Shower Direction Research Articles

The SHADOWS calorimeter — A pointing calorimeter for future beam dump experiments

This contribution presents advancements in the design and testing of an electromagnetic calorimeter intended for the detection of feebly interacting particles in future beam dump experiments. The calorimeter is designed to accurately reconstruct particle decays into photons, focusing on achieving precise energy and direction measurements. We propose a plastic scintillator-based calorimeter capable of providing the necessary resolution for these measurements. The pointing capability has been validated through GEANT4 simulations, optimizing scintillator granularity for effective shower direction reconstruction. Additionally, we detail the prototyping efforts and the first results of test beam measurements conducted at DESY.

Neural networks for separation of cosmic gamma rays and hadronic cosmic rays in air shower observation with a large area surface detector array

The Tibet ASγ experiment has been observing cosmic gamma rays and cosmic rays in the energy range from teraelectron volts to several tens of petaelectron volts with a surface detector array since 1990. The derivation of cosmic gamma-ray flux is made by finding the excess distribution of the arrival direction of air showers above background cosmic rays. In 2014, the underground water Cherenkov muon detector (MD) was added to separate cosmic gamma rays from the background on the basis of the muon-less feature of the air showers of gamma-ray origin; hybrid observations using these two detectors were started at this time. In the present study, we developed methods to separate gamma-ray-induced air showers and hadronic cosmic-ray-induced ones using the measured particle number density distribution to improve the sensitivity of cosmic gamma-ray measurements using the Tibet air shower array data alone before the installation of the MD. We tested two approaches based on neural networks. The first method used feature values representing the lateral spread of the secondary particles, and the second method used the shower image data. To compare the separation performance of each method, we analyzed Monte Carlo air shower events in the vertically incident direction with mono-initial-energy gamma rays and protons. When discriminated by a single feature, the feature with the highest separation performance has an area under the curve (AUC) value of 0.701 for a gamma-ray energy of 10 TeV and 0.808 for 100 TeV. A separation method with a multilayer perceptron (MLP) based on multiple features has AUC values of 0.761 for a gamma-ray energy of 10 TeV and 0.854 for 100 TeV, which represents an improvement of approximately 5% in the AUC value compared with the single-feature case. We also found that the feature values that effectively contribute to the separation vary depending on the energy. A separation method with a convolutional neural network (CNN) using the shower image data has AUC values of 0.781 for a gamma-ray energy of 10 TeV and 0.901 for 100 TeV, which are approximately 5% higher than those of the MLP method. We applied the CNN separation method to Monte Carlo gamma-ray and cosmic-ray events from the Crab Nebula in the energy range 10–100 TeV. The AUC values range from 0.753 to 0.879, and the significance of the observed gamma-ray excess is improved by 1.3 to 1.8 times compared with the case without the separation procedure.

Timing detectors setup prototype for determining EAS axis direction

This work presents a prototype setup for determining extensive air showers (EAS) axis direction. The detector system consists of four scintillation detectors (100x100x1 cm) using wavelength-shifted fibers light collection. This prototype will make it possible to create system of detectors with fast timing (timing detectors) and supplement the complex shower installation, located at 3340 m above sea level at the Tien Shan High-altitude Scientific Station (TSHSS) near Almaty, Kazakhstan. A method for determination the direction of extensive air showers is described. It is indicated that to assess the determination of extensive air showers direction, it is necessary to define azimuth and zenith angles with required accuracy. In this work, calibration of detectors with vertical cosmic muons is presented. To calibrate the detectors, a test bench was assembled, and its schematic representation is shown. The signals from scintillation detectors were analyzed using a CAEN DT 5725 8-channel analog-to-digital converter. In addition, there is a discussion of the preliminary results from calibration. Single-particle calibration of detectors will allow estimating the number of particles passed through the scintillation detector.

