If we can enlarge a file corn In your body, we will see that it consists of Electrons swarming in orbits around The nucleus of protons and neutrons. And if we could zoom in on one of those protons or neutrons, we would find that they themselves are made up of three particles so small that they have no size at all, which are just a few more points. These point-like particles are quarks.
Quarks are elementary particles. Like the electron, it is not made up of any other particles. You can tell that they are on the ground floor of Standard Form Particle physics.
Related: The strange quark star may have formed from a lucky cosmic merger
Keith Cooper is a freelance science journalist and editor in the UK, with a degree in Physics and Astrophysics from the University of Manchester.
The discovery of quarks
The theory of the existence of quarks was first put forward in 1964 in the work of two physicists, Murray Gillman (Opens in a new tab) and George Zweig, who were both at the California Institute of Technology (CalTech) but came to the conclusion that quarks exist independently of each other. Contrary to the way science is often portrayed in the media, Gell-Mann and Zweig’s conclusions weren’t “aha!” Rather, it was built on the back of many years of hard work and meticulous discoveries by the particle physics community.
By the 1950s, physicists were creating a library of known particles. It was somewhat similar to botany, cataloging the different species and their characteristics, but what was missing was the basic theory behind their existence. This theory eventually became known as the Standard Model, but in order to get there, many vital discoveries had to be made, including the discovery of quarks.
Most puzzling were the presence of particles called hyperons, which were unstable and decayed very quickly, but not in the particles they were expected to decay. Jill-Mann realized that there must be an unknown quantum property at work, which he called “strangeness” because it wasn’t all expected.
Quantitative numbers, such as eccentricity, charge and rotation, must be preserved. If a particle of a certain quantum number decays, then its byproducts must be added to those quantum numbers that the decaying particle had. Moreover, quantum numbers for a particular particle have “degrees of freedom” – essentially the range of values that these numbers can have. These degrees of freedom are called multiples, and the pattern in which these multiple groups can be arranged among different particles led Gil-Mann and Zweig to believe that particles and their multiples could be explained if each particle was made up of two or three smaller particles.
Zweig called these tiny elementary particles “aces,” but the name did not spread. Gill Mann, always one of the most memorable names for quarks, is derived from a line in James Joyce’s experimental novel, Awake Finnigan: “Three quarks for Mr. Mark!” In the novel, quarks refer to the three children of the main character, Mr. Mark.
These quarks are referred to as “up,” “down,” and “alien” quarks. The up and down quarks don’t actually refer to anything, while the odd quark has an oddness quantum number of -1, which is why it’s called “strange,” while up and down quarks have a weirdness of 0.
Quarks in quantum physics
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Although the theory was clever, it did not spread immediately because there was no experimental evidence for quarks. This came four years later in 1968 in Stanford Linear Accelerator Center (Opens in a new tab) (SLAC) in California. The experimenters fired electrons, and later muons at the protons, and found evidence that the electrons and muons were scattered from three smaller particles contained within the protons, and each of these smaller particles had its own electric charge. These particles are quarks.
It turns out that there are actually six types, or flavors, of quarks in total. Besides the up, down, and strange quarks, there are also “charm”, “up” and “down” quarks. Each one has its own set of quantum numbers, and their masses are completely different, the up and down quarks are the least massive, the up and down quarks The up quark is the heaviest It has a mass that is 61,000 times that of the top quark. Why it should be so massive is not fully understood, but it quickly decays into less massive quarks. The only reason scientists know that such up and down quarks exist is because particle accelerators like Large Hadron Collider Able to be produced for a short time.
Compounding the difficulty of studying quarks is the fact that, under normal conditions, they do not exist on their own. They are always linked together by strong nuclear power, allowing them to form complex particles called hadrons. Particles made of two quarks are called mesons, and particles made of three quarks are called baryons, which include protons (one up quark and one down quark) and neutrons (an up quark and one down quark). There are particles called tetraquarks which is made up of four quarks, and pentaquarks which has five quarks, some of which are almost stable (Opens in a new tab)but eventually decomposes.
to fit Quantum physics In theory, the behavior of quarks is governed by a model called Quantum chromodynamics (Opens in a new tab), or QCD for short. The “chromo” in the name stands for “color”—not the same as in red, green, or blue, but the name given to a particular quantum number that quarks possess. Consider that color plays the same role in the strong force that electric charge plays in the electromagnetic force. Therefore, like colors repel and unlike colors (i.e. color and anti-color) attract, forming stable pairs of quarks, and like other quantum numbers, they must also be conserved.
