Charm quark

Tiny bits make up our world.

One tiny bit is called charm. It is very small. It is a part of many things.

Scientists thought this bit existed first. They used math to find it. Later, they saw it in real tests.

It helps make other small things. These things are called mesons and baryons. Some have one charm bit. Some have two charm bits.

It is very heavy. It is heavier than the strange bit. It also has a plus charge.

Many things can turn into charm bits. This happens in big machines. It is a very special part of our world.

The charm quark is a tiny part of our world.

It is an elementary particle. This means it is a building block. It helps make larger particles called hadrons. These hadrons include things called mesons and baryons.

Scientists did not find it right away. In 1964, James Bjorken and Sheldon Glashow predicted it. They used math to guess it was there. In 1974, two teams found it. One team worked at Brookhaven National Laboratory. The other team worked at SLAC. They found a particle called the J/psi meson. This particle is made of a charm quark and its opposite. Scientists call this special pair charmonium.

The charm quark is very heavy. It is the third-most-massive quark. It is heavier than the strange quark. It also has a plus charge.

Many things can turn into charm quarks. Big machines called particle accelerators make them. Some particles, like the Higgs boson, can decay into them. This means the particle breaks apart to make them. In 2022, scientists found evidence of charm quarks inside a proton.

The charm quark is a tiny building block of our universe. It is an elementary particle, which means it cannot be broken down into anything smaller.

These quarks join together to form larger particles called hadrons. Some of these hadrons are called mesons, while others are called baryons.

The charm quark is a second-generation particle. It carries a special property called charm, which is a quantum number. It also has a positive charge of +e. Scientists also know it is quite heavy. In fact, it is the third-most-massive quark. It is much heavier than the strange quark.

There are many ways that charm quarks appear in nature. They can be made during collisions in particle accelerators. These machines smash particles together at very high speeds. Other particles can also break apart to create them. This is called decay. For example, the W and Z bosons can decay into charm quarks. The Higgs boson can also decay into them.

Sometimes, a charm quark and its opposite partner join together. This pair is called charmonium. This happens in special states called bound states. This shows how these tiny pieces work together to build matter.

Scientists did not find the charm quark by accident. They actually predicted it would exist many years before they saw it. In 1964, James Bjorken and Sheldon Glashow first theorized it. They wanted to find a way to make the math of particles match up. In 1970, Glashow worked with John Iliopoulos and Luciano Maiani. They showed how a charm quark would fix problems in older theories. They even suggested a way to produce these particles. Glashow called the name "charm" because of the symmetry it brought to the world. He even joked it was a magical way to stop unwanted particle decays.

In 1974, two different teams discovered the charm quark at the same time. One team was at Brookhaven National Laboratory. They were led by Samuel C. C. Ting. They found a particle they called the J meson.

Another team worked at the Stanford Linear Accelerator Center, or SLAC. They were led by Burton Richter. They found the same particle and called it the psi meson. Because they found it together, they called it the J/psi meson. This was a huge moment for science. In 1976, Ting and Richter even won the Nobel Prize in Physics for this discovery.

Since then, scientists have found even more strange and wonderful things. In 1975 and 1976, they found new particles like the D meson. They also found the charmed strange meson in 1977. In 2002, a team at Fermilab found a baryon with two charm quarks. This is a very rare particle. In 2022, researchers found evidence that charm quarks exist inside a proton.

They also studied how the Higgs boson connects to the charm quark. These discoveries help us understand how the smallest parts of our world behave.

The charm quark is a fundamental building block of our universe. It is an elementary particle, meaning it cannot be broken down into smaller parts.

This particle belongs to the second generation of quarks. It carries a specific property known as a quantum number called charm. It also possesses an electric charge of +e. Scientists classify it as an up-type quark. It is quite heavy compared to other particles. In fact, it is the third-most-massive quark known to science.

Charm quarks exist within larger composite particles called hadrons. These hadrons are divided into two main types: mesons and baryons. Mesons are made of a quark and an antiquark. One specific type is called charmonium. This occurs when a charm quark and a charm antiquark form a bound state. There are two forms of charmonium based on particle spin. In orthocharmonium, the spins are parallel. In paracharmonium, the spins align in opposite directions. Baryons are different because they contain three quarks. Some charmed baryons include the lambda charm or the xi charm.

These particles are produced through several complex processes. They can be created during collisions in particle accelerators. Scientists often use electron-positron colliders to produce charmonium. Hadron colliders are also used because they produce charm quarks at a higher cross section. Other heavy particles can also produce them through a process called decay. For example, the W and Z bosons can decay into charm quarks. The Higgs boson can also decay into them through a mechanism called Yukawa coupling. The charm quark can also decay into other quarks via the weak interaction.

Discovery of the charm quark was a major triumph for theoretical physics. In 1961, Murray Gell-Mann introduced the Eightfold Way to group particles. By 1964, Gell-Mann and George Zweig proposed that hadrons were made of quarks. Initially, scientists only knew about up, down, and strange quarks. In 1964, James Bjorken and Sheldon Glashow theorized the existence of charm. They wanted to create a parallel between quarks and leptons. In 1970, Glashow, John Iliopoulos, and Luciano Maiani proposed the charm quark specifically. They created the GIM mechanism to explain why certain particle decays were so rare. This mechanism helped unify the weak and electromagnetic forces.

In 1974, the existence of the charm quark was finally confirmed. Two separate teams made independent discoveries at almost the same time. Samuel C. C. Ting led a team at Brookhaven National Laboratory. They used an electron-pair detector to find a particle they named the J meson. Meanwhile, Burton Richter led a team at the Stanford Linear Accelerator Center. They found the same particle and named it the psi meson. Together, these particles are known as the J/psi meson. This discovery was so important that Ting and Richter shared the Nobel Prize in Physics in 1976.

Since that discovery, many other charmed particles have been identified. In 1975, researchers found evidence for charmed baryons. In 1976, Gerson Goldhaber and François Pierre identified the D meson. This was described as finding "naked charm" because it was a neutral charmed meson. In 1977, the charmed strange meson was also discovered. In 2002, the SELEX Collaboration at Fermilab found a doubly charmed baryon. This is a rare particle containing two charm quarks. Recent studies in 2022 have even found evidence of intrinsic charm quarks inside the proton.

Modern research continues to explore how the charm quark interacts with the universe. Scientists use the Large Hadron Collider to study the Higgs boson. They have looked at how the Higgs boson decays into charm quarks. They found the Higgs-charm coupling is weaker than the Higgs-bottom coupling. There is also evidence of CP violation in the decay of the D0 meson. This involves the way particles and antiparticles behave differently. Understanding these tiny interactions helps scientists map the entire Standard Model of physics. Every new measurement brings us closer to knowing how matter is built.