Clustering of electromagnetic showers and particle interactions with graph neural networks in liquid argon time projection chambers

Liquid argon time projection chambers (LArTPCs) are a class of detectors that produce high resolution images of charged particles within their sensitive volume. In these images, the clustering of distinct particles into superstructures is of central importance to the current and future neutrino physics program. Electromagnetic (EM) activity typically exhibits spatially detached fragments of varying morphology and orientation that are challenging to efficiently assemble using traditional algorithms. Similarly, particles that are spatially removed from each other in the detector may originate from a common interaction. Graph neural networks (GNNs) were developed in recent years to find correlations between objects embedded in an arbitrary space. The graph particle aggregator (GrapPA) first leverages GNNs to predict the adjacency matrix of EM shower fragments and to identify the origin of showers, i.e., primary fragments. On the PILArNet public LArTPC simulation dataset, the algorithm achieves a shower clustering accuracy characterized by a mean purity of 99.4%, a mean efficiency of 99.6% and a primary identification accuracy of 99.8%. It yields a relative shower energy uncertainty of $(4.1+1.4/\sqrt{E(\mathrm{GeV})})%$ and a shower direction uncertainty of $(2.1/\sqrt{E(\mathrm{GeV})})\ifmmode^\circ\else\textdegree\fi{}$. The optimized algorithm is then applied to the related task of clustering particle instances into interactions and yields a mean purity of 99.8% and a mean efficiency of 99.5% for an interaction density of $\mathcal{O}(1)\text{ }\text{ }{\mathrm{m}}^{\ensuremath{-}3}$.

Angular reconstruction of high energy air showers using the radio signal spectrum

The Hellenic Open University extensive air shower array (also known as Astroneu array) is a small scale hybrid detection system operating in an area with high levels of electromagnetic noise from anthropogenic activity. In the present study we report the latest results of the data analysis concerning the estimation of the shower direction using the spectrum of the RF system. In a recent layout of the array, 4 RF antennas were operating receiving a common trigger from an autonomous detection station of 3 particle detectors. The directions estimated with the RF system are in very good agreement with the corresponding estimations using the particle detectors demonstrating that a single antenna has the potential for reconstructing the shower axis angular direction.

On angular resolution limits for air shower arrays

The angular resolution limits achievable for perfect ground-based high-altitude gamma-ray air shower detectors are investigated, to serve as benchmarks for the design of real detectors. A ‘perfect’ detector is assumed to accurately measure impact position, time and energy of all electromagnetic shower particles reaching the ground. The shower direction is determined from a likelihood fit to all measured particles, using parametrized likelihood functions. The impact of energy thresholds of the particle detector, of detection efficiency, of finite time and energy resolution and of spatial granularity is discussed.

The HiSPARC experiment

The High School Project on Astrophysics Research with Cosmics (HiSPARC) is a large extensive air shower (EAS) array with detection stations throughout the Netherlands, United Kingdom, Denmark and Namibia. HiSPARC is a collaboration of universities, scientific institutes and high schools. The majority of detection stations is hosted by high schools. A HiSPARC station consists of two or four scintillators placed inside roof boxes on top of a building. The measured response of a detector to single incoming muons agrees well with GEANT4 simulations. The response of a station to EASs agrees with simulations as well. A four-scintillator station was integrated in the KASCADE experiment and was used to determine the accuracy of the shower direction reconstruction. Using simulations, the trigger efficiency of a station to detect a shower as function of both distance to the shower core and zenith angle was determined. The HiSPARC experiment is taking data since 2003. The number of stations (∼140 in 2019) still increases. The project demonstrates that its approach is viable for educational purposes and that scientific data can be obtained in a collaboration with high school students and teachers.

Meteoroid-stream complex originating from comet 2P/Encke

Aims. We present a study of the meteor complex of the short-period comet 2P/Encke. Methods. For five perihelion passages of the parent comet in the past, we modeled the associated theoretical stream. Specifically, each of our models corresponds to a part of the stream characterized with a single value of the evolutionary time and a single value of the strength of the Poynting–Robertson effect. In each model, we follow the dynamical evolution of 10 000 test particles via a numerical integration. The integration was performed from the time when the set of test particles was assumed to be ejected from the comet’s nucleus up to the present. At the end of the integration, we analyzed the mean orbital characteristics of those particles that approached the Earth’s orbit, and thus created a meteor shower or showers. Using the mean characteristics of the predicted shower, we attempted to select its real counterpart from each of five considered databases (one photographic, three video, and one radio-meteor). If at least one attempt was successful, the quality of the prediction was evaluated. Results. The modeled stream of 2P approaches the Earth’s orbit in several filaments with the radiant areas grouped in four cardinal directions of ecliptical showers. These groups of radiant areas are situated symmetrically with respect to the apex of the Earth’s motion around the Sun. Specifically, we found that showers #2, #17, #156, #172, #173, #215, #485, #624, #626, #628, #629, #632, #634, #635, #636, and #726 in the IAU-MDC list of all showers are dynamically related to 2P. In addition, we found five new 2P-related showers in the meteor databases considered.

