* These are not elementary particles.
* It was predicted for a long time that these composite particles should exist. So it is not "new" in the sense that it was unexpected, but we finally have the resolution (energy, luminosity etc.) to detect these with statistical significance.
* These belong to the same class as protons and neutrons - these are hadrons made with multiple quarks.
Here's a super simple overview of Quantum Field Theory & Particle Physics:
Everything is made of force fields and matter fields.
* We discovered that force fields (i.e. electromagnetism) is quantized, giving rise to quantum mechanics etc.
* Matter fields are also quantized, hence their excitations behave like discrete particles - the ones we observe at the atomic scale, for instance.
* In hindsight, we should've been able to predict this after E = mc^2 telling us energy <> matter, thus if energy is quantized so should matter.
Energy isn't necessarily quantized though. For instance, the spectrum of an unbound particle is continuous. So why does it follow that matter should be quantized from E = mc^2?
I assume you've heard of particle/wave duality, or how really tiny things are never exactly in only one place.
There are a set of wave equations that describe how this works.
There are also two kinds of things. Some things can go thru eachother, like photons. Other things bounce off eachother, like neutrons (and other things considered matter).
The equations for the kind of things that bounce off eachother would be a matter field.
There are also two kinds of things. Some things can go thru eachother, like photons. Other things bounce off eachother, like neutrons (and other things considered matter).
This is not true. The difference between bosons and fermions lies in the way swapping two of them works. The carriers of the weak force, W and Z bosons, are for example electrically charged and can therefore scatter off each other. Gluons, the carriers of the strong force, also interact with each other. Even photon photon scattering is thing. On the other hand you can try to collide two neutrinos, which are fermions, for quite some time and not much will happen.
The difference between bosons and fermions lies in the way swapping two of them works.
That sounds like what Wikipedia says is the rigorous version of the Pauli exclusion principle[1].
I was trying to get close to the not-rigorous version (1st paragraph of the link) in terms that are easily understandable without having taken a university QM course. I guess can/can't be in the same place at the same time would be a better approximation of it?
Loosely peaking the wave function of a quantum mechanical system specifies for each possible state of the system the probability of finding the system in that state. Actually it is not the probability but the probability amplitude, a complex number from which you can derive the probability by squaring it.
Assume you have two identical fermions, say two electrons, the first one in state x and the second one in state y. State means everything required to fully describe the particle, for example position and spin. Therefore x stands for the first electron being in a specific position and having a specific spin, similarly for y and the second electron.
Let A(x, y) be the probability amplitude for finding the first electron in state x and the second electron in state y, i.e. the first argument of A is the state of the first electron, the second argument is the state of the second electron. Now swap the two electrons, take the first and put it where the second one is, take the second one and put it where the first one was. Also change the spins as necessary. The probability amplitude is now A(y, x), the first electron is now in state y, the second electron is now in state x.
The important thing is now that the two electrons are identical, you can not tell the difference between the situations before and after swapping the two electrons. Had you painted one electron blue and one red, then you could easily tell the difference, but without that you can not. That was the entire point of swapping the electrons, bringing them into exactly the state of the other one.
But if you can not distinguish the two situations, then it better be the case, that they have the same probability, i.e. A(x, y) = A(y, x). But that is not quite right, A is the probability amplitude, not the probability. It turns out that there are actually two valid possibilities, A(x, y) = A(y, x) and A(x, y) = -A(y, x). As mentioned at the beginning, you get the probability by squaring the probability amplitude, so that the minus sign in the second case vanishes.
The first possibility is how bosons (particles with integer spin, for example photons and gluons) behave, the second one is how fermions (particles with half integer spin, for example quarks and electrons but also helium-3) behave. Now we finally arrive at the important point, what happens if both electrons are in the same state, i.e. if the first electron is in state x and the second electron is also in state x. Then the probability amplitude is A(x, x) and we have to satisfy A(x, x) = -A(x, x) because electrons are fermions.
But there is only one complex number identical to its negative and that is of course zero. Therefore the probability amplitude and in consequence the probability obtained by squaring the probability amplitude are both zero, which means that the probability of finding the system in the state where the first electron is in state x and the second electron is also in state x, is zero. The two electrons or more generally two fermions can never be in the exact same state.
I have actually! And I also know about bosons and fermions. I didn't realize the phrase "matter wave" was just the name for the wave in wave-particle duality, that's all :) thanks!
They are properly called fermionic fields [1] as opposed to bosonic fields. I also want to note that the »super simple overview of Quantum Field Theory & Particle Physics« really is super simple. As far as I can tell - I am not a physicist - none of the statements is actually correct.
Matter fields are indeed a real thing. a Google Books search will reveal hundreds of books etc. They're also called fermionic field.
