Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales.

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Do inelastic collisions have any effect on a large bodies movement (like the Earth)

Recently read a question regarding the temperature of the CMB & one of the comments got me thinking... From what I understand, collisions between subatomic particles and objects out in ...
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27 views

Why are the particles called irreps of Poincare group? [duplicate]

Why are particle excitations called irreducible representation of the Poincare group? It will be very helpful if someone can illustrate with one concrete example of a particle.
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42 views

Anything special about the internal structure of Carbon-12?

In trying to understand the various structures carbon forms, I'm wondering what, if anything, is so special about having 6 neutrons and 6 protons in the nucleus. I'm aware there are permutations ...
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What happens when an anti-proton and an electron collide with each other?

The vice versa case is also of interest (proton and positron). Are both processes actually symmetrical?
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62 views

Is possible to create water? [on hold]

Theoretically is relatively easy to create water, because it is formed by only the hydrogen and one oxygen molecules. I know that the oxygen and hydrogen is highly flammable, and to union the ...
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42 views

What is the property of neutrino? [on hold]

If mass of a particle is due to Higgs boson, spin is due to Z boson and translational energy is due to photons, what exactly is the innate property of a neutrino? If none exist, is neutrino truly a ...
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1answer
27 views

Counting higher-order corrections in “ABC theory”

I am trying to understand how to enumerate higher-order Feynman diagrams. In his book on Elementary Particle Physics, Griffiths considers a simple "ABC toy theory" which has: three (scalar, ...
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64 views

Is there scientific proof of god? [on hold]

Recently I've been having a discussion on whether there is scientific/mathematics proof for the existence of god. -- A probability model was put forward of which seems to have some errors/flaws in ...
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20 views

How can the uncertainty principle be used to deduce range of a force from properties of the force carrier?

Question: How can the uncertainty principle be used to deduce range of a force from properties of the force carrier? My thoughts? Not too sure how this can be done and would like some advice. ...
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1answer
23 views

Why are high energies needed in collision experiments?

Why are high energies needed in collision experiments? I believe it has something to do with the interactions needed between particles to find other particles only happening at high energies? Is this ...
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1answer
27 views

What is a collider detector [on hold]

I'm trying to understand what a collider detector is essentially. I have looked around the web and most of what I'm reading is way too advanced for me to understand. Would it be possible for someone ...
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2answers
63 views

Decay of matter

I was watching Stephen Hawking's documentary and in there he explained how he realized why black holes eventually disintegrate: ...
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1answer
32 views

How would one build an RF cavity?

How does an RF cavity, such as the RF cavities in the LHC, work mechanically and mathematically? How would one build an RF cavity? What equations govern the speed of a charged particle in an RF ...
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Why don't protons just bounce off each other in the LHC?

Ok, this might sound like a silly question, but I was wondering, when particles (e.g. protons) are smashed together in the LHC, why do they break up into dozens of other particles, as opposed to just ...
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SUSY without gaugino [closed]

In Minimal Supersymmetric Standard Model (MSSM) with $R$-parity, gauginos have Majorana mass. If we use $R$-symmetry instead of $R$-parity, gauginos do not have Majorana mass. But they can acquire ...
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34 views

How is $J^{PC}$ value experimentally determined for new types of particles?

How is $J^{PC}$ value experimentally determined for new types of particles? For example, this paper says ... Angular correlations in B+→X(3872)K+ decays, with X(3872)→ρ0J/ψ, ρ0→π+π− and J/ψ→μ+μ−, ...
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519 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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What if time translates into particle? [closed]

I had in idea waking up this morning, what if time as we know it, is made out of particles. Lets name them chronyons. And as a result of motion, these particles are traveling at the speed of light. ...
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29 views

Need help with which books I should buy [duplicate]

I need some help with witch books i should read. I would like to study science, physics, quantum physcics, astrophysics and all other kind of physics. Hit me with the best books inside of thoes ...
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25 views

Gamma matrices in Decay Calculations [closed]

I am trying to calculate the transition amplitude, $\lvert M^2\rvert$, for the process where a top quark (momentum p) decays to a bottom quark (momentum q) and a $W^+$ boson (momentum k). I am ...
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1answer
21 views

Apparatus for generating plasma

I'm working on a project which involves superheating nitrogen to a state of plasma. I was considering using my Fusor, but this project has nothing to do with plasma, and I believe that there are way ...
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2answers
39 views

Where does the mass of particle that is decaying go?

The particle of a heavy quark (such a s a bottom quark) into either an up or down is an actually change I'm mass (if I know what I'm talking about, which I don't think I do, but that's what this is ...
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1answer
24 views

Why performing axial symmetry, results in the same masses for pion and sigma mesons?

Under axial transformations, $\sigma$ and $\pi$ are rotated into each other: $\vec{\pi} \rightarrow \vec{\pi}+ \vec{\theta} \sigma $, $\sigma \rightarrow \sigma+ \vec{\theta}.\vec{\pi} $. In ...
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26 views

Regge trajectories for higher spins

I have read that Regge theory did/does predict higher spin meson states, but that at higher spins the data becomes fuzzy for spins greater than 4. Why is this so? In the book "A Brief History of ...
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286 views

Antineutron repelled by gravity?

I was reading an old post, Can gravity be shielded, like electromagnetism?. One of the responses had this comment. There are some experiments trying to measure whether antiprotons ( antimatter) ...
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the different settling speed of two solid particles in fluid

In a container full of fluid A, which can be water or oil, I have two solid particles, both of which are of the same material. These two particles are of different size. One is bigger than the other ...
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33 views

Direct and indirect CP violation

Experimentally, what is the difference between direct and indirect CP violation? An example of indirect CP violation is: $$ \Gamma(\overline{B}^0 \rightarrow B^0) \neq \Gamma(B^0 \rightarrow ...
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Is the $\nu_e$ massive?