Determination of the absolute energy scale of extensive air showers via radio emission: Systematic uncertainty of underlying first-principle calculations

Recently, the energy determination of extensive air showers using radio emission has been shown to be both precise and accurate. In particular, radio detection offers the opportunity for an independent measurement of the absolute energy scale of cosmic rays, since the radiation energy (the energy radiated in the form of radio signals) can be predicted using first-principle calculations involving no free parameters, and the measurement of radio waves is not subject to any significant absorption or scattering in the atmosphere. To quantify the uncertainty associated with such an approach, we collate the various contributions to the uncertainty, and we verify the consistency of radiation-energy calculations from microscopic simulation codes by comparing Monte Carlo simulations made with the two codes CoREAS and ZHAireS. We compare a large set of simulations with different primary energies and shower directions and observe differences in the radiation energy prediction for the 30–80 MHz band of 5.2%. This corresponds to an uncertainty of 2.6% for the determination of the absolute cosmic-ray energy scale. Our result has general validity and can be built upon directly by experimental efforts for the calibration of the cosmic-ray energy scale on the basis of radio emission measurements.

Performance of a scintillation detector array operated with LHAASO-KM2A electronics

A scintillation detector array composed of 115 detectors and covering an area of about 20000 m2 was installed at the end of 2016 at the Yangbajing international cosmic ray observatory and has been taking data since then. The array is equipped with electronics from Large High Altitude Air Shower Observatory Square Kilometer Complex Array (LHAASO-KM2A) and, in turn, currently serves as the largest debugging and testing platform for the LHAASO-KM2A. Furthermore, the array was used to study the performance of a wide field-of-view air Cherenkov telescope by providing accurate information on the shower core, direction and energy, etc. This work is mainly dealing with the scintillation detector array. The experimental setup and the offline calibration are described in detail. Then, a thorough comparison between the data and Monte Carlo (MC) simulations is presented and a good agreement is obtained. With the even-odd method, the resolutions of the shower direction and core are measured. Finally, successful observations of the expected Moon’s and Sun’s shadows of cosmic rays (CRs) verify the measured angular resolution.

Simulation studies of reconstruction of hadron shower direction in INO ICAL detector

The proposed Iron Calorimeter (ICAL) at India-based Neutrino Observatory (INO) will be a 50 kt magnetised iron detector for the detection of atmospheric neutrinos. The atmospheric neutrinos interact via both charged current (CC) and neutral current (NC) interactions with the target iron to produce the detectable final state particles. While CC νμ (ν̄μ) leave a muon track and a hadron shower in the detector, the NC will leave only a hadron shower apart from the secondary invisible neutrino. A GEANT4 based simulation studies to reconstruct hadron showers in CC and NC, using two techniques namely the Orientation Matrix Method (OMM) and the Raw Hit Method (RHM) are presented here. While OMM requires information about the interaction vertex obtained from muon track reconstruction, RHM requires only the shower hit positions and timings and no vertex information and hence can be used for NC events as well. Hadrons from neutrino events generated with NUANCE neutrino generator are analysed. For hadrons in the energy range 0.5–15 GeV produced in CC νμ and ν̄μ interactions, a Δθ′h resolution of around 19̂−9̂ (around 20.5̂−12̂) is obtained in the |cosθ′h|=[0.8, 1] bin with OMM (RHM). For NC events in the same true energy and direction bins, Δθ′h resolution varies from around 20.5̂−13̂, from RHM only. OMM (RHM) gives a resolution of about 55̂−20̂ (38̂−14̂) for the angle between the muon and the hadron shower, βμ h′, in the [E′had;cos θ′h] range [0.5–15 GeV; [0.8,1.0]].

