Neutrino-induced Showers Research Articles

Evaluation of the potential of a gamma-ray observatory to detect astrophysical neutrinos through inclined showers

We assess the capabilities of a ground-based gamma-ray observatory to detect astrophysical neutrinos with energies in the $100\,{\rm TeV}$ to $100\,{\rm PeV}$ range. The identification of these events would be done through the measurement of very inclined extensive air showers induced by downward-going and upward-going neutrinos. The discrimination of neutrino-induced showers in the overwhelming cosmic-ray background is achieved by analysing the balance of the total electromagnetic and muonic signals of the shower at the ground. We demonstrate that a ${\rm km^2}$-scale wide field-of-view ground-based gamma-ray observatory could detect a couple of Very-High to Ultra-High energy (VHE-UHE) neutrino events per year with a reasonable pointing accuracy, making it an interesting facility for multi-messenger studies with both photons and neutrinos.

Polarisation signatures in radio for inclined cosmic-ray induced air-shower identification

Autonomous radio-detection, i.e., detection of air-showers with standalone radio arrays, is one of the major technical challenges to overcome for the next generation astroparticle detectors. In this context, we study polarisation signatures of simulated radio signals to perform an identification of the associated air-showers initiated by cosmic-rays and neutrinos. We compare the two sources of radio emission (the charge excess and geomagnetic) and show that the former is almost negligible for inclined (zenith angle >65°) cosmic-ray air-showers. This provides an efficient background rejection criterion at the DAQ level, based on the projection of the total electric field along the direction of the local magnetic field. This relevant quantity can be computed, — even in an online treatment — for antennas measuring three orthogonal polarisations. Independently of the experimental antenna layout, we estimate that assuming a random polarisation of noise events, a rejection from ≈72% (for a non favourable detector location) to ≈93% (for a favourable one) of the noise induced events and a trigger efficiency of 86% (93%) with a 3σ (5σ) trigger threshold level should be achievable. We also show that neutrino-induced showers present a charge excess to geomagnetic signal ratio up to ∼10 times higher than for cosmic ray showers. Although this characteristic makes the identification of neutrino-induced showers challenging via the method developed here, it provides an efficient criterion to perform an offline discrimination between cosmic-ray and neutrino primaries. The stronger charge excess emission will also help the reconstruction of air-shower parameters, such as the core position.

Askaryan radiation from neutrino-induced showers in ice

We present a semi-analytical method for the calculation of coherent Askaryan radiation in showers induced by neutrinos of any flavor in ice. We compare our results with those of a full Monte Carlo simulation based on the ZHAireS code. This approach is able to reproduce the vector potential and hence electric field at any experimentally relevant observer position in the time domain. This work extends published results only valid for electron-induced showers. We establish the validity of the semi-analytical calculation of the radio signal produced by all types of neutrino-induced showers in ice. The method is computationally efficient and only requires as inputs the longitudinal charge excess profile of the showers and a parameterization of the vector potential in the far-field region of the shower at the Cherenkov angle that we also provide. Our methodology avoids tracking the contributions to the electric field from millions of particles every time the radio pulse has to be calculated at a given observer position. These results can be readily used in the interpretation of the data taken by experiments, and in the planning and design of future initiatives based on the radio technique in ice.

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

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

Methodological Issues of Gamma-Ray and Neutrino Searches at the Yakutsk Array

The method used to perform searches for extensive air showers (EAS) generated by neutral particles, such as high-energy gamma rays and astrophysical neutrinos, and the results of such searches are presented. A comprehensive analysis of relevant data, including those on EAS electrons, muons, and Cherenkov light and their time responses in scintillation and Cherenkov detectors, is performed for this purpose. An upper limit on the gamma-ray flux at the energies of 3 × 1018, 1019, and 3 × 1019 eV is set. A multivariate analysis of EAS properties of neutrino-induced air showers does not reveal neutrino-induced showers.

