Origin of Neutrino Signal Remains a Mystery
Physicists have studied the astrophysical neutrino signal as reported by the IceCube collaboration from a different angle with their ANTARES detector. The Milky Way centre was an obvious prime suspect to be a source, but this hypothesis is now only closer to debunked than confirmed. Publication in Physical Letters B.
Gotta catch ‘em all! Physicists are always in the hunt for any kind of particle raining down from the sky. Amongst them are neutrinos—one of the hardest to catch. These ultralight particles are so difficult to detect because they penetrate through anything, including detectors. This also means that they are extremely interesting for scientists, because they travel from the inside of space objects directly to Earth, without getting deflected along the way. And with that, they keep a bunch of information safely stored inside them.
To catch them, scientists need massive detectors made of several cubic kilometers of ice or water, like IceCube on Antarctica or ANTARES in the Mediterranean Sea. IceCube has recently reported many detected neutrinos, with a higher number coming from the Southern sky. The centre of the Mily Way is located there, so our Galaxy’s core was an obvious prime suspect to be responsible for a good part of this neutrino influx. However, the signal events in IceCube have a limited resolution, so it remained unclear where the mysterious signal comes from.
Now an international team of physicists, including Leiden University’s Dorothea Samtleben, have used the ANTARES detector to look at the signal at high resolution from a better angle. They show that under certain plausible assumptions on the neutrino flux properties only two of the events detected by IceCube could originate from the Milky Way. ANTARES will now continue with a newly developed reconstruction method to also probe even higher energetic neutrino fluxes from the Milky Way as cause.
‘We are assuming that the so far detected astrophysical neutrinos come from sources with violent “explosions”,’ says Samtleben. ‘We don't know whether the detected neutrinos come from our own galaxy or from outside, and so far also no significant correlation of the neutrino directions could be found with any other known astrophysical source’.
The ANTARES team publishes their results in Physics Letters B on 10 September, but the article is already accessible online.