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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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Calibration Method used in Compton Scattering project [closed]

In a project in which it studies experimentally the angle dependency of the energy of scattered radiation. The scatterer used in the experiment is an aluminum plate. The equipment can change the ...
Tansu A's user avatar
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5 votes
3 answers
1k views

Would normal atoms and antimatter atoms be attracted to each other?

I believe I have been holding a misconception for a long time, surely dating back to some sketchy science fiction. I would like to verify what truth there is in this. Say you had person $A$ floating ...
Paul Cusson's user avatar
2 votes
0 answers
50 views

Could supermassive black holes emit massive particles as part of the Hawking radiation (even if the probability is small)? [duplicate]

Supermassive black holes should have a very low Hawking temperature and therefore would emit very low energetic photons, only when the black hole has radiated most of its mass and becomes small it ...
vengaq's user avatar
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4 votes
1 answer
121 views

Supressing proton and neutron decay?

I was wondering whether the decay of neutrons and protons (if they happen to be able to decay, as it is predicted by some GUTs) could be avoided in some cases. Let's begin with neutrons: In principle ...
vengaq's user avatar
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3 votes
0 answers
39 views

How does crossing symmetry affect the value of an electroweak vertex (e.g. $u+W^-\to d$ vs. $W^-\to\pi^-$)?

Two of the weak charged current vertices I often encounter in my first foray into particle physics are $u+W^-\to d$ and $W^-\to\pi^-$, shown in the following Feynman diagrams: These feel like the ...
DanDan面's user avatar
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1 vote
0 answers
44 views

When a proton and neutron fuse in Big Bang Nucleosynthesis, do they emit a virtual neutral pion that emits two photons?

In Big Bang Nucleosynthesis, when a proton and neutron fuse to form a deuteron, how does the binding energy get shed? The binding is remanent strong nuclear force so does it emit a virtual neutral ...
Mongrav's user avatar
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0 votes
1 answer
55 views

Custodial symmetry of the standard model symmetry group $SU(2)_L \times SU(2)_R$

I am studying the standard model including the Higgs sector and electroweak interactions. Here, all of my terms have their usual meanings. Therefore my symmetry group is $SU(2)_L \times SU(2)_R \times ...
Chris G's user avatar
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3 votes
2 answers
391 views

Average momentum of particle/anti-particle pairs

I'm far from an expert in physics, I've gathered bits from wiki, books and educational videos. So I apologize in advance if my question is not well framed or plain stupid. It's about particle / anti-...
Antoine's user avatar
  • 133
1 vote
0 answers
39 views

Self-interference of nuclear decay

Consider a stationary atom undergoing radioactive decay. The probability density function for decaying at time $t$ is given by an exponential distribution: $$p(t)=\lambda e^{-\lambda x}$$ When ...
Riemann's user avatar
  • 1,440
2 votes
3 answers
228 views

Experimental status/test possibilities for baryon number conservation in LHC?

Violation of baryon number is hypothesized e.g. for baryogenesis (more matter than antimatter from Big Bang) or Hawking radiation (baryons -> black hole -> massless radiation) - quite extreme ...
Jarek Duda's user avatar
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0 answers
36 views

Threshold energy formula

In Krane's Introductory Nuclear Physics, in chapter 11, he uses the conservation of energy and momentum to derive the formula for the threshold energy of a reaction a + X → b + Y (with X being an ...
Pedro Nogueira's user avatar
0 votes
1 answer
45 views

Why don't we include diagrams with fermion and gauge boson external lines while calculating the effective potential of Standard model?

While calculating the effective potential of Higgs boson, we aim at $V_{eff}(h)$ instead of $V_{eff}(h, W^{+}, W^{-}, Z, quarks, leptons)$. I think the true vacuum should be the minimum of this ...
Bababeluma's user avatar
1 vote
1 answer
51 views

Effects of a hypothetical "proton-decay bomb" for a fictional story [closed]

I'm writing a science fiction story in which I need a devastating weapon of mass destruction that is far worse than nuclear bombs. For some reason, I'm fascinated by the idea of a "proton-decay ...
Nicola's user avatar
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2 votes
0 answers
32 views

General formula for a $f1\to f2$ gamma processes (e.g. $\mu \longrightarrow e\gamma$), understanding the detailed calculation in the paper by Lavoura

I want to work out in detail the paper by Lavoura to get some real practice as a beginning student. I have stumbled upon several problems as I am moving along with the arguments. Firstly, I am not yet ...
Hubert John's user avatar
1 vote
0 answers
73 views

What math do I need for Graduate level Particle Physics? [closed]

​I'm 13 years old and love and am fascinated with physics and math, currently I'm doing differential geometry after countless courses in the past, I'm sure the next course I need to take will be ...
Morty Levinson's user avatar
2 votes
1 answer
188 views

Determining free Fermi/Bose gas chemical potentials, given temperature, number density, and baryon density

I'm attempting to recreate some plots of individual particle chemical potentials from S. Reddy et. al.'s paper on neutrino interactions in hot and dense matter (of the same title). The specifics aren'...
10GeV's user avatar
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2 votes
1 answer
24 views

Theoretical Electron Bunching paper, variable question

What exactly is $\varphi$ referring to in this paper: Electron bunchers for industrial RF linear accelerators: theory and design guide? Specifically, within the context of this equation: $$\frac{dW}{...
Jais's user avatar
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-4 votes
1 answer
67 views

Yang-Mills mass gap caused by gluonballs or because dark matter WIMPs?

