Enhanced low-energy supernova burst detection in large liquid argon time projection chambers enabled by Q-Pix
Not Available
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Engineering topics
Varner, G. S.
Publications and source records attributed to Varner, G. S..
Analysis of a tau neutrino origin for the near-horizon air shower events observed by the fourth flight of the Antarctic Impulsive Transient Antenna
In this work, we study in detail the sensitivity of the Antarctic Impulsive Transient Antenna (ANITA) to possible ν τ point source fluxes detected via τ-lepton-induced air showers. This investigation is framed around the observation of four upward-going extensive air shower events very close to the horizon seen in ANITA-IV. We find that these four upgoing events are not observationally inconsistent with τ-induced EASs from Earth-skimming ν τ both in their spectral properties as well as in their observed locations on the sky. These four events as well as the overall diffuse and point source exposure to Earth-skimming ν τ are also compared against published ultrahigh-energy neutrino limits from the Pierre Auger Observatory. While none of these four events occurred at sky locations simultaneously visible by Auger, the implied fluence necessary for ANITA to observe these events is in strong tension with limits set by Auger across a wide range of energies and is additionally in tension with ANITA’s Askaryan in-ice neutrino channel above 10 19 eV. We conclude by discussing some of the technical challenges with simulating and analyzing these near horizon events and the potential for future observatories to observe similar events.
79 ASTRONOMY AND ASTROPHYSICS↗
A search for ultrahigh-energy neutrinos associated with astrophysical sources using the third flight of ANITA
The ANtarctic Impulsive Transient Antenna (ANITA) long-duration balloon experiment is sensitive to interactions of ultrahigh-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 potential IceCube-identified neutrino sources TXS 0506+056 and NGC 1068, 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. Finally, we proceed to place upper limits on the source classes. We further comment on potential application of this methodology to more sensitive future instruments.
79 ASTRONOMY AND ASTROPHYSICS↗
Unusual Near-Horizon Cosmic-Ray-like Events Observed by ANITA-IV
ANITA’s fourth long-duration balloon flight in 2016 detected 29 cosmic-ray (CR)-like events on a background of 0.37 - 0.17 + 0.27 anthropogenic events. CRs are mainly seen in reflection off the Antarctic ice sheets, creating a phase-inverted waveform polarity. However, four of the below-horizon CR-like events show anomalous noninverted polarity, a p = 5.3 × 10 - 4 chance if due to background. Furthermore, all anomalous events are from locations near the horizon; ANITA-IV observed no steeply upcoming anomalous events similar to the two such events seen in prior flights.
79 ASTRONOMY AND ASTROPHYSICS↗
The simulation of the sensitivity of the Antarctic Impulsive Transient Antenna (ANITA) to Askaryan radiation from cosmogenic neutrinos interacting in the Antarctic Ice
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. Lastly, 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.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Constraints on the ultrahigh-energy cosmic neutrino flux from the fourth flight of ANITA
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 ultrahigh-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 ${0.64}_{-0.45}^{+0.69}$ and an analysis efficiency of 82 ± 2 % . The second analysis has a background estimate of 0.34 $^{+0.66}_{-0.16}$ and an analysis efficiency of 71 ± 6 % . 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 ultrahigh-energy neutrinos at energies above 10 19.5 eV .
