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1answer
46 views

Which of the properties of particles are intrinsic properties and why?

For macroscopic objects it's clear that - once observed - the observed property does exist for a while, even if we are no longer observing it. That has to do with the complexity and stability of such ...
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0answers
83 views
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2answers
742 views

Why couldn't the decay $\pi^- \to e^- + \bar\nu_e$ occur if electrons were massless?

If we assume that electrons (just like neutrinos) are massless, why can’t the decay $\pi^- \rightarrow e^- + \bar{\nu}_e$ occur under the weak interaction?
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0answers
11 views

Order of the life time of the K± mesons [duplicate]

It is not a homework. I've just wanted to find the order of the life time of the K± mesons. I had some suggestions like Starting from Fermi’s model and dimensional analysis ,Considered decays like K ...
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1answer
40 views

Are the leptons in $\beta^-$ decay already present in the nucleus in some form?

In beta minus decay, beta-minus particle and anti-neutrino are ejected, leaving behind daughter nucleus. $\beta^-$ and anti-neutrino both are leptons. Were the leptons already present in the ...
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0answers
73 views

Is muon muon annihilation already realised?

As muon colliders do not yet exist, has muon-muon annihilation already been realized experimentally?
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1answer
49 views

How do we know that elementary particles possess definite parity?

As I was reading Griffiths' "Introduction to Elementary Particles" Wiley 2008, on chapter 4 "Symmetries", the question stroke me. The same as Parity operator (inversion in 3-dimensional space) we ...
0
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1answer
76 views

Does gluons have names?

I was trying to find in some general physics books and using the Internet the answer to my question - does each one of 8 gluons has its own name? For example quarks are named: Up Down Charm Strange ...
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1answer
77 views

What effects would a finding of Gravitational Repulsion Between Matter and Anti-Matter in the ALPHA Experiment have on Mainstream Theory? [closed]

The actual nature of the gravitational force between matter and anti-matter (attractive or repulsive) remains unsettled: See Are there experiments taking place right now that might show evidence for ...
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1answer
36 views

Can an atom be formed from a combination of subatomic particles other than electron, proton and neutron (or their antiparticle)?

I have read that there are plenty of elementary particles. Can some of them form some species other than proton and neutron that are able to form a stable atom together with an electron or an electron ...
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2answers
169 views

Can quarks be considered elementary?

In our current theories all hadrons are made up of quarks and gluons. This view reduces considerably the big family of hadrons by providing a very logical structure in which all quantum properties ...
0
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1answer
50 views

Relativistic Scattering

When we work out the relativistic general two-body scattering in the CM frame (like two elementary particles producing two other P1 +P2 -P3 -P4) , the cross section is proportional to absolute final ...
0
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1answer
73 views

Strangeness of elementary particles

What is the property, whose violation led to the assumption of strangeness? Prior to the discovery of strangeness was it assumed that particles that are produced by strong interactions can decay only ...
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2answers
403 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, ...
0
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1answer
77 views

Why are quarks elementary particles? [closed]

A neutron decays into a proton by changing one of its down quark into an up quark and releasing energy, positron and neutrino particle. If a down quark can decay into an up quark, why is it ...
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0answers
156 views

In a universe with four spatial dimensions would there be elementary particles with intrinsic isoclinic spin?

Elementary particles have an intrinsic property called spin which is different from classical spin as it does not involve actual rotation and the magnitude of spin cannot be changed but particles with ...
0
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1answer
53 views

How many fermions?

Quick question: I just read in a PhD thesis that there are 48 fermions. I count 6 quarks + 3 leptons + 3 neutrinos times 2 for anti-particles = 24 fermions. Am I missing something?
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2answers
64 views

Are electrons really elementary particles? [duplicate]

I know that physicist do accept that fact as "an assumption", or "as a fact" due to "proofs" (or missing unroof). But are electrons really to be considered as elementary particles?
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6answers
1k views

Good book about elementary particles for high school students?

I need a good book about elementary particles. I am a high school student and don't want anything to technical. I read a brief history of time and the universe in a nutshell but I want something that ...
0
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1answer
47 views

Particle Physics: Weak Interaction

Consider the following decay equation:- A Kaon(+) decays into a muon(-) and an antineutrino(?) The question is as follows :- State and explain whether the anti-neutrino is an electron, muon or tau ...
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0answers
40 views

Can an electron in empty space to create electromagnetic radiation?

Is it possible in the empty space to create electromagnetic radiation from oscillations of the charges only of one kind - positive or negative? This question stems from the fact that all man-made ...
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7answers
2k views

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles?

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles? It would appear to a layman such as myself that these ...
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2answers
109 views

Where do electrons come from in thermionic emission?

Let we suppose to have a HV Tube or CRT . The filament is connected to the secondary of the transformer used to supply the filament. At time $t=0$ the wires and cathode are neutrally charged. Then ...
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4answers
164 views

Why, fundamentally, are particles charged?

This is something that has long bothered me, and I have asked a few physicists and chemists and never gotten a very satisfying answer. Why are particles charged? And I'm not asking (and this is the ...
0
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1answer
72 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, ...
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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?
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1answer
207 views

Are electrons simple? Do they have any inner structure? [duplicate]

The Planck length is far smaller than the classical electron radius. Could the electron have structure?
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4answers
2k views

Intrinsic structure of electron

The electron contains finite negative charge. The same charges repel each other. What makes electron stable and why does it not burst? Is it a law of nature that the electron charge is the smallest ...
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0answers
100 views
1
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1answer
98 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?
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0answers
69 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 ...
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0answers
52 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 ...
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0answers
22 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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1answer
87 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 ...
0
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3answers
124 views

Which particles can go right through the atom?

Can elementary particles (like the electron, photon, or neutrino ) go through an atom (not the nucleus)?
9
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7answers
2k views

Why do physicists believe that particles are pointlike?

String theory gives physicists reason to believe that particles are 1-dimensional strings because the theory has a purpose - unifying gravity with the gauge theories. So why is it that it's popular ...
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2answers
82 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 ...
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6answers
263 views

Do the particles made in a collider exist outside the collider?

Below is the transcript of a section from Demystifying the Higgs Boson with Leonard Susskind. Around 1:02:23 Susskind says that the heaviest of the fermions is called the top quark. Top quark is ...
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3answers
303 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?
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3answers
3k views

Why do quarks have a fractional charge?

I am aware that evidence exists that strongly suggests the existence of quarks and do not doubt it. It is just simply really weird to me that they can have a fractional charge. While other ...
0
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1answer
66 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 ...
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2answers
143 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 ...
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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
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1answer
75 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
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1answer
693 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 ...
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2answers
63 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
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2answers
601 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 ...
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5answers
1k views

How can a point-particle have properties?

I have trouble imagining how two point-particles can have different properties. And how can finite mass, and finite information (ie spin, electric charge etc.) be stored in 0 volume? Not only that, ...
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2answers
51 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
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2answers
72 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 ...