Characterization of the astrophysical diffuse neutrino flux using starting track events in IceCube

Résumé fourni par la source

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 $\ensuremath{\gamma}=2.5{8}_{\ensuremath{-}0.09}^{+0.10}$ and per-flavor normalization of ${\ensuremath{\phi}}_{\mathrm{per}\text{-flavor}}^{\text{Astro}}=1.6{8}_{\ensuremath{-}0.22}^{+0.19}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\ifmmode\times\else\texttimes\fi{}{\mathrm{GeV}}^{\ensuremath{-}1}\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}\text{ }{\mathrm{sr}}^{\ensuremath{-}1}$ (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.

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