Search

The TAROGE-M radio observatory is a self-triggered antenna array on top of the ∼2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 1017 eV, including cosmic rays, Earth-skimming tau neutrinos, and particularly, the “ANITA anomalous events” (AAE) from near and below the horizon. The six AAE discovered by the ANITA experiment have signal features similar to tau neutrinos but that hypothesis is in tension either with the interaction length predicted by Standard Model or with the flux limits set by other experiments. Their origin remains uncertain, requiring more experimental inputs for clarification. The detection concept of TAROGE-M takes advantage of a high altitude with synoptic view toward the horizon as an efficient signal collector, and the radio quietness as well as strong and near vertical geomagnetic field in Antarctica, enhancing the relative radio signal strength. This approach has a low energy threshold, high duty cycle, and is easy to extend for quickly enlarging statistics. Here we report experimental results from the first TAROGE-M station deployed in January 2020, corresponding to approximately one month of livetime. The station consists of six receiving antennas operating at 180–450 MHz, and can reconstruct source directions of impulsive events with an angular resolution of ∼0.3°, calibrated in situ with a drone-borne pulser system. To demonstrate TAROGE-M's ability to detect UHE air showers, a search for cosmic ray signals in 25.3-days of data together with the detection simulation were conducted, resulting in seven identified candidates. The detected events have a mean reconstructed energy of 0.95-0.31 +0.46 EeV and zenith angles ranging from 25° to 82°, with both distributions agreeing with the simulations, indicating an energy threshold at about 0.3 EeV. The estimated cosmic ray flux at that energy is 1.2-0.9 +0.7 × 10-16 eV-1 km-2 yr-1 sr-1, also consistent with results of other experiments. The TAROGE-M sensitivity to AAEs is approximated by the tau neutrino exposure with simulations, which suggests comparable sensitivity as ANITA's at around 1 EeV energy with a few station-years of operation. These first results verified the station design and performance in a polar and high-altitude environment, and are promising for further discovery of tau neutrinos and AAEs after an extension in the near future.

Full list of authors: Kim, Minbin; Ripa, Jakub; Park, Il H.; Bogomolov, Vitaly; Brandt, Søren; Budtz-Jørgensen, Carl; Castro-Tirado, Alberto J.; Chang, Sheng-Hsiung; Chang, Yenyun; Chen, Chia Ray; Chen, C. -W.; Chen, Pisin; Connell, Paul; Eyles, Chris; Gaikov, Georgii; Hong, Gihan; Huang, Jian Jung; Huang, Ming-Huey Alfred; Jeong, Soomin; Kim, Jieun; Lee, Jik; Lim, Heuijin; Lin, Chih-Yang; Liu, Tsung-Che; Nam, Jiwoo; Panasyuk, Mikhail; Petrov, Vasily; Reglero, Victor; Rodrigo, Juana M.; Svertilov, Sergey; Vedenkin, Nikolay; Wang, Ming Zu; Yashin, Ivan.--This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., We developed an X-ray detector using 36 arrays, each consisting of a 64-pixellated yttrium oxyorthosilicate (YSO) scintillation crystal and a 64-channel multi-anode photomultiplier tube. The Xray detector was designed to detect X-rays with energies lower than 10 keV, primarily with the aim of localizing gamma-ray bursts (GRBs). YSO crystals have no intrinsic background, which is advantageous for increasing low-energy sensitivity. The fabricated detector was integrated into UBAT, the payload of the Ultra-Fast Flash Observatory (UFFO)/Lomonosov for GRB observation. The UFFO was successfully operated in space in a low-Earth orbit. In this paper, we present the responses of the X-ray detector of the UBAT engineering model identical to the flight model, using241 Am and55 Fe radioactive sources and an Amptek X-ray tube. We found that the X-ray detector can measure energies lower than 5 keV. As such, we expect YSO crystals to be good candidates for the X-ray detector materials for future GRB missions. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland., This study was supported by grants from the Korean National Research Foundation (NRF-2017K1A4A3015188, NRF-2021R1A2B5B03002645, and NRF-2019H1D3A2A02060090). The Russian work was partially supported by ROSCOSMOS grants and by RFFI grant No. 13-02-12175 and No.15-35-21038 and support from the Development Program of Lomonosov Moscow State University is acknowledged. AJCT acknowledges support from the Spanish MINECO Projects AYA 2009-14000-C03-01/ESP and AYA2015-1718-R (including EU/FEDER funds). The authors thank Taiwan’s National Science Council Vanguard Program (100-2119-M-002-025) and Ministry of Science and Technology (MOST) for the funding (104-2811-M-002-160). MBK acknowledges the support from NRF-2015-GPF., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We present a portable calibration pulser system applied to radio antennas in order to detect ultra-high energy cosmic rays and neutrinos. The system consists of a solid-state high-voltage impulse generator, a digital attenuator, a wide band (150-350 MHz) bi-cone antenna, and a differential GPS. Taking an advantage of light weight of each component (less than $1.4$ kg), we developed an airborne calibration system by attaching them on a commercial drone. This system will be used for TAROGE experiment in high mountains as well as in Antarctica. We will report on its design, construction, performance, and potential applications for future radio experiments.

The Askaryan Radio Array (ARA) is a ground-based radio detector at the South Pole designed to capture Askaryan emission from ultra-high energy neutrinos interacting within the Antarctic ice. The newest ARA station has been equipped with a phased array trigger, in which radio signals in multiple antennas are summed in predetermined directions prior to the trigger. In this way, impulsive signals add coherently, while noise likely does not, allowing the trigger threshold to be lower than a traditional ARA station. Early results on just a fraction of available data from this new system prove the feasibility of a low-threshold analysis.

