Quarks, electrons, neutrinos, and photons?

[diana]

Can someone please explain the four classes of fundamental particles? (Just the basics) I came here because I never learned any chem or physics in school so please explain like I’m five :)

 

[Drakkith]

Can someone please explain the four classes of fundamental particles? (Just the basics) I came here because I never learned any chem or physics in school so please explain like I’m five :)

Hi Diana! Welcome to PF! Unfortunately we don't usually regurgitate general information about a topic here at PF. There are many, many websites, videos, books, and other sources that already do a much better job of this than we could ever do and I encourage you to look into those. However, if you have specific questions on the topic please feel free to ask.

Some hopefully helpful links:
https://flexbooks.ck12.org/cbook/ck...1/primary/lesson/fundamental-particles-ms-ps/
https://en.wikipedia.org/wiki/Elementary_particle

 

[mathman]

Google particle physics and also names. Wikipedia should give you a start.

 

[Astronuc]

Quarks:
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html

Quarks and Leptons are the building blocks which build up matter, i.e., they are seen as the "elementary particles". In the present standard model, there are six "flavors" of quarks. They can successfully account for all known mesons and baryons (over 200). The most familiar baryons are the proton and neutron, which are each constructed from up and down quarks.

Leptons are light particles, the most familiar is the electron and its antiparticle, the positron.
http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/lepton.html


Neutrinos are small neutral particles.
http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/neutrino.html

The electron neutrino (a lepton) was first postulated in 1930 by Wolfgang Pauli to explain why the electrons in beta decay were not emitted with the full reaction energy of the nuclear transition.

http://hyperphysics.phy-astr.gsu.edu/hbase/emwav.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/mod2.html#c4
Photons are electromagnetic radiation from long wavelength (low energy) radiowaves to high energy gamma rays. Charged particles, or interactions of charged particles, are the source.

 

[PeroK]

Can someone please explain the four classes of fundamental particles? (Just the basics) I came here because I never learned any chem or physics in school so please explain like I’m five :)

When I went to school, we didn't start learning particle physics until we were at least seven years old.

 

[mathman]

When I went to school, we didn't start learning particle physics until we were at least seven years old.

|You must be kidding!

 

[Astronuc]

When I went to school, we didn't start learning particle physics until we were at least seven years old.

I had to wait until I was nine. My mother wanted me to study physiology and become a doctor, but I preferred learning chemistry and physics, with an interest in particle or subatomic physics, and astrophysics.

 

[PAllen]

I had to wait until I was nine. My mother wanted me to study physiology and become a doctor, but I preferred learning chemistry and physics, with an interest in particle or subatomic physics, and astrophysics.

I remember at 9 doing book reports on "educated layman" books with titles:

"Neutron Activation Analysis" and "Controlled Nuclear Fusion" (at that time covering such quaint topics as stellarator and pinch devices; tokomak was not on the horizon, of course).

 

[ohwilleke]

Can someone please explain the four classes of fundamental particles? (Just the basics) I came here because I never learned any chem or physics in school so please explain like I’m five :)

The problem with explaining "just the basics" is that each particle is part of an overall set of different kinds of particles that each follow their own rules, like chess pieces in a game of chess. It is hard, for example, to explain what a knight in chess is, without knowing most of the rules that apply to all of the different kinds of chess pieces.

In chemistry, we oversimplify reality and explain how different kinds of molecules and atoms form and interact with protons, neutrons, and electrons, which interact electromagnetically with each other. The proton-neutron-electron model of atoms gives us the "periodic table of the elements" that classifies the main properties of different kinds of atoms which are called elements.

But, to understand nuclear fusion (combining atoms into bigger atoms), nuclear fission (breaking atoms into multiple smaller atoms), nuclear radiation, certain kinds of behavior of light, and other kinds of interactions that happen only at high energies or in nuclear interactions, we need two more forces (the strong force and the weak force), a lot more particles, and more complicated equations, to get a complete picture. It also takes a lot more vocabulary and this answer will give you something close to the minimum number of terms needed to properly talk about these extra particles and forces.

This is necessary because protons and neutrons aren't actually fundamental. They are made up of smaller "point-like" subatomic particles that interact by exchanging other particles in a way that is scientifically described by "quantum mechanics." These additional particles are more accurately called "fundamental particles."

