comparison of these models in the frequency range from 10 to 408 MHz in order to estimate the systematic uncertainties on the predictions of the Galactic background. We do this comparison on a global level as well as adapted for selected radio arrays and discuss implications for applying the Galactic calibration method. Furthermore we study the influence of the quiet sun as an additional source of radio emission in the sky.

Speaker: Büsken, Max
• 1:30 PM 3:00 PM
Lunch 1h 30m
• 3:00 PM 4:40 PM
Air Data Analysis & Tools 1
• 3:00 PM
Radio interferometry applied to the observation of air showers 20m

We developed a Radio Interferometric Technique for the observation of extensive air showers initiated by cosmic particles. This technique leads to a four dimensional representation of the extensive air shower. From this representation shower parameters are reconstructed in a straightforward manner. In this contribution, we show the application on radio simulations of air showers and study the influence of time synchronisation errors. Also, we will provide an outlook on how this method can be incorporated in operational and future cosmic particle observatories.

Speaker: schoorlemmer, harm
• 3:20 PM
Expected performance of interferometric air-shower measurements with sparse radio-antenna arrays 20m

Inclined air showers open the window for the radio detection of ultra-high-energy cosmic rays with km-sparse radio-antenna arrays. The potential of those measurements would improve greatly with an accurate reconstruction of the depth of the shower maximum $X_\mathrm{max}$. However, traditional methods using the lateral signal amplitude distribution at the ground to reconstruct $X_\mathrm{max}$ with radio antennas developed for vertical air showers lose their sensitivity. A recently proposed interferometric technique promises measurements of the depth of the shower maximum $X_\mathrm{max}$ with an intrinsic accuracy of 3$\,$g$\,$cm$^{-2}$ for very inclined air showers, however, without considering instrumental uncertainties.

In this contribution, we evaluate the potential of interferometric $X_\mathrm{max}$ measurements of (simulated) inclined air showers with realistically dimensioned, sparse antenna arrays and account for imperfect time synchronisation between individual antennas. We find a strong correlation between the antenna multiplicity (per event) and the maximum acceptable inaccuracy in the time synchronisation of individual antennas. We formulate prerequisites for the design of antenna arrays for the application of interferometric measurements: For data recorded with a time synchronisation accurate to 1$\,$ns within the commonly used frequency band of 30$\,$MHz to 80$\,$MHz, an antenna multiplicity of $>\sim 50$ is needed to achieve an $X_\mathrm{max}$ reconstruction with an accuracy of 20$\,$g$\,$cm$^{-2}$. This multiplicity is achieved measuring inclined air showers with zenith angles $\theta \geq 77.5^\circ$ with 1$\,$km spaced antenna arrays, while vertical air showers with zenith angles $\theta \leq 40^\circ$ require an antenna spacing below 100$\,$m. Furthermore, we find no improvement in the $X_\mathrm{max}$ resolution applying the interferometric reconstruction to simulated radio signals at higher frequencies, i.e., up to several hundred MHz.

Speaker: Schlüter, Felix (Karlsruhe Institute of Technology - Institute for Astroparticlephysics)
• 3:40 PM
New features in the radio-emission of very inclined showers 20m

To probe the sources of ultra-high energy cosmic-rays, next generation of radio experiments such as GRAND and AugerPrime Radio are now focusing on the detection of showers arriving with very inclined trajectories. These inclined showers have a large footprint that allows us to cover large surfaces at low costs, but their radio emission exhibits numerous features that differentiate them from vertical ones. Yet, further studies are needed to fully characterize their complex radio emission. Using Monte-Carlo simulations we evidence here 2 major novel features of these inclined showers: a significant drop of more than one order of magnitude in the geomagnetic emission amplitude and a new polarization pattern. The latter possibly indicates a synchrotron emission taking over the Askaryan at large zenith angles. These two effects are challenging to describe with existing models of the radio emission but could strongly affect the detection and reconstruction strategies of next generation experiments. In this talk I will present our main results toward the understanding of these new features.

Speaker: Chiche, Simon (Institut d'Astrophysique de Paris)
• 4:00 PM
Signal model and event reconstruction for the radio detection of inclined air showers using sparse antenna arrays 20m

We present a signal- and reconstruction model for the radio emission of extensive air showers with zenith angles between 65$^\circ$ and 85$^\circ$ in the 30-80 MHz band. The model is derived from CoREAS simulations and explicitly takes into account the asymmetries introduced by the superposition of charge-excess and geomagnetic radiation as well as by early-late effects. We exploit correlations among fit parameters to reduce the dimensionality, thereby ensuring stability of the fit procedure. Our approach reaches a reconstruction efficiency near 100% with an intrinsic resolution for the reconstruction of the electromagnetic energy of well below 5% using a 1.5$\,$km-sparse antenna array. It can be employed in upcoming large-scale radio detection arrays using the 30-80 MHz band, in particular the AugerPrime Radio detector of the Pierre Auger Observatory, and can likely be adapted to experiments such as GRAND operating at higher frequencies.

