A tetraquark. Image Credit: CERN

A tetraquark. Image Credit: CERN

Discovery of Tetraquark

In recent decades, scientific research has vastly improved our understanding of the fundamental constitution of matter, such as the origin of the universe, the structure and function of biomolecules, the evolution of life on Earth, and many more. Meanwhile, progress made by scientists has provided unexpected power that makes it possible for us to change our lives, our future, and our world. Every scientific discovery helps us to find more and understand our astonishing world.

Particle physics has changed our perspective toward the understanding of the universe. Scientific research has given special consideration to understanding the structure of the atom. It has had a major impact on other areas of science, improved the everyday lives of people around the world, and trained a new generation of scientists and computer professionals. Research in particle physics has revolutionized our understanding of the world we live in. Recently, particle physicists at CERN discovered a new strange particle called Tetraquark. Such a mysterious exotic particle that it was suspected of being impossible was eventually identified by physicists in July 2020. The discovery of tetraquarks provides the strongest evidence that these strange particles do exist, paving the way for another imminent era of subatomic understanding.

Particle Zoo. Image source: hetdex.org

To find out what tetraquark is and why it is such an important discovery, We must look back at the time when particle physics was in the middle of a revolution. The idea of quarks was proposed by two particle physicists  Zweig and Gell-Mann in 1960. They suggested that most of the known particles at the time could be explained as being combinations of three fundamental particles. Now, what is fundamental is that particles which do not have a substructure and therefore cannot be divided. Zweig and Gell-Mann were trying to figure out the enormous number of particles discovered during the last two decades. Moreover, They were trying to understand what would happen if these particles were really made of tiny and unknown building blocks. George Zweig referred to these building blocks as aces, whereas Gell-Mann has chosen the term that we still use today called quarks.

Quarks are the particles that are one of the fundamental building blocks of matter. At the Stanford linear accelerator, electrons were shot at protons and were found to bounce back on tiny particles within them. Initially, the quark model stated that there were three kinds of quarks. They were called: up, down and strange quarks.  Protons contain more up quarks while neutrons contain more down quarks. Quarks have pretty strange names such as up and down quarks. These quarks were given names according to spin. Strange quarks were named “strange” because they were observed in particle disintegrations that had a slightly longer lifespan than they should have. Bottom and top quarks were named by a famous physicist Herari. The charm quark was given the name because of its fascinating behavior like the way it fascinated the physicists at that time.

Quarks were predicted to have some unusual properties. The proton and electron have equal and opposite electrical charges and further, they are understood to have a fundamental (that is, the smallest possible) electrical charge. The charge on a proton is 1 unit, while the electron carries -1 unit of electrical charge. However, quarks, as originally imagined, were thought to have an even smaller charge.

Types of Quarks. Image Courtesy: check123.com

Particles consisting of quark and antiquark are named meson, while baryons are formed when three quarks are bound together. Protons and neutrons of atomic nuclei are examples of baryons. For example, a tetraquark is formed when two quarks and two antiquarks stick together, while a pentaquark is formed when four quarks and an antiquark stick together. The latest tetraquark found by LHCb is made up of four quark charms which is generated during high-energy proton collisions at the Large Hadron Collider.

Furthermore, quarks possess a fundamental property called colour, which is divided into three types: red, blue and green. Color plays a similar role in the theory of the strong force as electric charge does in the theory of electromagnetism. Antiparticles have anticolor: antired, antiblue and antigreen. All hadrons must be colorless—a baryon must have one quark of each color. Leptones do not possess colour, and therefore do not feel strong force.

LHCb Detector. Image Courtesy: The conversation

Large Hadron Collider beauty (LHCb) is a detector where physicists perform experiments to find the differences between matter and antimatter because we know we live in a universe filled with matter and there is a very little antimatter in this universe. They want to find out why there was this asymmetry that made matter dominate over antimatter. Tetraquark is particularly interesting because it consists not only of heavy quarks, but also of four quarks of the same type which makes it a unique specimen for testing our understanding of how quarks bind.

In addition to the interesting particles about which we are now familiar, there also exist forces that bind the particles together into useful configurations.  At our present level of knowledge, there appear to exist four forces. These forces are gravity, the electromagnetic force, the strong (or nuclear) force and the radiation-causing weak force. Gravity is perhaps the most familiar. It keeps us on Earth and guides the stars and planets through the cosmos. Gravity is always an attractive force, which means gravity will always make two particles want to move closer to one another.   The force of electromagnetism, the reader will no doubt recall, is one that explains both the phenomena of electricity and magnetism. When we think about strong nuclear forces, then the nucleus of an atom should not exist.

Fundamental forces of nature. Image credit: Sciencedoze

This discovery of tetraquark will help physicists better understand quarks, a type of elementary particle that is a basic element of all matter. This groundbreaking discovery can help scientists understand the intricate way in which quarks bind to form these composites.

The strong nuclear forces that hold the atom together can be understood with the help of tetraquarks. The discovery of the new tetraquark is a major step forward and indicates that there are still a lot of exotic particles out there, waiting for someone to reveal them.


LHCb discovers a new type of tetraquark at CERN. (2020). From CERN: https://home.cern/news/news/physics/lhcb-discovers-new-type-tetraquark-cern

Lincoln, D. (2004). Understanding the Universe.

Tetraquarks back in the spotlight. (2020, September).

Tuttle, K. (2013). Why particle physics matters. From Symmetry Magazine: https://www.symmetrymagazine.org/article/october-2013/why-particle-physics-matters


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