Also, the premise of your question isn't quite right. There are really eight main kinds of particles, not four (plus one hypothetical kind to explain gravity, that may or may not exist) if you really want to be as exact as possible about it.

Fundamental fermions (u, c, t, d, s, b, e, mu, tau, v-e, v-mu, v-tau)

There are four kinds of "fundamental fermions": (1) up-type quarks (called up, charm, and top), (2) down-type quarks (called down, strange, and bottom), (3) charged leptons (called electron, muon, and tau), and (4) neutrinos (electron-neutrino, muon-neutrino, and tau-neutrino).

Each fundamental fermion has an anti-particle.

Each fundamental fermion and each anti-particle of fundamental fermions comes in three "generations" that differ only by mass (and by some subtle details of their weak force interactions).

Each quark and lepton (both particle and anti-particle) comes in a left handed and a right handed version. Neutrinos are left handed; antineutrinos are right handed. There are no right handed neutrinos and no left handed antineutrinos.

To oversimplify, fermions can't be in the same place at the same time. Physicists assign a quantity called spin (also called "total angular momentum") to fundamental particles, and all fundamental fermions are spin-1/2.

Fundamental bosons (photon, W+, W-, Z, gluon, Higgs boson).

There are also several kinds of "fundamental bosons": (5) the photon (associated with electromagnetism), (6) the W+, W- and Z boson (associated with the weak force and collectively called the "weak force bosons" and sometimes abbreviated "V" when something could be either a W boson or a Z boson), (7) gluons (associated with the strong force), and (8) the Higgs boson.

To oversimplify, bosons can be in the same place at the same time. Physicists assign a quantity called spin (also called "total angular momentum") to fundamental particles, and all fundamental fermions are spin-1, except for the Higgs boson which is spin-0. A particle with spin-1 is also called a "vector" particle, and a particle with spin-0 is also called a "scalar" particle.

Fundamental Particle Masses

Each of the six "flavors" of quarks and each of the three charged leptons has an associated rest mass that is shared by its antiparticle. There are also three neutrino masses.

W bosons (both W+ and W-) have a fundamental rest mass, as do the Z boson and the Higgs boson.

Gluons and photons have zero mass.

In all there are fifteen different fundamental particle masses in the Standard Model. We don't know why they have the values that they do. Some are known very precisely, others are known only very approximately.

The Higgs field created by the Higgs boson imparts mass, at least, to the quarks, charged leptons, W+, W- and Z bosons, and to itself. The means by which neutrinos acquire mass is unknown and an active topic of research.

The fundamental particle masses aren't really "constant", however. Their exact values depend upon the energy and momentum of the particles interacting with them. Generally speaking, they get less massive at higher energies.

Fundamental Particle Electromagnetic Charge

In chemistry and basic physics, we usually think only about electrons which have electromagnetic charge -1, protons which have electromagnetic charge +1, and neutrons which have electromagnetic charge of 0. And, instead of thinking about photons, we use a few simple laws of physics called Maxwell's Equations that are a close but imperfect approximation of how electromagnetism works. Sometimes, we don't even use Maxwell's Equations, and instead use an even more crude approximation called the circuit laws, that explain how electricity behaves when it is trapped in wires that are connected by standard parts like resistors and capacitors.

But, if you are looking for a more exact description you have to consider subatomic particles, because the protons and neutrons that you use in chemistry and basic physics are actually made up of quarks and gluons and also interact through other kinds of particles.

Up-type quarks have an electromagnetic charge of +2/3, down type quarks have an electromagnetic charge of -1/3, charged leptons and W- bosons have an electromagnetic charge of -1, W+ bosons have an electromagnetic charge of +1 and are the antiparticles of W- bosons. Anti-particles have the opposite electromagnetic particles of the particles to which they are anti-particles.

Photons, gluons, Z bosons and neutrinos have an electromagnetic charge of zero and don't interact via emit and absorb photons which is how the electromagnetic force operates.

The electromagnetic force should be familiar to you, at least somewhat. Atoms in molecules and electrons bound to atoms are held in place by the electromagnetic force.

The strength of the electromagnetic force isn't "constant", however. Its strength depends upon the energy and momentum of the particles interacting with photons. It gets stronger at higher energies.