Speaker: Schlüter, Felix (Karlsruhe Institute of Technology - Institute for Astroparticlephysics)
• 4:20 PM
Parameterization of the frequency spectrum in the 30-80 MHz of radio emission from inclined air showers 20m

The frequency spectrum of the short transient radio pulses from air showers contains valuable information. Its shape depends on several factors, most importantly on the lateral distance of the observer from the shower axis, the arrival direction, i.e. the zenith angle, and on the distance between core position and shower maximum $X_{\mathrm{max}}$. To exploit this wealth of information, we investigated the spectral content of CoREAS simulations for showers covering energies from $10^{18.4}$ eV up to $10^{20.2}$ eV and zenith angles from $65.0\,^\circ$ up to $85\,^\circ$. We derived a full parameterization of the spectral shape in the 30-80 MHz frequency band, exploited by several experiments, including the radio antennas of the Pierre Auger Observatory. For both geomagnetic and charge-excess components of the signals, the parameterization is expressed as a function of the distance to the shower axis and the geometrical distance between core and $X_{\mathrm{max}}$. These pieces of information can be employed in event reconstruction to constrain the geometry, i.e. the core position.

Speaker: Martinelli, Sara
• 4:40 PM 5:10 PM
Coffee and tea 30m
• 5:10 PM 7:10 PM
Air Data Analysis & Tools 2
• 5:10 PM
Absolute calibration and investigation of ageing of the AERA radio detectors 20m

The Auger Engineering Radio Array (AERA) is currently the largest facility to measure radio emissions from extensive air showers. Located at the Pierre Auger Observatory in Argentina, it comprises 150 autonomous radio-detector stations, covering an area of 17 km$^2$, and measures radio waves in the frequency range from 30 to 80 MHz. For the correct interpretation of data collected by AERA stations, the detector response has to be carefully calibrated. For this, we use the radio emission from the Galaxy. A model of the full radio sky is propagated through the system response, including the antenna, filters and amplifiers, and compared to the average spectra recorded by the stations. The method to determine the calibration constants, as the results, for each antenna will be presented. The behavior of the calibration constants is studied as a function of time from 2014 to 2020. We do not see any ageing effect over a timescale of 10 years, showing that radio detectors could help to monitor possible ageing effects of other detector systems during long-term operations, stressing their importance in determining an absolute energy scale.

Speaker: Prof. Almeida, Rogerio Menezes de (Universidade Federal Fluminense)
• 5:30 PM
Unfolding the Electromagnetic Field from Voltage Time Traces using a Neural Network Approach 20m

The Auger Engineering Radio Array (AERA), part of the Pierre Auger Observatory, probes cosmic ray induced air showers via radio measurements. Recovering the three-dimensional electromagnetic field around an antenna from the measured voltage time traces is a challenging task, because the measurement process introduces noise and applies a complex frequency and direction-dependent response. We use conditional Invertible Neural Networks (cINNs) to learn posterior distributions, from which the most likely electromagnetic field given a measured voltage time trace can be inferred. We extend the method with an
autoencoder to further enhance robustness, reduce the parameter space, and decouple the cINN from data shape. We will present an overview of the method and its application to mock data in the context of AERA and evaluate the method’s reconstruction quality.

Speaker: Straub, Maximilian
• 5:50 PM
Simulations of the antenna response for the Auger Radio Detector 20m

After more than 15 years of successful operation, the Pierre Auger Observatory is currently undergoing a major upgrade called AugerPrime. The aim is to study the mass composition of ultra-high energy cosmic rays. Part of this upgrade consists in installing a Short Aperiodic Loaded Loop Antenna (SALLA) atop each of the 1660 water-Cherenkov detectors.
To obtain an absolute calibration for the SALLA, the frequency and directionally dependent antenna response (or vector effective length) must be known. The characteristics of the SALLA depend on various parameters. Most prominent is the considered frequency of reception and the antenna geometry. Moreover, the interaction with the structure elements and the presence of the ground has an impact. The measurement of the characteristics of the SALLA is an immense experimental effort. In this view, investigation by numerical antenna simulations provides an important and useful tool. In this contribution, we describe the method used to calculate the vector equivalent length of the SALLA using an advanced and widely used software for antenna simulations like the Numerical Electromagnetics Code (NEC).

