Physicists discover a ‘charming’ new particle

A “charming” new particle is discovered at the world’s largest nuclear crusher

By Clara Moskowitz edited by Claire Cameron

Physicists have just discovered a brand new particle that appears to be an exotic cousin to the protons and neutrons that make up atoms.

These mundane subatomic particles are made up of even smaller building blocks of matter called “up” and “down” quarks, which are the lightest types of quarks. But quarks also come in heavier flavors, including “charm”, “weird”, “bottom” and “top” (the most massive fundamental particle known).

The new particle, discovered at the world’s largest nuclear crusher, the Large Hadron Collider (LHC) in Geneva, Switzerland, contains two charm quarks and a thump quark. Like protons and neutrons, its total of three quarks classifies it in particle physics as a baryon, which is a type of hadron – or a particle made of quarks. The discovery brings the current number of known hadrons detected by LHC experiments to 80.

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The new particle, which physicists call a doubly charmed baryon, essentially replaces the two up quarks in a proton with charm quarks, giving it about four times the mass of the more common and stable proton.

The LHC accelerates protons to more than 99 percent of the speed of light and then smashes them together. The protons are destroyed, and the energy from the crash gives rise to new particles in the wake. Whenever a doubly charmed baryon was created in the collider, it rapidly decayed into lighter particles.

The new particle was discovered by the LHCb experiment, one of nine detectors stationed around the LHC’s 17-mile-long ring. It is the first new particle seen at the experiment since scientists upgraded LHCb in 2023.

The doubly charmed baryon is only the second baryon with two heavy quarks ever seen – the rest have all contained two up or down quarks and only one of the heavier flavors. The previous heavy baryon was discovered in 2017, also at LHCb, and consists of two charm quarks and an up quark. Despite their similarities, the newly discovered particle is even less stable than the other heavy baryon, with a lifetime predicted to be about six times shorter.

Finding this type of particle helps physicists learn about the strong force, which is the most powerful force in nature and binds hadrons together. The strong force is also the most mysterious and confusing force, governed by a complex theory called quantum chromodynamics. Physicists hope to understand how the strong force holds quarks together and how the composite particles’ properties, such as mass and spin, arise.

Physicists announced the discovery this week at the Moriond particle physics conference in Italy.

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