Difference between Leptons and Quarks

In previous centuries, the common perception among scientists was that an atom is the smallest component of matter. However, according to the latest researches, an atom is in fact made up of a number of other smaller particles. These particles, which make up an atom, are called subatomic particles. Two main examples of these particles are leptons and quarks. There are a lot of similarities between leptons and quarks, but there are also some significant differences between the two. Considered the most fundamental particles that exist, quarks and leptons cannot be broken down into further constituent particles.

Leptons consist of electron, electron neutrino, muon, muon neutrino, tau and tau neutrino particles. On the other hand, quarks are made up of up, down, top, bottom, charm and strange particles. Leptons have integer charge, whereas quarks have a fractional charge. Quarks are not able to exist freely but leptons can move and exist without any hurdle. Another major difference between the two is that leptons are independent particles and can be separated, but this is not the case with quarks.


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    There are four fundamental forces in nature: the strong force (which is the joining force between quarks and atomic nuclei), the weak force (which causes radioactive decay), the electromagnetic force (which keeps the atoms together) and the gravitational force (which acts on any object with energy or mass in the universe). Leptons are subject to all these fundamental forces except for the strong force. The reason behind this exception is that the strong force has a very short range, even shorter than that of an atomic nucleus, which is the reason why the strong force is limited to that area.

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    Quarks were named by Murray Gell-Mann, a Nobel Prize winner, after a word in James Joyce's book 'Finnegan’s Wake'. Quarks have fractional charge, which is the reason why they are not able to exist freely as per a fundamental force called ‘strong force’. Mediated by force-carrying particles called gluons, the strong force keeps quarks attracted to one another and acts within the nucleus of an atom.

    As quarks move apart, the force between them increases; however, some quarks are never detected. The field of study which concerns itself with the interactions between quarks and gluons is known as Quantum Chromo Dynamics (QCD). Quarks are subject to all the fundamental forces which are mentioned above.

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