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0
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1answer
61 views

Fractional number of particles in the universe?

Is it possible, that the metagalaxy contains a fractional (non whole) number of particles or fractional number of a particular kind of particles (such as electrons)? Sorry, if my question is stupid, ...
0
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0answers
16 views

Evidence electrons are fundamental particles [duplicate]

Is there any evidence that entities like electrons and quarks are indivisible, i.e. not composed of other, smaller entities? And have I just made a category error by even asking this question?
1
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1answer
37 views

How many combination can quarks form?

How many different combinations can quarks produce? E.g. 2 up quarks + 1 down quark = proton. Is this value going to be infinite?
1
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0answers
70 views

Are we able to store low energy positrons in a magnetic field for arbitrarily long time?

And if not, what prevents us? Is there a mathematical equation describing the loss rate?
1
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0answers
65 views

What are these arcs in bubble chamber photos?

In photos such as this one, or this one (too large to fit inside post), what are the highly frenzied arcs that are really prominent in these photos? Are they simply physical walls in/of the ...
1
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0answers
13 views

Identifying interaction responsible for this particular Eta-prime decay

$$\eta ' \rightarrow \eta + \pi^{-} + \pi^{+}$$ To identity the interaction responsible for the above reaction/ decay, observe that the strangeness number sums to zero on both sides. Conservation ...
1
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0answers
37 views

Why doesn't the decay mode of negative omega conserve rest mass?

There are 3 modes of decay via which a $$\Omega ^{-}$$ particle can decay This is one of the decay: $$\Omega ^{-} \rightarrow \Xi ^{0} + \pi^{-}$$ Baryon number is conserved. Strangeness number is ...
1
vote
1answer
46 views

Conservation of Baryon number for this proton decay

The conservation law requires that Baryon number be conserved; that is, the sum of the Baryon number before and after a reaction/ decay must always equal the sum of the Baryon number after the ...
2
votes
2answers
58 views

How to prove or disprove that elementary particle has no spatial extention?

We are told that elementary particles has dimension zero and take up no space. For example, the electron is a point particle that have a negative unit charge, also has mass and spin, but no size. My ...
1
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3answers
156 views

What is the smallest observable structure in the universe?

I've been wondering about the Planck length recently, but it is not observable. What is the smallest actually observable structure in the universe?
0
votes
1answer
62 views

Black Holes: Are “elementary” particles just decomposing into sub-particles that we don't yet understand? [closed]

You often hear that black holes are so strong in their gravitational pull that matter, even light cannot escape. But this seems to contradict the laws of conservation of energy. Is it possible that ...
0
votes
2answers
89 views

How does electron gets negative charge and proton gets positive charge? [duplicate]

I researched much in physics but I still do not know how does electron gets negative charge and proton gets positive charge? What is the source of this charge and energy? How can this particles ...
0
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0answers
28 views

Why doesn't the electron fall into the nucleus? [duplicate]

Electrons move around the nucleus, which contain protons and neutrons. I know that quantum mechanics tells us that the nucleus is made up of fundamental particles, but why (quantum mechanically ...
1
vote
1answer
45 views

Are all ground state protons the exact same mass and have the same number of elementary particles?

I have read that it is a misconception that a proton only has 3 quarks (2 up and one down). In reality, it seems there are many, many ("zillions" is the number I saw quoted) quarks in a proton. Do ...
5
votes
1answer
635 views

What does it mean for a particle to have spin of 2? [duplicate]

When I first started to study quantum mechanics, my physics text book told that particles have spin of either 1/2 or -1/2. Then I recently read an article saying that gravitons are expected to be ...
0
votes
2answers
55 views

Since nucleons are not elementary particles more, how we call nucleons and electrons together now? [closed]

In the time before the discovery of quarks the nucleon particle proton and neutron together with electrons were called elementary particles. It's a little bit boring to have only the possibility to ...
2
votes
2answers
562 views

What experiment(s) have or can refute the existence of an electron-particle “system” over the separate existence of a neutron within itself?