The Askaryan Radio Array (ARA) is an ultra-high energy (UHE) neutrino ($E_{\nu}$ > $10^{17}$ eV) detector at South Pole. ARA aims to utilize radio signals detected from UHE neutrino interactions in the glacial ice to infer properties about the interaction vertex as well as the incident neutrino. To retrieve these properties from experiment data, the first step is to extract timing, amplitude and frequency information from waveforms of different antennas buried in the deep ice. These features can then be utilized in a neural network to reconstruct the neutrino interaction vertex position, incoming neutrino direction and shower energy. So far, vertex can be reconstructed through interferometry while neutrino reconstruction is still under investigation. Here I will present a solution based on multi-task deep neural networks which can perform reconstruction of both vertex and incoming neutrinos with a reasonable precision. After training, this solution is capable of rapid reconstructions (e.g. 0.1 ms/event compared to 10000 ms/event in a conventional routine) useful for trigger and filter decisions, and can be easily generalized to different station configurations for both design and analysis purposes.

The TAROGE-M observatory is an autonomous antenna array on the top of Mt.~Melbourne ($\sim2700$ m altitude) in Antarctica, designed to detect radio pulses from ultra-high energy (over $10^{17}$ eV) air showers coming from near-horizon directions. The targeted sources include cosmic rays, Earth-skimming tau neutrinos, and most of all, the anomalous near-horizon upward-going events of yet unknown origin discovered by ANITA experiments. The detection concept follows that of ANITA: monitoring large area of ice from high-altitude and taking advantage of strong geomagnetic field and quiet radio background in Antarctica, whereas having significantly greater livetime and scalability. The TAROGE-M station, upgraded from its prototype built in 2019, was deployed in January 2020, and consists of 6 log-periodic dipole antennas pointing horizontally with bandwidth of 180-450 MHz. The station is then calibrated with drone-borne transmitter, with which the event reconstruction obtained $\sim0.3^\circ$ angular resolution. The station was then smoothly operating in the following month, with the live time of $\sim30$ days, before interrupted by a power problem, and its online filtering has identified several candidate cosmic-ray events and sent out via satellite communication. In this paper, the instrumentation of the station for polar and high-altitude environment, its radio-locating performance, the preliminary result on cosmic-ray detection, and the future extension plan are presented.

Owing to their small interaction cross-section, neutrinos are unparalleled astronomical tracers. Ultra-high energy (UHE; E > 10 PeV) neutrinos probe the most distant, most explosive sources in the Universe, often obscured to optical telescopes. Radio-frequency (RF) detection of Askaryan radiation in cold polar ice is currently regarded as the best experimental measurement technique for UHE neutrinos, provided the RF properties of the ice target can be well-understood. To that end, the Askaryan Radio Array (ARA) experiment at the South Pole has used long-baseline RF propagation to extract information on the index-of-refraction ( n = ϵ r ) in South Polar ice. Owing to the increasing ice density over the upper 150–200 m, rays are measured along two, nearly parallel paths, one of which refracts through an inflection point, with differences in both arrival time and arrival angle that can be used to constrain the neutrino properties. We also observe (first) indications for RF ice birefringence for signals propagating along predominantly horizontal trajectories, corresponding to an asymmetry of order 0.1% between the ordinary and extra-ordinary birefringent axes, numerically compatible with previous measurements of birefringent asymmetries for vertically-propagating radio-frequency signals at South Pole. Qualitatively, these effects offer the possibility of redundantly measuring the range from receiver to a neutrino interaction in Antarctic ice, if receiver antennas are deployed at shallow (z ∼ −25 m) depths. Such range information is essential in determining both the neutrino energy, as well as the incident neutrino direction.

The NASA supported High-Altitude Calibration (HiCal)-2 instrument flew as a companion balloon to the ANITA-4 experiment in December 2016. Based on a HV discharge pulser producing radio-frequency (RF) calibration pulses, HiCal-2 comprised two payloads, which flew for a combined 18 days, covering 1.5 revolutions of the Antarctic continent. ANITA-4 captured over 10,000 pulses from HiCal, both direct and reflected from the surface, at distances varying from 100-800 km, providing a large dataset for surface reflectivity measurements. Herein we present details on the design, construction and performance of HiCal-2., Comment: Published in NIM-A, final version

We present a new radio array experiment on the top of the highest mountains in Antarctica, to detect upward moving air-showers similar to those recently reported by the ANITA experiment. The detection concept follows ANITA, but has significantly greater livetime and extendibility. We propose to install 10 stations over the next 5 years to obtain sufficient sensitivity to test ANITA’s `mystery events'. As the first step, we installed a prototype station (TAROGE-M) consisting of 5 LPDA antennas, atop Mt. Melbourne, Antarctica at an elevation of 2730 m, in Feb-Mar 2019. We present the scientific potential, detector design and construction, as well as the initial performance of the prototype station.

