arXiv subjects

Aya Ishihara

Publications and source records attributed to Aya Ishihara.

13 recordsLinked to original sources

arXiv2026

Cherenkov Neutrino Telescopes: Recent Progress and Next Steps

Neutrino telescopes provide a unique observational gateway to the high-energy universe, enabling the study of cosmic accelerators and extreme environments that remain inaccessible to the other high-energy messengers. Although they share core detection principles with neutrino experiments in particle physics, such as the observation of Cherenkov radiation, their scientific objectives and operational constraints diverge markedly. This paper reviews the motivations behind astrophysical neutrino detection, outlines key design strategies across various media and deployment environments, and highlights the critical role of neutrino telescopes in the context of multimessenger astronomy. In particular, we emphasize their potential to illuminate the origins of cosmic rays and to probe the mechanisms driving the most energetic phenomena in the universe.

astro-ph.HE↗

arXiv2023

The next generation neutrino telescope: IceCube-Gen2

The IceCube Neutrino Observatory, a cubic-kilometer-scale neutrino detector at the geographic South Pole, has reached a number of milestones in the field of neutrino astrophysics: the discovery of a high-energy astrophysical neutrino flux, the temporal and directional correlation of neutrinos with a flaring blazar, and a steady emission of neutrinos from the direction of an active galaxy of a Seyfert II type and the Milky Way. The next generation neutrino telescope, IceCube-Gen2, currently under development, will consist of three essential components: an array of about 10,000 optical sensors, embedded within approximately 8 cubic kilometers of ice, for detecting neutrinos with energies of TeV and above, with a sensitivity five times greater than that of IceCube; a surface array with scintillation panels and radio antennas targeting air showers; and buried radio antennas distributed over an area of more than 400 square kilometers to significantly enhance the sensitivity of detecting neutrino sources beyond EeV. This contribution describes the design and status of IceCube-Gen2 and discusses the expected sensitivity from the simulations of the optical, surface, and radio components.

astro-ph.HE↗

arXiv2022

Identifying High Energy Neutrino Transients by Neutrino Multiplet-Triggered Followups

Transient sources such as supernovae (SNe) and tidal disruption events are candidates of high energy neutrino sources. However, SNe commonly occur in the universe and a chance coincidence of their detection with a neutrino signal cannot be avoided, which may lead to a challenge of claiming their association with neutrino emission. In order to overcome this difficulty, we propose a search for $\sim10-100$ TeV neutrino multiple events within a timescale of $\sim 30$ days coming from the same direction, called neutrino multiplets. We show that demanding multiplet detection by a $\sim 1$ km$^3$ neutrino telescope limits distances of detectable neutrino sources, which enables us to identify source counterparts by multiwavelength observations owing to the substantially reduced rate of the chance coincidence detection of transients. We apply our results by constructing a feasible strategy for optical followup observations and demonstrate that wide-field optical telescopes with a $\gtrsim4$ m dish should be capable of identifying a transient associated with a neutrino multiplet. We also present the resultant sensitivity of multiplet neutrino detection as a function of the released energy of neutrinos and burst rate density. A model of neutrino transient sources with an emission energy greater than ${\rm a~few}\times 10^{51}$erg and a burst rate rarer than ${\rm a~few}\times 10^{-8}\ {\rm Mpc}^{-3}\ {\rm yr}^{-1}$ is constrained by the null detection of multiplets by a $\sim 1$km$^3$ scale neutrino telescope. This already disfavors the canonical high-luminosity gamma ray bursts and jetted tidal disruption events as major sources in the TeV-energy neutrino sky.

astro-ph.HE↗

arXiv2021

Performance studies for a next-generation optical sensor for IceCube-Gen2

We present performance studies of a segmented optical module for the IceCube-Gen2 detector. Based on the experience gained in sensor development for the IceCube Upgrade, the new sensor will consist of up to eighteen 4 inch PMTs housed in a transparent pressure vessel, providing homogeneous angular coverage. The use of custom molded optical `gel pads' around the PMTs enhances the photon capture rate via total internal reflection at the gel-air interface. This contribution presents simulation studies of various sensor, PMT, and gel pad geometries aimed at optimizing the sensitivity of the optical module in the face of confined space and harsh environmental conditions at the South Pole.

