Context: Astrophysicists have observed the most energetic neutrino ever seen. The particle was spotted by the Cubic Kilometre Neutrino Telescope (KM3NeT), which is still under construction at the bottom of the Mediterranean Sea.
Relevance of the Topic: Prelims: Key facts about Neutrinos; Cubic Kilometre Neutrino Telescope.
Major Highlights:
- KM3NeT detected an ultra-high energy neutrino having 30 times more energy than any previously detected neutrino. The energy was 220 petaelectronvolts.
- An electronvolt is the energy of an electron accelerated by a voltage of just one volt.
- This means that the neutrino had:
- 100 trillion times more energy than a typical particle at the centre of the Sun.
- Trillion times more energy than medical X-rays
- Ten billion times more than the most dangerous radioactive particles.
- Twenty thousand times more energetic than any particle in the most powerful particle collider (Large Hadron Collider).
- It is anticipated that the particle came from outside the Milky Way galaxy; its exact source still remains to be detected.
What are Neutrinos?
- Neutrinos belong to a group of fundamental particles called leptons in the Standard Model of Particle Physics.
- They have no electric charge and very little mass (nearly massless).
- They are the second-most abundant particles after photons (particles of light) and the most abundant among particles that make up matter.
- They very rarely interact with matter and that is why they are called ghost particles. This means they can travel through vast distances, including entire planets, almost undetected.
- There are three main types of neutrinos: Electron neutrino, Muon neutrino and Tau neutrino. These particles are produced when particles called leptons interact with matter.
- For example, when a type of lepton called a muon interacts with matter, the interaction produces a muon-neutrino. The same goes for electrons (electron-neutrino) and tauons (tau-neutrino).
- Source of Neutrinos: Stars, Supernovae, Galaxies, Nuclear reactions.
Cubic Kilometre Neutrino Telescope (KM3NeT)
- KM3NeT is a gigantic deep sea neutrino telescope, being built by an international collaboration of more than 300 scientists and engineers from 21 countries. The enormous device is still under construction.
- KM3NeT consists of two deep-sea components:
- ARCA (Astroparticle Research with Cosmics in the Abyss): 3.4 km deep near Sicily, Italy, focused on detecting high-energy neutrinos.
- ORCA (Oscillation Research with Cosmics in the Abyss): 2.4 km deep near Provence, France, to study low-energy neutrinos.
- KM3NeT will be made up of more than 6,000 light detectors inside the ocean. When the telescope is complete, it will cover about a cubic kilometre of sea.
Working
- Neutrino interacts with matter so weakly that it can pass through kilometres of ocean (and even thousands of kilometres of Earth itself) to reach the KM3NeT detector.
- Most of the neutrinos would pass through the detector unnoticed. In very rare cases, a neutrino will collide with a water molecule.
- This collision will produce secondary particles (like muons etc.).
- These secondary particles travel faster in the water than the speed of the light in the water, thus producing a faint bluish glow known as Cherenkov radiation.
- The light detectors (KM3NeT’s optical sensors) will detect the Cherenkov radiation and send a signal to the surface.
- By studying the pattern of Cherenkov radiation, scientists can reconstruct/ study the original energy of the neutrino and its direction.
Why study Neutrino?
The study of neutrinos is an area of immense interest among particle physicists and astrophysicists.
- Neutrinos can travel vast distances with minimal interaction, hence, they carry information about the early universe, moments after the Big Bang. Studying them can provide insights into the universe's evolution.
- The mechanism by which neutrinos acquire mass is still not fully understood. Studying their properties might shed light on the Higgs mechanism and mass generation in general.
- There are discrepancies between Standard Model's predictions (Neutrino is massless) and the observed behaviour of neutrinos (have non-zero mass). Studying these anomalies could lead to the discovery of new physics beyond the Standard Model.