Session J10: Particle Astrophysics

Live

Astrophysical observations at the highest energies are an excellent probe of fundamental physics. With its sensitivity to gamma rays with energies of $\sim~300$ GeV to past 100 TeV---as well as its large instantaneous field-of-view of $\sim2$ sr and a duty cycle over 95\%---the High Altitude Water Cherenkov (HAWC) Observatory is uniquely suited to search for signatures of beyond-the-standard-model physics in astrophysical environments. In its first five years of operations, we have used HAWC data to constrain the local Primordial Black Hole burst rate density, performed indirect dark matter (DM) searches from a multitude of targets including dwarf galaxies, the galactic halo, the Virgo cluster, and the Sun, and to test for possible signatures of Lorentz Invariance Violation as well as constrain its energy scale. HAWC has also joined forces with other gamma-ray experiments to cover a wide range of DM masses from multi-GeV to multi-TeV. We present recent results for this diverse set of searches for new physics, placing some of the strongest limits in the world.   

Live

The Radar Echo Telescope is a proposed detector that aims to target neutrinos at energies at and above 10$^{16}$ eV, in an effort to extend the neutrino spectrum beyond the highest energy neutrinos detected to date. When a high-energy particle (like a neutrino) interacts in a dense material, it produces a relativistic cascade of charged particles, leaving an ionization trail behind. Radio waves can be transmitted toward---and reflected from---this ionization trail, to be detected by distant receivers. This radar echo method can be used to detect ultra high-energy neutrino interactions in the ice. As a pilot implementation, the Radar Echo Telescope for Cosmic Rays (RET-CR) aims to detect radar echoes from the ionized trail left in the ice as an ultra-high energy cosmic ray air shower core impacts the surface of a high-elevation ice sheet, creating a cascade in the ice. In this talk we will present the concept for RET-CR and discuss it as a pathfinder for the eventual Radar Echo Telescope for Neutrinos (RET-N), which seeks to detect neutrinos at energies of 10$^{16}$ eV and beyond.   

Live

Indicators of extragalactic neutrino production, ultra-high energy tau neutrinos play an important role in the field of multi-messenger astrophysics. The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is novel concept that searches for radio emission from upgoing tau leptons produced by tau neutrino interactions in the Earth using a compact antenna array on a high elevation mountain. The prototype design is based on an interferometric trigger that coherently sums the signals from 4 dual-polarized antennas operating in the 30-80 MHz range located at the White Mountain Research Station. The array was upgraded in Fall 2019 to use custom electrically short dipole antennas and longer baselines. We present the current performance of the array, which has a goal of triggering on impulsive transients such as cosmic rays to demonstrate the performance of a full scale BEACON instrument.   

Live

The astrophysical neutrino flux measured by IceCube has demonstrated the important role neutrinos play in multi-messenger astrophysics, but a larger exposure enabled through new technology is needed to expand the reach of neutrino telescopes to higher energies. Planned for the NSF-run Summit Station in Greenland, the Radio Neutrino Observatory in Greenland (RNO-G) consists of 35 autonomous stations that will comprise the first neutrino telescope with access to the Northern sky at energies greater than 100 PeV. Each station includes a deep component deployed with a phased array trigger and a surface component for event characterization and cosmic ray identification. In addition to discussing the unique role RNO-G will play in multi-messenger observations, we will present the instrument design and deployment timeline, including the plans for the first several stations to be deployed in the summer of 2020.   

Live

Aiming at detecting ultra-high energy (UHE) neutrinos ($E_\nu > 10^{17}$ eV), ARA is an experiment based at the South Pole consisting of antenna stations buried deep in the ice ($\sim 200$ m). These antennas are designed to detect radio waves emitted by relativistic particle showers that are byproducts of UHE neutrino interactions with ice. In this talk, I will discuss the latest results of a search for a diffuse flux of UHE neutrinos with four years of data from two stations. This work resulted in the best limit set by an in-ice radio experiment above $\sim 10^{17}$ eV.   

Live

IceCube has discovered a flux of astrophysical neutrinos, and more recently has used muon-neutrino datasets to present evidence for one source; a flaring blazar known as TXS 0506+056. However, the sources responsible for the majority of the astrophysical neutrino flux remain elusive. Opening up new channels for detection can lead to improved sensitivity and increase the chance of a discovery. In this work I present the preliminary sensitivity of a new IceCube neutrino dataset using cascade events produced from NC interactions of all flavors and CC interactions with flavors other than muon-neutrino. Despite the reduced angular resolution of cascade events, the resulting dataset has a lower southern sky energy threshold and a lower background which offers an improved sensitivity to sources in the southern sky when compared to muon-neutrino datasets. This improvement is particularly promising for identifying transient neutrino sources in the southern sky and neutrino production from the galactic plane.   

Live

ESTES is an ongoing event selection for use in the IceCube detector searching for astrophysical muon neutrinos at TeV energies that interact within the detector volume. These events, also referred to as starting tracks, are composed of an initial hadronic cascade followed by an outgoing muon. The high angular resolution achieved from muons and high purity of events in the southern sky allow us to perform a search for neutrino sources. Due to the high purity of ESTES in the southern sky, we will be able to unlock a region of the neutrino sky previously not used in IceCube. An estimate of our sensitivity to these searches with a comparison to previous IceCube results will be shown. In addition, the good energy resolution of ESTES allows us to perform a measurement of the astrophysical diffuse neutrino spectrum down to TeV energies. This will provide insights as to whether there exists a hardening of the diffuse neutrinos towards lower energies. We will also be showing sensitivities to the astrophysical diffuse neutrino spectrum. Advancements in particle identification techniques and systematic uncertainties and the impact on our result will also be shown.   

Not Participating

Experiment T-576, performed at the SLAC National Accelerator Laboratory, investigated the technique of using radar to detect high-energy particle cascades. This was done by directing high energy electrons from a linear accelerator into a high-density polyethylene target and reflecting radio waves off the ionization left in the wake of the resulting cascade. The goal of the experiment was to validate a new ultra-high energy neutrino detection technique. We present here a Finite Difference Time Domain (FDTD) simulation that was developed to validate T-576 using the commercial EM solver software XFdtd. The primary features of the experiment (the target, plasma, and antennas) were implemented directly into the simulation, which returns a clear signal in good agreement with the results of the T-576 experiment and theoretical expectations. In this talk, T-576 will be briefly introduced before we detail the FDTD simulation, assumptions, validation, and results.   

Not Participating

With a distributed array of photosensors over more than 1 cubic-kilometre of the deep Antarctic ice sheet near South Pole Station, IceCube is designed to detect neutrinos above approximately 100 GeV to beyond the PeV-scale. Key to reconstructing the relatively rare neutrino interactions is applying detailed knowledge of the photon transport in the glacial Cherenkov medium. Models based on in-situ calibrations provide the optical properties of the deep ice used to describe the photon propagation. Harnessing the parallel computing power of graphical processing units makes it possible to fully simulate the photon evolution of individual events on-the fly and has opened the possibility of improved precision in reconstructing the event properties. This method of ``direct reconstruction'' (or DirectReco) may also be used for detailed studies of ice-related systematic errors. Presented will be a description of the DirectReco algorithm as well as the initial estimations of the performance of the IceCube event reconstruction.