This question actually came about from a discussion of another question posed here The neutron is known to be comprised of an electron and a proton, and there are observations that the neutron can be ...
0
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2answers
48 views

On Elementary Particles

The mass of positron and electron are same. Also their charges are equal in magnitude but opposite in nature. Then why positron is not called one of the elementary particles? Is this only because it ...
3
votes
2answers
51 views

Is the only difference between two particles their location and momentum?

Maybe this would be better suited for philosphy.se, if so, then let me know and i'll move it, but this seemed like a reasonable place to start. Let's start with my motivations for asking such a ...
3
votes
1answer
24 views

LArTPC muon sign determination

What are some techniques for muon sign determination (w/o magnetic field) for fully contained muons, using statistical analysis? Especially because liquid Argon time projection chambers' sign ...
5
votes
3answers
102 views

How is the conservation of momentum satisfied in long-range attraction such as electromagnetism and gravity?

I'm not a physicist, but my understanding is that electromagnetism (including attraction between opposite charges) is mediated by the photon, and gravity is probably (hypothetized to be?) mediated by ...
0
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0answers
54 views

W boson one loop electroweak contribution to muon g-2

I want to calculate the one loop W boson contribution (triple gauge boson vertex WW-Photon) to the muon anomalous magnetic moment g-2 with the help of Dimensional Regularization. Diagram given below: ...
2
votes
0answers
66 views

Nature of particle spectra at ALICE

I have a question regarding the nature of the particle spectrum at ALICE as a function of momentum. The spectra in question can be seen here. My question is, why is it that the particle spectrum in ...
2
votes
2answers
70 views

What are the “generations of matter”?

After a series of clicks on New Scientist and Wikipedia, I ended up on the Wiki article for "generations of matter", and I didn't quite understand it. I believe (and this may be wrong) that different ...
5
votes
1answer
1k views

Is a photon technically a set of two particles?

When looking at the classification of massless particles, one finds that there is the (half-integer) quantum number "helicity" $h$. For every possible $h$ there is a certain particle kind. In the case ...
15
votes
6answers
2k views

What happens before a radioactive element decays?

What happens to a radioactive element just before it decays? In school, I've been told that the decay process of an element is absolutely random, and it is impossible to determine which unstable ...
1
vote
1answer
69 views

In what sense are photons emergent?

Recently I read in an essay by Wilczek: "Photons are mixtures of weak B3 and hypercharge C mesons. It is those objects, not the emergent photon, whose properties are ideally simple." Until now I ...
0
votes
1answer
54 views

What are the building blocks of objects? [closed]

We are always told everything is made of atoms, but that seems to me to be a to vague response. The atom is the smallest construction block for all things; if this is true, what are all the other ...
1
vote
2answers
65 views

Number of different massless particle an odd number

Why are there only three massless particles and not four? I thought for each kind of matter particle there is a corresponding particle. What makes this any different from everything else?
3
votes
1answer
93 views

Thickness of electromagnetic waves

Radio wave photons and light photons have a different wavelength. But they also appear to have a much different "thickness" in that light photons "fit" cleanly through small pigeonholes, where the ...
0
votes
2answers
205 views

How many elementary particles are there?

I was reading QED by Feynman (a dated book) and he seemed to be suggesting we have discovered hundreds of particles. But I thought there were only the ones we saw in the standard model (ie leptons, ...
-1
votes
1answer
139 views

Synchrotron radiation and special relativity

My questions below are for all those who assume the point-like electron of special relativity, that strange entity with no inner structure (!), but with intrinsic (?) rest energy, magnetic moment and ...
-2
votes
1answer
161 views

Emission and absorption of photons by electrons [closed]

Two questions occur at a critical review of the two famous experiments devised by Millikan in 1914, respectively Duane, Hunt and others in 1917-1920, which confirmed the action constant calculated by ...
3
votes
4answers
970 views

Must Matter Particles Have A Hard Edge?

