Neutrinos provide a unique window into the cosmos. They are able to travel cosmological
distances unimpeded, due to their small cross-section, and point back towards their sources,
since they are electrically neutral. Neutrinos are naturally produced by cosmic rays
interacting with ambient gas and photons in astrophysical sources and through interactions in
extragalactic propagation. In particular, ultrahigh energy neutrinos, with energies $>10$ PeV,
are smoking gun signatures of ultrahigh energy cosmic rays and probe particle physics beyond
LHC energies. Though an ultrahigh energy neutrino flux is expected based on observations
of ultrahigh energy cosmic rays, none have yet been observed.
Neutrinos arriving at Earth can initiate particle showers. If such a shower develops in a dense dielectric
medium, such as glacial ice, it will produce a pulse of radio emission via the Askaryan effect. Radio
waves have long, km-scale attenuation lengths in ice, so that radio detectors embedded in ice can
efficiently monitor enormous volumes for neutrino interactions. The Askaryan Radio Array (ARA) is one
such detector, located at the South Pole. First deployed in 2013, ARA consists of five independent stations
consisting of strings of antennas roughly 200 m below the ice surface. ARA has brought the radio detection
technique to maturity and has implemented powerful new techniques, in particular an interferometric trigger,
which have significantly increased its sensitivity. After nearly a decade of observation, ARA has accumulated
25 station-years of data and is poised to make the first ultrahigh energy neutrino detection, or set
world-leading limits on neutrinos in the 1-100 EeV energy range.
The Radio Neutrino Observatory in Greenland (RNO-G) builds on the heritage of ARA, as well as the ARIANNA detector.
Currently deploying at Summit Station in Greenland, RNO-G will consist of 35 independent stations combining
the interferometric trigger pioneered by ARA and antennas deep in the ice with surface channels. These complementary
systems maximize RNO-G's neutrino sensitivity while enabling improved background rejection and event reconstruction.
With just 7 stations deployed, RNO-G is already the largest radio neutrino detector in the world and will have the
best neutrino sensitivity of any ultrahigh energy detector. This will enable RNO-G to probe a diverse range of
astrophysical models for the sources of cosmic rays. Additionally, RNO-G is the only ultrahigh energy neutrino monitor
of the Northern sky, giving it a unique place in the multimessenger landscape of the next decade.
Below are some selected results from my work:
