Questions tagged [particle-physics]

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. DO NOT USE THIS TAG for point particles in classical mechanics.

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Determining the single particle energies in a neutrino opacity calculation

I'm attempting to recreate some plots from this paper on neutrino opacity calculations for interacting matter at supra-nuclear densities. Namely, I'm trying to write a Python script to perform the ...
-1 votes
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Can you give me some examples of infinity that we see in physics? [closed]

Otherwise I would have to accept the kalam (not necessarily William Lane Craig's) cosmological argument (without getting into an equivocation based discussion) to be most reasonable explanation on the/...
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1 answer
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Shouldn't there be a Particle for Changing Left-handed to Right-handed Particles and Vice Versa?

There must be a particle for changing Left-handed to Right-handed particles: $$e_l + Z^0_T \to e_r$$ Where $Z^0_T$ has Weak Isospin = 1/2 and Spin = 1, and no other quantum numbers.
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Problem with Bohr Frequency in Quantized Radiation - Matter interaction

Consider an Hydrogenic Atom (no relativistic corrections and no reduced-mass effects) in a Quantized Electromagnetic Pulse given by the wave-packet: $$ \underline{\hat{A}}(\underline{\hat{r}}, t) = \...
15 votes
3 answers
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What's the argument(s) against dark matter being "normal" baryonic dust?

So I just finished watching "dark matter is not a theory". An understanding I gleaned from it is that dark matter is observed from the discrepancy between the amount (or perhaps energy? in ...
4 votes
1 answer
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Surprisingly substantial 1980's popular science book about particle physics

As a teenager, back in the late 1980s or possibly very early 1990s, I came across a very nice popular science book on particle physics in my hometown library, that I probably borrowed and read at ...
6 votes
5 answers
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How does the Wave Particle Duality fit with Quantum Field Theory?

It's heard quite often that fundamental particles (photons, quarks, etc) act as both particles and waves. Now, I'm looking at it from a Quantum Field perspective. Is this localized energy ripple ...
-1 votes
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Trying to understand the motion of a high speed particle?

To start we have a single proton. We place are proton in a circular particle accelerator, and bring the proton up to speed of 0.99C. we then accelerate the entire particle accelerator on the ...
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What is meant by "there are no actual particles?" [closed]

Am I understanding the meaning of "virtual particles" or the idea of "there are no actual particles" correctly? So if I understand correctly, let's say I have a one cubic meter ...
6 votes
1 answer
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Are Weinberg's soft theorems relevant when making predictions about collider physics?

In a seminal paper, Weinberg has shown that one can relate a $n \to m$ scattering amplitude to the $n \to m + k$ scattering amplitude that involves the same particle content plus $k$ additional ...
2 votes
1 answer
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How to convert from momentum to energy distribution? (relativistic electrons)

I am using a gyro-kinetic simulation tool 2103.16457 which solves the 3D Fokker-Planck equation for the electron population in tokamak plasmas and evolves plasma parameters self-consistently. In many ...
1 vote
4 answers
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$\beta^-$ decay: expression for maximum electron energy

I'm having some trouble finding an expression for the maximum electron energy in $\beta^-$ decay. In the frame where the neutron is initially at rest, conservation of momentum reads: $$\vec{p}_p+\vec{...
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1 answer
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Hypercharge of the complex scalar doublet

I often see the complex scalar doublet $Φ_A$, $A=1,2$ with the opposite hypercharge arising in the Yukawa couplings as $\tildeΦ_A = iτ{_2}_{AB}Φ_B^*$ where $τ_r$ $(r=1,2,3)$ denote isospin pauli ...
1 vote
1 answer
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Why are $W$ and $Z$ bosons called 'intermediate' vector bosons?

What does the 'intermediate' part mean? Somehow, I thought an answer would be easy to come across, but I have yet to find one.
1 vote
1 answer
192 views

Product of Lorentz invariant factors may be Lorentz non-invariant

I'm evaluating an integral and I have three cases to consider. The result of that integral must be Lorentz invariant and independent of center-of-mass momentum. One of the cases I'm certain is in fact ...
0 votes
2 answers
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Confusion with Weinberg's QFT book, Volume I, Equation 2.5.3 (one-particle states as irreps of Poincare group)

I am reading Sec. 2.5 of Weinberg's Quantum Theory of Fields, Volume I. There he talks about the classification of relativistic one-particle states according to their transformation under the Poincare ...
9 votes
3 answers
817 views

Can the protium nucleus be in an excited state?