Here's the full range of elementary particles, all 19 of them, in the Standard Model:
Fermions:
- Leptons (6) (electrons, neutrinos etc.)
- Quarks (6) (protons and neutrons are made of this)
Bosons:
- Gauge Bosons (aka Force Carriers) (4)
- Higgs Boson (gives mass to stuff) (1)
What classical physics called force fields (i.e. Maxwell's equations), now we call them gauge bosons.
Electromagnetism : Photon
Strong Force: Gluon
Weak Force: W&Z boson
Gravity: No one knows!
One extra boson that gives everything mass - the higgs.
Force fields are quantized (see re: Photoelectric effect & Einstein's paper in 1905, winning a nobel).
Matter fields aka fermionic fields are also quantized, which makes these fields behave as if they are composed of discrete states -- giving raise to the particles & discrete states.
Indeed, in the Wikipedia article you link to, the first sentence reads: "fermionic field is a quantum field whose quanta are fermions".
ie: matter/fermionic fields are quantum fields, whose quanta are fermions, i.e. electrons, protons.
So, actually, all my statements are correct. Do you care to give a concrete example as to which one is not correct?
This is the best summary I've read (not that I've read much) but it really puts things in perspective.
Correct me if I'm wrong, but I'm going to try to summarize to make sure I understand:
The properties of protons, neutrons, and electrons that make them unique/distinct from each other (mass, electric charge) arise from the composition of each out of smaller particles, which each are/carry/act as the respective mass + charge + the other properties.
Is there any theory as to what this "looks" like? Or is the best we can do "it's a bunch of these things mashed together and the only way to see them individually is to bash them together until they break"?
If the strong and weak forces are particles, does that mean they're 1: literally everywhere, not necessarily stuck to any larger particle and 2: like glue?
I'm also confused about the relationship between gravity and mass, given that the higgs is stated as corresponding to mass, mass is traditionally thought of as what gravity acts upon, but the wikipedia chart states that gravity acts upon all particles.
There are a few errors in your comment. I hope my comment can clarify some of them.
Electrons, Positrons, Neutrinos, Muons, ... are elementary particles. You can't break them.
Protons, Neutrons, ... are composed by three quarks. Quarks are elementary particles that you can't break.
The quarks inside the proton and neutron are bounded by the strong force. The strong force is really strong so no one have seen an isolated quarks.
We only know they are formed by three quarks because if we make them collide at high speed the quarks from one of them can be recombined with the quark of the other and form a few new particles.
It's more complicated, because during the collisions it is possible to create a pair of quark-antiquark. So if you collide a proton and an antiproton at a high speed, after the collision you have to rearrange the 3 quarks from the proton, the 3 antiquarks from the antiproton, and all the quarks and antiquarks that appeared in the collision.
The exact number of pairs of quarks and antiquarks and their favors are determined by probabilities derived from difficult calculations.
And actually, all this mess is not instantaneous, the quarks can rearrange themselves in some particles that later decay in other particles with other quarks.
In particular in this experiment they didn't see the "new" particles directly, because they live for a very short time. They only saw the particles that were formed after the "new" particle decayed.
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About
> If the strong and weak forces are particles
No. It's important to distinguish the difference between a force and the particles that are the carriers of the force. The differences and relations are subtle, so it's better do delay the discussion for another day
> gravity ... mass ... higgs
They are also different things, that are interrelated but different.
You've got it backwards. Fields are fundamental. Nature is just one big complicated multi-component field. The field is quantized in various ways that make state 'clump' in discrete ways: these are particles. The strong and weak force are mediated by particles because strong and weak interactions are comprised of quantized state transitions.
Gravity is a field, and mass is a property of how it is quantized. The Higgs particle is a description / side-effect of this quantization.
The properties of protons, neutrons, and electrons that make them unique/distinct from each other (mass, electric charge) arise from the composition of each out of smaller particles, which each are/carry/act as the respective mass + charge + the other properties.
Protons and neutrons are composite, made out of two up and one down respectively two down and one up quark. Plus gluons holding them together. There are also four other quarks, bottom, top, charm, and strange. And of course one antiquark for each of the six quarks. There is a huge number of particles made out of quarks, called hadrons. Hadrons are either baryons like the proton and neutron made out of three quarks, or mesons made out of one quark and one anti quark. There are also exotic things like tetraquarks.
Electrons are, as far as we know, fundamental and not made out of other particles. The same goes for the muon, the tau, and the three accompanying neutrinos. There is again an antiparticle for each particle. This group is called leptons.
The properties of composite particles are determined by their constituents, but not in a trivial way. The mass for example is usually bigger than the mass of the constituents because the binding energy contributes to the mass.