The Askaryan Radio Array (ARA) is an ultra-high energy (UHE, $>10^{17}$ eV) neutrino detector designed to observe neutrinos by searching for the radio waves emitted by the relativistic products of neutrino-nucleon interactions in Antarctic ice. In this paper, we present constraints on the diffuse flux of ultra-high energy neutrinos between $10^{16}-10^{21}$ eV resulting from a search for neutrinos in two complementary analyses, both analyzing four years of data (2013-2016) from the two deep stations (A2, A3) operating at that time. We place a 90 % CL upper limit on the diffuse all flavor neutrino flux at $10^{18}$ eV of $EF(E)=5.6\times10^{-16}$ $\textrm{cm}^{-2}$$\textrm{s}^{-1}$$\textrm{sr}^{-1}$. This analysis includes four times the exposure of the previous ARA result, and represents approximately 1/5 the exposure expected from operating ARA until the end of 2022., 12 pages, 7 figures; Accepted to PRD

The ANtarctic Impulsive Transient Antenna (ANITA) long-duration balloon experiment is sensitive to interactions of ultra high-energy (E > 10^{18} eV) neutrinos in the Antarctic ice sheet. The third flight of ANITA, lasting 22 days, began in December 2014. We develop a methodology to search for energetic neutrinos spatially and temporally coincident with potential source classes in ANITA data. This methodology is applied to several source classes: the TXS 0506+056 blazar and NGC 1068, the first potential TeV neutrino sources identified by IceCube, flaring high-energy blazars reported by the Fermi All-Sky Variability Analysis, gamma-ray bursts, and supernovae. Among searches within the five source classes, one candidate was identified as associated with SN 2015D, although not at a statistically significant level. We proceed to place upper limits on the source classes. We further comment on potential applications of this methodology to more sensitive future instruments., 23 pages, 7 figures, version accepted to JCAP

The balloon-borne ANITA [1] experiment is designed to detect ultra-high energy neutrinos via radio emissions produced by in-ice showers. Although initially purposed for interactions within the Antarctic ice sheet, ANITA also demonstrated the ability to self-trigger on radio emissions from ultra-high energy charged cosmic rays [2] (CR) interacting in the Earth's atmosphere. For showers produced above the Antarctic ice sheet, reflection of the down-coming radio signals at the Antarctic surface should result in a polarity inversion prior to subsequent observation at the ∼35–40 km altitude ANITA gondola. Based on data taken during the ANITA-1 and ANITA-3 flights, ANITA published two anomalous instances of upcoming cosmic-rays with measured polarity opposite the remaining sample of ∼50 UHECR signals [3, 4]. The steep observed upwards incidence angles (25–30 degrees relative to the horizontal) require non-Standard Model physics if these events are due to in-ice neutrino interactions, as the Standard Model cross-section would otherwise prohibit neutrinos from penetrating the long required chord of Earth. Shoemaker et al. [5] posit that glaciological effects may explain the steep observed anomalous events. We herein consider the scenarios offered by Shoemaker et al. and find them to be disfavored by extant ANITA and HiCal experimental data. We note that the recent report of four additional near-horizon anomalous ANITA-4 events [6], at >3σ significance, are incompatible with their model, which requires significant signal transmission into the ice.

The Payload for Ultrahigh Energy Observations (PUEO) long-duration balloon experiment is designed to have world-leading sensitivity to ultrahigh-energy neutrinos at energies above 1 EeV. Probing this energy region is essential for understanding the extreme-energy universe at all distance scales. PUEO leverages experience from and supersedes the successful Antarctic Impulsive Transient Antenna (ANITA) program, with an improved design that drastically improves sensitivity by more than an order of magnitude at energies below 30 EeV. PUEO will either make the first significant detection of or set the best limits on ultrahigh-energy neutrino fluxes., Comment: 40 pages, 17 figures. Version accepted to JINST

We report on a search for ultra-high-energy (UHE) neutrinos from gamma-ray bursts (GRBs) in the data set collected by the Testbed station of the Askaryan Radio Array (ARA) in 2011 and 2012. From 57 selected GRBs, we observed no events that survive our cuts, which is consistent with 0.12 expected background events. Using NeuCosmA as a numerical GRB reference emission model, we estimate upper limits on the prompt UHE GRB neutrino fluence and quasi-diffuse flux from $10^{7}$ to $10^{10}$ GeV. This is the first limit on the prompt UHE GRB neutrino quasi-diffuse flux above $10^{7}$ GeV., Comment: 14 pages, 8 figures, Published in Astroparticle Physics Journal

Recently, the ANITA collaboration reported on two upward-going extensive air shower events consistent with a primary particle that emerges from the surface of the ice. These events may be of $\nu_\tau$ origin, in which the neutrino interacts within the Earth to produce a $\tau$ lepton that emerges from the Earth, decays in the atmosphere, and initiates an extensive air shower. In this paper we estimate an upper bound on the ANITA acceptance to a diffuse $\nu_\tau$ flux detected via $\tau$-lepton-induced air showers within the bounds of Standard Model (SM) uncertainties. By comparing this estimate with the acceptance of Pierre Auger Observatory and IceCube and assuming SM interactions, we conclude that a $\nu_\tau$ origin of these events would imply a neutrino flux at least two orders of magnitude above current bounds., Comment: 12 pages, 7 figures

The ANtarctic Impulsive Transient Antenna (ANITA) NASA long-duration balloon payload completed its fourth flight in December 2016, after 28 days of flight time. ANITA is sensitive to impulsive broadband radio emission from interactions of ultra-high-energy neutrinos in polar ice (Askaryan emission). We present the results of two separate blind analyses searching for signals from Askaryan emission in the data from the fourth flight of ANITA. The more sensitive analysis, with a better expected limit, has a background estimate of $0.64^{+0.69}_{-0.45}$ and an analysis efficiency of $82\pm2\%$. The second analysis has a background estimate of $0.34^{+0.66}_{-0.16}$ and an analysis efficiency of $71\pm6\%$. Each analysis found one event in the signal region, consistent with the background estimate for each analysis. The resulting limit further tightens the constraints on the diffuse flux of ultra-high-energy neutrinos at energies above $10^{19.5}$ eV., 11 pages, 7 figures

A Monte Carlo simulation program for the radio detection of Ultra High Energy (UHE) neutrino interactions in the Antarctic ice as viewed by the Antarctic Impulsive Transient Antenna (ANITA) is described in this article. The program, icemc, provides an input spectrum of UHE neutrinos, the parametrization of the Askaryan radiation generated by their interaction in the ice, and the propagation of the radiation through ice and air to a simulated model of the third and fourth ANITA flights. This paper provides an overview of the icemc simulation, descriptions of the physics models used and of the ANITA electronics processing chain, data/simulation comparisons to validate the predicted performance, and a summary of the impact of published results.

