News Excerpt:

The international NOvA collaboration presented new results at the Neutrino 2024 conference in Milan, Italy.

What is NOvA?

• NOvA, short for NuMI Off-axis νe Appearance, is an experiment managed by the U.S. Department of Energy’s Fermi National Accelerator Laboratory. 
• It creates a beam of neutrinos that fly towards a 14,000-tonne detector located 800 km away.
• NOvA aims to learn more about the ordering of neutrino masses. 
• Physicists know that there are three types of neutrinos with different masses, but they don’t know the absolute mass, nor which is heaviest.
• Theoretical models predict two possible mass orderings, normal or inverted. 
• In the normal ordering, there are two light neutrinos and one heavier neutrino; in inverted order, there is one light neutrino and two heavier ones.
• By measuring the neutrinos and their antimatter partners, antineutrinos, in both locations, physicists can study how these particles change their type as they travel, a phenomenon known as neutrino oscillation.

New data from NOvA

• Scientists presented the latest results from the NOvA collaboration at a conference in Italy on June 17. 
• The collaboration doubled their neutrino data since their previous release four years ago, including adding a new low-energy sample of electron neutrinos. The new results complemented the previous ones with greater precision.
• NOvA was designed to determine the role of neutrinos in the evolution of the cosmos. It does this by trying to understand which neutrino type has the most mass and which type the least. This is an important detail because neutrinos may get their mass through a different mechanism from other matter particles. Unraveling it could answer many open questions in physics.
• In pursuit of this goal, on July 11, a study at the Large Hadron Collider in Europe also reported observing electron-neutrinos at a particle collider for the first time.

The history of Neutrino research:

• Physicists first detected extraterrestrial neutrinos coming from a supernova in 1987, when a star exploded around 150,000 light years away. 
• Three hours before light from the explosion reached the earth, three underground detectors in Japan, Russia, and the U.S. recorded a spike in the number of neutrinos coming from the explosion. This event was the birth of neutrino astronomy.
• For almost 50 years, physicists thought neutrinos were massless particles, like photons. 
• According to the special theory of relativity, a massive particle can’t travel at the speed of light (in vacuum). So a light signal could overtake the neutrino and it would appear right-handed when viewed in the opposite direction, i.e. with its directions of motion and spin aligned with each other. However, physicists had never detected right-handed neutrinos, so they concluded neutrinos are massless.
• But from the late 1990s, scientists in Japan and Canada found evidence to overturn this view and prove neutrinos actually have mass. They found that when neutrinos travel through space, they can change from one type to another, which massless particles can’t do.
• The existing theory of how particles behave and their properties, called the Standard Model of particle physics, doesn’t predict massive neutrinos. Incorporating them in the Standard Model will require far-reaching changes that physicists are still working out.

Studying these neutrinos can reveal how light or radio waves from the explosion diffuse after traveling a certain distance.

How Neutrinos are the best information carriers?

• Because neutrinos pass through most matter untouched, they can carry information across large distances. Humans currently use electromagnetic waves to do this job because they are easier to transmit and to detect. But in some situations, they don’t work well.
• For example, seawater is opaque to electromagnetic radiation of shorter wavelength, which impedes the transmission of waves of certain frequencies to submarines. Neutrinos on the other hand can easily pass through 1,000 light years (9,400 million million km) of lead, so an ocean will hardly be a barrier.
• We only need to find a way to transmit and capture them, which is tied to understanding them fully. If this happens, it wouldn’t be far-fetched to say we can replace electromagnetic waves in communication channels with neutrino beams within a few decades.