An Algorithm for the Reconstruction of Neutrino-induced Showers in the ANTARES Neutrino Telescope

Abstract Muons created by charged current (CC) interactions in the water surrounding the ANTARES neutrino telescope have been almost exclusively used so far in searches for cosmic neutrino sources. Due to their long range, highly energetic muons inducing Cherenkov radiation in the water are reconstructed with dedicated algorithms that allow for the determination of the parent neutrino direction with a median angular resolution of about 0.°4 for an neutrino spectrum. In this paper, an algorithm optimized for accurate reconstruction of energy and direction of shower events in the ANTARES detector is presented. Hadronic showers of electrically charged particles are produced by the disintegration of the nucleus both in CC and neutral current interactions of neutrinos in water. In addition, electromagnetic showers result from the CC interactions of electron neutrinos while the decay of a tau lepton produced in CC interactions will, in most cases, lead to either a hadronic or an electromagnetic shower. A shower can be approximated as a point source of photons. With the presented method, the shower position is reconstructed with a precision of about 1 m; the neutrino direction is reconstructed with a median angular resolution between 2° and 3° in the energy range of 1–1000 TeV. In this energy interval, the uncertainty on the reconstructed neutrino energy is about 5%–10%. The increase in the detector sensitivity due to the use of additional information from shower events in the searches for a cosmic neutrino flux is also presented.

Recent results from the ARIANNA neutrino experiment

The ARIANNA experiment is currently taking data in its pilot-phase on the Ross ice-shelf. Fully autonomous stations measure radio signals in the frequency range from 100 MHz to 1 GHz. The seven station HRA was completed in December 2014, and augmented by two special purpose stations with unique configurations. In its full extent ARIANNA is targeted at detecting interactions of cosmogenic neutrinos (> 1016eV) in the ice-shelf. Downward-pointing antennas installed at the surface will record the radio emission created by neutrino-induced showers in the ice and exploit the fact that the ice- water surface acts as a mirror for radio emission. ARIANNA stations are independent, low-powered, easy to install and equipped with real-time communication via satellite modems. We report on the current status of the HRA, as well as air shower detections that have been made over the past year. Furthermore, we will discuss the search for neutrino emission, future plans and the energy-dependent sensitivity of the experiment.

Radio-interferometric Neutrino Reconstruction for the Askaryan Radio Array

The Askaryan Radio Array (ARA) is a neutrino telescope array under phased deployment near the South Pole. The array aims to discover and determine the ultra-high energy neutrino flux via detection of the Askaryan signal from neutrino-induced showers. This novel detection channel makes ARA the most cost-effective neutrino observatory in probing the neutrino flux from 10 17 eV – 10 19 eV. This contribution will discuss an interferometric vertex reconstruction technique developed for ARA, taking into account the curved paths traveled by EM radiation in inhomogeneous ice. Preliminary results on the directional reconstruction of an in situ calibration pulser as well as simulated neutrino vertices will be presented.

Background Rejection in the ARA Experiment

The Askaryan Radio Array (ARA) is a radio frequency observatory under construction at the South Pole that is searching for ultrahigh energy neutrinos via the Askaryan effect. Thermal fluctuations currently dominate the trigger-level background for the observatory and anthropogenic sources also introduce a significant source of noise. By taking advantage of the observatory’s regular geometry and the expected coincident nature of the RF signals arriving from neutrino-induced events, this background can be filtered efficiently. This contribution will discuss techniques developed for the ARA analyses to reject these thermal signals, to reject anthropogenic backgrounds, and to search for neutrino-induced particle showers in the Antarctic ice. The results of a search for neutrinos from GRBs using the prototype station using some of these techniques will be presented.

Publisher’s Note: Transition radiation at radio frequencies from ultrahigh-energy neutrino-induced showers [Phys. Rev. D93, 043010 (2016)

Publisher’s Note: Transition radiation at radio frequencies from ultrahigh-energy neutrino-induced showers [Phys. Rev. D<b>93</b>, 043010 (2016)

Transition radiation at radio frequencies from ultrahigh-energy neutrino-induced showers

Coherent radiation at radio frequencies from high-energy showers fully contained in a dense radio-transparent medium - like ice, salt or regolith - has been extensively investigated as a promising technique to search for ultra-high energy (UHE) neutrinos. Additional emission in the form of transition radiation may occur when a neutrino-induced shower produced close to the Earth surface emerges from the ground into atmospheric air. We present the first detailed evaluation of transition radiation from high-energy showers crossing the boundary between two different media. We found that transition radiation is sizable over a wide solid angle and coherent up to $\sim$ 1 GHz. These properties encourage further work to evaluate the potential of a large-aperture UHE neutrino experiment based on detection of transition radiation.