We report on analysis of englacial radio-frequency (RF) pulser data received over horizontal baselines of 1--5 km, based on broadcasts from two sets of transmitters deployed to depths of up to 1500 meters at the South Pole. First, we analyze data collected usingtwo RF bicone transmitters 1400 meters below the ice surface, and frozen into boreholes drilled for the IceCube experiment in 2011. Additionally, in Dec., 2018, a fat-dipole antenna, fed by one of three high-voltage (~1 kV), fast (~(1-5 ns)) signal generators was lowered into the 1700-m deep icehole drilled for the South Pole Ice Core Experiment (SPICE), approximately 3 km from the geographic South Pole. Signals from transmitters were recorded on the five englacial multi-receiver ARA stations, with receiver depths between 60--200 m. We confirm the long, >1 km RF electric field attenuation length, test our observed signal arrival timing distributions against models, and measure birefringent asymmetries at the 0.15% level.

We report on an upward traveling, radio-detected cosmic-ray-like impulsive event with characteristics closely matching an extensive air shower. This event, observed in the third flight of the Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload, is consistent with a similar event reported in a previous flight. These events may be produced by the atmospheric decay of an upward-propagating $\tau$-lepton produced by a $\nu_{\tau}$ interaction, although their relatively steep arrival angles create tension with the standard model (SM) neutrino cross section. Each of the two events have $a~posteriori$ background estimates of $\lesssim 10^{-2}$ events. If these are generated by $\tau$-lepton decay, then either the charged-current $\nu_{\tau}$ cross section is suppressed at EeV energies, or the events arise at moments when the peak flux of a transient neutrino source was much larger than the typical expected cosmogenic background neutrinos., Comment: 5 pages, 4 figures. Supplemental material available from corresponding author by request

Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made., The payload of the UFFO (Ultra-Fast Flash Observatory)-pathfinder now onboard the Lomonosov spacecraft (hereafter UFFO/Lomonosov) is a dedicated instrument for the observation of GRBs. Its primary aim is to capture the rise phase of the optical light curve, one of the least known aspects of GRBs. Fast response measurements of the optical emission of GRB will be made by a Slewing Mirror Telescope (SMT), a key instrument of the payload, which will open a new frontier in transient studies by probing the early optical rise of GRBs with a response time in seconds for the first time. The SMT employs a rapidly slewing mirror to redirect the optical axis of the telescope to a GRB position prior determined by the UFFO Burst Alert Telescope (UBAT), the other onboard instrument, for the observation and imaging of X-rays. UFFO/Lomonosov was launched successfully from Vostochny, Russia on April 28, 2016, and will begin GRB observations after completion of functional checks of the Lomonosov spacecraft. The concept of early GRB photon measurements with UFFO was reported in 2012. In this article, we will report in detail the first mission, UFFO/Lomonosov, for the rapid response to GRB observations. © The Author(s) 2017., The Korean work is supported by the National Research Foundation grants funded by MSIP of Korea (Creative Research Initiatives program for RCMST, No. 2015R1A2A1A01006870, and No. 2015R1A2A1A15055344). The Russian work was partially supported by ROSCOSMOS grants and by RFFI grants No. 13-02-12175 and No. 15-35-21038 and acknowledges support from the Development Program of Lomonosov Moscow State University. AJCT acknowledges support from the Spanish MINECO Projects AYA 2009-14000-C03-01/ESP and AYA 2015-71718R (including EU/FEDER funds). The Taiwanese authors thank Taiwan's National Science Council Vanguard Program (100-2119-M-002-025) and Ministry of Science and Technology (MOST) funding (104-2811-M-002-160). SJ acknowledges the support from the Korea Basic Science Research Program through NRF-2014R1A6A3A03057484 and NRF-2015R1D1A4A01020961. MBK acknowledges the support from NRF-2015-GPF.

The Antarctic Impulsive Transient Antenna (ANITA), a NASA long-duration balloon payload, searches for radio emission from interactions of ultra-high-energy neutrinos in polar ice. The third flight of ANITA (ANITA-III) was launched in December 2014 and completed a 22-day flight. We present the results of three analyses searching for Askaryan radio emission of neutrino origin. In the most sensitive of the analyses, we find one event in the signal region on an expected a priori background of $0.7^{+0.5}_{-0.3}$. Though consistent with the background estimate, the candidate event remains compatible with a neutrino hypothesis even after additional post-unblinding scrutiny., Comment: 15 pages, 15 figures, Accepted to PRD

