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Questions tagged [elementary-particles]

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3
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2answers
244 views

Doesn't the fact that elementary particles are not black holes prove they are not point structures? [duplicate]

De Schwarzschild radius of a mass $m$ is defined as $$r_s=\frac{2mG}{c^2}(m).$$ So if we insert in this formula the mass of an electron (a point particle, according to mainstream physics), which ...
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1answer
76 views

How was electrical charge formed in the Big Bang?

We know that fundamental particles (Quarks, electrons, etc.) were formed a while after the Big Bang. How was their electrical charge (its value and sign) determined? Was electrical charge present in ...
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3answers
1k views

Is there an electric dipole moment in an electron?

I just read an article in Science News (p7, 11/10/2018, link here) where researchers looked for an electric dipole moment in an electron. They spoke of charge separation between the positive and ...
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0answers
41 views

Is Quantum spin greater than $1$ possible? [duplicate]

I know that fermions have a spin of half of and bosons have a spin of 1 but at many places I have seen that their is written that spin for a boson can be 0,1,2.... Is there any physical meaning of ...
0
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0answers
41 views

Could every particle encode the distances to all other particles?

I was thinking about quantum gravity and pre-geometry and wondering this question: "If space does not exist. How does a particle know how far away it is from another particle?" i.e. there are no ...
1
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1answer
58 views

Are particles of fields that arise from compactification and strings treated differently in string theory?

I am aware that particles in string theory are different vibrating modes of strings. I am also aware that compactification leads to emergent fields from the parts of the metric of the compactified ...
1
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2answers
409 views

What constitutes the mass of electron?

Electron has mass of $9.10938356 \times 10^{-31}$ kilograms. Since an electron has mass, it should be made of some material. I understood that electron is nothing but negative charge. If this is the ...
8
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1answer
1k views

Is it a coincidence that quarks have exactly -1/3 or 2/3 the electron's charge? [duplicate]

I have read these questions: Why do quarks have a fractional charge? Is there an explanation for the 3:2:1 ratio between the electron, up and down quark electric charges? Hypercharge for $U(1)$ ...
2
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2answers
186 views

Why is boson spin number related to attraction and repulsion?

The accepted answer to this question says Since the electroweak interaction is mediated by spin 1 bosons, it is the case that "like (charge) repels like and opposites attract". Another answer ...
1
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0answers
53 views

Elementary particles and halo of matter - rookie question [duplicate]

I'm super new to this Stack and even newer to physics. To be honest, I am currently reading an introductory book on physics called "Seven brief lessons of physics" by Carlo Rovelli (the very first ...
2
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1answer
146 views

Can Virtual particles be knocked on shell (become real)?

I have read these questions: Can virtual particles be 'boosted' into becoming real particles by fields other than gravity? where dmckee specifically mentions J/Ψ meson production as a clear ...
0
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1answer
243 views

Is a neutron attracted to a proton in an isolated system?

As we know that if a neutral body comes near a charged body charges are induced on it and the nearer end experiences more force than the farther end, hence it attracts. What happens if the neutral ...
0
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1answer
91 views

What are flavor-diagonal interactions changes and how do they relate to the strong force?

I am a high school student taking a modern physics course. I am reading the 1983 journal article New Tests for Quark and Lepton Substructure which covers some science and mathematics behind quark and ...
2
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1answer
93 views

What is compositeness at energy scale $\Lambda$?

I am a high school student taking a modern physics course. I am reading the 1983 journal article New Tests for Quark and Lepton Substructure which covers some science and mathematics behind quark and ...
0
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2answers
52 views

How can particle decay all work out in the universe?

Unfortunately, I'm ignorant on this topic, and my main source is: https://en.m.wikipedia.org/wiki/Particle_decay If particles only decay into less massive particles, what keeps all the different ...
1
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1answer
69 views

Strong gravity at the micro level?

I have read this: https://resonance.is/black-holes-elementary-particles-revisiting-pioneering-investigation-particles-may-micro-black-holes/ where it says: For the case of hadrons, it is at least ...
0
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1answer
41 views

How do electrons absorb and reflect photons 100% of the times if their existence is based on probabilities in the density cloud? [closed]

Shouldnt there be observations where we never see the color of an object because none of their electrons existed in the space where photons would hit them ? Or does this not happen because of how many ...
2
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0answers
38 views

A question on the existence of elementary particles with relation to time

Suppose that the universe started existing at time $t = 0$ and we chose another arbitrary point in time $t =\tau$. Is it true that for every positive real number $\tau$ every single elementary ...
1
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1answer
166 views

Can elementary particles be confined to a smaller region then their Compton wavelength?

