Questions tagged [elementary-particles]
The fundamental subatomic particles that have no (currently known) substructure. These include fermions (quarks, leptons, antiquarks, and antileptons) and bosons (gauge bosons and the Higgs boson). A particle containing two or more elementary particles is a composite particle.
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Correlation between Entangled Particles in a Chain Sequence [closed]
Suppose we have two entangled particles, A and B. If we measure particle A and then subsequently entangle particle B with a third particle, C, would the state of particle A influence the combined ...
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How does Weinberg definition of particle states from standard momentum work?
In his first volume, part 2.5, Weinberg define one particle states $Φ_{p,𝜎}$ ($p$ is the momentum and $𝜎$ another quantum number) in the following way :
Choose a Standard momentum $k$
Find a ...
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Do different quantum fields of the same type have different creation and destruction operators?
[Context: I'm a math guy, self-studying QFT, using intro texts by Schwichtenberg, Klauber, Lancaster & Blundell; and also the web. Long-time reader of StackExchange, first-time questioner.]
In ...
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Quantum beats as temporal interferences : whats does that mean?
I've already seen the expression "temporal interference" used to designate these "quantum beats"; often to contrast with the "spatial" interference that would be ...
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Electroweak Interaction and SSB
I read that above unification energy, on the order of 100 GeV, electromagnetic force and weak force would merge into a single electroweak force.
I do not really understand how and when exactly two ...
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Can black holes be expressed as elementary particles?
I recently read somewhere that black holes with their radius (Event horizon's of course) being equal to the Planck length and their mass equalling Plank's mass, the black holes can be treated as ...
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Simplifying some momentum and gamma matrices algebra in invariant amplitude calculation
I'm calculating some `$B_0 \rightarrow K^* \nu_R \nu_L$ decay and right now I'm stuck at invariant amplitude $\mathcal{M}$, which leads from the tensor part of Lagrangian. I'm having trouble ...
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When is the OZI rule applicable?
According to wikipedia, the OZI rule states that any strongly occurring process will be suppressed if, through only the removal of internal gluon lines, its Feynman diagram can be separated into two ...
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Experimental method for measuring electric dipole momentum of electron
Is there any experiment for finding the electric dipole momentum of electron?
Provided that, The Standard Model predicted EDM for leptons including electrons.
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Particles, strings, and field theories
I work in quantum field theory in curved spacetime. Within QFTCS, we have a bunch of phenomena showing that the notion of "particle" is quite subtle. For example, the Unruh effect let's us ...
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Main subatomic particles [closed]
I've come across a question that asks what the subatomic particles are. The answer being the proton, neutron and electron. However, from my understanding subatomic particles also include quarks etc. ...
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Is an electron a point charge? [closed]
Doesn't electron capture imply an electron is not a point charge?
It needs to have a radius that overlaps with the proton. If it was a point charge, no matter how close it got to the proton, the ...
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Redefinition of fields and interpretation of the particle content
Suppose I have some Lagrangian $\mathcal L_1$ involving multiple fields $\phi_i$ with interactions. I can reparametrize the Lagrangian in terms of new fields $\psi_i$ by inserting some ...
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Is there something special about the $b$ quark?
I have seen many papers about measurements related to $b$ quarks, for example the forward-backward asymmetry of the $b$ quark or the decay width of $Z$ to $b \bar b$ pairs, but not so many for the ...
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'Elementary' particles (electrons) vs non-elementary particles (protons) regarding relativistic mass
Is there a possible slight difference between protons and electrons behaviour while they are accelerated at speeds that cause relativistic changes to their mass. Why am I asking that? Because for a ...
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Roundness of electrons [duplicate]
I have seen articles online discussing the roundness of electrons. This goes a bit against my understanding of electrons as elementary point like particles. How can a point have a shape? What does ...
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Elementary particles and distortion of spacetime? [closed]
Are elementary particles distorted when hit by gravitational waves?
If they are, how much can they be distorted near a black hole merger? Can that distortion somehow break the particle? In that case, ...
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Why do we insist that the electron be a point particle when calculation shows it creates an electrostatic field of infinite energy?
I've heard compelling reasons to think that it is one although why do we assert this in light of the calculation which shows a point particle creates an electrostatic field of infinite energy (see e.g....
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Vertex function QED and Deeply Virtual Compton Scattering (DVCS)
In QED we have one vertex where one line is virtual and the other two are physical:
But recently I came across the so-called Deeply Virtual Compton Scattering in which, after the interaction of an ...
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What is stopping us from splitting an electron? [closed]
If we could split an electron, we would probably find new things. So, why don't we shoot a lot of energy at it, and see what happens? I tried looking up what happens, but I got no good answers.
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Orbital angular momentum of in-out particles in Feynman diagrams
I have two main questions:
Do elementary particles have orbital angular momentum?
If the answer to (1) is yes. How do I calculate the probability amplitude of an event where in-out particles have ...
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Are all elementary particles consequential?
Apologies if the title is misleading. Really what I'm curious about is if every elementary has a point, at least in what we know. I know the different types of quarks are important of course, as they ...
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How to calculate ratios of cross sections?
I am a first year physics student taking an introductory course in particle physics. For the exercises below, I need to calculate the ratio of cross sections. I believe my understanding of cross ...
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Elementary particle detection post-collision
How do you detect elementary particles? What do you aim your detector at? What's a detector physically? How do you know that a particle "happened", if (I assume) you can't see it? Is the ...