The balloon-borne HiCal radio-frequency (RF) transmitter, in concert with the ANITA radio-frequency receiver array, is designed to measure the Antarctic surface reflectivity in the RF wavelength regime. The amplitude of surface-reflected transmissions from HiCal, registered as triggered events by ANITA, can be compared with the direct transmissions preceding them by O(10) microseconds, to infer the surface power reflection coefficient $\cal{R}$. The first HiCal mission (HiCal-1, Jan. 2015) yielded a sample of 100 such pairs, resulting in estimates of $\cal{R}$ at highly-glancing angles (i.e., zenith angles approaching $90^\circ$), with measured reflectivity for those events which exceeded extant calculations. The HiCal-2 experiment, flying from Dec., 2016-Jan., 2017, provided an improvement by nearly two orders of magnitude in our event statistics, allowing a considerably more precise mapping of the reflectivity over a wider range of incidence angles. We find general agreement between the HiCal-2 reflectivity results and those obtained with the earlier HiCal-1 mission, as well as estimates from Solar reflections in the radio-frequency regime. In parallel, our calculations of expected reflectivity have matured; herein, we use a plane-wave expansion to estimate the reflectivity R from both a flat, smooth surface (and, in so doing, recover the Fresnel reflectivity equations) and also a curved surface. Multiplying our flat-smooth reflectivity by improved Earth curvature and surface roughness corrections now provides significantly better agreement between theory and the HiCal 2a/2b measurements., Comment: submitted to Astropart. Phys

Ultra-high energy neutrinos are detectable through impulsive radio signals generated through interactions in dense media, such as ice. Subsurface in-ice radio arrays are a promising way to advance the observation and measurement of astrophysical high-energy neutrinos with energies above those discovered by the IceCube detector ($\geq$1 PeV) as well as cosmogenic neutrinos created in the GZK process ($\geq$100 PeV). Here we describe the $\textit{NuPhase}$ detector, which is a compact receiving array of low-gain antennas deployed 185 m deep in glacial ice near the South Pole. Signals from the antennas are digitized and coherently summed into multiple beams to form a low-threshold interferometric phased array trigger for radio impulses. The NuPhase detector was installed at an Askaryan Radio Array (ARA) station during the 2017/18 Austral summer season. $\textit{In situ}$ measurements with an impulsive, point-source calibration instrument show a 50% trigger efficiency on impulses with voltage signal-to-noise ratios (SNR) of $\le$2.0, a factor of $\sim$1.8 improvement in SNR over the standard ARA combinatoric trigger. Hardware-level simulations, validated with $\textit{in situ}$ measurements, predict a trigger threshold of an SNR as low as 1.6 for neutrino interactions that are in the far field of the array. With the already-achieved NuPhase trigger performance included in ARASim, a detector simulation for the ARA experiment, we find the trigger-level effective detector volume is increased by a factor of 1.8 at neutrino energies between 10 and 100 PeV compared to the currently used ARA combinatoric trigger. We also discuss an achievable near term path toward lowering the trigger threshold further to an SNR of 1.0, which would increase the effective single-station volume by more than a factor of 3 in the same range of neutrino energies., Comment: 19 pages, 19 figures, submitted to Nuclear Instruments and Methods in Physics Research A

Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made., The Ultra-Fast Flash Observatory (UFFO) Burst Alert and Trigger Telescope (UBAT) has been designed and built for the localization of transient X-ray sources such as Gamma Ray Bursts (GRBs). As one of main instruments in the UFFO payload onboard the Lomonosov satellite (hereafter UFFO/Lomonosov), the UBAT’s roles are to monitor the X-ray sky, to rapidly locate and track transient sources, and to trigger the slewing of a UV/optical telescope, namely Slewing Mirror Telescope (SMT). The SMT, a pioneering application of rapid slewing mirror technology has a line of sight parallel to the UBAT, allowing us to measure the early UV/optical GRB counterpart and study the extremely early moments of GRB evolution. To detect X-rays, the UBAT utilizes a 191.1 cm scintillation detector composed of Yttrium Oxyorthosilicate (YSO) crystals, Multi-Anode Photomultiplier Tubes (MAPMTs), and associated electronics. To estimate a direction vector of a GRB source in its field of view, it employs the well-known coded aperture mask technique. All functions are written for implementation on a field programmable gate array to enable fast triggering and to run the device’s imaging algorithms. The UFFO/Lomonosov satellite was launched on April 28, 2016, and is now collecting GRB observation data. In this study, we describe the UBAT’s design, fabrication, integration, and performance as a GRB X-ray trigger and localization telescope, both on the ground and in space., The Korean work is supported by the National Research Foundation grants funded by MSIP of Korea (Creative Research Initiatives program for RCMST, No. 2015R1A2A1A01006870, and No. 2015R1A2A1A15055344). SJ acknowledges the support of the Korea Basic Science Research Program through NRF-2015R1D1A4A01020961. MBK acknowledges support from the NRF-2015-Global Ph.D. Fellowship Program in Korea. The Russian work was partially supported by ROSCOSMOS grants and by RFFI grants No. 13-02-12175 and No. 15-35-21038 and also acknowledges support from the Development Program of Lomonosov Moscow State University. AJCT acknowledges support from the Spanish MINECO Projects AYA 2009-14000-C03-01/ESP and AYA 201571718R (including EU/FEDER funds). The Taiwan authors thank Taiwan's National Science Council Vanguard Program (100-2119-M-002-025) as well as the Ministry of Science and Technology (MOST) for its funding (104-2811-M-002-160). We also acknowledge the support of the National Space Organization (NSPO) of Taiwan.

In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope , UBAT, during the preliminary calibration with MAPMTs of 64 2.88 × 2.88 mm2 pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode . The simulation reproduced more than 70% of the crosstalk and explained it as a consequence of the total reflection produced by the photocathode. The result indicated that the crosstalk mechanism could be a common case in most of the contact-assembled scintillation detectors. The concept of the Inverted-Conical light guide was to suppress the total reflection by contracting the incident angle of the scintillation. We optimized the design in the simulation and fabricated a test sample. The test sample reduced 52% crosstalk with a loss of 6% signal yield. The idea of the Inverted-Conical light guide can be adapted by scintillation detectors multi-pixel, imaging-purpose scintillation detectors such as the ultra-fast GRB observatory UFFO-UBAT, whose performances are sensitive to responding time, image resolution, and geometrical modifications.