Speaker: Giaccari, Ugo Gregorio (IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands)
• 6:10 PM

A major upgrade of the Pierre Auger Observatory, AugerPrime, whose main purpose is to improve mass sensitivity studies, will soon be completed. The role of the AugerPrime Radio Detector is to extend the mass-sensitive measurements to high zenith angles in the range of 65 to 85 degrees. Discrimination power between two different primaries also depends on the uncertainty. The main cause of this uncertainty, propagated from the Radio Detector, is the mismatch between the antenna model and actual construction. To determine this uncertainty, we reconstruct the CORSIKA/CoREAS Monte Carlo air shower simulations using the antenna model geometry modified in various ways. In addition, we also study the influence of different ground conditions. This work aims to determine a realistic uncertainty of the reconstructed electromagnetic energy propagating from the Radio Detector.

Speaker: Fodran, Tomáš
• 6:30 PM
Model of the Lateral Distribution of the Radio Emission from Air Showers in the 70 - 350 MHz Frequency Band 20m

The radio emission from air showers is beamed forward during shower development and produces a characteristic footprint on the ground. This emission imprints the content of electromagnetic particles in the cascade and, via measurements with radio antennas, can be used to study cosmic ray and particle physics. Compared to that of particle detectors, the radio footprint is more complex, generally including a Cherenkov ring as well as azimuthal asymmetries in the shower plane due to interference. Understanding the structure of this emission is important for an accurate description of the electromagnetic content in air showers and has been used directly in likelihood-based reconstructions. In this work, we describe an analytical model for the distribution of signal in the frequency band from 70 to 350 MHz based on CoREAS simulations for the South Pole location. We model both the geomagnetic and charge excess emissions in this band and characterize the evolution of the respective patterns for showers which reach maximum both above and below ground.

Speaker: Coleman, Alan
• 6:50 PM
A neural network to classify GRAND radio time traces 20m

GRAND is a UHE cosmic particles detection project, consisting in a giant, self-triggered, antenna array. Wherever we decide to setup the antennas, we will generally face a high rate of anthropic signals, orders of magnitude higher than the rate of extensive air showers. To avoid the saturation of the acquisition, we need to reject a significant part of the data at the antenna level, with a more sophisticated method than just a peak over baseline selection. We present here an attempt to discriminate air showers and anthropic radio time traces with a convolutional neural network, using experimental data rather than simulations. These data come from TREND, a self triggered 50 antennas-array, which was the seed project for GRAND.

Speaker: LE COZ, Sandra
• Thursday, June 9
• 9:00 AM 11:30 AM
Air Data Analysis & Tools 3
• 9:00 AM
The Depth of the Shower Maximum of Air Showers Measured with AERA 20m

The Auger Engineering Radio Array (AERA) is an array of $153$ radio antennas spanning an area of $17$ km$^2$, currently the largest of its kind, that probes the nature of ultra-high energy cosmic rays at energies around the transition from Galactic to extra-galactic origin. It measures the MHz radio emission of extensive air showers produced by cosmic rays hitting our atmosphere. The elemental composition of cosmic rays is a crucial piece of information in determining what the sources of cosmic rays are and how cosmic rays are accelerated. This composition can be obtained from the mass-sensitive parameter $X_\mathrm{max}$, the depth of the shower maximum. We reconstruct $X_\mathrm{max}$ with a likelihood analysis by comparing the measured radio footprint on the ground to an ensemble of footprints from Monte-Carlo CORSIKA/CoREAS air shower simulations. We compare our $X_\mathrm{max}$ reconstruction with fluorescence $X_\mathrm{max}$ measurements on a per-event basis, a setup unique to the Pierre Auger Observatory, and show the methods to be compatible. Furthermore, we extensively validate our reconstruction by identifying and correcting for systematic uncertainties. We determine the resolution of our method as a function of energy and reach a precision up to $11.3\pm4.5$ gcm$^{-2}$ at the highest energies. With a bias-free set of around $600$ showers, we find a light to light-mixed composition at energies between $10^{17.5}$ to $10^{18.8}$ eV, also in agreement with Auger fluorescence measurements.

Speaker: Dr Pont, Bjarni (Radboud University)
• 9:20 AM
Mass composition of cosmic rays from Xmax reconstruction with LOFAR 20m

We present the results of a new cosmic ray composition analysis above $10^{16.8}$ eV, based on measurements of the depth of air shower maximum $X_{\rm max}$ using the LOFAR radio telescope.
The reconstruction is done by simulating the radio signal for an ensemble of showers using Corsika and CoREAS.
The radio footprints on the ground are fitted to the measured radio data, yielding an $X_{\rm max}$ estimate to a precision of about 20 g/$\mathrm{cm^2}$.
Improvements on previous results include accounting for variations in the atmosphere by producing simulations with event-specific profiles for the pressure, humidity, and refractive index. Moreover, the energy estimate and the fitting procedure are now done exclusively on the radio signals, based on an improved antenna calibration using the Galactic background signal.
The combination of these and other improvements lead to a considerable reduction in systematic uncertainties on $X_{\rm max}$ and the shower energy.

