Speaker
Description
In this work, we present a search for high-energy astrophysical neutrinos coincident with the ultrahigh-energy event KM3-230213A using data from Super-Kamiokande (SK).
KM3-230213A is a muon neutrino with an estimated energy of approximately 220 PeV, observed by the KM3NeT observatory. As the most energetic neutrino event detected to date, its origin remains unknown. Possible production scenarios include emission from a cosmic accelerator distinct from those producing the cosmic neutrinos observed so far, interactions of ultra-high-energy cosmic rays with the cosmic microwave background, or emission from a point source.
Using SK data, we perform the search under the point source assumption to investigate whether an excess neutrino flux is present in the GeV energy range.
We first conduct a time-integrated search for continuous neutrino emission from the direction of KM3-230213A using SK data collected between 1996 and 2019. The analysis employs an unbinned maximum-likelihood method that incorporates all three high-energy SK data samples, with the energy spectrum fitted by the relative event fractions among the samples.
In addition, we perform a time- and direction-coincident search to examine the possibility of transient neutrino emission associated with KM3-230213A. In this search, events occurring within a ±500 s time window centered on the detection time of KM3-230213A are examined.
No statistically significant excess is observed in either search. Consequently, upper limit on the neutrino flux in the GeV energy range is set in the direction of KM3-230213A.