The Big Bang and Quark-Gluon Plasma
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The strong force that binds quarks inside hadrons is carried by another type of tiny elementary particle called gluons, which are exchanged between quarks. To separate individual quarks requires an enormous amount of energy (it’s not called the strong force for no reason). This amount of raw energy was only present in nature about 10 billionths of a second to about a millionth of a second after the great explosionwhen the temperature was about 3.6 trillion degrees Fahrenheit (2 trillion degrees Celsius (Opens in a new tab)). During this short early period, the infant universe was filled with a form of matter known as quark-gluon plasma, a particle soup of free-floating quarks and gluons. As temperature and pressure rapidly decreased as the nascent universe expanded, quarks became bound together, forming hadrons that eventually formed the basis of all the visible matter we see today in the universe, from stars And the galaxies to me planets and people.
Although quark-gluon plasmas only existed 13.8 billion years ago in the immediate aftermath of the Big Bang, scientists have succeeded in recreating it in particle accelerator experiments by smashing two heavy nuclei, such as lead nuclei, into close proximity to each other. light’s speed. The first time this was achieved was at CERN Super Proton Synchrotron (Opens in a new tab) in 2000.
As such, studying quark-gluon plasmas in particle accelerator experiments is an important way to better understand conditions in the universe. In the aftermath of the Big Bang (Opens in a new tab).
The other location in nature where conditions can be so intense that quarks become infinite is in a hypothetical object called a “star quark”.
If they exist, then quark stars are a kind of extreme neutron starThey are the most compact objects known in the universe that did not collapse under the influence of gravity to form a black hole. A neutron star is born in A Supernovaa violent explosion indicates the destruction of a huge star. As the star’s outer layers are blown apart, the star’s core collapses beneath them gravity The pressure there becomes so great that the protons with their positive electric charge fuse with the negatively charged electrons, canceling their charge to form neutral neutrons. Neutron stars are about 6 miles (10 kilometers) in diameter, and a spoonful of neutron star matter can have the mass of a Mt.
However, in theory, it may be possible for the cores of dying stars to become more compact. In this scenario, the neutrons decay, releasing their quarks to freedom. This will be a quark star.
However, for now, quark stars are still purely hypothetical. Astronomers have not definitively discovered one yet, although there are a few candidates that appear to have slightly different properties than regular neutron stars, such as a smaller diameter and greater mass.
One of the candidates is an object that did not actually form in a supernova but from the merger of two neutron stars that produced gravity wave event known as GW 190425 (Opens in a new tab)which were captured by the gravitational wave detectors LISA and Virgo here a land In 2019. The mass of the compact body ranges between 3.11 and 3.54 solar masses. That’s too massive to be a neutron star (which in theory couldn’t be bigger than About 2.4 solar masses) but it is not huge enough to be a file Black hole (which should be about five solar masses minimum). Could it be a quark star instead?
One other possibility is that some neutron stars could be hybrid objects, with normal neutron star material in their outer layers and Quark matter is deep in its core (Opens in a new tab).
Read more about quarks here Resources from CERN (Opens in a new tab). Learn more about the discovery of quarks with CERN (Opens in a new tab) Explore quarks and gluons in more detail with Energy Department (Opens in a new tab).
The First Three Minutes: A Modern View of the Origin of the Universe by Stephen Weinberg (1977, revised edition 1993, HarperCollins)
Particle Physics by Brian R. Martin (2011, One World Publications)
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First observation of quark-gluon plasma? American Physical Society. (1998, July). Retrieved on November 1, 2022 from https://www.aps.org/publications/apsnews/199807/observation.cfm (Opens in a new tab)
^ Fritzsch, H.; (September 27, 2012). QCD history. CERN Courier. Retrieved on November 1, 2022 from https://cerncourier.com/a/the-history-of-qcd/ (Opens in a new tab)
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SLAC home page. SLAC National Accelerator Laboratory. Retrieved on November 1, 2022 from https://www6.slac.stanford.edu/ (Opens in a new tab)
Super Proton Synchrotron. CERN. Retrieved on November 1, 2022 from https://home.cern/science/accelerators/super-proton-synchrotron (Opens in a new tab)