Speaker: Corstanje, Arthur (Vrije Universiteit Brussel (VUB))
• 9:40 AM
A new method to determine Xmax based on the reconstruction of longitudinal profile of air showers using radio signals 20m

Precise measurement of the composition of cosmic rays in the energy range of $10^{16}$ to $10^{18}$ eV may settle the long standing issue of the galactic or extra galactic origin of these particles in the energy region. Ground-based experiments mostly rely on the determination of the depth of air shower maximum ($\rm X_{max}$) to measure the type of cosmic-ray particle. One efficient technique is to record images of the air-shower development using fluorescence telescopes. An alternative technique that has made significant advances in recent years is to measure the radio emission from air showers. Methods for $\rm X_{max}$ determination in radio detection technique include fitting a two dimensional radio intensity profile observed at the ground with Monte Carlo showers which is computationally quite expensive, and others that are based on parameterization obtained from simulation.

In this contribution, we propose a new method to determine $\rm X_{max}$ purely from the observed data with minimal input from simulation. The method involves geometrical reconstruction of the longitudinal profile of air shower by backtracking radio signals observed at the ground to their emission points. The method will allow an event-by-event reconstruction of $\rm X_{max}$ without uncertainty and bias inherited from simulation unlike other existing methods. Details of the method and some preliminary results based on simulated data will be presented.

Speaker: Ms Jhansi, V.B. (Khalifa university)
• 10:00 AM
Constraining the cosmic-ray mass composition by measuring the shower length with SKA 20m

The current generation of air shower radio arrays has demonstrated that the atmospheric depth of the shower maximum Xmax can be reconstructed with high accuracy. These experiments are now contributing to mass composition studies in the energy range where a transition from galactic to extragalactic cosmic-ray sources is expected. However, we are still far away from an unambiguous interpretation of the data. Here we propose to use radio measurements to derive a new type of constraint on the mass composition.

The radio footprint contains information about the exact shape of the longitudinal development of the shower. A practical description of this development is in terms of the L and R parameters that describe the width and asymmetry of the longitudinal shape. We have performed various studies that show that L and R have a significant impact on the radiation pattern and that this can be observed with high-density radio arrays. In fact, in some LOFAR events the impact of L is already observed.

The low-frequency part of the Square Kilometer Array will have an extremely high antenna density of roughly 60.000 antennas within one square kilometer, and is the perfect site for high-resolution studies of air showers. In this contribution, we discuss the impact of being able to reconstruct R and L, and the unique contribution that SKA can make to cosmic-ray science.

Speaker: Buitink, Stijn (Vrije Universiteit Brussel (VUB))
• 10:20 AM
Potential of the Askaryan Fraction of the Radio Emission from Cosmic-Ray Air Shower for Xmax Reconstruction 20m

There is an ongoing effort to improve the sensitivity of the IceTop surface array at the South Pole by the addition of surface radio antennas. With a simulation study, we investigated the dependencies of the Akaryan relative to the geomagnetic emission in the band of 70-350 MHz at the South Pole. We used CoREAS to simulate the radio emission from cosmic-ray air showers at that location using a star-shape pattern and used the polarization of the radio emission on the ground to calculate the relative Askaryan fraction at the Cherenkov ring of the radio footprint. We then investigated the dependence of the Askaryan fraction with several shower parameters, among them, the distance to shower maximum ($d_{X_{\rm max}}$). Based on the finding, we have developed a model that uses the average fraction as well as the shower geometry to reconstruct the mass-sensitive depth of shower maximum ($X_{\rm max}$) for the given atmosphere. The theoretically achievable precision can compete with other methods for $X_{\rm max}$ measurement by radio arrays. Therefore, the Askaryan fraction - or more generally - the polarization of the radio signal may serve as an additional input for future multivariate approaches of $X_{\rm max}$ reconstruction.

Speaker: Paudel, Ek Narayan
• 10:40 AM
Energy and Xmax Reconstruction for Cosmic-Ray Events Recorded by a Prototype Station of the IceCube Surface Enhancement 20m

The IceTop array, located at the surface of the IceCube Neutrino Observatory, is currently used as a veto for the in-ice neutrino detection as well as a cosmic-ray detector. Over the years, snow accumulated on the IceTop detector reducing its sensitivity and resolution. In order to mitigate this issue as well as further increase the accuracy of cosmic-ray measurements, an enhancement is planned in the next few years. It consists of an array of scintillation detectors and radio antennas that will be deployed within the whole IceTop footprint. Upgrading IceTop with radio antennas will provide precise X$_{max}$ measurements, a variable widely used to reconstruct the cosmic-ray mass composition.

