Search for Diffuse Galactic Neutrinos with the Full ANTARES Telescope Dataset

TL;DR

This work analyzes the final 15-year ANTARES upgoing neutrino dataset with a template-based unbinned maximum-likelihood framework to test several Galactic diffuse emission models, including KRA$_\text{\gamma}$ (with spatially varying diffusion), Diffuse plus Unresolved Sources (DiffUSE), and CRINGE, against a $ abla$-shaped grid of spatial-energy templates. The analysis uses three event channels (tracks and two shower samples), constructs detector-convolved signal PDFs and background PDFs, and employs pseudo-experiments and bootstrap resampling to calibrate test statistics and account for systematics; energy-bin overlapping is used to stabilize spectra. No significant Galactic neutrino signal is detected; 90% C.L. upper limits are derived, with the best sensitivity for KRA$_\gamma$ templates, though all limits exceed unity. A model-independent Galactic Ridge analysis yields a 1.9σ hint of a Galactic signal in the track channel, reinforcing previous indications while remaining compatible with IceCube results and illustrating the method's potential for KM3NeT data.

Abstract

The diffuse emission of gamma-rays and neutrinos, produced by interactions of cosmic rays with interstellar matter in the Milky Way, provides valuable insights into cosmic ray propagation and Galactic processes. Emission models incorporating different assumptions about cosmic ray diffusion, source distribution, and target gas density are tested using data from neutrino telescopes. In this study, the final all-flavor neutrino dataset, collected over 15 years (2007--2022) by the ANTARES neutrino telescope, is analyzed. A maximum likelihood ratio method built to handle templates of Galactic emission models is employed to evaluate the compatibility of these models with the observed spatial and energy distributions of neutrino events. The results do not yield stringent constraints on the tested models and upper limits on the diffuse neutrino flux are derived, which are compatible with the results obtained by other experiments.

Figures (6)

• Figure 1: Energy spectrum over the full sky for the different models introduced in the text. The integration is done over all flavors, including both neutrinos and anti neutrinos. While the models predict overall a similar flux, they differ more within specific regions of the Galaxy.
• Figure 2: Neutrino plus antineutrino all-flavor flux at $\sim 1$ TeV as a function of the Galactic latitude $\ell$ and integrated over Galactic longitude for the different models described in the text. $\mathrm{KRA}_\gamma$ models are more peaked toward the Galactic Center ($|\ell| < 50^\circ$). DiffUSE model predicts a smooth diffuse flux, as gas targets are modelled using an analytical parametrisation.
• Figure 3: Spatial PDFs of the signal hypothesis as predicted by $\mathrm{KRA}_\gamma^\mathrm{max}$ model for the track (top), shower-low (middle) and shower-high (bottom) channels. The predicted neutrino flux is convolved with the ANTARES detector response for each event topology. A logarithmic colored scale is applied going from $-10$ to $-3.5$. The sky-maps are plotted in equatorial coordinates, with a cut in declination to not surpass the ANTARES acceptance limit. The fine spatial structure of the template is preserved, especially for the track channel.
• Figure 4: Principle of the overlapping bins of energy. For every bin of size $\delta E$ in energy, the associated spatial PDF is generated using events in the nearby bins (covering a range of $n\delta E$). Taking a fixed amount of nearby bins instead of a generic $\Delta E$ helps to keep track how many times an event is being resampled (see subsec. \ref{['bootstrap']}).
• Figure 5: Comparison of the ANTARES upper limits (solid lines) at $90\%$ C.L.. The grey band represents the area covered by the flux predicted by the different models (except $\pi^0$). The upper limits are plotted according to a transparent gradient, to highlight the energy range of the ANTARES detector (hundreds of GeVs to a few TeVs).