astro-ph.IM↗

arXiv2021

Performance of the D-Egg Optical Sensor for the IceCube Upgrade

New optical sensors called the "D-Egg" have been developed for cost-effective instrumentation for the IceCube Upgrade. With two 8-inch high quantum efficient photomultiplier tubes (PMTs), they offer increased effective photocathode area while retaining as much of the successful IceCube Digital Optical Module design as possible. Mass production of D-Eggs has started in 2020. By the end of 2021, there will be 310 D-Eggs produced with 288 deployed in the IceCube Upgrade. The D-Egg readout system uses advanced technologies in electronics and computing power. Each of the two PMT signals is digitised using ultra-low-power 14-bit ADCs with a sampling frequency of 240 megaSPS, enabling seamless and lossless event recording from single-photon signals to signals exceeding 200 PE within 10 nanosecond, as well as flexible event triggering. In this paper, we report the single photon detection performance as well as the multiple photon recording capability of D-Eggs from the mass production line which have been evaluated with the built-in data acquisition system.

physics.ins-det↗

arXiv2021

A next-generation optical sensor for IceCube-Gen2

For the in-ice component of the next generation neutrino observatory at the South Pole, IceCube-Gen2, a new sensor module is being developed, which is an evolution of the D-Egg and mDOM sensors developed for the IceCube Upgrade. The sensor design features up to 18 4-inch PMTs distributed homogeneously in a borosilicate glass pressure vessel. Challenges arise for the mechanical design from the tight constraints on the bore hole diameter (which will be 2 inches smaller than for IceCube Upgrade) and from the close packing of the PMTs. The electronics design must meet the space constraints posed by the mechanical design as well as the power consumption and cost considerations from over 10,000 optical modules being deployed. This contribution presents forward-looking solutions to these design considerations. Prototype modules will be installed and integrated in the IceCube Upgrade.

astro-ph.IM↗

arXiv2019

Electronics Development for the New Photo-Detectors (PDOM and D-Egg) for IceCube-Upgrade

The planned IceCube-Upgrade will enhance the capability of IceCube in the detection of GeV-scale neutrino physics and enable an improved measurement of the properties of the glacial ice. Three types of new optical sensors will be deployed during the Upgrade: PDOM, D-Egg, and mDOM. Since the design of the PDOM and D-Egg are very similar, the development of the front-end electronics for the two optical sensors has been merged. The photo-electron signals detected by the PMTs are digitized with high-speed ultra-low power ADCs and processed in an FPGA, before being sent to the data acquisition system located on the surface of the South-Pole glacier. The almost final revision of the front-end electronics is equipped with the common microcontroller unit and the communication daughter board for simplifying the communication scheme for the three different modules. This contribution focuses on the design of the front-end electronics and presents first results from the performance tests.

astro-ph.IM↗

arXiv2019

Calibration LEDs in the IceCube Upgrade D-Egg Modules

The IceCube Upgrade, planned for deployment in the 2022/2023 South Pole Summer, will involve deployment of a greater density of optical modules (vertically spaced ~3 m). Improvements in the calibration of optical sensors and an enhanced understanding of the optical properties of the deep glacial ice, due to the more closely-spaced modules, are projected to have a large impact on neutrino reconstruction. A new optical sensor module called the "Dual optical sensors in an Ellipsoid glass for Gen2" (D-Egg), is planned for installation in both the IceCube Upgrade and IceCube-Gen2, and has both an upward and downward facing 8" high quantum efficiency PMT. The D-Egg modules will make use of a downward-facing LED calibration system to measure the optical properties of the refrozen drill holes ("hole ice"). An inner section of the hole ice contains some impurities, which modify the optical properties of the ice; this area is known as the "bubble column". The measurement of this "hole ice" is critical both for the upgraded IceCube detector as well as the current generation IceCube, as refrozen ice contributes significant systematic uncertainties to the reconstruction of low energy neutrinos. A simulation was performed, where the size and optical properties of the bubble column were varied. A log likelihood function is constructed from the geometry of the D-Eggs and properties of the hole ice. The minimization recovers best fit values close to the Monte Carlo truth.