The electromagnetic force operates at distances a short as the inside of a proton (about 1/1,000,000,000,000,000th of a meter) and as long as billions of light years of distance.

The quantum mechanical version of electromagnetism is called "quantum electrodynamics" or QED for short.

The Weak Force

The weak force operates by emitting and absorbing W+, W- and Z bosons.

This force only interacts with left handed particles and right handed antiparticles.

All massive fundamental particles in the Standard Model interact via the weak force. All fundamental particles in the Standard Model with zero rest mass do not interact via the weak force.

Z bosons are basically heavy, short range photons that are much weaker than regular photons and product particle-antiparticle pairs when they decay.

W bosons can change one kind of quark into another kind of quark, or can change a charged lepton into a neutrino (or visa versa). There are four experimentally measured physical constants that explain the probability of one quark changing into another kind of quark. There are another four experimentally measured physical constants that explain the probability of one neutrino transitioning into another kind of neutrino (to oversimplify). The value of these eight physical constants depends upon the energy and momentum of the particles interacting with W bosons.

The W boson is the only particle whose interactions described going forward in time are different than its interactions described going backward in time. In contrast, photons, gluons, and Z bosons behave exactly the same way going forward in time and going backward in time.

The weak force is what causes the beta decay of atoms (something that radioactive elements do as they decay into lighter elements).

The strength of the weak force isn't "constant", however. Its strength depends upon the energy and momentum of the particles interacting with W and Z bosons. It gets weaker at higher energies.

The weak force only operates at very short distances (shorter than the diameter of a proton).

There are deep connections between the electromagnetic force, the weak force and the Higgs boson. So sometimes we talk about them for theoretical purpose as a single force with different aspects to it, in what is known as "electroweak unification."

The Strong Force

Quarks and gluons interact via the strong force which is driven by "color charge". There are three kinds of quark color charge (commonly called red, green and blue, but with no relation to actual physical colors, they are just arbitrary labels), and there are eight kinds of gluon color charges. Quarks interact via the strong force by emitting and absorbing gluons. Gluons can also interact with each other via the strong force. The other particles do not interact via the strong force.

The strength of the strong force isn't "constant", however. Its strength depends upon the energy and momentum of the particles interacting with gluons. It gets weaker at higher energies.

Protons are (to oversimplify) made of two up quarks and one down quark bound by gluons. Neutrons are (to oversimplify) made of one up quark and two down quarks bound by gluons.

There are lots of other composite particles made up of quarks held together by gluons are called hadrons. Many are made up of a quark and an antiquark bound by gluons and called "mesons". If they are made up of three quarks bound by gluons, or three antiquarks bound by gluons, they are called "baryons" (a group of hadrons that includes protons and neutrons). There are also hadrons that we know are composite particles with four, five or six quarks, and there are hadrons that we don't know the formula for creating just their properties as a combined object.

Most of the time, quarks and gluons are only found bound together in hadrons, which is something called "confinement". But there are two exceptions to this rule: First, when top quarks and anti-top quarks are created (the heaviest quarks which are much heavier than any other kind of quark), they decay into other particles (most often bottom quarks) before they can form hadrons. Second, at very high temperatures (much hotter than the Sun and only reached in the biggest atom smashers and just after the Big Bang) quarks and gluons form a big mush of strongly interacting particles called a "quark gluon plasma" (QGP).

The physics of the strong force is called "quantum chromodynamics" or QCD for short.

A residual of the strong force that holds protons and neutrons together holds atomic nuclei together. It is sometimes known as the nuclear binding force. This force is transmitted by composite mesons including pions (which are, to oversimplify, made up of an up or down type quark and an up or down type antiquark bound by gluons).

Basically, the strong force is only relevant at very short distances of roughly the size of an atomic nucleus or less.

Recap

While there are six main kinds of quarks, once you consider the three color charges that each kind of quark can have, the fact that they can be left or right handed, and the fact that they each have antiparticles, there are actually 6 times 3 times 2 time 2 kinds of quarks for a total of 72 different variations.

There are three main kinds of charged leptons that can be left or right handed and each has antiparticles, for a total of 3 times 2 times 2 kinds of charged leptons for a total of 12 different variations.

There are three main kinds of neutrinos that each have antiparticles, for a total of 3 times 2 for a total of 6 different variations.