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Comprehensive analysis of anomalous ANITA events disfavors a diffuse tau-neutrino flux origin
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 Antarctic ice sheet. These events may be of ν τ origin, in which the neutrino interacts within the Earth to produce a τ 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 ν τ flux detected via τ-lepton-induced air showers within the bounds of standard model uncertainties. Furthermore, by comparing this estimate with the acceptance of Pierre Auger Observatory and IceCube and assuming standard model interactions, we conclude that a ν τ origin of these events would imply a neutrino flux at least two orders of magnitude above current bounds.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
HiCal 2: An instrument designed for calibration of the ANITA experiment and for Antarctic surface reflectivity measurements
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 high-voltage (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-2, both direct and reflected from the surface, at distances varying from 100–700 km, providing a large dataset for surface reflectivity measurements. In view of this, we present details on the design, construction and performance of HiCal-2.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Observation of an Unusual Upward-Going Cosmic-Ray-like Event in the Third Flight of ANITA
We report here 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 could be produced by the atmospheric decay of an upward-propagating τ lepton produced by a ν τ interaction, although their relatively steep arrival angles create tension with the standard model neutrino cross section. Each of the two events have a posteriori background estimates of ≲ 10 - 2 events. If these are generated by τ -lepton decay, then either the charged-current ν τ 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.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Studies of MCP-PMTs in the miniTimeCube neutrino detector
This report highlights two different types of cross-talk in the photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube detector has 24 8×8-anode Photonis MCP-PMTs Planacon XP85012, totalling 1536 individual pixels viewing the 2-liter cube of plastic scintillator.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Antarctic surface reflectivity calculations and measurements from the ANITA-4 and HiCal-2 experiments
We report that 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 R. The first HiCal mission (HiCal-1, Jan. 2015) yielded a sample of 100 such pairs, resulting in estimates of R at highly glancing angles (i.e., zenith angles approaching 90°), with measured reflectivity for those events which exceeded extant calculations [P. W. Gorham et al., Journal of Astronomical Instrumentation, 1740002 (2017)]. The HiCal-2 experiment, flying from December 2016–January 2017, provided an improvement by nearly 2 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 [D. Z. Besson et al., Radio Sci. 50, 1 (2015)]. 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. Lastly, multiplying our flat-smooth reflectivity by improved Earth curvature and surface roughness corrections now provides significantly better agreement between theory and the HiCal-2 measurements.
47 OTHER INSTRUMENTATION↗
Picosecond timing of microwave Cherenkov impulses from high-energy particle showers using dielectric-loaded waveguides
Here, we report on the first measurements of coherent microwave impulses from high-energy particle-induced electromagnetic showers generated via the Askaryan effect in a dielectric-loaded waveguide. Bunches of 12.16 GeV electrons with total bunch energy of ∼10 3 – 10 4 GeV were preshowered in tungsten, and then measured with WR-51 rectangular (12.6 mm by 6.3 mm) waveguide elements loaded with solid alumina (Al 2 O 3 ) bars. In the 5–8 GHz 𝑇𝐸 10 single-mode band determined by the presence of the dielectric in the waveguide, we observed band-limited microwave impulses with amplitude proportional to bunch energy. Signals in different waveguide elements measuring the same shower were used to estimate relative time differences with 2.3 ps precision. These measurements establish a basis for using arrays of alumina-loaded waveguide elements, with exceptional radiation hardness, as very high precision timing planes for high-energy physics detectors.
43 PARTICLE ACCELERATORS↗
Constraints on the diffuse high-energy neutrino flux from the third flight of ANITA
The Antarctic Impulsive Transient Antenna, a NASA long-duration balloon payload, searches for radio emission from interactions of ultrahigh-energy neutrinos in polar ice. The third flight of the Antarctic Impulsive Transient Antenna was launched in December 2014 and completed a 22-day flight. Here, 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 background of 0.7$+0.5\atop{-0.3}$. Though consistent with the background estimate, the event remains compatible with a neutrino hypothesis even after additional postunblinding scrutiny.
47 OTHER INSTRUMENTATION↗
Characteristics of Four Upward-Pointing Cosmic-Ray-like Events Observed with ANITA
Not Available
Gorham, P. W.↗
Energy and flux measurements of ultra-high energy cosmic rays observed during the first ANITA flight
Not Available
Schoorlemmer, H.↗
Invited Article: miniTimeCube
We present the development of the miniTimeCube (mTC), a novel compact neutrino detector. The mTC is a multipurpose detector, aiming to detect not only neutrinos but also fast/thermal neutrons. Potential applications include the counterproliferation of nuclear materials and the investigation of antineutrino short-baseline effects. The mTC is a plastic 0.2% 10 B - doped scintillator (13 cm) 3 cube surrounded by 24 Micro-Channel Plate (MCP) photon detectors, each with an 8×8 anode totaling 1536 individual channels/pixels viewing the scintillator. It uses custom-made electronics modules which mount on top of the MCPs, making our detector compact and able to both distinguish different types of events and reject noise in real time. The detector is currently deployed and being tested at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) nuclear reactor (20 MW th ) in Gaithersburg, MD. A shield for further tests is being constructed, and calibration and upgrades are ongoing. The mTC's improved spatiotemporal resolution will allow for determination of incident particle directions beyond previous capabilities.
47 OTHER INSTRUMENTATION↗