Session D07: High Energy Particle Astrophysics

Cosmic Neutrino Searches at the Highest Energies

Neutrinos trace the acceleration of hadrons in the high-energy universe. Accelerators powered by neutron stars or supermassive black holes, for instance, may explain the recent discovery of a TeV-PeV neutrino flux. Even higher-energy neutrinos, if discovered, may uncover the origin of the highest-energy hadrons ever observed. High-energy neutrino searches rely on enormous volumes of naturally occurring material, from the waters of the Mediterranean, to rock in the Argentinian mountains, to the vast ice sheet of Antarctica. In this talk, I will review these experiments and discuss future concepts aimed at understanding these great cosmic engines and exploring particle interactions at the highest energies.   

Highlights from the HAWC Observatory

The High Altitude Water Cherenkov (HAWC) Observatory enters its fourth year of operation since its inauguration in 2015. Located on the Volcan Sierra Negra in Mexico, HAWC is a versatile instrument primarily designed for the observation of the TeV gamma-ray sky. With a wide field-of-view, high duty-cycle, and large energy range, HAWC surveys 2/3rd of the sky and monitors for variable sources and transients. HAWC is a powerful instrument to study key aspects of astrophysics and particle physics, including the production, propagation, and interaction of cosmic rays, searches for dark matter, and Lorentz invariance violation. It has unique capabilities to observe extended sources and pushes energy measurements to unexplored regions, which led e.g. to the discovery of TeV halos around middle-aged nearby pulsars and shed new light on the positron excess puzzle. An outrigger array is currently being deployed to improve the high energy response even further. HAWC is looking at a variety of galactic and extragalactic objects, such as PWN, SNR, binaries, blazars, GRBs, or the Fermi-bubbles. New sources are discovered, some of which are unidentified and are being investigated jointly with other gamma-ray instruments such as IACTs and satellites. Analysis of GRBs, gravitational wave events, and neutrino events are also performed. This talk will present the status, highlight the recent results, and discuss future prospects of the experiment.   

New results from ultra-high energy cosmic ray physics

Ultra-high energy cosmic rays (UHECRs) are the most energetic particles observed in nature and encompass some of the greatest puzzles of modern physics. Since their first observation in the 1960s, several experiments have been performed in order to enlarge the statistics and improve the quality of their detection. The study of UHECRs contributes to a better understanding of the Universe regarding the identity of astrophysical sources and the mechanisms of production, acceleration and propagation in the interstellar environment, but also the study of fundamental physics at energies that cannot be achieved at today's accelerators. In this talk, I will present the most recent measurements of the energy spectrum and composition observables of cosmic rays with the highest energies and the searches for anisotropies in the distribution of their arrival directions. Special attention will be given to the first observation of a large scale anisotropy signal recently reported by the Pierre Auger Collaboration. I will discuss the present scenario and some of the experimental efforts for the upcoming years towards an understanding of the nature and origin of the UHECRs.