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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How to calculate angular velocity given constant tangential acceleration?

A car starts moving in a circle with a radius of $200 \text{ m}$. It has a constant tangential acceleration of $1{\text{m}\over {\text{s}}^{2}}$. a. What is the angular acceleration? b. What is the ...
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What if time translates into particle?

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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508 views

Deriving Feynman rules from a Lagrangian for vertex factors for “more complicated” interactions

I am trying to derive Feynman rules from a given Lagrangian and I got stuck on some vertex factors. What for example is the vertex factor that corresponds to the four-scalar interaction that is ...
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26 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 ...
3
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1answer
99 views

Proton flux model or data at energy range up to 100 keV

I am looking for a model or at best the database of proton fluxes (solar p+) at a energy range of some eV up to 100 keV. I have already found the SOHO database: http://umtof.umd.edu/pm/ But the ...
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16 views

Gamma matrices in Decay Calculations

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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47 views

Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy? [on hold]

I want to know the configuration where the system would be most stable. But I cannot think of a way to start solving the problem. I've solved it for 4 charges and 6 charges and they have a symmetric ...
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2answers
36 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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229 views

Scalar field divergent mass correction interpretation question (hierarchy problem)

Simple power counting tells you that a scalar field coupled to some fermions at one-loop picks up a correction to the mass of the order $\Lambda^2$. Based on this people say things like "it's natural ...
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1answer
18 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 ...
0
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1answer
76 views

What is the general definition of signal acceptance?

Suppose I have a beyond Standard Model theory and want to test it. I want to test if some experiments, say conduced in LHC, show signals of the theory. In this case, what is "signal acceptance"?
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4answers
822 views

Origin of lepton/quark generations?

What theoretical explanations exist for the fact that there are three generations of leptons and quarks? I'm not so much asking why there are exactly 3 generations, but rather what makes electron, ...
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21 views

could the alternating current resistance of a device depend on afrequency? [on hold]

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1answer
53 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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14 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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1answer
74 views

Leptogenesis with singlet neutrinos

(i) The Lagrangian of electroweak model extended with right-chiral singlet neutrinos $N_{iR}$ contains the Yukawa coupling term+ the bare Majorana mass term $$f_{\alpha ...
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25 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 ...
2
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1answer
278 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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3answers
842 views

Why does positronium decay into 2 photons more often than into 3 photons?

I cannot find the answer to the above question. I know that para-positronium is created with a probability of $25\%$ and decays into 2 photons, while ortho-positronium is created with a probability ...
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13 views

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 ...
2
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2answers
84 views

Could synchrotron radiation be produced by a gravitational field instead of a magnetic field?

I know that synchrotron radiation is produced when a charged particle is accelerated radially by a magnetic field, but I was wondering if synchrotron radiation could also be produced by an uncharged ...
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Does the weak force obey a symmtery/conservation law that is broken by the EM and strong forces?

It always seems that the weak force breaks everything that is otherwise obeyed by the other fundamental forces, but there something that only the weak force is known to follow?
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Are all electrons identical?

Why should two sub-atomic (or elementary particle) - say electrons need to have identical static properties - identical mass, identical charge? Why can't they differ between each other by a very ...
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Which quarks will I find in a neutron? [closed]

A: Three up quarks. B: Two up quarks and a down quark. C: Two down quarks and an up quark. D: One charm quark, one up quark and one down quark. please expain why
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92 views

Is there a fundamental interaction responsible for quantum entanglement?

Quantum entanglement seems to share information between particles instantaneously, as well as characteristics of these particles through changes that occur in each particle. If forces transfer energy ...
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1answer
62 views

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 ...
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1answer
28 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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1answer
46 views

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. ...
2
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1answer
50 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
57 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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3answers
2k views

What is lepton number?

What exactly is a lepton number of a particle? With the charge (eg proton is just 1, not the exact charge), I can understand because it's a physical property, put a particle with charge + next to ...
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25 views

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
24 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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32 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
48 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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1answer
61 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
41 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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1answer
37 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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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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2answers
55 views

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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54 views

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 ...
4
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1answer
233 views

Fierz identity for Weyl spinors in tensor currents

Using Fierz identity I found that certain four-fermion operator with left $l_i$ and right-chiral $r_i$ Weyl spinors vanish $\bar{l}_1\sigma_{\mu\nu} r_2 \bar{r}_3 \sigma^{\mu\nu} l_4 =$ $ ...
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1answer
30 views

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
35 views

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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34 views

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 ...
7
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3answers
2k views

Does a particle annihilate only with its antiparticle? If yes, why?

Or to put the question another way - what is the result of a proton-positron collision, or an up quark-charm antiquark collision, etc.? As far as I know, annihilation happens only between particles of ...
2
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1answer
60 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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1answer
79 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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351 views

Precise statement of Mermin–Wagner theorem

Roughly speaking, Mermin-Wagner theorem states that continuous symmetries cannot be spontaneously broken at finite temperature in systems with sufficiently short-range interactions in dimensions ...