Tag: quarks

What are Quarks? – Definition, Properties and Types

In the early models of the atom were simple, with protons and neutrons forming a nucleus and negatively charged electrons orbiting it, it seemed like a tiny solar system. In the early 1930s, however, analysis of cosmic rays and experiments with particle acceleration showed the existence of new particles by the dozen. In the early of 1960s American physicist Murray Gell-Mann and George Zweig independently conjectured that protons and neutrons were made of even more fundamental particles. They named the subatomic particles as Quark in 1964. The word quark came from James Joyce’s novel “Finnegan’s Wake” in which it is a nonsense word made by Joyce.  He key evidence for their existence came from a series of inelastic electron-nucleon scattering experiments conducted between 1967 and 1973 at the Stanford linear accelerator center. Other theoretical and experimental advances of the 1970s confirmed this discovery, leading to the standard model of elementary particle physics currently in force.

Properties of Quarks

Quarks are most commonly found inside protons and neutrons. They have many properties including mass, electric, charge, and color. There are six types of quarks, up quark, down quark, top quark, bottom quark, strange quark, charm quark. They can have positive (+) or negative (-) electric charge. Up, charm and top quarks have a positive 2/3 charge. Down, strange, bottom quarks have a negative 1/3 charge. So protons are positive because there are two quarks (+2/3) ups and one down quark (-1/3), giving a net positive charge (+2/3+2/3-1/3 =1). These three quarks are known as valence quarks, but the proton could have an additional up quark and anti-up quark pair.

 An anti-quark is the anti-particle of a quark and it could have other types of quarks. It includes pairs of strange quarks and anti-strange quarks, charm quarks, and anti-charm quarks. In fact, the proton has tons of quarks, anti-quarks pairs. The quarks are held together by the strong force which is carried by particles called gluons. So inside the proton, there are zillions of gluons and quarks all moving around close to the speed of light. The quarks that comprise a proton only make of 1% of the mass of that proton. A neutron consist two down quarks and one up quark which gave it an overall charge of 0. The quarks have a property called color change. It includes three color, red, blue, green and each of them is complemented with an anti-color. When we mix these three colors, we get white, that’s why proton is called colorless. The quarks change their colors constantly but, In order to maintain colorless state, the ant-color mix into it.The interaction between quarks and gluons is responsible for almost all the perceived mass of protons and neutrons and is therefore where we get our mass.

Conclusion

The discovery of quarks was a gradual process that took over a decade for the entire sequence of events to unfold. A variety of theoretical insights and experimental results contributed to this discovery, but the MIT-SLAC deep inelastic electron scattering experiments plays a vital role. The existence of quarks is recognized today as a cornerstone of the standard model. I numerous experiments at CERN including those at the Large Hadron Collider (LHC), physicists are measuring the properties of Gell-Mann and Zweig’s particles with ever-greater precision.

                  “Three quarks for muster mark!” – Author James Joyce

Large Hadron Collider-the world’s largest machine

The smallest thing that we can see with a light microscope is about 500 nano-meters. A typical atom is anywhere from 0.1 to 0.5 nano-meters in diameter. So we need an electron microscope to measure these atoms. The electron microscope was invented in 1931. Beams of electrons are focused on a sample. When they hit it, they are scattered, and this scattering is used to recreate an image. Then what about protons or neutrons? Or what about quarks? The quarks are the most fundamental building blocks of matter. So how did we find such small particles exist? The answer is a particle collider. A particle collider is a tool used to accelerate two beams of particles to collide since 1960s.

The largest machine built by man, the Large Hadron Collider (LHC) is a particle accelerator occupying an enormous circular tunnel of 27 kilometres in circumference, ranging from 165 to 575 feet below ground. It was situated near Genoa, Switzerland. It is so large that over the course of its circumference crosses the border between France and Switzerland. That’s the giant collaboration going on between over 100 countries and 10,000 scientists. The tunnel itself was constructed between 1983 and 1988 to house another particle accelerator, the Large Hadron Collider, which operated until 2000, its replacement, the LHC, was approved in 1995, and was finally switched on in September 2008.

The Larger Hadron Collider (LHC) covers the circumference of 27 kilometres

Working of the Large Hadron Collider

 The LHC is the most powerful particle accelerator ever built and has designed to explore the limits of what physicists refer to as the standard Model, which deals with fundamental sub-atomic particles. There are two vacuum pipes are installed inside the tunnel which intersects in some places and 1,232 main magnets are connected to the pipe. For proper operation, the collider magnets need to be cooled to -271.3 °C. To attain this temperature, 120 tons of liquid helium is poured into the LHC. These powerful magnets can accelerate protons near the speed of light, so they can complete a circuit in less than 90 millionths of a second. Two beams operate in opposite directions around the ring. At four separate points the two beams cross, causing protons to smash into each other at enormous energies, with their destruction being witnessed by super-sensitive instruments. But it’s not that easy to do this experiment. Each beam consists of bunches of protons and most of the protons just miss each other and carry on around the ring and do they it again. Because, atoms are mostly empty space, so getting them to collide is incredibly difficult. It’s like colliding a needle into a needle, provided that the distance between them is 10 kilometres.

Collision of protons at near the speed of light

The aim of these collisions is to produce countless new particles that stimulate, on a micro scale, some of the conditions postulated in the Big Bang at the birth of the universe. Higgs Boson was discovered with the help of LHC. This so called ‘God Particle’ that could be responsible for the very existence of mass. If it disappeared, all particles in the universe will become absolutely weightless and fly around the universe in the speed of light (299,792,458 m/s). that means we can reach our moon in 1.3 seconds from earth.

“When you look at a vacuum in a quantum theory of fields, it isn’t exactly nothing.” – Peter Higgs