Neutrino oscillations imply that the $\nu_\tau$ is more massive than the $\nu_\mu$, and the $\nu_\mu$ is more massive than the $\nu_e$, so it's inferred that the $\nu_\mu$ and $\nu_\tau$ have mass. ...
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67 views

Do subatomic particles have dimensions?

We know atoms are mostly "made" out of empty space, so the nucleus and all the subatomic particle are very small in compared to the magnitude of the atoms. We also know that atoms are incredibly ...
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Colliding proton-proton and antiproton-antiproton?

Would there be any difference in the measurable observables between collisions of proton-proton and antiproton-antiproton? I guess that colliding protons with anti-protons enable far more ...
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1answer
26 views

What is the charge/matter distribution?

I am a mathematics student who is doing an introductory course in nuclear physics and since the course is rather elementary a lot of the definitions/derivations are skipped which makes it quite tough ...
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1answer
59 views

Why does gg fusion dominate over q qbar annihilation at the LHC?

The cross section of top quark pair production is dominated at the LHC by gluon-gluon fusion, whereas at Tevatron, quark-antiquark annihilation is more prevalent. Why is this? I know the fundamental ...
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36 views

Pion decay exercise in Griffiths books

I have questions about pion decay problem. In Griffith "Introduction to Elementary Particles" 1st edition, 1987, question number 10.10 : Analyze $\pi^-$ decay as a scattering process, using the ...
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1answer
54 views

First-order EM Feynman diagram?

Is there any 1st order electromagnetic Feynman diagram? I.e. a process whose probability is just $\propto \alpha_{EM}$? If not, is there any physical reason why? We always need at least two particles ...
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54 views

Order of Feynman diagrams for electroweak processes?

I want to compare two Feynman diagrams and be able to say which one describes a process that is more likely to happen. As far as I understand, this is done by considering the order of the diagram. ...
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1answer
63 views

how can a particle can have a spin of 2 [duplicate]

i have seen some analogies of spin using playing cards but i am struggling to grasp the concept due to this making no sense in terms of playing cards
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1answer
45 views

Is it possible that neutrinos or some other sub-atomic particle contributes to radioactive decay?

According to Wikipedia: For most radioactive nuclides, the half-life depends solely on nuclear properties and is essentially a constant. It is not affected by external factors such as ...
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Why do the $u$ and $d$ quark not have an associated quantum number?

All the other quarks ($c$,$s$,$b$ and $t$) have quantum numbers of charmness, strangeness, bottomness and topness that are conserved in strong interactions. This allows, among other things, flavour ...
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Neutral $K$ and $B$ mesons decay to 2 photons?

The neutral pion $\pi^0$ decays almost exclusively to 2 photons, $\pi^0 \rightarrow \gamma \gamma$, which got me thinking: Can we have $K^0 \rightarrow \gamma \gamma$ and $B^0 \rightarrow \gamma ...
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1answer
42 views

Why does the pion not undergo netural particle oscillation?

$K$, $B$ and now $D$ mesons exhibit neutral particle oscillation, where we see the spontaneous interchange between a particle and its antiparticle, i.e. $K^0 \Leftrightarrow \overline{K}^0$, $B^0 ...
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1answer
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Particle physics: Why is J^P called spin parity if J is the total angular momentum?

Here is the question I am working on: "The Ξ- has spin parity=½+. It decays through the weak interaction into a Λ0 and a π- meson. If the spin parity of the Λ0 particle is 1/2+ and the spin parity of ...
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Will the new LHC data falsify some theories? [closed]

There are plenty of extensions of the Standard Model, that all agree until the energy scales that have already been explored, but will differ at the new energy range of 14 TeV. This means the data ...
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Does a photon emitted in a potential well due to transitions undergoe a blueshift?

This idea is related to that of gravitational redshift. As a photon climbs away from a gravity source it loses energy. In case of the finite potential well or infinite potential well as the transition ...
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1answer
81 views

Gravitinos the key to theory of everything?

Theory of everything The theory of everything aims to unite all the four forces of nature into one single elegant equation. Super-symmetry Super-symmetry is important as it explains the nature of ...
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1answer
61 views

Pair-annihilation why does it occour? [duplicate]

Why does pair annihilation occur with particles and only their matching anti-particle? E.g., electrons and positrons, but not protons and positrons? What is the difference?
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2answers
89 views

Gravity vs. Electromagnetism Scenario

Imagine a two dimensional world where there are only two electrons. They are set right beside each other. Of course, immediately they will start to separate, being repelled. My question is, as they ...
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1answer
26 views

Understanding percentage dose-depth curves

I just have a little question regarding dose-depth curves. When you look at them, you have on the y-axis the dose, and on the x-axis the depth into your material. What I'm not sure of is how I ...
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1answer
47 views

What is the energy threshhold to produce Cherenkov radiation?

I am in a nuclear course right now and am getting some misleading information from different sources. I am trying to figure out what the minimum total energy is that a proton must have in order to ...
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38 views

Maximum Momentum of Neutral Pion

I'm considering the reaction $p + p \rightarrow p + p + \pi^0$. To find the maximum momentum that the $\pi^0$ can have after this reaction in the center-of-mass frame, what I am doing is assuming the ...
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Why can't a high intensity beam be injected into the LHC when the machine is empty

Watching this YouTube video about the LHC at around 3 minutes and 50 seconds into the video the narrator says... For machine protection reasons we are not allowed to inject a high intensity beam ...