In January 2020, a prototype station comprising three antennas and eight scintillation panels was deployed at the South Pole. We developed the tools necessary to use a template-matching method for energy and X$_{max}$ reconstruction and applied it to some of the radio events recorded. This template method uses Monte Carlo simulations and compares them to recorded data. For this, a set of simulated air showers was created using the values reconstructed by IceTop as input to the CORSIKA/CoREAS simulation software. In this talk, we will present the method and discuss the preliminary results obtained with this technique.

Speaker: Turcotte-Tardif, Roxanne
• 11:00 AM
Measuring the muon content of inclined air showers using AERA and the particle detector of the Pierre Auger Observatory 20m

A first measurement of the muon content of an air shower using hybrid radio and particle detection is presented. For inclined air showers with zenith angles above 60°, the water-Cherenkov detector (WCD) of the Pierre Auger Observatory performs an almost pure measurement of the muonic component, whereas the Auger Engineering Radio Array (AERA) allows reconstructing the electromagnetic energy independently using the radio emission of the air shower. The analysis of more than six years of AERA data shows a deficit of muons predicted by all current-generation hadronic interaction models for energies between 4 EeV and 20 EeV. This deficit, already observed with the Auger Fluorescence Detector, is now confirmed for the first time with radio data. The analysis is limited by low statistics due to the small area of AERA and the high energy threshold originating from the WCD reconstruction. With the AugerPrime Radio Detector currently being deployed, this analysis can be extended to the highest energies to allow for in-depth tests of hadronic interaction models with large statistics.

Speaker: Mr Gottowik, Marvin (Bergische Universität Wuppertal)
• 11:30 AM 12:00 PM
Coffee and tea 30m
• 12:00 PM 1:40 PM
Air Shower Simulations 1
• 12:00 PM
Simulating radio emission from air showers with CORSIKA 8 20m

CORSIKA 8 (C8) is a new framework for air shower simulations implemented
in modern C++17, based on past experience with existing codes like
CORSIKA 7. It is a project structured in a modular and flexible way that allows
the inclusion and development of independent modules that can produce a
fully customizable air shower simulation. The calculation of radio emission
from the simulated particle showers is incorporated as an integral module of
C8, including signal propagation and electric field calculation at each antenna
location using the “Endpoint” and ZHS formalisms simultaneously. Due to C8’s
flexibility, the radio functionality can be used both to validate other physics
modules and to investigate specific physical scenarios. In this work, we are
going to present air shower simulations generated with C8 and compare their
predicted radio emission with corresponding air showers simulated with
CORSIKA 7 and ZHAireS. The incorporation of both calculation formalisms in
the same code also allows detailed comparisons for the same underlying
shower, which we will discuss as well.

Speaker: Karastathis, Nikolaos
• 12:20 PM
Practical and Accurate Calculations of Radio Emission from Extensive Air Showers 20m

We present a novel semi-analytical treatment of the radio emission of air showers that is able to reproduce the results of full ZHAireS simulations, in theory at a fraction of the computational cost. Traditionally, the contribution to the vector potential of every single particle track in the shower is calculated separately. Instead, in our approach we divide the air shower into 4-D spacetime volumes, so that the contribution of the whole bin needs to be calculated only once, based on the average particle track inside it. This almost amounts to a macroscopic treatment of the shower, but retaining the precision of the successful microscopic approach.
The size of the 4-D spacetime volumes is chosen so that the traditional vector potential expression can be further simplified, as many of its terms can be taken to be the same for the whole bin. Computationally expensive terms, such as the the effective refractive index from the track to the observer, can then be calculated only once, making it possible to obtain the precise radio emission at a fraction of the cost.
This approach also allows us to perform more precise calculations that would otherwise be too expensive to apply on a track-by-track basis. These could include a more detailed treatment of atmospheric effects for near horizontal showers and high altitude detectors, such as balloons and satellites.

Speaker: Carvalho Jr., Washington
• 12:40 PM
Template synthesis approach for radio emission from extensive air showers 20m

The study of high-energy cosmic-ray air showers relies on Monte-Carlo techniques to simulate the particles and corresponding radio emission. These microscopic simulations require a lot of computing time, which not only limits our analyses but also negatively impacts the environment. Other techniques exist, using macroscopic quantities instead, but these currently lack the required precision.

We therefore present a novel way to synthesise the radio emission from air showers. It is a hybrid approach which uses a single microscopic simulation to generate the radio emission from a shower with a different longitudinal evolution, primary particle type and energy. The method employs semi-analytical relations which only depend on the shower parameters to transform to radio signal in the simulated antennas.

The central idea of the template synthesis, is to slice up the atmosphere and consider the radio emission from each slice separately. In this way we only need to account for shower age effects when synthesising the required signal, as geometric effects are already taken care of. The former are handled by rescaling the frequency spectra in each slice, according to aforementioned semi-analytical relations.

As a first step we tested this approach for vertical air showers, using CORSIKA together with the CoREAS plugin for the radio emission. We generated a library of 600 showers, with primary energies ranging from $10^{17} \; \text{eV}$ to $10^{19} \; \text{eV}$. From this library we extracted the necessary parameters for the semi-analytical expressions, after which we used randomly selected showers to gauge the reconstruction quality of the template synthesis. We achieve a reconstruction quality of $5 - 10 \; \%$.

Speaker: Desmet, Mitja
• 1:00 PM
Air-Shower Radio Simulations - where we stand and where we go 20m

Simulations of the radio emission from extensive air showers have been key in establishing radio detection as a mature and competitive technique. In particular, microscopic Monte Carlo simulations have proven to very accurately describe the emission physics and are at the heart of practically all analysis approaches. Yet with new applications - for example very inclined air showers, cross-media showers, extreme antenna densities, and higher-frequency measurements - come new challenges for accurate and efficient simulations. I will review the state of the art of the existing simulation approaches and discuss where further improvements might be needed and how they can be achieved.

Speaker: Huege, Tim
• 1:30 PM 3:00 PM
Lunch 1h 30m
• 3:00 PM 8:00 PM
Social events: Excursion
• 9:30 PM 11:30 PM
Social events: Social dinner
• Friday, June 10
• 9:00 AM 10:20 AM
Future experiments: Ice & Air
• 9:00 AM
Towards IceCube-Gen2: Plans for the in-ice radio array 20m

Building on the success of IceCube at the South Pole, the next generation experiment IceCube-Gen2 is taking shape. Next to an extension of the optical array, further developing the optical detector learning for the IceCube-Upgrade currently in preparation, IceCube-Gen2 is planned to feature a large in-ice radio array targeting neutrinos beyond PeV energies. This radio array will build on heritage from many former and existing radio neutrino experiments. It will dominate the sensitivity of IceCube-Gen2 at EeV energies, improving at least an order of magnitude in sensitivity over existing arrays. IceCube-Gen2 will also feature a much enlarged surface array, including in-air radio antennas targeting air showers.
This contribution will highlight the current status of IceCube-Gen2 with a focus on the in-ice radio array.

Speaker: Nelles, Anna (DESY Zeuthen)
• 9:20 AM
Design and Expected Performance of the IceCube-Gen2 Surface Array and its Radio Component 20m

IceCube-Gen2, the next generation of the IceCube Neutrino Observatory at the South Pole, will consist of three co-located arrays: a deep optical array and a more shallow and larger radio array for neutrino detection in the ice, and a surface array above the footprint of the optical array. The surface array will be comprised of hybrid stations featuring elevated radio antennas and scintillation detectors, following the design of a prototype station successfully operating at the South Pole since 2020. Besides providing a veto for neutrino detection, the surface array will make IceCube-Gen2 a unique laboratory for cosmic-ray air showers. Compared to the current IceCube detector with its IceTop surface array, the aperture for coincident air-shower measurements detected by both, the deep optical and surface arrays, will increase by about a factor of 30. In addition to particle physics questions, such as the production of PeV muons and neutrinos in prompt decays, these surface-deep coincidences will be used to target astrophysical questions of the most energetic Galactic cosmic rays. The combination of particle and radio measurements at the surface and high-energy muons measured in the ice promises unprecedented accuracy for the mass composition in the energy range of the presumed Galactic-to-extragalactic transition – complementing the multimessenger science case of IceCube-Gen2.

Speaker: Schröder, Frank G. (Bartol Research Institute, Department of Physics and Astronomy, University of Delaware; and Institute for Astroparticle Physics, Karlsruhe Institute of Technology)
• 9:40 AM
The Global Cosmic Ray Observatory - GCOS 20m

The Global Cosmic Ray Observatory (GCOS) is an initiative for a new large-scale observatory to measure the properties of ultra-high-energy cosmic rays after 2030. In 2021 more than 200 scientists from around the world came together to discuss possible science cases and detector layouts. We aim to answer several questions: In ten years from now what do we expect to unveil on the origin of cosmic rays, on their nature, energy and arrival directions? If a next generation ground based experiment is built, which are the main characteristics to improve upon the results expected from the Pierre Auger Observatory and the Telescope Array? Based on these expectations and the science case(s), which is the energy range to be addressed by this new Observatory? We will present possible configurations and prototype studies from fluorescence detectors and ground arrays as well as the science results that might be achievable with GCOS in different detector configuration scenarios. Among the layouts discussed is a large ground array (order of 40\,000 km$^2$) with segmented water Cherenkov detectors and radio detectors with the aim to measure arrival direction, energy and particle type with high resolution.

