First Double Cascade Tau Neutrino Candidates in IceCube and a New Measurement of the Flavor Composition

• Main Author: Stachurska, Juliana
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: arXiv 2019
• Subjects: High Energy Astrophysical Phenomena astro-ph.HE; High Energy Physics - Experiment hep-ex; FOS Physical sciences; South Pole; South pole
• Online Access: https://dx.doi.org/10.48550/arxiv.1908.05506; https://arxiv.org/abs/1908.05506

The IceCube Neutrino Observatory at the South Pole, which detects Cherenkov light from charged particles produced in neutrino interactions, firmly established the existence of an astrophysical high-energy neutrino component. The expected neutrino flavor composition on Earth is $ν_e:ν_μ:ν_τ$ of about 1:1:1 for neutrinos produced in astrophysical sources through pion decay. A measurement of the flavor composition on Earth can provide important constraints on sources and production mechanisms within the standard model, and can also constrain various beyond-standard-model processes. Here the measurement of the flavor composition performed on IceCube's High-Energy Starting Events sample with a livetime of about 7.5 years is presented. IceCube is directly sensitive to each neutrino flavor via the single cascade, track and double cascade event topologies. In IceCube, $ν_τ$-CC interactions above $\sim$ 100 TeV can produce resolvable double cascades, breaking the degeneracy between $ν_e$ and $ν_τ$ present at lower energies. IceCube's first two identified double cascades are presented and the properties of the two $ν_τ$ candidates are discussed. : Presented at the 36th International Cosmic Ray Conference (ICRC 2019). See arXiv:1907.11699 for all IceCube contributions