The UFFO/Lomonosov has been successfully launched into Sun synchronous orbit and is operational through tests and calibrations since its launch on Apr. 28, 2016. As a pathfinder of UFFO, it will be the first space instrument to use a fast slewing mirror which reduce the trigger latency of optical telescope, less than a second, to explore early time domain of GRB evolution. In this article, we will report in detail the first mission, UFFO/Lomonosov, for the rapid response to observe early photons from GRBs in orbit.

We will report on the setup and calibration of the instrumentation for sFLASH. The sFLASH experiment is a measurement of the air fluorescence from ∼10$^{21}$ eV artificial air showers developed in an alumina target by an electron beam provided from End Station A of the Stanford Linear Accelerator Center (SLAC). sFLASH employs Photomultiplier tubes (PMTs) to detect the fluorescence photons and an Integrating Charge Transformer (ICT) to measure the beam current. The PMTs are positioned ~10m perpendicular to shower axis are used to measure the air fluorescence photons. The absolute gain of the PMTs was measured using CRAYS at the Institute of Cosmic-Ray Research, Japan. CRAYS is a PMT photo-gain calibration system consisting of a vessel containing nitrogen gas and a 14μJ nitrogen (337.1 nm) laser. The gain of each PMT was monitored during the course of the experiment using a YAP pulser (YAlO: Ce + $^{241}$Am) potted into an ultraviolet optical filter attached to the surface of the PMT window. We expect to achieve an overall experimental uncertainty of ~6%. The ICT (Bergoz) consists of 20 turns of coil to measure the beam current. In the sFLASH experiment we set it ~1 m away from beam exit to measure the beam current just prior to entering the target material. The ICT was calibrated with 2 ns pulse generator at Jet Propulsion Laboratory. The calibration uncertainty of the ICT is ~1%.

The primary science goal of the NASA-sponsored ANITA project is measurement of ultra-high energy neutrinos and cosmic rays, observed via radio-frequency signals resulting from a neutrino- or cosmic ray- interaction with terrestrial matter (atmospheric or ice molecules, e.g.). Accurate inference of the energies of these cosmic rays requires understanding the transmission/reflection of radio wave signals across the ice-air boundary. Satellite-based measurements of Antarctic surface reflectivity, using a co-located transmitter and receiver, have been performed more-or-less continuously for the last few decades. Satellite-based reflectivity surveys, at frequencies ranging from 2--45 GHz and at near-normal incidence, yield generally consistent reflectivity maps across Antarctica. Using the Sun as an RF source, and the ANITA-3 balloon borne radio-frequency antenna array as the RF receiver, we have also measured the surface reflectivity over the interval 200-1000 MHz, at elevation angles of 12-30 degrees, finding agreement with the Fresnel equations within systematic errors. To probe low incidence angles, inaccessible to the Antarctic Solar technique and not probed by previous satellite surveys, a novel experimental approach ("HiCal-1") was devised. Unlike previous measurements, HiCal-ANITA constitute a bi-static transmitter-receiver pair separated by hundreds of kilometers. Data taken with HiCal, between 200--600 MHz shows a significant departure from the Fresnel equations, constant with frequency over that band, with the deficit increasing with obliquity of incidence, which we attribute to the combined effects of possible surface roughness, surface grain effects, radar clutter and/or shadowing of the reflection zone due to Earth curvature effects., updated to match publication version

The Antarctic Impulsive Transient Antenna (ANITA) is a NASA long-duration balloon experiment with the primary goal of detecting ultra-high-energy ($>10^{18}\,\mbox{eV}$) neutrinos via the Askaryan Effect. The fourth ANITA mission, ANITA-IV, recently flew from Dec 2 to Dec 29, 2016. For the first time, the Tunable Universal Filter Frontend (TUFF) boards were deployed for mitigation of narrow-band, anthropogenic noise with tunable, switchable notch filters. The TUFF boards also performed second-stage amplification by approximately 45 dB to boost the $\sim\,��\mbox{V-level}$ radio frequency (RF) signals to $\sim$ mV-level for digitization, and supplied power via bias tees to the first-stage, antenna-mounted amplifiers. The other major change in signal processing in ANITA-IV is the resurrection of the $90^{\circ}$ hybrids deployed previously in ANITA-I, in the trigger system, although in this paper we focus on the TUFF boards. During the ANITA-IV mission, the TUFF boards were successfully operated throughout the flight. They contributed to a factor of 2.8 higher total instrument livetime on average in ANITA-IV compared to ANITA-III due to reduction of narrow-band, anthropogenic noise before a trigger decision is made., 27 pages, 19 figures

Ultra-Fast Flash Observatory pathfinder(UFFO-p) was launched onboard Lomonosov on 28th of April, 2016, and now is under various types of calibration for detection of Gamma Ray Bursts (GRBs). Since last September UFFO-p has taken X-ray data in space with UFFO Burst Alert & Trigger telescope (UBAT), those X-rays are mostly diffused backgrounds however, the rate turns out to be higher than expected by a factor of three. We assumed cosmic rays can contribute by making the count rate higher. We did such a simulation to investigate the effect of cosmic rays. In December 2016, we irradiated fragmented high energy heavy ions at CERN on the UBAT detector. We will report the result of comparison between simulation and beam test.