An electron in protium can absorb a photon and jump to an orbit of higher energy. Is an analogous procedure possible for the nucleus of protium (a single proton)? Can this nucleus be in an excited ...
3 votes
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How does path integral quantization ensure unitarity?

Unitarity can be verified post hoc by examining the optical theorem. In the context of path integral quantization where formal derivation starting from canonical quantization is unavailable, is it ...
2 votes
0 answers
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Why is it valid to only consider linear-order gauge transformation when quantizing non-Abelian gauge theory?

To quantize the non-Abelien gauge theory. We multiply the path integral by: $f[A]=\int \mathcal{D}\pi exp[-i\int d^4 x {1\over \xi}(\partial_\mu D_\mu \pi^a)^2]$ then we can shift the argument in the ...
-2 votes
1 answer
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Transmitting data via quantum fields [closed]

Actually I was thinking that currently we are able to transmit data via Photons which are excitation in the EM FIELD, but if there exist any other quantum fields, why couldn't we use the excitation in ...
2 votes
1 answer
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Connection between particle physics and weight diagrams

I have a hard time combining two topics that are often discussed in physics in a coherent way. In a lot of Introduction to particle physics-classes one will hear about "multiplets", which ...
4 votes
3 answers
212 views

If an electron is an elementary particle, where is charge "stored"?

In particular, how can you have both positrons and electrons if there is no "bit" to set or unset? I hope this is not a stupid question, but if a particle has no internal structure, where ...
0 votes
2 answers
225 views

A charged particle, a magnetic field and the particle's path

Quoted below is a question & the provided answer: Question: Describe the path of the $\alpha$ particles in the space between the magnetic poles. Answer: curved path stated or drawn path at ...
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2 answers
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Detection of the Higgs-Boson Graph Interpretation

I am reading up on the detection of the Higgs-Boson at the LHC and more specifically at CMS. I found the following graphic: I understand that the peaks correspond to the mass of the Higgs-Boson but I ...
6 votes
2 answers
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Are particles merely "relatively stable" patterns that can appear on their respective fields?

With quantum field theory, particles are seen as excitation on various fields. Am I mistaken to think that then particles merely refer to "relatively stable" patterns that can appear on ...
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1 answer
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Can we prevent the Higgs field interaction with particles? [closed]

if not why? is it possible in future? Because if it is possible there may be chance of more advance invention
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Why is an alpha emitter used in smoke alarms?

So basically I was wondering the main reasons why alpha particle emitters are used over (beta and gamma) in smoke alarms
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1 answer
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What is the meaning of dynamically generated states in particle physics?

In hadron spectroscopy, a structure may be interpreted as various "configurations", such as conventional quark-antiquark states, tetraquarks, hybrid states, dynamically generated states or ...
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Is the intrinsic parity necessarily $\pm 1$?

Intrinsic parities of various particles we know are $\pm 1$. My question is, can it be a more general phase? It seems it's sometimes argued (like page 140 in "Introduction to elementary particles&...
0 votes
2 answers
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$\beta$ decay paths question

Can the $\beta^-$ decay proceed by the absorption of a $W^{+}$ boson or the $\beta^+$ by the absorption of a $W^-$ boson? The $\beta^-$ decay is known as the decay of a $d$ quark into an $u$ quark and ...
3 votes
1 answer
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Would it be possible to generate muons using neutrinos and electrons?

The decay products for a muon are an electron, a muon neutrino, and a electron antineutrino. As the decay products for a neutron (electron, proton, neutrino) can combine together to form a neutron ...
1 vote
1 answer
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How was the tau lepton predicted?

I know the tau lepton has been predicted before it was discovered – unlike the muon. But how does our theory (SM/electroweak theory) predict the existence of a third lepton generation?
1 vote
1 answer
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Where does the baryon number appear in the Lagrangian of the standard model?