astro-ph.HE↗

arXiv2019

The IceCube Upgrade -- Design and Science Goals

The IceCube Neutrino Observatory at the geographic South Pole has reached a number of milestones in the field of neutrino astrophysics. The achievements of IceCube include the discovery of a high-energy astrophysical neutrino flux, and the temporal and directional correlation of neutrinos with a flaring blazar. The IceCube Upgrade, which will be constructed in the 2022/23 Antarctic Summer season, is the next stage of the IceCube project. The IceCube Upgrade consists of seven new columns of photosensors, densely embedded near the bottom center of the existing cubic-kilometer-scale IceCube Neutrino Observatory. An improved atmospheric neutrino event selection efficiency and reconstruction at a few GeV can be achieved with the dense infill of the Upgrade's photosensor array. The Upgrade will provide world-leading sensitivity to neutrino oscillations and will enable IceCube to take unique measurements of tau neutrino appearance with a high precision. Furthermore, the new array will also improve the existing IceCube detector. The Upgrade strings will include new calibration devices designed to deepen the knowledge of the optical properties of glacial ice and the detector response. The improved calibration resulting from the Upgrade will be applied to the entire archive of IceCube data collected over the last 10 years, improving the angular and spatial resolution of the detected astrophysical neutrino events. Finally, the Upgrade represents the first stage in the development of IceCube-Gen2, the next-generation neutrino telescope at the South Pole.

astro-ph.HE↗

arXiv2019

Coherent radio emission from the electron beam sudden appearance

We report on the measurement of coherent radio emission from the electron beam sudden appearance at the Telescope Array Electron Light Source facility. This emission was detected by four independent radio detector setups sensitive to frequencies ranging from 50 MHz up to 12.5 GHz. We show that this phenomenon can be understood as a special case of coherent transition radiation by comparing the observed results with simulations. The in-nature application of this signal is given by the emission of cosmic ray or neutrino induced particle cascades traversing different media such as air, rock and ice.

astro-ph.HE↗

arXiv2015

Neutrino Astronomy (Rapporteur Talk)

This report is the write-up of a rapporteur talk on neutrino astronomy given at the 34th International Cosmic Ray Conference in The Hague, Netherlands, in 2015. Here, selected contributions on the neutrino astronomy from the total of 40 talks and 90 posters presented in NU sessions at the 34th ICRC are summarized in the attempt of providing a status report on this rapidly glowing new field. The field of neutrino astronomy has recently experienced a "phase transition" since the first observation of high energy cosmic neutrinos. Extensive efforts have been made to identify the origin of the neutrino flux observed in the 100 TeV to PeV region, from both theoretical and experimental perspectives. In addition, the search for neutrino fluxes beyond the observed level has become increasingly important for further understanding the origin of the observed cosmic-ray up to $10^{20}$ eV. Although the IceCube Neutrino Observatory is the only experiment currently measuring this neutrino flux, its initial measurements have been confirmed via analysis using several independent detection channels. Further, there have been a number of developments in the search for neutrino point sources, while no successful observations have yet been reported. Following the IceCube observations, a large number of studies of next-generation neutrino detectors, including up-scaled underground Cherenkov neutrino detectors and Cherenkov radio neutrino detectors, have been reported.

astro-ph.HE↗

arXiv2012

Constraints on the origin of the ultra-high energy cosmic-rays using cosmic diffuse neutrino flux limits: An analytical approach

Astrophysical neutrinos are expected to be produced in the interactions of ultra-high energy cosmic-rays with surrounding photons. The fluxes of the astrophysical neutrinos are highly dependent on the characteristics of the cosmic-ray sources, such as their cosmological distributions. We study possible constraints on the properties of cosmic-ray sources in a model-independent way using experimentally obtained diffuse neutrino flux above 100 PeV. The semi-analytic formula is derived to estimate the cosmogenic neutrino fluxes as functions of source evolution parameter and source extension in redshift. The obtained formula converts the upper-limits on the neutrino fluxes into the constraints on the cosmic-ray sources. It is found that the recently obtained upper-limit on the cosmogenic neutrinos by IceCube constrains the scenarios with strongly evolving ultra-high energy cosmic-ray sources, and the future limits from an 1 km^3 scale detector are able to further constrain the ultra-high energy cosmic-rays sources with evolutions comparable to the cosmic star formation rate.

astro-ph.HE↗

arXiv2006

The EHE Neutrino Search Capability of the IceCube Observatory

An initial study of the extremely high energy (EHE) physics capabilityof the IceCube neutrino observatory is demonstrated by considering a GZK mechanism neutrino production model, which is a guaranteed source for EHE neutrinos. We study EHE event properties in the energy range $10^{5}$ $<$ E $<$ $10^{11}$ GeV observed by IceCube using detailed Monte Carlo simulation. Results of a simulation study show that about 0.7 EHE neutrino events per year is expected with the full IceCube configuration over a 0.03 atmospheric muon background which passed an EHE event criteria. It is also shown that with the present partial IceCube detector with the same criteria is capable of studying EHE physics and the sensitivity improves with the number of deployed strings in the ice.

astro-ph↗