Neutrinos at High Energies: Disentangling Galactic and Extra-galactic components

Project Information

nuHEDGE

Grant agreement ID: 843418

DOI

10.3030/843418

Project closed

EC signature date 11 April 2019

Start date 1 June 2019

End date 31 May 2021

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 184 707,84

EU contribution

€ 184 707,84

Coordinated by

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
France

Periodic Reporting for period 1 - nuHEDGE (Neutrinos at High Energies: Disentangling Galactic and Extra-galactic components)

Reporting period: 2019-06-01 to 2021-05-31

Summary of the context and overall objectives of the project

Cosmic-rays have been discovered in 1912 by Victor Hess. The observed energy spectrum of cosmic-rays is described by a power law with
spectral index of about 2.7 up to energies of a few PeV, where the spectrum gets steeper and a feature called the "knee" originates.
The knee is believed to mark the maximum energy for cosmic-rays accelerated by Galactic source.

Neutrinos are particles that rarely interact with matter and do not feel the magnetic field. For this reason, they can carry information on
the physics of acceleration of particles and on the most energetic and distant phenomena in the Universe.
Neutrinos can permit to discriminate unambiguously between leptonic and hadronic scenarios. Thus, they are "smoking gun" signature of
cosmic-rays accelerators.

A multi-messenger search is mandatory for the identification of the origin of cosmic neutrinos. Gamma-ray data are necessary to make correct
estimations of neutrino fluxes from point-sources. The characteristic gamma-ray feature of a PeVatron include an hadronic, hard spectrum
that extends until at least several tens of TeV.
Thus, a gamma-ray experiment with sensitivity to make detections up to about 100 TeV is of fundamental importance.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have studied the neutrino signal expected for the eHWC J1825-134 source and also for an extended region around the source, where the latter is motivated by
the Fermi-LAT analysis of this part of the sky.
We found that about a 4 to 5$\sigma$ detection has to be expected after ten years of observations at KM3NeT, depending on the details of the considered scenario.

Afterwards, we moved to an analysis of recent sources detected by HAWC, for which we studied the event rates at the IceCube detector.
A detection at 3$\sigma$ or more for the eHWC J1907+063 and the eHWC J2019+368 sources is expected within the next decade of running of IceCube.
Considering, instead, the 2HWC J2019+367 region, the detection can reach about 3$\sigma$ in the next decade, but for a neutrino energy threshold of about 10 TeV.
Finally, the detection at about 3$\sigma$ of 2HWC J1857+027 source will depend on the specific value of the flux, on the extension of the source and on the cut-off
energy.

Moreover, we studied the case in which the gamma-ray emission from the direction of Andromeda can be described by a cosmic ray origin, considering a non standard
cosmic ray propagation scenarios.
This would imply the existence of a giant cosmic ray halo surrounding M31. If cosmic ray halos, as the one observed around M31, are a common feature of galaxies,
including the Milky Way, the isotropic diffuse flux of neutrinos observed by Icecube could be explained.

We have finally studied the emission in gamma rays and neutrinos from the RX J1713.7-3946 source. Considering an hadronic scenario, a 5$\sigma$ detection at KM3NeT
has to be expected in 10 years running. Instead, considering a lepto-hadronic origin of the gamma-ray emission, 20 years of running are needed to detect an excess in
neutrino from this region.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The recent detection of gamma-ray sources with the characteristics of PeVatrons, by the HAWC and LHAASO experiments, makes the study of neutrinos expected at
IceCube and KM3NeT a timely prediction to firmly shed lights on the origin of galactic cosmic rays.
On the other hand, the gamma-ray emission from M31 opens the possibility of a diffuse origin of the detected neutrino flux by IceCube. This can be further scrutinized
by future data from gamma-ray experiments, like LHAASO.

Neutrino event rate for the source ehwc J1907 as compared to the expected background