On the feasibility of RADAR detection of high-energy neutrino-induced showers in ice

In this article we try to answer the question whether the radar detection technique can be used for the detection of high-energy-neutrino induced particle cascades in ice. A high-energy neutrino interacting in ice will induce a particle cascade, also referred to as a particle shower, moving at approximately the speed of light. Passing through, the cascade will ionize the medium, leaving behind a plasma tube. The different properties of the plasma-tube, such as its lifetime, size and the charge-density will be used to obtain an estimate if it is possible to detect this tube by means of the radar detection technique. Next to the ionization electrons a second plasma due to mobile protons induced by the particle cascade is discussed. An energy threshold for the cascade inducing particle of 4PeV for the electron plasma, and 20PeV for the proton plasma is obtained. This allows the radar detection technique, if successful, to cover the energy-gap between several PeV and a few EeV in the currently operating neutrino detectors, where on the low side IceCube runs out of events, and on the high side the Askaryan radio detectors begin to have large effective volumes.

Neutrino-induced showers in the ANTARES deep-sea telescope

Reconstruction of neutrino-induced showers, initiated by neutral-current interactions, can extend the sensitivity of the ANTARES detector to all neutrino flavors. A major challenge in reconstructing showers is their selection from an overwhelming background of down-going atmospheric muons. We have developed a shower selection strategy in order to select up-going showers with high efficiency and purity. We have tuned the selection strategy on Monte-Carlo simulations containing the proper amount of background and atmospheric neutrino-induced showers. The obtained results indicate an efficiency of 21% with a purity better than 90% for the shower selection. We applied the selection strategy to ANTARES experimental data and observed a satisfactory performance of the discriminating variables.

Towards acoustic UHE neutrino detection in the Mediterranean sea

Acoustic detection is proposed as a promising detection technique for Extreme High energy neutrinos. This technique is based on the detection of the acoustic signature of neutrino-induced showers in water: a bipolar signal, having a bandwidth of few 10kHz, with cylindrical wave front. During the last decade, the possibility of access to deep-sea infrastructures developed for Cherenkov telescopes, allowed start-up of intense R&D activities on acoustic detection. In the framework of the activities of ANTARES, NEMO and KM3NeT, several small size experiments were run in order to measure acoustic noise in deep sea and test “neutrino-like” acoustic event detection. These activities have set milestones both for future HE neutrino detectors, for innovative deep-sea technology and for Earth-Sea science. A review on acoustic neutrino detection and projects running in the Mediterranean Sea is presented.

First search for atmospheric and extraterrestrial neutrino-induced cascades with the IceCube detector

We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. A total of 14 events with energies above 16 TeV remained after event selections in the diffuse analysis, with an expected total background contribution of $8.3\pm 3.6$. At 90% confidence we set an upper limit of $E^2\Phi_{90%CL}<3.6\times10^{-7} GeV \cdot cm^{-2} \cdot s^{-1}\cdot sr^{-1} $ on the diffuse flux of neutrinos of all flavors in the energy range between 24 TeV and 6.6 PeV assuming that $\Phi \propto E^{-2}$ and that the flavor composition of the $\nu_e : \nu_\mu : \nu_\tau$ flux is $1 : 1 : 1$ at the Earth. The atmospheric neutrino analysis was optimized for lower energies. A total of 12 events were observed with energies above 5 TeV. The observed number of events is consistent with the expected background, within the uncertainties.

Radio pulses from electromagnetic, hadronic and neutrino-induced showers up to EeV energies

The radio pulses emitted by electromagnetic, hadronic, and neutrino-induced showers are calculated for showers of energies in the EeV range and above in ice and in air. These are obtained in three-dimensional simulations of both the shower and the radio emission. An AIRES-based Monte Carlo code, ZHA ireS, has been developed for this purpose that allows us to predict the radio emission in both the time and frequency domains. The algorithms used, obtained from first principles, predict the radio emission due to all emission mechanisms, including the deflection of charged particles in the Earth's magnetic field. The code which has been extended to calculate in the Fresnel regime can reproduce the full complexity of the relevant shower phenomena.

