Speaker
Description
POEMMA-Balloon with Radio (PBR) is a scaled-down version of the Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) design, optimized to be flown as a payload on one of NASA's sub-orbital super pressure balloons circling over the southern oceans for a mission duration of as long as 50 days. One of the main science objectives of PBR is to follow up astrophysical event alerts in search for neutrinos of very high energy ($10^8 \lesssim E_\nu /{\rm GeV} \lesssim 10^{10}$). Of particular interest for anticipated PBR observations, the KM3NeT Collaboration has recently reported the detection of the neutrino KM3-230213A with $10^{8.1} \lesssim E_\nu/{\rm GeV} \lesssim 10^{8.9}$. Such an unprecedented event is in tension with 90\% CL upper limits on the cosmic neutrino flux from IceCube and the Pierre Auger Observatory, unless it was produced by a transient activity in its source. We calculate the PBR horizon-range sensitivity to expose a population of similar bursting sources in the Universe. We also consider the possibility that the KM3NeT/ARCA event was produced by the decay of superheavy dark matter broadly distributed in the Galactic halo.