Studies for the electro-magnetic calorimeter SplitCal for the SHiP experiment at CERN with shower direction reconstruction capability

This paper describes the basic ideas and the first simulation results of a new electro-magnetic calorimeter concept, named SplitCal, aimed at optimising the measurement of photon direction in fixed-target experiment configuration, with high photon detection efficiency. This calorimeter was designed for the invariant mass reconstruction of axion-like particles decaying into two photons in the mass range 200 MeV to 1 GeV for the proposed proton beam dump experiment SHiP at CERN. Preliminary results indicate that angular resolutions better than obtained by past experiments can be achieved with this design. An implementation of this concept with real technologies is under study.

A deep learning-based reconstruction of cosmic ray-induced air showers

We describe a method of reconstructing air showers induced by cosmic rays using deep learning techniques. We simulate an observatory consisting of ground-based particle detectors with fixed locations on a regular grid. The detector’s responses to traversing shower particles are signal amplitudes as a function of time, which provide information on transverse and longitudinal shower properties. In order to take advantage of convolutional network techniques specialized in local pattern recognition, we convert all information to the image-like grid of the detectors. In this way, multiple features, such as arrival times of the first particles and optimized characterizations of time traces, are processed by the network. The reconstruction quality of the cosmic ray arrival direction turns out to be competitive with an analytic reconstruction algorithm. The reconstructed shower direction, energy and shower depth show the expected improvement in resolution for higher cosmic ray energy.

Radio detection of air showers with the ARIANNA experiment on the Ross Ice Shelf

The ARIANNA hexagonal radio array (HRA) is an experiment in its pilot phase designed to detect cosmogenic neutrinos of energies above 1016 eV. The most neutrino-like background stems from the radio emission of air showers. This article reports on dedicated efforts of simulating and detecting the signals of cosmic rays. A description of the fully radio self-triggered data-set, the properties of the detected air shower signals in the frequency range of 100–500 MHz and the consequences for neutrino detection are given. 38 air shower signals are identified by their distinct waveform characteristics, are in good agreement with simulations and their signals provide evidence that neutrino-induced radio signals will be distinguishable with high efficiency in ARIANNA. The cosmic ray flux at a mean energy of 6.5−1.0+1.2×1017 eV is measured to be 1.1−0.7+1.0×10−16 eV−1 km−2 sr−1 yr−1 and one five-fold coincident event is used to illustrate the capabilities of the ARIANNA detector to reconstruct arrival direction and energy of air showers.

Tunka-Rex: energy reconstruction with a single antenna station

The Tunka-Radio extension (Tunka-Rex) is a radio detector for air showers in Siberia. From 2012 to 2014, Tunka-Rex operated exclusively together with its host experiment, the air-Cherenkov array Tunka-133, which provided trigger, data acquisition, and an independent air-shower reconstruction. It was shown that the air-shower energy can be reconstructed by Tunka-Rex with a precision of 15\% for events with signal in at least 3 antennas, using the radio amplitude at a distance of 120\,m from the shower axis as an energy estimator. Using the reconstruction from the host experiment Tunka-133 for the air-shower geometry (shower core and direction), the energy estimator can in principle already be obtained with measurements from a single antenna, close to the reference distance. We present a method for event selection and energy reconstruction, requiring only one antenna, and achieving a precision of about 20\%. This method increases the effective detector area and lowers thresholds for zenith angle and energy, resulting in three times more events than in the standard reconstruction.

Radio detection of high-energy cosmic rays with the Auger Engineering Radio Array

The Auger Engineering Radio Array (AERA) is an enhancement of the Pierre Auger Observatory in Argentina. Covering about 17km2, AERA is the world-largest antenna array for cosmic-ray observation. It consists of more than 150 antenna stations detecting the radio signal emitted by air showers, i.e., cascades of secondary particles caused by primary cosmic rays hitting the atmosphere. At the beginning, technical goals had been in focus: first of all, the successful demonstration that a large-scale antenna array consisting of autonomous stations is feasible. Moreover, techniques for calibration of the antennas and time calibration of the array have been developed, as well as special software for the data analysis. Meanwhile physics goals come into focus. At the Pierre Auger Observatory air showers are simultaneously detected by several detector systems, in particular water-Cherenkov detectors at the surface, underground muon detectors, and fluorescence telescopes, which enables cross-calibration of different detection techniques. For the direction and energy of air showers, the precision achieved by AERA is already competitive; for the type of primary particle, several methods are tested and optimized. By combining AERA with the particle detectors we aim for a better understanding of cosmic rays in the energy range from approximately 0.3 to 10EeV, i.e., significantly higher energies than preceding radio arrays.