So there are actually 90 different variations of fundamental fermions.

There are eight kinds of gluons, three kinds of weak force bosons, one kind of Higgs boson, and one kind of photon for a total of 13 different variations of fundamental bosons.

So there are actually 103 different discrete distinct variations of fundamental particles in the Standard Model that interact according to a formula. Each of these 103 kinds of particles is exactly like every one of the other particles of that kind except for some qualities that vary continuously like the direction and speed it is traveling, its location, frequency/wave length (different ways of saying the same thing) for bosons, and also by a property called "helicity" for bosons which is similar to being left handed or right handed, and a property called "polarity" for bosons,

The formulas for the electromagnetic force, the strong force, and the weak force are very similar to each other mathematically. If you want to understand these interactions better, I would recommend reading a short book by Richard Feynman called "QED" that is intended for non-mathematicians and non-physicists, but still takes some basic chemistry and physics to understand well. Feynman (he's dead now) was famous for explaining very complicated ideas, in very simple ways, that were still accurate scientifically.

The Standard Model v. Beyond The Standard Model New Physics

Everything I've explained above is our "state of the art" understanding of the most fundamental physics of everything but gravity from which everything else, in principle, in the universe can be figured out (spoiler alert: we can't actually do the math to get all other science from these laws of physics this way even though we think it is possible to do so).

The formula that combines the interactions of all of these particles in all of the possible ways that they can interact is called the "Standard Model Lagrangian". You could fit it on a t-shirt if you get the print small enough.

These laws of physics are called the Standard Model of Particle Physics, and they do an excellent job of explaining experiments. But, at any given time, there are a small number of experimental results that don't seem to be a perfect fit for reasons we don't fully understand. And, we also can't test the Standard Model of Particle Physics in all possible conditions (in particular, we can't test it at the extremely high energies present just after the Big Bang).

Physicists spend a lot of time considering ways to change the rules of the Standard Model of Particle Physics (SM), and when they do they are working on what is called "Beyond the Standard Model" (BSM) physics or "New Physics." Physicists also spend lots of time and money doing experiments at very high energies (mostly in particle colliders, but sometimes using other methods too) to see if the real world behaves more like the SM, or more like some BSM theory.

There are lots and lot of different BSM theories of physics and most of them have new particles and/or different forces. None of them have really solid evidence to back them up yet by physics standards, because if they did, they would be part of the SM instead of BSM theories. String theory, supersymmetry, and supergravity are popular BSM theories.

Gravity

We talk about four fundamental forces: electromagnetism, the weak force, the strong force, and gravity. But only three of them are described above.

The idea of a force of gravity was invented by Isaac Newton in the 1600s. It says that the force of gravity between two objects is equal to their masses multiplied together, divided by the distance between them multiplied by itself, times a physical constant called Newton's constant. This oversimplified theory of gravity is easy to use and is still good enough for most purposes. It is even simpler than Maxwell's equations for electromagnetism.

But, when things are really dense, or really fast moving, you need Einstein's theory of General Relativity, which is more precise and accurate. General Relativity (GR) doesn't involve quantum mechanics or fundamental particles. It is summed up by one equation (with about ten subparts that aren't visible in the usual one line equation) and two physical constants, Newton's constant, and another physical constant called the cosmological constant (a.k.a. lambda) which is related to the rate at which the universe is expanding and is only important to understand things billions of lights years away from us.

The Standard Model plus General Relativity is often called "Core Theory".

Maxwell's equations, Newton's theory of gravity, and General Relativity are all "classical physics equations" that are "deterministic" in that if you give it the present situation they will predict exactly one outcome at a set time in the future.

The Standard Model, in contrast, involves "quantum physics" and predicts exactly the likelihood that something will happen, but not exactly what will happen and uses a quantum mechanics way of thinking about things.

Mostly for reasons related to the differences between classical physics equations and quantum mechanics, making the other three forces play nice mathematically with General Relativity is a problem. Most physicists think that General Relativity is just an approximation of a more fundamental theory of gravity known as quantum gravity. But, despite more than a century trying to come up with a workable theory of quantum gravity, we haven't managed that yet.