One of the key aspects of the upcoming Ultra-Fast Flash Observatory (UFFO) pathfinder for Gamma Ray Bursts (GRBs) identification is the UFFO Burst Alert & Trigger Telescope (UBAT). The scientific propose of UBAT is to detect and locate as fast as possible the GRBs in the sky. This is achieved by using a coded mask aperture camera scheme with a wide field of view (FOV) and selecting a X-ray detector of high quantum efficiency and large detection area. This X-ray detector of high quantum efficiency and large detection area is called the UBAT detector. The UBAT detector consists of 48 × 48 Yttrium Oxyorthosilicate (YSO) scintillator crystal arrays and Multi Anode Photomultiplier Tubes (MAPMTs), analog electronics equipped with ASIC chips, digital electronics equipped with Field Programmable Gate Array (FPGA) chips, and a mechanical structure that supports all components of the UBAT detector. The total number of the pixels in the UBAT detector is 2304, and the total effective detection area is 191 cm2 . We will present the design and construction, and performance of the UBAT detector including the responses of the UBAT detector to X-ray sources.

The Ultra-Fast Flash Observatory (UFFO) Pathfinder for Gamma-Ray Bursts (GRBs) consists of two telescopes. The UFFO Burst Alert & Trigger Telescope (UBAT) handles the detection and localization of GRBs, and the Slewing Mirror Telescope (SMT) conducts the measurement of the UV/optical afterglow. UBAT is equipped with an X-ray detector, analog and digital signal readout electronics that detects X-rays from GRBs and determines the location. SMT is equipped with a stepping motor and the associated electronics to rotate the slewing mirror targeting the GRBs identified by UBAT. First the slewing mirror points to a GRB, then SMT obtains the optical image of the GRB using the intensified CCD and its readout electronics. The UFFO Data Acquisition system (UDAQ) is responsible for the overall function and operation of the observatory and the communication with the satellite main processor. In this paper we present the design and implementation of the electronics of UBAT and SMT as well as the architecture and implementation of UDAQ.

Astrophysics, National Taiwan University, Taipei, Taiwan. 7 Dept. of Physics, Univ. of Delaware, Newark, DE 19716, USA. 8 Dept. of Physics, Stanford University, Stanford, CA, 94305, USA. 9 Dept. of Physics and Astronomy, Univ. of Hawaii, Manoa, HI 96822, USA. 10SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA. 11Karlsruher Institut fur Technologie, Institut fur Kernphysik , 76021 Karlsruhe, Germany. 12Physics Dept., College of William & Mary, Williamsburg VA 23187, USA. 13Dept. of Physics and Astronomy, University College London, London, United Kingdom. 14Karlsruher Institut fur Technologie, Institut fur Experimentelle Kernphysik, 76128 Karlsruhe

We report on four radio-detected cosmic-ray (CR) or CR-like events observed with the Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload. Two of the four were previously identified as stratospheric CR air showers during the ANITA-I flight. A third stratospheric CR was detected during the ANITA-II flight. Here we report on characteristics these three unusual CR events, which develop nearly horizontally, 20-30~km above the surface of the Earth. In addition, we report on a fourth steeply upward-pointing ANITA-I CR-like radio event which has characteristics consistent with a primary that emerged from the surface of the ice. This suggests a possible $\tau$-lepton decay as the origin of this event, but such an interpretation would require significant suppression of the Standard Model ${\tau}$-neutrino cross section., Comment: 5pp,4 figures, referees' comments addressed, this version accepted to Phys. Rev. Letters. Supplemental PDF material available; see source files

For fifty years, cosmic-ray air showers have been detected by their radio emission. We present the first laboratory measurements that validate electrodynamics simulations used in air shower modeling. An experiment at SLAC provides a beam test of radio-frequency (RF) radiation from charged particle cascades in the presence of a magnetic field, a model system of a cosmic-ray air shower. This experiment provides a suite of controlled laboratory measurements to compare to particle-level simulations of RF emission, which are relied upon in ultra-high-energy cosmic-ray air shower detection. We compare simulations to data for intensity, linearity with magnetic field, angular distribution, polarization, and spectral content. In particular, we confirm modern predictions that the magnetically induced emission in a dielectric forms a cone that peaks at the Cherenkov angle and show that the simulations reproduce the data within systematic uncertainties., 5 pages, 7 figures

The neutrino mass hierarchy is one of the neutrino fundamental properties yet to be determined. We introduce a method to determine neutrino mass hierarchy by comparing the interaction rate of neutral current (NC) interactions, $\nu(\hat{\nu}) + p\rightarrow\nu(\hat{\nu}) + p$, and inverse beta decays (IBD), $\bar{\nu}_e + p\rightarrow n + e^+$, of supernova neutrinos in scintillation detectors. Neutrino flavor conversions inside the supernova are sensitive to neutrino mass hierarchy. Due to Mikheyev-Smirnov-Wolfenstein effects, the full swapping of $\bar{\nu}_e$ flux with the $\bar{\nu}_x$ ($x=\mu,~\tau$) one occurs in the inverted hierarchy, while such a swapping does not occur in the normal hierarchy. As a result, more high energy IBD events occur in the detector for the inverted hierarchy than the high energy IBD events in the normal hierarchy. By comparing IBD interaction rate with the mass hierarchy independent NC interaction rate, one can determine the neutrino mass hierarchy., Comment: 18 pages, 6 figures

We describe a concept for an instrument to measure the thickness of the ice shell on a planetary body such as Jupiter’s moon Europa. Unlike a high powered and massive device such as an ice-penetrating radar, the instrument would be a passive receiver of a naturally occurring signal generated by interactions of deep penetrating cosmic ray neutrinos. We discuss the basic concept and consider the instrument design requirements from the perspective of a NASA Outer Planet Orbiter Mission. We show results of simulations, compare signal-to-noise estimates, and examine possible components and configurations for the antenna, receiver, and electronics. We note some options that can be used to reduce mass and power. Finally, we present a list of issues that would need further study to produce a more concrete design.