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What is the sequence of symmetry-breaking events in the very early universe?
My current understanding of the very early universe is that all particles were completely symmetrical at one instance, but a chain of symmetry breaking events split these perfectly symmetrical ...
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Is the Planck mass the minimum required to form a black hole?
I have heard this stated before, even that this is reason elementary particles do not collapse into a black holes no matter how much they are compressed and why we don't need to worry about them being ...
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Lowest order Feynman diagram for $e^++e^-\rightarrow\mu^++\mu^-+\tau^++\tau^-$
This exercise’s aim is to draw all lowest-order Feynman diagrams for this process. I hadn’t encountered an electron-positron annihilation with four byproducts, so I am not sure how to proceed. It also ...
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Elementary charge of electron and elementary magnetic moment of electron?
There is an elementary electric charge that is equal to the electron charge. Beside this electric charge, the electron has also a constant value of its magnetic moment. Is there an elementary magnetic ...
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Why photons have not magnetic moment? [closed]
Spin of a particle is a magnetic moment.
Photon have spin-1, so why photon have not a magnetic moment because only 0-spin particles can not have a magnetic moment?
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Are Proton and Electron Charges a Coincidence? [duplicate]
I was curious why protons and electrons have opposite and equal charges which brought me to this post. Essentially, I was told that there wasn’t really an explanation and that the charges are only ...
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If quarks and electrons are both 0-dimensional, how can they have different masses?
If they are zero-dimensional but have different masses, wouldn't that have to suggest they have different densities meaning they are composed of different things?
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Have fundamental particles been observed?
Addendum: the answer appears to be either "no" or "depends on what you mean". Most of the "depends" involve a meaning of "particle" that is clearly jargon. My ...
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Classification of elementary particles that have been proposed to explain dark matter
I'd like to write a paragraph about elementary particles that have been proposed to explain dark matter, but I don't know exactly how to classify these particles or arrange them:
Scaler field
-- ...
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Can the number of each particle in the universe have changed after a black hole evaporation?
Imagine a black hole that has formed from a neutron star, so from neutrons only. The neutrons appeared from a proton and an electron while an electron neutrino was sent into the surrounding universe.
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Can singularities' spin be related to the quantum spin of elementary particles?
We do know that black holes can and sometimes do have angular momentum, as described by the Kerr metric. Though I have not found anything about the description of the angular momentum of the contained ...
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Standard Model searching for new physics in the wrong direction? [closed]
What makes the SM so confident that any possible new discrete elementary particles must exist outside and separated from the known elementary particles?
What is the definitive theoretical proof we ...
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Are all elementary massive particles distortions in the Higgs field? [closed]
I am confused, as I understand it, all elementary massive particles are sourcing from the Higgs scalar field thus are all distortions in the Higgs field. How this differs elementary from the old ...
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Is spin of elementary particles same as the rotation of a planet? [duplicate]
By the word spin of elementary particle, one would imagine the particle to be rotating around its own axis, just like a planet rotates, but is it actually true? While spinning does an elementary ...
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About QFT and wave packets as particles
I read Ryder's book on QFT but I couldn't understand what in facts are localized particles which are really observed and do they have any place at all in QFT. So I watched a Zee lecture in YT https://...
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Neutron star near black hole mass in a moving frame [duplicate]
Consider a neutron star with a mass close to that necessary to form a black hole. In a moving frame, it has additional kinetic energy, and its energy density should increase.
Why is it not possible ...
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Mesons sea and valence contribution
I want some clarity regarding sea and valence quarks.
Is sea quarks and gluons contribute in the properties of mesons like masses, spin distribution etc. and how they will contribute?
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Can an elementary particle truly be destroyed?
Much like the title above, can they be created (from absolute nothing) or destroyed (into absolute nothing), with nothing in this case being nonexistence. Taking into account the idea of quantum ...
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Is it possible that there is a third class of fermions?
There exist six types of quarks, and six types of leptons, both divided in three generations.
Could there be some other new class of exactly six particles, similar to these, but with properties such ...
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(Solved) Why does this Kaon interaction need the intermediate up quarks?
In the answers to a set of practice questions my lecturer shows that we need these up and antiup quarks in the middle, but I don't quite understand why we can't go straight from the down to strange ...
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How can beta decay change elementary particles?
From what I read on beta minus decay, when it happens a neutron gets "converted" into a proton, an electron and an electron-antineutrino. I also read that both the neutron and the proton are ...
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Extending Wigner's Classification with Gauge Symmetry
In Wigner's Classification, as far as I understand, one uses unitary irreps. of the Poincare group for treating an elementary particle, since then mass $m$ and helicity $h$ emerge naturally as ...
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Could a non-pointlike structure of elementary particles explain their spin?
Elementary particles are considered point-like. Which makes the concept of spin rather problematic. It can neatly be described by group theoretical considerations, but that offers no explanation what ...
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Neutrino Oscillation and Probability
I am a fresher in a university pursuing physics major. I have been very passionate about neutrinos.
So, I started studying them. But I have realised that, it requires a lot of mathematical physics ...
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Can fundamental particles have magnetic/electric quadrupoles, octopoles, and higher-order moments?
Fundamental particles come with magnetic and electric charge, which makes the particles into a monopole source for the magnetic and electric fields. Of course, the magnetic charge is zero for all ...
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Is inertia present at the level of elementary particles?
Is a more massive elementary particle will experience more inertia in a one-on-one particle interaction?
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