If quantum gravity is real, there is another fundamental boson out there that carries the gravitational force called the "graviton", which like the photon has zero mass and operates at all distances from tiny to vast. But it would have spin-2, rather than spin-1 like a photon, and it would interact with the mass-energy of a particle, rather than with its electromagnetic charge, or weak force charge, or strong force color charge. A spin-2 particle is also called a "tensor" particle.

 

[diana]

Thank you!

 

[mattt]

The problem with explaining "just the basics" is that each particle is part of an overall set of different kinds of particles that each follow their own rules, like chess pieces in a game of chess. It is hard, for example, to explain what a knight in chess is, without knowing most of the rules that apply to all of the different kinds of chess pieces.

In chemistry, we oversimplify reality and explain how different kinds of molecules and atoms form and interact with protons, neutrons, and electrons, which interact electromagnetically with each other. The proton-neutron-electron model of atoms gives us the "periodic table of the elements" that classifies the main properties of different kinds of atoms which are called elements.

But, to understand nuclear fusion (combining atoms into bigger atoms), nuclear fission (breaking atoms into multiple smaller atoms), nuclear radiation, certain kinds of behavior of light, and other kinds of interactions that happen only at high energies or in nuclear interactions, we need two more forces (the strong force and the weak force), a lot more particles, and more complicated equations, to get a complete picture. It also takes a lot more vocabulary and this answer will give you something close to the minimum number of terms needed to properly talk about these extra particles and forces.

This is necessary because protons and neutrons aren't actually fundamental. They are made up of smaller "point-like" subatomic particles that interact by exchanging other particles in a way that is scientifically described by "quantum mechanics." These additional particles are more accurately called "fundamental particles."

Also, the premise of your question isn't quite right. There are really eight main kinds of particles, not four (plus one hypothetical kind to explain gravity, that may or may not exist) if you really want to be as exact as possible about it.

Fundamental fermions (u, c, t, d, s, b, e, mu, tau, v-e, v-mu, v-tau)

There are four kinds of "fundamental fermions": (1) up-type quarks (called up, charm, and top), (2) down-type quarks (called down, strange, and bottom), (3) charged leptons (called electron, muon, and tau), and (4) neutrinos (electron-neutrino, muon-neutrino, and tau-neutrino).

Each fundamental fermion has an anti-particle.

Each fundamental fermion and each anti-particle of fundamental fermions comes in three "generations" that differ only by mass (and by some subtle details of their weak force interactions).

Each quark and lepton (both particle and anti-particle) comes in a left handed and a right handed version. Neutrinos are left handed; antineutrinos are right handed. There are no right handed neutrinos and no left handed antineutrinos.

To oversimplify, fermions can't be in the same place at the same time. Physicists assign a quantity called spin (also called "total angular momentum") to fundamental particles, and all fundamental fermions are spin-1/2.

Fundamental bosons (photon, W+, W-, Z, gluon, Higgs boson).

There are also several kinds of "fundamental bosons": (5) the photon (associated with electromagnetism), (6) the W+, W- and Z boson (associated with the weak force and collectively called the "weak force bosons" and sometimes abbreviated "V" when something could be either a W boson or a Z boson), (7) gluons (associated with the strong force), and (8) the Higgs boson.

To oversimplify, bosons can be in the same place at the same time. Physicists assign a quantity called spin (also called "total angular momentum") to fundamental particles, and all fundamental fermions are spin-1, except for the Higgs boson which is spin-0. A particle with spin-1 is also called a "vector" particle, and a particle with spin-0 is also called a "scalar" particle.

Fundamental Particle Masses

Each of the six "flavors" of quarks and each of the three charged leptons has an associated rest mass that is shared by its antiparticle. There are also three neutrino masses.

W bosons (both W+ and W-) have a fundamental rest mass, as do the Z boson and the Higgs boson.

Gluons and photons have zero mass.

In all there are fifteen different fundamental particle masses in the Standard Model.

<<snip>>

👏👏👏 I enjoyed it a lot!

(There are some typos, btw)

 

[ohwilleke]

👏👏👏 I enjoyed it a lot!

(There are some typos, btw)

I'm sure there are some typos. I can only devote so much time to correcting typos in old posts. If a typo causes confusion, please ask for clarification.

 

[berkeman]

I can only devote so much time to correcting typos in old posts.

Have you considered converting that into an Insights article?