I have read this question: Elementary particle (electron) and non-elementary (proton) spagettification and the comments where it says: But no real elementary particle can be confined in a region ...
2
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1answer
122 views

How many elementary particles are contained in a molecule of $H_2O$?

I was wondering about how many elementary particles form up one molecule of $H_2O$. What I thought of is the following: Hydrogen : 0 neutrons, 1 electron, 1 proton; electron is elementary and proton ...
0
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1answer
503 views

Bhabha scattering Energy conservation

Griffiths Ex. 2.4 in his book "Elementary particles" says: "Determine the mass of the virtual photon in each of the lowest-order diagrams for Bhabha scattering (assume the electron and positron ...
0
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1answer
75 views

Equality of positron and proton charge problem statement

When I hear that the equality of positron and proton charge is an unsolved problem I assume that we are putting the electric charge by hand in the electroweak section of the SM Lagrangian. Is this ...
1
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2answers
173 views

Are elementary particles with inertial mass actually composite particles?

In the standard model, electrons, muons and taus are elementary particles i.e. they aren't composed of more fundamental particles. But after watching this YouTube video animated by an actual scientist,...
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0answers
121 views

How do I transform this angular distribution from CMS frame to lab frame?

One can derive that the angular distribution of a 1 -> 2 + 3 decay process is given by: \begin{equation}\frac{d\Gamma}{d\Omega} = \frac{1}{32\pi^2}\frac{|\boldsymbol{p}_2|}{M^2}|T_{fi}|^2\end{...
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0answers
22 views

Role of higher fermion generations in ordinary matter

Do the second and third generation fermions play any significant role in ordinary, everyday matter or physical processes? Could a hypothetical alternate universe without higher generation fermions (...
1
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2answers
52 views

Can we (in principle) obtain molecular bound systems by modelling fundamental particles and their interactions?

Is it possible, at least in principle, to start with the Schrodinger/Dirac/Klein-Gordon equations to model elementary particles and their interactions and to obtain in the end molecular bound systems? ...
0
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0answers
88 views

A particle with null properties

Let's imagine a particle with spin 0, zero mass, zero electrical charge, and so on - each of it's inherent quantum properties or charges is zero (like those in the list on the side here). The particle'...
0
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1answer
88 views

Is the “size” of fundamental particles invariant under Special Relativity?

I was reading this paper about invariance of quantum-mechanical equations in relativistic conditions. Although I couldn't understand most of it, I was curious to know if the "size" of fundamental ...
2
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1answer
91 views

What is “fundamental” in physics?

Sorry about the broad question. I'm still learning to frame the questions on Physics StackExchange. Currently researching the nature of interactions in philosophy. My question is: When physicists ...
3
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2answers
347 views

Higgs couplings and fermion masses

As far as I understand, the Higgs mechanism is a crucial component of the standard model, which is responsible for the weak gauge bosons acquiring mass, otherwise forbidden by renormalizability ...
2
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2answers
273 views

Angle in pair production

Assuming a very high energy photon (energy $E$) crosses the atmosphere and produces an electron-positron pair, I would like to know what is the angle between these to leptons produced. I was trying to ...
3
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3answers
123 views

Is there a basic/elementary mass in the universe? [duplicate]

When speaking about electrical charges, it seems every particle either has a charge $+1$ or $-1$, in units of the electron charge. Therefore, we have a fundamental charge. But what about mass? Is ...
1
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1answer
178 views

What color are elementary particles?

I was visualizing particle interactions one night and I realized I didn't know what color the particles actually are. I did a little research, but the search results were dominated by the color charge ...
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2answers
127 views

What is the reason for a wide B$_S$ peak in dimuon plot?

Why is the B$_s$ meson peak in dimuon invariant mass spectrum wider than the others? Upsilon meson has a lifetime of several orders of magnitude shorter, which by my intution should lead the wider ...
11
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1answer
1k views

Experimental boundaries for size of electron?

