Characterization of the Astrophysical Diffuse Neutrino Flux using Starting Track Events in IceCube

A measurement of the diffuse astrophysical neutrino spectrum is presented using IceCube data collected from 2011-2022 (10. 3 years). We developed novel detection techniques to search for events with a contained vertex and exiting track induced by muon neutrinos undergoing a charged-current interaction. Searching for these starting track events allows us to not only more effectively reject atmospheric muons but also atmospheric neutrino backgrounds in the southern sky, opening a new window to the sub-100 TeV astrophysical neutrino sky. The event selection is constructed using a dynamic starting track veto and machine learning algorithms. We use this data to measure the astrophysical diffuse flux as a single power law flux (SPL) with a best-fit spectral index of = 2. 58 ^+0. 10-₀. ₀₉ and per-flavor normalization of ^Astro₏₄ₑ-₅₋₀ₕ₎ₑ = 1. 68 ^+0. 19-₀. ₂₂ 10^-18 GeV^-1 cm^-2 s^-1 sr^-1 (at 100 TeV). The sensitive energy range for this dataset is 3 - 550 TeV under the SPL assumption. This data was also used to measure the flux under a broken power law, however we did not find any evidence of a low energy cutoff.