Charm quark facts for kids

Charm quarks, also called c quarks, are tiny building blocks of matter. They are the third heaviest of the six types of quarks. Scientists believe quarks are so small they can't be broken down into anything smaller. That's why they are called elementary particles.

Like up quarks, charm quarks have an electric charge of +2/3. This means they carry a small positive electrical force. Even though charm quarks are not super common, you can find them inside other particles. These particles are often made in huge machines called particle accelerators, which smash atoms together at incredibly high speeds. Examples of particles containing charm quarks include J/ψ mesons and D mesons.

Charm quarks are also a type of particle called a fermion. This means that no two charm quarks can be in the exact same place at the exact same time. They also have a property called spin of 1/2, which is like a tiny internal rotation.

What are Charm Quarks?

Charm quarks are fundamental particles, meaning they are not made of anything smaller. They are part of the "second generation" of quarks. Each quark has a special property called "flavor." The six flavors are up, down, strange, charm, bottom, and top. Charm quarks get their name from this "charm" flavor.

How were Charm Quarks Discovered?

The discovery of the charm quark was a huge moment in physics! It happened in November 1974, almost at the same time, by two different groups of scientists. One group was at the Stanford Linear Accelerator Center (SLAC) in California, and the other was at the Brookhaven National Laboratory in New York.

The November Revolution

The discovery was so important that it's often called the "November revolution" in particle physics. Both groups found a new particle that was much heavier than expected. This particle was later named the J/ψ meson. Its existence strongly suggested that a new type of quark, the charm quark, had to exist. This discovery helped confirm the "Standard Model" of particle physics, which describes the basic forces and particles that make up the universe.

Where can we find Charm Quarks?

You won't find charm quarks floating around by themselves. They are always found inside other particles, usually with other quarks. These particles are called hadrons.

Charmed Particles

• J/ψ meson: This was the first particle discovered that contained a charm quark and an anti-charm quark. It's very important because its discovery led to understanding charm quarks.
• D mesons: These particles contain one charm quark and one lighter quark (like an up or down quark).
• Charmed baryons: These particles are made of three quarks, with at least one being a charm quark.

Scientists study these charmed particles using powerful particle accelerators. By smashing particles together, they can create these short-lived charmed particles and learn more about the charm quark's properties.