There is some confidence that electron is a perfect point e.g. to simplify QFT calculations. However, searching for experimental evidence (stack), Wikipedia article only points argument based on g-...
0
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1answer
26 views

What is regular mass spacing?

In a book I'm reading, there is a sentence as follows: Muons and taus are not extra-dimensional versions of electrons, because they don’t have a regular mass spacing and don’t have the same weak-...
1
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0answers
76 views

Does space cause matter to move in a 3D fashion, or, does the movement of matter in a 3D fashion cause space to appear 3D? [closed]

What is the mechanism that allows matter (elementary particles) to move with three degrees of dimensional freedom of movement but no more or less? I know it's not a question that has been discussed in ...
0
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2answers
36 views

Is there an instrument to separate a beam of mixed charged particle into its components (kaons, electrons, positrons…)?

Is there a method to separate a beam of particles into its constituents such as electrons, muons and kaons? Is there a method to separate a mixed beam of particles into pure beams?
3
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7answers
328 views

If we know spin isn't actually rotation, why do we still speak of intrinsic angular momentum? [duplicate]

The spin of an electron was classically thought of a spinning ball of charge. We know that that is not the case in the quantum picture, as the electron is pointlike. So why, then, do we still ...
-1
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1answer
129 views

What is a subatomic particle? [closed]

I am curious as to what a subatomic particle is and have done a bit of research but have turned up with nothing of any help.
12
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1answer
2k views

Stability of elementary particles

Are elementary particles stable, like many atoms or molecules are stable if there are no reaction partners nearby? Or can they be observed just for very short instances of time?
2
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1answer
67 views

Elementary particle and Gravitational fields

Does an elementary particle that doesn't interact with gravity, just like how dark matter doesn't interact with EM radiation, exist? If so could this particle go in and out of Black holes without ...
2
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1answer
66 views

Can the reaction ${\rm n}+{\rm p} \rightarrow {\rm d} + \pi^0$ give a deuteron in excited state?

I'm trying to find the isospin quantum numbers of the deuteron on the right hand side of this equation. I know that $|\rm p\rangle = |{1\over2},{1\over2}\rangle$, $|\rm n\rangle = |{1\over2},-{1\over2}...
2
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1answer
111 views

Why is the typical lifetime so different depending on the type of interaction?

Why is $\tau$ so different when it comes to Quantum Electrodynamics ($10^{-16}$s), Quantum Flavordynamics ($>10^{-13}$s) and Quantum Chromodynamics ($10^{-23}$s)? Does this have something to do ...
0
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0answers
38 views

How to estimate the ratio $BF(B^0 \rightarrow \pi^- e^+ \nu_e)/BF(B^0 \rightarrow D^- e^+ \nu_e)$

I would like to estimate the ratio of branching fractions $\frac{BF(B^0 \rightarrow \pi^- e^+ \nu_e)}{BF(B^0 \rightarrow D^- e^+ \nu_e)}$. The difference between the two decays is that in the first ...
5
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1answer
71 views

If we had enough energy available in particle colliders, what reactions could show up if the quark and electron fields weren't fundamental?

Suppose the quark and lepton fields weren't the fundamental fields of Nature, but that a "deeper" Lagrangian connected to a generic model of sub-quarks and -leptons would take over the conventional ...
0
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0answers
67 views

Specific coupling constants, fermions and string theory

Can string theory answer why the Yukawa couplings or the v.e.v.s.have the values they have in our Universe? I mean, why can string theory answer( and EXPLAIN) the question of why the top coupling to ...
1
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0answers
49 views

Can a particle be identified when one knows $\left<dE/dx\right>$ and the Cherenkov angle $\theta_c$?

I have a question about if it would be possible to identify a particle by measuring the energy loss due to ionization $\langle dE/dx\rangle$ and the Cherenkov angle $\theta_c$. I assume that we know ...
1
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1answer
41 views

Electrons in the nuclei

Is it possible that electrons would switch place with the protons in the atom? So that the electrons in the nuclei and the protons hover around them. Is it even possible? And why?
1
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1answer
247 views

Are mass, and therefore time, emergent phenomena?

As I understand, massless particles such as gluons and photons do not experience time due to the principles of relativity. An electron isn't sincerely an elementary particle - doesn't it exist more ...