Inside the Quark

Dr. S. S. VERMA; Department of Physics, S.L.I.E.T., Longowal; Distt.-Sangrur (Punjab)-148 106

2020-03-26 06:52:15



Scientific endeavors are continuing to reach to the conclusion about the understanding of elementary particles leading towards matter formation in nature which is seen all around of us. This doesn’t mean that scientists have not discovered the elementary particle before. Take the atom for example. John Dalton and his atomic theory stated that atoms are indivisible and are the smallest building blocks of nature. This was incorrect because J.J. Thomson discovered that atoms are made of electrons, and Ernest Rutherford discovered the nucleus, proving the proton and the existence of smaller constituents of the atom (and later, James Chadwick discovering the neutron). This reached to the level of finalizing elementary particles to three i.e., electron, proton and neutron.

We know atoms are formed from protons and neutrons because of deep inelastic scatterings which showed that the atoms have a hard core, so they are not a uniformly distributed matter. Then from the periodic table of elements which organizes itself well counting protons and neutrons. It is concluded that protons and neutrons are formed from quarks as we have the results from painstaking experiments that showed us once more that deep inelastic scattering shows a hard core inside the protons and neutrons. The study of the interaction products organized the particles and resonances into what is now called the standard model, a grouping in families that have a one to one correspondence with the hypothesis that the hadrons (protons neutrons resonances) are composed out of quarks.

Years later, Murray Gell-Mann theorized the so-called Quark, which was discovered in 1968. Electrons aren't made of quarks, only protons and neutrons are made of quarks. Thus, everything we see around is made up of elementary particles called quarks and leptons, which can combine to form bigger particles such as protons or atoms. This revolutionized Physics because every time a Physicist developed a theory on a smaller building block of the universe, and it was proven to be true, there was always another theory surpassing the previous, and proving that there are even smaller building blocks of nature. Just as we now understand the diverse elements to be combinations of only three particles (protons, neutrons, and electrons), the Eightfold Way explained protons, neutrons, kaons, pions, etc. as combinations of particles that we now call quarks. Only five years after Gell-Mann proposed his theory, these quarks were observed at the Stanford Linear Accelerator Center. And this is where it stands today.  As far as we know, quarks are indivisible; i.e., quarks are the smallest unit matter in the nucleus. We can only hope that Quarks are made of smaller pieces, because that would mean a whole new field of study opening up for Physics, leading to revolutionary changes in the way we think. Quarks, as we understand them, are said to elementary particles, which mean that they do not have constituents. They are excitation of their corresponding quantum field. Of course, this could be completely incorrect, and quarks can consist of tiny, vibrating strings, as theorized by M-Theory (String Theory), but there is no clear evidence of smaller particles that make up the quark. This doesn’t mean that we won’t discover what they’re made of, if they are made of tiny particles. Quarks are considered the most fundamental constituent of matter until now which combine to form different composite particles, the most stable of which are proton and neutron.


Quarks have many intrinsic properties charge, colour, spin and mass. There are six types of quarks which we call its flavours, up, top, down, bottom, strange and charm. But what are constituents of Quarks scientists are unable to answer yet. A quark is a fundamental particle that is smaller than any measuring instrument we currently have but does that mean there's nothing smaller than quark.  Following the discovery of quarks inside protons and neutrons in the early 1970s, some theorists suggested quarks might themselves contain particles known as ‘preons’. The idea wasn’t entirely fanciful, but raises further, as-yet-unanswered questions; for the time being, most physicists believe that quarks, electrons and all other particles are best described as being vibrations of ‘superstrings’, multi-dimensional entities far smaller than the smallest sub-atomic particle. In particle physics, preons are point particles, conceived of as sub-components of quarks, and leptons. Each of the preon models postulates a set of fewer fundamental particles than those of the Standard Model, together with the rules governing how those fundamental particles combine and interact.


It’s been long known that matter has a Russian-doll nature. Atoms are made of protons and neutrons (together called hadrons), along with lighter electrons. In turn, hadrons consist of particles called quarks, of which there are six varieties. In addition, there are six varieties of fundamental particles related to the electron, called leptons. In 1974, physicists Jogesh Pati and Abdus Salam speculated that a small family of particles they called preons could explain the proliferation of quarks and leptons. In 1999, Hansson and his coworkers proposed that three types of preons would suffice to build all the known quarks and leptons. Then in 2005, Hansson and his student Sandin went on to explore whether some matter could have got stuck at the preon stage, rather than ‘condensing’ into quarks or hadrons. They predict that it could. Such lumps of preons would be even denser than quark stars or neutron stars. Most physicists agree that quarks are the fundamental building blocks of all matter. But some researchers believe quarks may contain constituents called preons that are well beyond the detection limits of current and most future particle colliders. A research team describes two strategies for detecting them in space, in the form of preon “nuggets” that might also be a form of dark matter. Although many researchers are skeptical that preons exist, the team receives high marks for looking beyond conventional particle physics in a new way.