It's my understanding that electrons are particles, and it's also my understanding that their location while orbiting an atom cannot be determined precisely and must be determined by statistics and ...
6
votes
4answers
1k views

Are atoms made of protons, electrons and neutrinos?

If neutrons decay into proton, electron and (anti)neutrino of electron type, then is it safe to say that atoms are protons, electrons and neutrinos?
7
votes
2answers
120 views

Can an elementary particle be reduced to its properties?

For instance, is an up quark merely its particular mass, 2/3 electrical charge and 1/2 spin? I was wondering if there was a 1:1 correspondence with a particle and its properties, but I noticed a gluon ...
6
votes
2answers
165 views

What are fundamental dimensions used to describe the physical universe? [closed]

I have heard that the universe can be explained in terms of the four fundamental forces. I have also heard it can be explained in terms such as space, time, energy, mass or even motion. To further ...
0
votes
1answer
49 views

If matter and antimatter were produced equally during the big bang, where is the rest of the antimatter? [duplicate]

As far as my understanding goes, during the 'Big Bang' equal amounts of matter and antimatter (matter's oppositely charged twin) were produced, and the physical matter that remains within this ...
2
votes
3answers
170 views

Self-energy of electron from classical reasoning

If it takes energy to group charge together(self energy) how can it be possible for every single electrons, etc, to have exactly same amount of charge? (think of if we hold some sand in our hand, then ...
4
votes
2answers
311 views

How does electron spin change instantaneously without violating inertia principle?

The inertia in one of the main properties of matter. That is why all process in macro world do not happen instantaneously. What I do not understand is how we should apply this general idea of inertia ...
4
votes
1answer
128 views

Why should I believe that “elementary” particles are indeed elementary?

Atoms were once thought to be indivisible (i.e. have no substructure), until it was discovered that they are made of protons and neutrons. Protons and neutrons in turn are made of quarks, and that's ...
3
votes
0answers
40 views

Are the electric charges of an electron and a proton equal or approximately equal? [duplicate]

I read in Auletta's quantum mechanics (section 11.2) that the charge of the proton is, apart from the sign, approximately equal to that of the electron.. What ...
1
vote
0answers
28 views

Conservation of charge on Higgs production by bremsstrahlung

The Higgs production channel $$q+\bar{q} \rightarrow W^++ H^0,$$ depicted below, seems to be violating charge conservation, or am I missing something? The quark and its antiquark have the same ...
3
votes
1answer
124 views

Magnetic moment of uncharged particles

As we know that particles, only having charge, can have magnetic moment, then how particle like neutrino (having mass) can have magnetic moment? Don't bother about neutron because it has charge ...
12
votes
3answers
2k views

An electron has no known internal structure, does that imply it has an unknown one?

I'm currently reading Alonso and Finn's Electromagnetism book. It explains that the spin contributes to the magnetic moment and is somewhat comparable to a rotation of the particle around its own ...
0
votes
2answers
212 views

What does temperature look like at the subatomic level?

I am trying to get a better understanding of the definition of temperature at the subatomic level. I have a background in molecular biology with some college physics, but no deep quantum mechanics ...
1
vote
1answer
57 views

Does quark have fixed energy?

Does a quark, for example a up-quark has a fixed energy? The standard model gives well defined masses in MeV which is energy too.
2
votes
0answers
69 views

Young Tableau Projectors: Does the order of symmetric and anti-symmetric projectors matter?

Given a Young Tableau we find the irreducible basis of an arbitrary tensor by projecting, The projectors are usually defined as first symmetrise over the row entries and then anti-symmetrise over the ...
31
votes
6answers
5k views

Do electrons have shape?

According to the Wikipedia page on the electron: The electron has no known substructure. Hence, it is defined or assumed to be a point particle with a point charge and no spatial extent. Does ...
26
votes
5answers
2k views

Is the graviton hypothetical?

Wikipedia lists the graviton as a hypothetical particle. I wonder whether graviton is indeed hypothetical or does its existence directly follow from modern physics? Does observation of gravitational ...