Questions tagged [elementary-particles]

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1answer
37 views

Theoretical Enneaquark?

First of all I'm new to physics. I'm teaching my self as of late and I'm wondering if a particle composed of 4 up quarks and 5 down(= 1 charge) could theoretically form a 'stable' particle under the ...
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6answers
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Can elementary particles be explained adequately by a wave-only model?

I have been watching quantum mechanics documentaries and reading a layman's book called "The Quantum Universe". I believe I understand why the double slit experiments exclude a particle only model. ...
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1answer
56 views

Why do macroscopic objects not move at the same speed their constituents are made of?

How can subatomic particles move at relativistic speeds while the things they make up are moving much slower?
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3answers
11k views

What is the evidence for 'billions of neutrinos pass through your body every second'?

This statement is repeated so often that it has become somewhat of a cliche: 'billions of neutrinos pass through your body every second'. For example see 1, 2, 3, 4, 5, 6. What is the evidence for it,...
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1answer
36 views

Would both life as well as elementary particles no longer exist upon “heat death?

Would the elementary particles in the standard model still exist upon “heat death”? Would electrons stop orbiting around the nucleus? Would the periodic table of elements still be relevant assuming ...
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3answers
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Do all the elementary particles in the standard model have their own wave functions?

Is it possible to derive the wave functions of all particles in the standard model? Would this be through the Schrödinger equation?
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1answer
76 views

Can we split an electron (or any other elementary particle) like we split a photon?

On this site, there are many questions and answers about splitting a photon. Most of them right away clearly state, that the term splitting is not quite right, because in most cases, the original ...
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1answer
78 views

If an electron is a singularity do we talk about a black hole? [duplicate]

As the standard model states an electron is a pointlike particle. If it is really so it has all features to be thought of as a mini black hole but then there is the problem how a such black hole can ...
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2answers
54 views

Pressing questions about the annihilation of a particle & an antiparticle

A charged particle (e.g. proton) meeting with its own charged antiparticle (e.g., antiproton) annihilates and energy is given off in the form of radiation. Do we have any clue why this happens? Does ...
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0answers
72 views

Particles in curved space-time and group representation

It is well-known, that particles in Minkowski space can be constructed as unitary projective representations of the Poincaré group, i.e. isometry group of Minkowski space $M_d= \frac{Poincare_d}{SO(1,...
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1answer
92 views

Are matter particles really excitations of fields?

So it is said that particles are excitations of fields. We are given examples like photons for electromagnetic field, gravitons for gravity, etc. We are also told that normal matter is an excitation. ...
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2answers
67 views

What is the simplest, smallest matter in the universe? [closed]

per wiki, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms. what is the simplest, smallest matter ...
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3answers
814 views

How would we know that Dirac equation does not describe composite spin-1/2 fermions?

How do we know that the quanta of a quantized Dirac field describe elementary spin-1/2 fermions (or point particles of spin-1/2) and not composite spin-1/2 fermions (or extended structure of spin-1/2) ...
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4answers
230 views

Are entangled particles indistinguishable?

I have read this question: https://physics.stackexchange.com/a/462620/132371 where John Rennie says: When the two particles become entangled the means the total wavefunction Ψ can no longer be ...
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2answers
76 views

Relative size of electrons and quarks

Today, we consider quarks and electrons (leptons) as point-like or fundamental (structureless). Is there any way to indirectly probe quark/lepton substructure and guess if they are composite of ...
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2answers
174 views

Can elementary particles be nicely classified into “force transmitters” and “force emitters”?

This well-received answer begins with First of all, you can't compare photons with electrons. They are different types of particles (spin 1 vs spin1/2; force transmitter vs force emitter). I'd ...
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0answers
11 views

Dual Nature of Light Explanation Please [duplicate]

I am a high school student and I have studied that light has dual nature, i.e. wave nature and particle nature. So, how can any matter can posses two different behavior at the same time. Can we ...
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4answers
2k views

Can we stop electrons from moving? [closed]

We know that electrons have a dual nature just like EM waves (of course all the materials are said to have dual nature, noticeable or not). So looking at the wave nature of an electron and comparing ...
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5answers
1k views

What is the cross-section size of a photon?

How "wide" is a photon, if any, of its electromagnetic fields? Is there any physical length measurement of these two orthogonal fields, $E$ and $M$, from the axis of travel? When a photon hits a ...
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1answer
65 views

In QED why is the electron a point particle? [duplicate]

I read Feynman's book but this still unclear to me.
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1answer
82 views

Does the electron have size? [duplicate]

Can we ascertain the size of the electron? If it really is zero radius, then it can't be matter because it doesn't occupy space? Definition of matter (Google): physical substance in general, as ...
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2answers
241 views

Is there a reason, other than mass hierarchy, that we associate each quark generation with a particular lepton generation?

The Standard Model contains three generations of quarks, and three generations of leptons. We generally pair off these generations into the "light" generation ($e, \nu_e, u, d$), the "medium" ...
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0answers
59 views

What are the allowed $W$ bosons in Muon decay?