Speaker: Hörandel, Jörg
• 10:00 AM
Radiation of ionization electrons: the key-role of their 2-pt function of velocities 20m

Several attempts to detect extensive air showers (EAS) induced by ultrahigh-energy cosmic rays have been conducted in the last decade based on the molecular Bremsstrahlung radiation (MBR) at GHz frequencies from quasi-elastic collisions of ionisation electrons left in the atmosphere after the passage of the cascade of particles. These attempts have led to the detection of a handful of signals only, all of them forward-directed along the shower axis and hence suggestive of originating from geomagnetic and Askaryan emissions extending into GHz frequencies close to the Cherenkov angle. In this contribution, the lack of detection of events is explained by the coherent suppression of the MBR in frequency ranges below the collision rate due to the destructive interferences impacting the emission amplitude of photons between the successive collisions of the electrons. The spectral intensity at the ground level is shown to be several orders of magnitude below the sensitivity of experimental setups.

Consequently the MBR cannot be seen as the basis of a new detection technique of EAS for the next decades. The formalism developed to get at this conclusion allowed the key role of the two-point correlation function of the ionisation electron velocities to be highlighted. This can serve to study the intensity of the re-radiation of these ionization electrons subject to the passage of an incoming coherent wave from a radar transmitter. Some hints on this will be presented.

Speaker: Deligny, Olivier
• 10:20 AM 11:30 AM
Air Shower Simulations 2
• 10:20 AM
Simulation Study of the Detection of Inclined Photon Air Showers with the AugerPrime Radio Detector 20m

The Pierre Auger Observatory is the largest Cosmic Ray (CR) observatory with a size of $\approx$ 3000 km$^2$. Its size makes it feasible to not only look for CRs but also for presumably rare primaries like photons at energies larger than 1 EeV.
Strong upper limits on the photon flux have been set in the past using the Surface Detector (SD). Additionally, air showers with photon-like properties were detected. However, the uncertainty remains for these photon candidate events regarding whether they are of photon origin or possibly misinterpreted hadrons.
With the AugerPrime upgrade, the SD is complemented by the Radio Detector. The combination of both detectors yields new information about air showers and will improve the certainty of primary identification. Here, inclined photon showers are of special interest as they have a reduced particle footprint but strong radio emission. This characteristic contrasts with hadronic primaries, where a strong particle footprint is also expected for inclined air showers. The difference is investigated in simulation studies to determine the primary discrimination power of the AugerPrime detector. We will quantify the discrimination power and introduce parameters for the photon-hadron separation. We will present an outlook on the future prospects of the analysis and a concept for the triggering of photon air showers.

Speaker: Pawlowsky, Jannis
• 10:40 AM
RDSim, a fast and comprehensive simulation of radio detection of air showers 20m

We present RDSim, a fast and comprehensive framework for the simulation of the radio detection of downgoing air showers. It can handle any downgoing shower that can be simulated with ZHAireS, including those induced by CC and NC neutrino interactions and $\tau$ decays. RDSim is based on a superposition toymodel that disentangles the Askaryan and geomagnetic components of the shower emission. By using full ZHAireS simulations as input, it is able to estimate the radio footprint anywhere on the ground. A single input simulation at a given energy and arrival direction can be scaled in energy and rotated in azimuth by taking into account all relevant effects. This makes it possible to simulate a huge number of geometries and energies using just a few ZHAireS input simulations.

The framework takes into account the main characteristics of the detector, such as trigger setups, thresholds and antenna patterns. To accommodate arrays that use particle detectors for triggering, such as the Auger RD extension, it also features a second toymodel to estimate the muon density at ground level, which is used to perform simple particle trigger simulations.

It's speed makes it possible to investigate in detail events with a very low trigger probability, as well as many geometrical effects, such as those due to asymmetric arrays, infills and other border effects. In case more detailed studies of the radio detection are needed, RDSim can also be used to sweep the phase-space for the efficient creation of dedicated full simulation sets. This is particularly important in the case of neutrino events, that have extra variables that greatly impact shower characteristics, such as interaction or $\tau$ decay depth as well as the type of interaction and it's fluctuations.

Speaker: Carvalho Jr., Washington
• 11:00 AM
Simulation of radiopulses from Atmosphere-Skimming Extensive Air Showers with ZHAireS-RASPASS 20m

Earth-skimming neutrinos and Atmosphere-skimming neutrinos and cosmic rays can induce extensive air showers that present some peculiarities in comparison to the better-characterized down-going showers. For some geometries, cascades can take place high in the atmosphere and develop over several hundred of kilometers, giving ample time for the geomagnetic field to deflect the particles. For other geometries, cascades can develop very close to the ground where the density is high and on the contrary are very short. Development in a thinner or denser atmosphere will shift the balance between the average interaction length and decay length of particles, giving showers that can have very different hadronic/electromagnetic components with respect to regular down-going showers.

In this work we will showcase ZHAireS-RASPASS, a custom-built modification to the ZHAireS suite capable of simulating Atmosphere-Skimming and up-going (from Earth-skimming) showers and their radio-emission, focusing on how it could be used to inform the design and data interpretation of balloon-borne and satellite-borne experiments looking at these type of events.

