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Questions tagged [elementary-particles]

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What elementary particles have properties that vary by spin direction?

This table of elementary particles indicates that electron spin = 1/2. My understanding is that electron spin may proceed in two directions which may be denoted by spin sign and that electron spin ...
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1answer
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Two possible directions of the B field in relation to the E field in radio waves. How induce the left-handed direction?

In vacuum the two field components of a radio wave are directed perpendicular on each over. $\mathbf{E}$, $\mathbf{B}$ and $\mathbf{k}$ form a right hand system ($\mathbf{k}$ is the direction of ...
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0answers
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Shape of electron [duplicate]

Today, in the BBC Science section, a headline reads that the Imperial College of London has determined that the shape of the electron is completely spherical. In a physics book I'm reading now, the ...
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2answers
68 views

Why are the generations of leptons/quarks regarded as fundamental particles?

My understanding is that 'fundamental' pertains to there being a distinct quantum field corresponding to the particle. I ask the question above based on the fact that the heavier generations of ...
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2answers
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Elementary particles and Bosons

Which of the elementary particles in particular are called ‘Bosons’? It is a trivial knowledge that electrons are Fermions obeying Fermi-Dirac statistics. Fermions follow Pauli Exclusion Principle ...
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6answers
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Is the Higgs boson an elementary particle? If so, why does it decay? [duplicate]

The Higgs boson is an excitation of the Higgs field and is very massive and short lived. It also interacts with the Higgs field and thus is able to experience mass. Why does it decay if it is ...
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2answers
56 views

Can an electron pass through a gap smaller than an electron?

If an electron (photon) can pass through a gap smaller than an electron (photon) then it is a wave otherwise it it a particle. Is this a correct way of reasoning?
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Elementary particles & their reactions: literature

I would like to find a book which contains lot of examples of different reactions with elementary particles (for instance, electron-electron scattering, electron-positron annihilation, electron ...
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2answers
63 views

Removing zero-counts in exponential decay measurement

I'm doing an experiment where I'm measuring the mean-lifetime of muons. I have a set of data points for the number of decays against time, resembling an exponential distribution (of course). But in ...
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0answers
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Universe under Point Reflection — or why is the Neutrino not its own anti-particle?

The spin of a anti-neutrino points into the same direction as its momentum. The spin is a cross-product, so under point reflection it remains the same, whereas the momentum gains a factor of $(-1)$. ...
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2answers
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Could there be elementary particles with electric charge $> 2e$?

There are many quantum field theories, which extend the Standard Model and have new particles. For example, X boson of Georgi-Glashow model has charge $4e/3$ and some Higgs models involve a Higgs ...
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1answer
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Composite particles and Weinberg Witten (WW) theorem

I am quite familiar with the proof of Weinberg Witten (WW) theorem. One major result which follow from WW is that the graviton cannot be a composite particle. I have 2 questions here: How do we tell (...
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2answers
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What does a fundamental particle really look like? [closed]

After reading a lot and trying to understand people explain it, I made an image in my mind that "fundamental particles are a given position in space to which is given properties", these properties ...
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2answers
181 views

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

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
59 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
961 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
35 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 ...
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0answers
38 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 ...
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1answer
53 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 ...
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2answers
170 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 ...
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1answer
848 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 $U(1)$ ...
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2answers
120 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 ...
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0answers
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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 ...
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1answer
109 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 ...
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1answer
126 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 ...
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1answer
63 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 ...
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1answer
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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 ...
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2answers
50 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 ...
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1answer
60 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 ...
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1answer
37 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 ...
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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 ...
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1answer
131 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 ...
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1answer
103 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 ...
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1answer
333 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 ...
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1answer
72 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 ...
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2answers
145 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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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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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 (...
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2answers
48 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? ...
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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'...
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1answer
83 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 ...
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1answer
85 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 ...
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2answers
239 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 ...
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2answers
171 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 ...
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3answers
122 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 ...
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0answers
100 views

Theory of physical vacuum (ether) [closed]

Recently, I came across this : Theory of physical vacuum (ether) Postulate. All fields and material objects in the Universe are various perturbations of physical vacuum, which is dense ...
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0answers
11 views

What is angular momentum of an elementary particle? [duplicate]

I have read that "spin" is an intristic property of elementary particles. I am confused wheather if the particle is acctually spinning or if it is the slant of the particle, or is it something totally ...
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1answer
147 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
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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 ...
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1answer
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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-...