Is there any theory as to what this "looks" like? Or is the best we can do "it's a bunch of these things mashed together and the only way to see them individually is to bash them together until they break"?
Quantum chromo dynamics is the theory of quarks and gluons.
If the strong and weak forces are particles, does that mean they're 1: literally everywhere, not necessarily stuck to any larger particle and 2: like glue?
The electromagnetic, the strong, and the weak interaction are mediated by their respective bosons, we also suspect it for gravity. You can observe the bosons on their own, they are not like springs and rubber bands connecting particles between wich they mediated forces. Actually there are not really any photons bouncing back and forth between two electrons pushing them away from each other due to their like charges. But I can not offer any good model, that is something I never managed to really understand.
I'm also confused about the relationship between gravity and mass, given that the higgs is stated as corresponding to mass, mass is traditionally thought of as what gravity acts upon, but the wikipedia chart states that gravity acts upon all particles.
Most mass comes from [binding] energy, the Higgs mechanism contributes only a small bit. The Higgs boson has nothing to to with that at all, it is just an excitation in the Higgs field. Gravity acts on energy. As far as I can tell mass is just an abstraction. If you put massless photons into a mirror box to bounce around, they add energy to the box which makes the box harder to move, i.e. you have to push against the photons hitting the wall you are pushing on. As a convenient abstraction we say the box got heavier, it has more mass, but there is actually nothing fundamentally heavy in the box, the photons have no mass, only their energy and momentum with which they hit the wall making it harder for you to push it.
I am not a physicist, take all this with grains of salt.
We discovered that force fields (i.e. electromagnetism) is quantized, giving rise to quantum mechanics etc.
You are confusing quantum mechanics with relativistic quantum field theory. Quantum mechanics was developed as consequence of many different experiments showing quantization phenomena or requiring quantization to explain them, among them the spectrum of black-body radiation and the photo electric effect, but also the quantization of charge and spin. Quantum mechanics and non-relativistic quantum field theory are unable to describe electromagnetic fields, the former because it can not handle the creation and annihilation of particles, the later because photons are always relativistic particles and therefore require a relativistic description. Only with the development of quantum electrodynamics, a relativistic quantum field theory, was a quantum mechanical treatment of the electromagnetic field possible. But this was 20 or 40 years after the inception of quantum mechanics, depending on from where you count.
Matter fields are also quantized, hence their excitations behave like discrete particles - the ones we observe at the atomic scale, for instance.
It is important to understand, that quantum field theory is very different from quantum mechanics. In quantum mechanics a wave function describes the state of a system in Hilbert space, it describes properties of particles. But this runs into problems if the system contains many particles. Two electrons, for example, are indistinguishable and swapping them does not change the state, at least up to a sign change of the wave function which is the difference between fermions and bosons. This complicates the mathematical treatment. And as mentioned before, this approach is unable to handle the creation and annihilation of particles. Quantum field theory therefore takes a very different approach and describes with occupation numbers in Fock space how many particles are in each state.
In consequence the fields in quantum field theory are just a mathematical tool to handle many particle states. We started with particles and introduced fields to describe them mathematically, we did not discover that a field is quantized and therefore looks like a collection of particles. Admittedly this is a contentious issue, there are people claiming that those fields are real and more than a mathematical tool.
In hindsight, we should've been able to predict this after E = mc^2 telling us energy <> matter, thus if energy is quantized so should matter.
We knew or at least suspected that matter is quantized long before we discovered the photon, atoms and particles in general are a very old idea. So at best we could have inferred that energy is quantized from the quantization of matter, not the other way round. But the idea of photons actually predates E = mc², too. You are also probably misinterpreting what E = mc² actually says, you can not use it to link the quantization of energy to the existence of particles, at the very least not in any obvious way. The relationship between mass, energy, and particles is complicated.
And again, I am not a physicist, do not take what I say as the final truth, use it as a starting point. Corrections from actual physicist welcome.
* These are not elementary particles. * It was predicted for a long time that these composite particles should exist. So it is not "new" in the sense that it was unexpected, but we finally have the resolution (energy, luminosity etc.) to detect these with statistical significance. * These belong to the same class as protons and neutrons - these are hadrons made with multiple quarks.
Here's a super simple overview of Quantum Field Theory & Particle Physics:
Everything is made of force fields and matter fields.
* We discovered that force fields (i.e. electromagnetism) is quantized, giving rise to quantum mechanics etc.
* Matter fields are also quantized, hence their excitations behave like discrete particles - the ones we observe at the atomic scale, for instance.
* In hindsight, we should've been able to predict this after E = mc^2 telling us energy <> matter, thus if energy is quantized so should matter.