Analysis of IceCube neutrino data with focus on the study of the angular uncertainty

• Main Author: SOMMANI, GIACOMO
• Other Authors: Franckowiak, Anna, Razzano, Massimiliano
• Format: Text
• Language: Italian
• Published: Pisa University 2022
• Subjects: FISICA; Amundsen Scott South Pole Station; Amundsen-Scott; Amundsen-Scott South Pole Station; Antarctic; South Pole; The Antarctic; Antarc*; Ice Sheet; South pole
• Online Access: http://etd.adm.unipi.it/theses/available/etd-10032022-153127/

IceCube is a neutrino observatory with 5160 optical sensors embedded in 1 km^3 of the Antarctic ice sheet close to the Amundsen-Scott South Pole Station. IceCube detects neutrino interactions with the surrounding ice or nearby bedrock through detection of Cherenkov radiation of charged secondary particles produced in the interaction. The IceCube Neutrino Observatory announced a significant detection of a diffuse astrophysical neutrino flux above 30 TeV in 2013. However, having not yet identified any sources at the 5-sigma level, their origin is still unknown. Multimessenger observations can play a significant role in this search. IceCube identifies events with a higher probability of being astrophysical and updates the astronomical community with realtime alerts acting as triggers for follow-up observations. However, an accurate localization with appropriate angular errors is necessary. Neutrinos have three flavors, electron, muon, and tau, and can interact with charged or neutral currents (CC or NC). In the case of a CC interaction, the respectively charged lepton is produced. At high energies, the charged lepton and neutrino directions are strongly correlated. A high-energy muon (with energies larger than TeV) can travel in ice for several kilometers and emit light along its track via the Cherenkov effect and indirectly from the particles produced in stochastic energy losses. Thus, the recorded light from an ultra-relativistic muon has a track signature. The best estimations of neutrino directions result from the reconstruction of muon tracks. The system currently used by IceCube to estimate angular uncertainties is known as Millipede. Maximizing a likelihood, Millipede fits the stochastic energy losses among the muon's track. This system implemented in IceCube has two main disadvantages: it is hard to study and characterize using large Monte Carlo samples because of its high computational cost, and it strongly depends on systematic uncertainties. It is possible to reconstruct the direction using a completely ...