Speaker: Dr Tueros, Matías (Instituto de Fisica La Plata - CONICET)
• 11:30 AM 12:00 PM
Coffee and tea 30m
• 12:00 PM 2:00 PM
Acoustic Detection
• 12:00 PM
Overview of Acoustic Detection 15m
Speaker: Lahmann, Robert (Friedrich Alexander Univ. Erlangen (DE))
• 12:15 PM
Development of a Trigger for Acoustic Neutrino Candidates in KM3NeT 20m

The KM3NeT Collaboration is constructing two large neutrino detectors in the Mediterranean Sea: ARCA, located near Sicily and aiming at neutrino astronomy, and ORCA located near Toulon and designed for neutrino oscillation studies. The two detectors together will have hundreds of Detection Units (DUs) with Digital Optical Modules (DOMs) maintained vertical by buoyancy forming a large 3D optical array for detecting the Cherenkov light produced after the neutrino interactions. To properly reconstruct the direction of the incoming neutrino, the position of the DOMs must be monitored, which are not static due to the sea currents. For this purpose, there is an Acoustic Positioning System, which is composed of fixed acoustic emitters on the sea bottom, a hydrophone in each DU base and a piezoceramic sensor in each DOM, as acoustic receivers. This network of acoustic sensors can be used not only for positioning, but also for acoustic monitoring studies such as bioacoustics, ship noise monitoring, environmental noise control, and acoustic neutrinos detection. This work explores the possibility of creating a trigger for saving the data for ultra-high-energy neutrino candidates detected acoustically by the hydrophones. The acoustic signal caused by the neutrino interaction in a fluid is a short-time duration Bipolar Pulse (BP), with a wide range of frequency and extremely directive. A study of signal detection and background has been done by simulating BP produced by the interaction of a 1020 eV neutrino at 1 km from the detector at zero-degree incidence added to the experimental real acoustic data. Finally, a trigger proposal has been developed in order to record candidates of BPs and it has been tested. The number of candidates per second, precision, and recall have been monitored according to the cuts applied and parameters calculated by the algorithm.

Speaker: Diego-Tortosa, Dídac (Universitat Politècnica de València - IGIC)
• 12:35 PM
New sensors for acoustic neutrino detection 20m

The scientific prospects of detecting cosmic neutrinos with an energy close or even higher than the GKZ cut-off energy has been discussed extensively in literature. It is clear that due to their expected low flux, the detection of these ultra-high energy neutrinos (E_ν > 10 18 eV) requires an telescope with an effective detection volume larger than 100 km 3 . Acoustic detection may provide a way to observe these ultra-high energy cosmic neutrinos, as sound induced in the deep sea by their loss travels undisturbed for many kilometers so that a large neutrino telescope can be established. To realize such a telescope, acoustic detection technology must be developed that allows for a large deep sea sensor network.

Fiber optic hydrophone technology is a promising means to establish large a scale sensor network with the proper sensitivity to detect the small signals from neutrino interactions. The combination of the sensitivity and the cost-effective implementation of hydrophones may prove to be an enabler for a large scale deployment that is required for an acoustic neutrino telescope. TNO is involved in the development of the fiber optic hydrophone technology that can be operated in the deep sea with the required sensitivity. In this talk we report on the progress of i) the hydrophone development and of ii) the neutrino signal simulations and methods to extract the signal from background.

Speaker: Buis, Ernst-Jan
• 12:55 PM
Simulation of acoustic signals from ultra-high-energy neutrinos 20m

Acoustic detection provides a promising approach to build volume-efficient detectors, for the observation of ultra high energy cosmic neutrinos. In this work, the energy deposition profile of particle showers in water above EeV energies is simulated. An adaptation of the program CORSIKA is used for this purpose. The energy deposition profiles of the showers are used to compute the acoustic signals, by means of an implementation of the thermo-acoustic mechanism.

For hadronic showers, it is observed that two acoustic pulses are created at close radial distances from the shower axis (r $\leq$ 500 m for a 1e11 GeV shower). The first observed pulse is created by the extended tail of hadronic showers, characteristic of the Landau–Pomeranchuk–Migdal (LPM) effect. The second observed pulse arises from the maximum energy deposition region of the shower.

The nature of the first observed pulse, which has not been reported in previous works, is studied, and its characteristics are derived. Besides, a review of the properties of the pulse arising from the maximum energy deposition region of the hadronic shower is done.

Lastly, the acoustic signal created by the combination of an electromagnetic and hadronic shower is briefly investigated.

Speaker: Gatius Oliver, Clara (Nikhef, KM3NeT)
• 2:00 PM 3:30 PM
Lunch 1h 30m
• 3:30 PM 5:30 PM
Extra time for discussions (no contributions)