Why Quark Named Quark?

“Three quarks for Muster Mark!”

In the mid-20th century, physicists discovered a large number of hadronic particles (e.g., pions, kaons, protons, and neutrons). However, there was no unified explanation for the properties and interactions of these particles. To understand these properties and their interactions, physicists began to explore the internal structure of these particles.

In 1961, Murray Gell-Mann proposed the “Eightfold Way,” a classification scheme based on SU(3) symmetry to describe the relationships among hadrons. This model successfully classified known hadrons into different multiplets and predicted the existence of new particles. However, it did not explain the fundamental structure of hadrons.

In 1964, Gell-Mann and Zweig independently proposed the quark model, suggesting that hadrons are composed of more fundamental particles called quarks. Gell-Mann initially introduced three types of quarks: up (u), down (d), and strange (s), assuming they have fractional charges (+2/3 or -1/3). These quarks combine through strong interactions to form hadrons such as protons and neutrons.

Murray Gell-Mann proposed the name “quark” in 1963 when he introduced the quark model. He found the term in James Joyce’s novel “Finnegans Wake,” where the phrase “Three quarks for Muster Mark!” appears. Gell-Mann thought “quark” was a unique and interesting word that fit well for the fundamental particles he was describing. Although the pronunciation in Joyce’s novel would likely be [kvark], Gell-Mann chose to pronounce it as [kwark].

This literary reference provided a distinctive name with a touch of whimsy, appropriate for a new and fundamental concept in particle physics. Additionally, the choice of the word “quark” hinted at the multiplicity of quark types (or “flavors”), such as up, down, and strange, which align with the idea of three quarks combining to form protons and neutrons, the building blocks of matter. Thus, the name “quark” not only captured the essence of the new particles but also had a serendipitous alignment with the notion of different types or flavors of quarks, much like the “three quarks” in Joyce’s text.

Although the quark model garnered significant attention theoretically, there was no direct experimental evidence for the existence of quarks in the 1960s and early 1970s. It wasn’t until the mid-1970s, through deep inelastic scattering experiments, that indirect evidence emerged, indicating that protons indeed contained more fundamental components consistent with the quarks predicted by the quark model.

Over time, more types of quarks were discovered, including charm (c), bottom (b), and top (t). The quark model gradually became an integral part of the Standard Model, which includes not only the six types of quarks but also leptons, gauge bosons, and the Higgs boson, forming a comprehensive description of fundamental particles and interactions.

Why Call Up and Down Up and Down?

In fact, the names “up” and “down” do not have any deeper physical meaning beyond this distinction in electric charge and the need for simple, memorable terminology in the early development of the quark model.

When Murray Gell-Mann and George Zweig independently proposed the quark model in 1964, they introduced the concept of quarks to explain the properties of hadrons (such as protons and neutrons) and their interactions.

Electric Charge:

• Up Quark (u): It has an electric charge of +2/3.
• Down Quark (d): It has an electric charge of -1/3.

The names “up” and “down” were chosen to distinguish these two fundamental quarks simply and intuitively. The “up” quark has a higher positive charge compared to the “down” quark, which has a less negative charge. This difference in charge is crucial for forming protons and neutrons:

• Proton: Composed of two up quarks and one down quark, giving it a total charge of +1.
• Neutron: Composed of one up quark and two down quarks, giving it a total charge of 0.

Unexpected Strangeness and Elegant Charm

Unlike up and down quarks and top and bottom quarks, strange and charm quarks were not thought to be paired at the time of their discovery.

The strange quark was named due to the unusual properties of the particles that contain it. In the 1950s, physicists observed particles that had longer lifetimes and different behaviors compared to other known particles. These particles were termed “strange” because of these unexpected properties. When Murray Gell-Mann introduced the quark model, he named the quark responsible for these properties the “strange” quark.

The charmed quark was named to reflect its introduction into the quark model and the charm it brought to solving theoretical issues. The discovery of the J/ψ particle in 1974, which contains a charm quark and its antiparticle, provided strong evidence for the existence of the charmed quark. This discovery was crucial in supporting the quark model and the Standard Model of particle physics, thus the name “charmed” reflected the positive and elegant resolution it provided.

Completion of the Third Generation of Quarks

The discovery of the third generation of quarks is an event of the last 30 years.

The naming of the top and bottom quarks follows a pattern and rationale similar to that of the other quarks, aiming for simplicity, distinction, and consistency within the quark model:

The top quark was named to complement the bottom quark. Originally, the names “truth” and “beauty” were considered for these quarks, but the scientific community later adopted the more straightforward “top” and “bottom” names for ease of use and to maintain a simpler, more intuitive naming convention. The top quark, discovered in 1995, is the heaviest of all quarks, fitting the notion of being at the “top” in terms of mass and energy scale within the quark family.

The bottom quark was named in conjunction with the top quark. It was discovered in 1977 and, together with the top quark, completes the third generation of quarks. The name “bottom” is used to maintain symmetry and balance with “top,” reflecting their relationship within the quark model.

From the whimsical literary origins of the name “quark” to the thoughtful and descriptive naming conventions for up, down, strange, charm, top, and bottom quarks, each choice reflects a blend of scientific rigor and creative insight. These names not only provide a practical means to distinguish between different quark types but also capture the essence of their unique characteristics and roles within the Standard Model. As our comprehension of fundamental particles continues to evolve, the legacy of these names remains a testament to the ingenuity and curiosity that drive scientific exploration. Of course, the journey from “Three quarks for Muster Mark!” to the comprehensive Standard Model exemplifies the enduring quest for knowledge and the poetic beauty inherent in the pursuit of understanding the universe’s most elementary constituents.