Cosmogenic neutrinos1 are expected from ultrahigh energy cosmic rays undergoing the GZK process2,3 and anticipated to be observed by detection of the air showers from the decays of tau leptons. We use CORSIKA simulated shower structure to Calculate the coherent geosynchrotron radio emissions of the tau decay showers above 1017 eV. We present the pattern and spectrum of the radio waves and discuss their detections by radio antennae.

We report the development of laboratory astrophysics program in Taiwan. We begin with outlining Taiwan's participation in the FLASH collaboration for measuring the fluorescence yield using SLAC 28.5 GeV electron beam. We then report the domestic effort of studying cosmic ray shower properties using NSRRC 1.5 GeV electron beam.

Metastatic carcinoma involving the hyoid bone has rarely been mentioned in the literature. The most frequent malignant lesion involving the hyoid bone metastasized from the larynx, followed by the vallecula and pyriform sinus. The authors report a unique case of occult prostate cancer that presented with an anterior midline neck mass diagnosed as a thyroglossal duct cyst. Two foci of metastatic carcinoma lesions in the hyoid bone were detected after Sistrunk's operation and occult prostate cancer was confirmed by immunohistochemical staining of prostate-specific antigen. Prostate cancer with metastasis to hyoid bone has not been described previously in the literature. The authors report this case which raises important pathological considerations for diagnosis. The unique presentation also reiterates the importance of prostate cancer bone metastasis.

Observation of ultra-high energy astrophysical neutrinos and identification of their flavors have been proposed for future neutrino telescopes. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. The flavor transition mechanisms are well-classified with our model-independent parametrization. We find a new parameter R={\phi}_e/({\phi}_{\mu} + {\phi}_{\tau}) can probe directly the flavor transition in the framework of our model-independent parametrization, without the assumption of the {\nu}_{\mu}-{\nu}_{\tau} symmetry. A few flavor transition models are employed to test our parametrization with this new observable. The observational constraints on flavor transition mechanisms by the new observable is discussed through our model-independent parametrization., Comment: 22pages, 7 figures

Taiwan astroparticle radiowave observatory for geo-synchrotron emissions (TAROGE) is an antenna array on the high mountains of Taiwan’s east coast for the detection of ultra-high energy cosmic rays (UHECRs) in an energy above [Formula: see text] eV. The antennas point toward the ocean to detect radiowave signals emitted by the UHECR-induced air-shower as a result of its interaction with the geomagnetic field. Looking down from the coastal mountain, the effective area is enhanced by collecting both direct-emission as well as the ocean-reflected signals. This instrument also provides the capability of detecting earth-skimming tau-neutrino through its subsequent tau-decay induced shower. In order to prove the detection concept, initial two stations were successfully built at 1000 m elevation near Heping township, Taiwan, in 2014–2015. Each station consists of 12 log-periodic dipole array antennas for 110–300 MHz. The stations have been operating smoothly for radio survey and optimization of instrumental parameters. In this report, we discuss the design of TAROGE, the performance of the prototype station and the future prospect.

I.H. Park, S. Ahmad, P. Barrillon, S. Brandt, C. Budtz-Jorgensen, A.J. Castro-Tirado, P. Chen, Y.J. Choi, P. Connell, S. Dagoret-Campagne, C. Eyles, B. Grossan, M.–H.A. Huang, A. Jung, S. Jeong, J.E. Kim, M.B. Kim, S.-W. Kim, Y.W. Kim, A.S. Krasnov, J. Lee, H. Lim, E.V. Linder, T.–C. Liu, N. Lund, K.W. Min, G.W. Na, J.W. Nam, M.I. Panasyuk, J. Ripa, V. Reglero, J.M. Rodrigo, G.F. Smoot, J.E. Suh, S. Svertilov, N. Vedenkin, M.–Z. Wang, I. Yashin Ewha Womans University, Seoul, Korea University of Paris-Sud 11, Orsay, France Technical University of Denmark, Copenhagen, Denmark Instituto de Astrofisica de Andalucia CSIC, Granada, Spain National Taiwan University, Taipei, Taiwan Korea Advanced Institute of Science and Technology, Daejeon, Korea University of Valencia, Valencia, Spain University of California, Berkeley, USA National United University, Miao-Li, Taiwan Yonsei University, Seoul, Korea Moscow State University, Moscow, Russia E-mail: ipark@ewha.ac.kr

The Ultra-Fast Flash Observatory (UFFO) is a space observatory for optical follow-ups of gamma ray bursts (GRBs), aiming to explore the first 60 seconds of GRBs optical emission. UFFO is utilized to catch early optical emissions from GRBs within few sec after trigger using a Gimbal mirror which redirects the optical path rather than slewing entire spacecraft. We have developed a 15 cm two-axis Gimbal mirror stage for the UFFO-Pathfinder which is going to be on board the Lomonosov satellite which is to be launched in 2013. The stage is designed for fast and accurate motion with given budgets of 3 kg of mass and 3 Watt of power. By employing stepping motors, the slewing mirror can rotate faster than 15 deg/sec so that objects in the UFFO coverage (60 deg × 60 deg) can be targeted in ~1 sec. The obtained targeting resolution is better 2 arcmin using a close-loop control with high precision rotary encoder. In this presentation, we will discuss details of design, manufacturing, space qualification tests, as well as performance tests.