LOPES — Recent Results and Open Questions on the Radio Detection of Air Showers

LOPES was a digital antenna array operating for approximately 10 years until spring 2013 at the Karlsruhe Institute of Technology (KIT). Triggered by the co-located KASCADE-Grande air-shower experiment, it measured the radio signal of around 1000 cosmic-ray air showers with energies E ≳ 1017 eV in an effective band of 43 – 74 MHz. Using the interferometric technique of cross-correlation beamforming, LOPES could reconstruct the shower direction with an accuracy < 0.7°, the shower energy with a precision < 20%, and the atmospheric depth of the shower maximum, Xmax, with a precision < 95g/cm2. In particular the reconstruction of the shower maximum suffers from significant measurement uncertainties due to the radio-loud environment of the site. This article summarizes our latest results on the reconstruction of the shower maximum, using two independent methods: the steepness of the hyperbolic radio wavefront and the slope of the lateral distribution of the radio amplitude. Moreover, we show vectorial measurements of the electric field with the tripole antennas of the latest LOPES setup. Finally, we discuss open questions as well as the potential impact of the lessons learned at LOPES for future antenna arrays.

Observations of the new Camelopardalids meteor shower using a 38.9 MHz radar at Mohe, China

The Camelopardalids meteor shower was predicted to occur for the first time on 24 May 2014, based on optical observations of the comet 209P/LINEAR. Using a 38.9MHz meteor radar located at Mohe, China, we were able to detect approximately 590 shower meteors originating from an average pre-infall radiant of R.A.=129.1°±9.8°, declination=79.4°±1.6° (J2000) with a geocentric velocity of 16.0±1.6kms−1. Measurements of the shower duration, direction, velocity, and individual meteor detection heights facilitated a detailed analysis of the parent debris stream. Orbital parameters were calculated including a semi-major axis of 2.86AU, eccentricity of 0.659, and inclination of 21.1°. Combining orbital parameters with the shower activity duration FWHM of 5.09h, it was found that the stream has a FWHM of at least 211,000km at 1AU, as measured perpendicular to the direction of orbital motion. A comparison of shower meteor detection heights and diffusion coefficient estimates with the sporadic background is consistent the prediction of Ye and Wiegert (Ye, Q., Wiegert, P. [2014]. Mon. Not. R. Astron. Soc. 437, 3283–3287) that Camelopardalid meteoroids are biased towards larger sizes or that Cameloppardalid meteoroids are less fragile than sporadic background meteoroids.

The Relevance of the Strength and Direction of Return Signals from Foreign and Domestic Markets to Investment Strategies

This paper investigates whether a particular magnitude and direction of meteor showers in returns dominates the performance of domestic trading in U.S., European and Australasian global markets. Direct and indirect channels of foreign information transmission are modelled by stochastic parameter regressions and combined with domestic momentum information to generate trading signals. Filters that control for magnitude and direction of information are then used to investigate incremental impact on economic performance of trading strategies. The results indicate that at reasonable levels of transaction costs very profitable trades that are fewer in number do not increase investment performance as much as trades based on foreign information of a specific low-to-medium daily return magnitude of 0.5% to 0.75%. These information-based strategies are profitable on risk-adjusted bases and relative to a market. The persistent return predictability calls for a re-examination of extant pricing models.

Distributions for spherical data based on nonnegative trigonometric sums

A family of distributions for a random pair of angles that determine a point on the surface of a three-dimensional unit sphere (three-dimensional directions) is proposed. It is based on the use of nonnegative double trigonometric (Fourier) sums (series). Using this family of distributions, data that possess rotational symmetry, asymmetry or one or more modes can be modeled. In addition, the joint trigonometric moments are expressed in terms of the model parameters. An efficient Newton-like optimization algorithm on manifolds is developed to obtain the maximum likelihood estimates of the parameters. The proposed family is applied to two real data sets studied previously in the literature. The first data set is related to the measurements of magnetic remanence in samples of Precambrian volcanics in Australia and the second to the arrival directions of low mu showers of cosmic rays.