Position calibration for the future KM3NeT detector

Deep-sea neutrino telescopes consist of an array of photomultipliers to detect Cherenkov light emitted by neutrino-induced muons and particle showers in the surrounding sea water, allowing for reconstruction of the neutrino direction from position and timing of the Cherenkov photons. Since the photomultipliers are in most cases mounted on flexible structures, e.g. lines, and move with the sea current, a positioning system is required to determine the precise location of each sensor. The positioning system of the ANTARES neutrino telescope is based on acoustic triangulation using hydrophones mounted along the lines in combination with tiltmeters and compasses and provides centimetre precision alignment. For the future KM3NeT detector an Optical Module with integrated Piezo sensors for position calibration is proposed as a cost-effective solution. The performance of this system is tested with several sensors of the AMADEUS project, which is integrated in ANTARES to study the background for acoustic detection of highest energy neutrinos.

Neutrino identification with Auger and [formula omitted] flux limit

The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming ν τ . The topological properties of such showers are quite different from hadronic events. Neutrino-induced showers are characterized by very elongated and asymmetric footprints and a significant electromagnetic component. Electrons and gammas produce broad timing signals, whereas hadronic showers give rise to signals mostly due to the surviving secondary muons with a shorter signal in time with respect to an electromagnetic signal. The data collected between 1st January 2004 and 31st August 2007 is used to place an upper limit on the diffuse flux of ν τ . Over this perio there is not a single event that fulfills the selection criteria. The limit for an E −2 differential energy spectrum at 90% C.L. is: E 2 d N ν τ / d E 1.3 × 10 − 7 GeV cm − 2 s − 1 sr − 1 .

AURA—A radio frequency extension to IceCube

The excellent radio frequency (RF) transparency of cold polar ice, combined with the coherent Cherenkov emission produced by neutrino-induced showers when viewed at wavelengths longer than a few centimeters, has spurred considerable interest in a large-scale radio-wave neutrino detector array. The AURA (Askaryan Under-ice Radio Array) experimental effort, within the IceCube collaboration, seeks to take advantage of the opportunity presented by IceCube [A. Karle, Nucl. Instr. and Meth. A (2009), this issue, doi: 10.1016/j.nima.2009.03.180. [1]; A. Achtenberg et al., The IceCube Collaboration, Astropart. Phys. 26 (2006) 155 [2]] drilling through 2010 to establish the RF technology needed to achieve 100– 1000 km 3 effective volumes. In the 2006–2007 Austral summer, three deep in-ice RF clusters were deployed at depths of ∼ 1300 and ∼ 300 m on top of the IceCube strings. Additional three clusters will be deployed in the Austral summer of 2008–2009. Verification and calibration results from the current deployed clusters are presented, and the detector design and performances are discussed. Augmentation of IceCube with large-scale ( 1000 km 3 sr ) radio and acoustic arrays would extend the physics reach of IceCube into the EeV–ZeV regime and offer substantial technological redundancy.

Development of a radio-detection array for the observation of UHE neutrino-induced showers

The recent demonstration by the CODALEMA collaboration of the ability of the radio-detection technique for the characterization of ultra-high-energy cosmic-rays (UHECR) calls for the use of this powerful method for the observation of UHE neutrinos. For this purpose, an adaptation of the already existing 21CM-Array (CMA) in China, is presently under achievement. In an exceptionally low electromagnetic noise level, 10160 log-periodic 50–200 MHz antennas sit along two high-altitude valleys, surrounded by mountain chains. This layout results in 30–60 km effective rock thicknesses for ν interactions with low incidence trajectories along the direction of two 4–6 km baselines. We will present first in-situ radio measurements demonstrating that this environment shows particularly favourable physical conditions for the observation of electromagnetic decay signals of τ's leptons originating from the interaction of 10 17–20 eV ν τ neutrinos.