Context
In the scenario of multi-messenger astronomy, high-energy neutrinos provide a unique window into hadronic processes occurring in the most extreme astrophysical environments. These neutrinos are thought to originate from the same sites that accelerate cosmic rays, or their surroundings, supplied with sufficient target material or radiation fields to convert a fraction of the energy into secondary particles, making these regions potential neutrino sources. Understanding the physical processes behind their production, however, requires extensive observational data, as astrophysical sources exhibit complex and diverse emission behaviors. Regardless, being neutral and weakly-interacting, neutrinos can travel cosmological distances without being absorbed or deflected, preserving information about their origins. Their detection can therefore help pinpoint the sources of cosmic rays, even at the highest energies. To address this need, neutrino telescopes are being constructed worldwide at multiple sites. In particular, the KM3NeT Collaboration, relying on the experience of the ANTARES telescope, is instrumenting two Cherenkov neutrino telescopes in the deep waters of the Mediterranean Sea: KM3NeT/ARCA and KM3NeT/ORCA. KM3NeT/ARCA (Astroparticle Research with Cosmics in the Abyss), mainly dedicated to neutrino astronomy, will have a volume of a cubic kilometer and will be sensitive to neutrinos across a wide range of energies, from 100 GeV up to multi-PeV. Thanks to its modular design, KM3NeT/ARCA is already collecting data during construction and, in the coming years, is expected to complement existing observations and provide new insights into unanswered questions.
My Ph.D. research
My research focuses on the searches for point-like sources of cosmic neutrinos with KM3NeT/ARCA, specifically targeting blazars as potential extragalactic neutrino factories. With the aim of obtaining expected neutrino fluxes from high-frequency-peaked BL Lacs, to be tested in the analysis, I've modeled the neutrino emission from the blazar PKS 2155-304 using the LeHa-Paris numerical code, which simulates radiative processes in jets of supermassive black holes and the associated photo-meson interactions. This framework is then extended to a broader subclass of sources selected from the 3HSP catalogue. The phenomenological approach allows the determination of expected neutrino fluxes, which are subsequently used as templates for a stacking binned likelihood analysis with the data from KM3NeT/ARCA, considering its configurations with 6, 8, 19, and 21 deployed detection units.
As an additional study, an unbinned likelihood analysis was implemented to improve KM3NeT point source sensitivity with respect to a binned approach. Using both binned and unbinned likelihood-based statistical methods, the detector performances to identify point-like neutrino sources are investigated. Finally, the first implementation of a time-dependent unbinned likelihood framework has been developed, laying the basis for more sensitive neutrino point source searches as well as searches for neutrino flares with KM3NeT/ARCA.