I am curious about the allowed Feynman diagrams in Muon decay and whether the $W$ boson can be either the $W^+$ or $W^-$. Muon decay follows the reaction: \begin{equation} \mu^-\rightarrow e^-+\...
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0answers
57 views

Can string theory explain why the charge of the positron and of the proton are equal? [duplicate]

There is not much more to elaborate. Can string theory say why electrons and protons have exactly opposite charge? And thus why hydrogen atoms are neutral? I guess that the answer is no, because ...
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0answers
20 views

Approximating the wave functions of multiple electrically charged elementary particles as a function of time and position

As I understand it the wave function of a free particle in natural units is defined by the equation $$\Psi(\vec{r},t)=\left(\frac{a}{a+it/m}\right)^\frac{3}{2}e^{-\frac{{\vec{r}}^2}{2(a+it/m)}}$$ with ...
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2answers
93 views

Minimal size of physical entities

I know that per current knowledge there are layers of size of physical entities going from elementary particles to molecules (and from molecules to molecular structures such as bricks or organism ...
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1answer
79 views

How do we know that the charges in an electron and a proton are equal? [duplicate]

An electron and a proton have opposite charges. But how can we be so sure that they have equal amount of charge but opposite? Can't there be a slight difference?
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1answer
54 views

Is it possible for a charged particle to have no spin? [duplicate]

Can a charged point particle ever have spin zero? If not why?
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1answer
67 views

Question about quantum fields, elementary particles, and quantum numbers, and fundamental forces

As I understand it the allowable spin states of elementary particles is tied to the number of space and time dimensions, so for any two universes with the same number of space and time dimensions the ...
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1answer
54 views

Spin of the particle and degrees of freedom

Wigner showed that irreducible representations of the Poincare group can be listed, depending of the mass being zero or larger then zero, as $2J+1$ dimensional representations where $J$ is half-...
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1answer
41 views

Can a hydrogen atom emit characteristic X-ray?

Is it not possible that incoming electron excite the hydrogen atom and then when it de-excites it releases radiation? Here please don't answer no because hydrogen is light. My actual query is can ...
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1answer
182 views

Why doesn't string theory predict the existence of infinitely many elementary particles?

I'm a physicist, but my knowledge of string theory is extremely minimal. My naive conceptual understanding is that the vacuum is modeled as a certain topology (and geometry?) for the spacetime, and ...
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1answer
55 views

Quantum particle definition

I'm reading a-lot of articles lately which mention "quantum particle" I was wandering what defines quantum particle in opposed to "regular particle"? from what I've read on the web, there are two ...
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1answer
107 views

How can electrons and quarks be composite?

There are theories suggesting that the electrons and quarks are not elementary particles, but instead are composite particles of two or more yet undiscovered elementary particles. However ...
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1answer
91 views

What does color represent in quarks?

Im sure I'm pretty undereducated to be asking a question like this, but what do the colors represent in quark chromodynamics? A I understand it, each color represents a sort of charge, but what kind ...
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1answer
78 views

Are all bound states entangled?

In QM, a bound state is a special state of a particle subject to ta potential such that the particle tends to remain localized in space. The potential may be external or it may be the result ...
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2answers
36 views

How to interpret air movement when we breath in terms of fundamental laws of nature?

How to interpret the movement of air in nose in the two parts of breath : inspire and expire in terms of the 4 interactions of nature, gravitational, electromagnetic, weak, strong interactions ?
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2answers
77 views

Pauli's exclusion principle in elementary particles

Elementary particles such as Quarks obey Pauli's exclusion principle since they exist in three colors (RBG). Where as electrons which is also elementary that does not have any color quantum numbers ...
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2answers
89 views

Can elementary particles quantum entangle?

I just want to know if elementary particles, such as a quark, can entangle with another elementary particle of the same kind. If so, does entanglement for elementary particles follow the same ...
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4answers
6k views

Is there anything in the universe that cannot be compressed?

I've always thought that there is nothing in the universe that cannot be compressed or deformed under enough force but my friend insists that elementary particles are exempt from this. My thought is ...
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2answers
154 views

Half life of elementary particles

Do elementary particles have half life? Can we theoretically calculate half of a particle which is in complete isolation?
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1answer
69 views

Why do electrons have rest energy?

E=mc² so inserting the value of m and c we get 0.511 MeV for electron but then what does this energy account for coz according to me electrons are not made up of any particles so this doesn't account ...
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0answers
77 views

Why don't strings have a Planck mass? (version 2)

The Energy $E$ of a fundamental string due to its length $L$ goes like $$E\sim TL$$ where string tension $T$ is given by $$T \sim \frac{1}{l_P^2}$$ (Using natural units $\hbar=c=1$ with planck ...
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0answers
118 views

Why don't strings have a Planck mass?

I understand that strings have a size of roughly the Planck length $l_P$ of $10^{-35}$ m. If that is the case then one would expect that their mass would be roughly the Planck mass which is an ...
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1answer
263 views

If quarks don't exist individually how can we say baryons are made up of three quarks?

We know the composite subatomic particles are made up of odd number of quarks (at least 3 for baryons ) or combination of quarks and antiquarks (mesons). My question is if they don't exist ...
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0answers
58 views

Possible Feynman diagram for $\tau^+ \rightarrow p \mu^+ \mu^-$ and $\tau^+ \rightarrow \bar{p} \mu^+ \mu^+$?

I want to know the possible Feynman diagram for these two lepton family, lepton and baryon number violating tau decays. These decays are forbidden in the Standard Model. But the further extension of ...
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0answers
82 views

Are there compelling reasons not to organize the elementary particles by charge and spin? [closed]

I don't like the way the standard model is currently displayed (see second picture for reference). It does a poor job of abstracting the information into something understandable. As far as I ...
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1answer
137 views

Do elementary particles have a density?

The SM supposes elementary particles are structureless unless composite objects like hadrons. For bosons, that can occupy the same state, we can define energy or mass density. The same happens but ...
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3answers
145 views

Can there be interference between a proton and an electron?

For example, we know that we can interfere two different electrons or two different protons by employing them in a double-slit experiment. Now suppose, we mix protons and electrons and shoot them ...
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2answers
1k views

How are quarks elementary when they can become leptons? [duplicate]

From a recently reignited [casual] curiosity into particle physics thanks to the Fermilab YouTube channel, I read about the g-2 experiment, followed by muons, naturally. Muons, it turns out have short ...

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