IceCubeObservatory

Yes, there has been no evidence that anything can move faster than the speed of light in the vacuum. When people commented on the 'Cherenkov light' being emitted when a particle travels 'faster than light', that means it will be 'faster than the speed of light in that particular medium'. - NP

1. The observed neutrinos in these analyses are muon neutrinos. IceCube Neutrino Observatory sees neutrinos through the light that is emitted by charged particles that are induced by the neutrino interaction with matter. In the case of the announced result these charged particles were muons that were produced by the muon neutrinos. Keep in mind that it does not mean the source has been producing muon neutrinos only. The neutrinos oscillate and can change flavor as they travel through the cosmos.
2. The astrophysical neutrinos that IceCube can see are in the range of 100 GeV to 10’s of PeVs. Basically, the expected neutrino energy depends on the source class that produces neutrinos. There are astrophysical neutrinos produced in Supernovae explosions that have lower energies of 100’s of MeV. There are other predicted class of astrophysical neutrinos from interaction of ultra high-energy cosmic rays that will have energies larger than 10 PeV.
3. Could you be more specific about 6.3 PeV neutrino? Are you referring to a reported event by IceCube?
4. Deep learning and Machine learning are the tools that has been used in some of IceCube's analyses. For instance, an ongoing analysis for Taus uses these techniques.

Thanks for you interest in IceCube and Happy Birthday!

-- AK

NP / Focusing on the neutrino related multi-messenger astronomy, I think the biggest question we can answer is the origin of ultra high energy cosmic rays - where are they accelerated up to 10^21 eV energy - the acceleration mechanism, energetics, environment, and so on. (Note that, at this ultra high energy range, cosmic-rays we measure at the Earth are all hadronic -atomic nuclei.) As we gather more evidence in the future (with larger exposure , better detectors, continuous observation of multiwavelength EM (electromagnetic) observations on neutrino signals), we will learn which kind of astrophysical objects can produce high energy neutrinos and learn what kind of extreme environment can produce these highest energetic particles.

IceCube’s main driver is basic science to understand the Universe.  I think my IceCube colleague Ignacio Taboada put it well: basic science is a very long term, very high risk, very high return investment in society.  In addition to the understanding of nature that basic science provides, it also drives technological breakthroughs that can be very practical to society.  The same photon sensor technology that was developed for particle physics experiments (including IceCube) is also used for PET scans to treat cancer and other diseases. — JV

In order to see neutrinos we need a transparent media. The south pole has the cleanest and transparent ice on Earth. Neutrinos are not observed directly, but when they happen to interact with the ice they produce electrically charged secondary particles that in turn emit light, as a result of traveling through the ice faster than light travels in ice. -- AK