In the standard model Lagrangian, the electric charges of the particles are the coefficients of the interaction terms (e.g. $(-2/3e)u'Au$ for the up quark shows it's charge is $(2/3)e $) How can we ...
1 vote
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Energy and momentum conservation on a vertex in a time-ordered diagram and in a Feynman diagram

I read in the book Modern particle physics(page 114-119) from Mark Thomson that for a time-ordered diagram, the energy at each vertex is not conserved, but the momentum is. Furthermore, the energy-...
0 votes
2 answers
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What particles are described by the Klein-Gordon Equation?

The Klein-Gordon equation $$\left(\frac{\partial ^2}{\partial t^2} - |\nabla|^2 + m^2\right)\phi = 0\tag{1}$$ should describe non interacting particles without spin. So what particles in the standard ...
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Calculating the proportion of incident energy transferred to kinetic energy in the photoelectric effect

Light of two wavelengths, $λ_1$ and $λ_2$, is incident on a metal surface of work function $ϕ$. If there is an equal number of photons of each wavelength incident per second, what is the maximum ...
1 vote
1 answer
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Do all antiquarks carry and anti-color charge, or can they carry RGB color charges as well?

I know there are antiquarks with anticolor charges. Are there also antiquarks that instead carry color charges? Basically, which of these lists describes the types of quarks that there are: List one: ...
0 votes
2 answers
247 views

Neutrino-Antineutrino oscillation

I read somewhere about $\nu$-$\bar{\nu}$ oscillations. For this purpose Majorana mass of neutrinos was considered. But I could not understand through the mathematics (involving Lagrangian) how it is ...
34 votes
3 answers
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Would a spin-2 particle necessarily have to be a graviton?

I'm reading often that a possible reason to explain why the Nobel committee is copping out from making the physics Nobel related to the Higgs could be, among other things, the fact that the spin of ...
0 votes
0 answers
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Energy of electron during Tunnel ionisation

I have been studying an emission mechanism that exploits the ionization, disassociation and subsequent fluorescent recombination of nitrogen molecule by a femtosecond laser for velocimetry. The ...
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1 answer
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Imaginary Contribution to Diagrams with one $\gamma^5$ Vertex

It is possible to write down a Feynman diagram as below for production of a Higgs boson. I am slightly confused because the fermion-fermion-$Z$ vertex has a factor of $c_V - c_A \gamma^5$, but the $...
7 votes
3 answers
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The word 'sector' in Particle Physics

What exactly is meant when one uses the word sector in Particle Physics? As in, the Hidden Sector or the Electroweak Sector. Does it refer to a specific part of the Lagrangian? Or does it refer to ...
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2 answers
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Could polaroid filters with somewhat strange properties violate Bell's inequality without non-locality?

Imagine a world where polaroid filters have somewhat strange properties, in such a way that this is impossible or very hard to know. The inhabitants use polaroid filters to determine what polarization ...
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1 answer
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Interference pattern of relativistic particles

I wanted to know if it is possible to perform a double slit experiment with electrons travelling at 0.99c as the wavelength is very short.
16 votes
2 answers
2k views

How is time measured in particle experiments?

I was reading about the half life measurements and was curious to understand the experimental setups that allows so minute measurements to be captured. Specifically looking into half life of Higgs ...
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1 answer
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Does every field correspond to a particle?

I know that particles in QFT are just excitations of its corresponding field. But is it possible to have a field which cannot generate particles? If yes, what terms must be added to the Lagrangian so ...
36 votes
5 answers
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Why do we observe particles, not quantum fields?

My understanding is that, in the context of quantum field theory, particles arise as a computational tool. We perform an expansion in the path integral in some parameter, and the terms in these ...
0 votes
0 answers
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Is there any reason for the mass of the electrons? [duplicate]

I've recently read Feynman's QED in which he mentioned the possibility that the seemingly random numbers that correspond to the mass of the electron and heavier charged particles (mu and tau electrons)...
-2 votes
1 answer
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Do particles, quarks, atoms really move in space, or is it field disturbance-wave that moves in S-T with speed $c$? How particles move in S-T in QFT? [closed]

As I understand particles are localized fields (16fields+g). Can you explain on hydrogen atom example that moves in space vacuum. Does it really moving, or it is continious field disturbance ...
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1 answer
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Electron Interference when produced by $W$ boson

Hi I was wondering about the following setup. Let’s say we have a radioactive atom which decays via beta decay which produces a $W$ boson. The $W$ boson has a chance of turning into an electron or a ...

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