UNIVERSITY PARK, Pa. — Stephanie Wissel, associate professor of physics and of astronomy and astrophysics in the Penn State Eberly College of Science, is part of an international research team that was awarded a 14 million euros — equivalent to $16.3 million — European Research Council (ERC) Synergy Grant to support a multi-institutional collaboration focused on detecting rare neutrinos. These ultra-high-energy subatomic particles are emitted by high-energy sources in the universe, like supernovae or the environments around black holes, but neutrinos have no charge and are nearly massless, making them incredibly difficult to find. A portion of the grant will fund Wissel’s work on building a phased array, an assortment of antennas that digitally form beams to enhance the signal from neutrinos, at Penn State.
Wissel, who directs the Center for Multimessenger Astrophysics in the Penn State Institute for Gravitation and the Cosmos, is the only co-primary investigator based in a non-European Union country on the project, titled “Opening a new window on the violent Universe with the Hybrid Elevated Radio Observatory for Neutrinos (HERON).” The award is shared among Wissel and three other co-primary investigators and their respective institutions: Kumiko Kotera, who serves as the coordinator the project, from the Institut d’Astrophysique de Paris in the Centre National de la Recherche Scientifque in France; Olivier Martineau from the Université Sorbonne in France; and Jaime Álvarez-Muñiz from the Universidade de Santiago de Compostela in Spain. The team is also working with Federico Sanchez from the Comisión Nacional de Energía Atómica, in Argentina. Their project was one of 66 awarded out of 712 proposals.
“HERON is an ambitious project where we have a shot at discovering the most energetic neutrinos,” Wissel said. “Since neutrinos rarely interact with matter, they can travel across the universe unimpeded and they can probe the deep inner workings of dense and violent environments like massive stellar explosions, jets driven by black holes and more.”
To detect neutrinos, highly specialized equipment is needed. The HERON project’s goal is to build a new observatory atop the mountains of San Juan province in Argentina. A network of antennas distributed along nearly 45 miles of the mountainous region will observe the radio flashes that neutrinos can produce when they impact the Earth’s crust. HERON will also connect to the global multi-messenger network — a system of observatories that look for different types of cosmic signals allowing events detected by one to be followed up by others — responding to and sending alerts of possible neutrino emitters like gamma ray bursts, active galaxies and other high-energy cosmic events.
There are two components to the HERON telescope: the phased array Wissel is leading and a standalone antenna array that improves the telescope’s ability to figure out where the neutrino came from.
HERON will combine the approaches of two previous projects, both of which are concepts for large-scale neutrino detectors that can also detect cosmic rays: BEACON and GRAND. Wissel and her team demonstrated that they could deploy phased arrays on an elevated mountain surface with a prototype for BEACON at the White Mountain Research Center in California. GRAND, the second project, showed that an extended network of autonomous radio antennas could detect cosmic rays, which are more prevalent than neutrinos and provide proof-of-concept for the experimental approach. The combination of these two technologies — the phased system and the ability to reconstruct neutrinos with high precision and reject background noise with antennas separated by long distances through the standalone array — aim to increase neutrino detection and identification.
“My understanding is that neutrinos are the second most abundant form of matter in the universe, surpassed only by photons,” said Aleksandra Slavković, associate dean for research in the Eberly College of Science. “This project brings to Penn State an exciting international collaboration in which Dr. Wissel and her team are leading the development and implementation of a critical component of the HERON instrument. HERON will be one of the most sensitive instruments in the world for detecting ultra-high-energy neutrinos — potentially enabling their first direct observation. It is an extraordinary scientific opportunity; one aligned with discoveries of Nobel-level significance.”