Yang-Mills quantum field theory predicts the existence of the lightest massive Bosonic (i.e. integer spin) particle. This massive Boson will be much lighter than the $W$ and $Z$ Boson and therefore ...
Markoul11's user avatar
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0 votes
1 answer
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Can we prove in general that gauge fields associated with broken generators form representations of the unbroken group?

The title is a bit ambiguous. More specifically, I'm asking: Are all coupling between massive gauge fields (associated with broken generators) and massless gauge fields of the unbroken group are in ...
Bababeluma's user avatar
1 vote
0 answers
50 views

Magnetic Monopoles and Its Antimatter and Mirror Particle Counterparts [closed]

I'm trying to understand how magnetic monopoles and how its potential mirror and antiparticle counterparts would behave. So according to the modified lorentz force law $$\vec{F}=q_e\left(\vec{E}+\frac{...
CrazyDolphin's user avatar
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0 answers
24 views

Production spin density matrix $R$ in particle physics and quantum state tomography

I want to perform quantum state tomography. For that, I need to construct a production spin density matrix $R$ . But I am unable to write it. I can write the matrix element for the process eg. $\tau^+ ...
Lelouch's user avatar
  • 199
0 votes
1 answer
29 views

Are there different ways of using the term 'energy scale'?

Are there a few different ways of using the term 'energy scale' that differ in their precise meanings? For instance, in the context of the chart provided, 'energy scales' denotes the magnitude of ...
qazwsx's user avatar
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0 answers
38 views

Variation in the context of symmetries

I’m rephrasing a suggestion as a question because there was an aspect to it where I wanted to know more as well. I have studied both general relativity and particle physics, though in both cases my ...
Steven Dorsher's user avatar
0 votes
0 answers
54 views

What level of energy could an amateur particle accelerator achieve?

I am a member of a group of high schoolers and we've been looking to set our sights on a challenging project to dump some time into. Currently we're investigating how realistic it is to attempt ...
bakedsteak's user avatar
-1 votes
2 answers
73 views

What exactly is kinetic energy? [duplicate]

What exactly is kinetic energy? I know that kinetic energy is the energy that an object obtains by the virtue of its motion, but I need an exact answer. So, potential energy, like there are three main ...
Aronld Manki's user avatar
1 vote
0 answers
39 views

Colour Factor in QCD Pair Annihilation

My question occurred when I was reading Introduction to Elementary Particles by David J. Griffiths. In chapter 8, part 8.5, he is calculating the colour factor of quark-antiquark annihilation. My ...
quantumology's user avatar
2 votes
0 answers
27 views

Can we stabilize particles other than the neutron in a lab setting?

There are so many elementary and composite particles out there, but only a few that are stable and isolatible - namely protons, electrons, photons and neutrinos (oscillating in the three flavors). ...
Opisthokont's user avatar
2 votes
1 answer
150 views

Is there really a strong CP problem?

The strong CP problem is considered one of the biggest unsolved physics problems. A nonvanishing value of $\theta$ in QCD $\theta$-term violates CP-symmetry. A primary strong CP violating observable ...
MadMax's user avatar
  • 3,854
3 votes
2 answers
193 views

Why are all observed particles on-shell?

I've been trying to self-learn how to do basic QFT calculations and I'm a little bit confused as to what's considered "an interaction". If I want to model an electron releasing a photon I ...
Opisthokont's user avatar
18 votes
1 answer
2k views

Have all the symmetries of the standard model of particle physics been found?

Background The standard model of particle physics is entirely determined by writing down its Lagrangian or, equivalently, writing down the corresponding system of PDEs. Every set of PDEs has a ...
William Wright's user avatar
0 votes
0 answers
71 views

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) = \...
Matteo Menghini's user avatar
0 votes
1 answer
116 views

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.
talanum1's user avatar
15 votes
3 answers
2k views

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 ...
user151841's user avatar
  • 1,619
6 votes
1 answer
237 views

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 ...
Níckolas Alves's user avatar
1 vote
1 answer
63 views

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.
Kurt Hikes's user avatar
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0 votes
2 answers
48 views

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 ...
Solidification's user avatar
3 votes
0 answers
49 views

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 ...
Bababeluma's user avatar
9 votes
3 answers
833 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 ...
azerbajdzan's user avatar
2 votes
0 answers
63 views

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 ...
Bababeluma's user avatar
-2 votes
1 answer
53 views

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 ...
X B Jesrin Celas's user avatar
0 votes
1 answer
39 views

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
BHAVAN KUMAR P MECH's user avatar
0 votes
0 answers
44 views

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&...
liyiontheway's user avatar
1 vote
1 answer
85 views

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?
MBZL's user avatar
  • 11
1 vote
1 answer
60 views

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 ...
KaraboMadisa's user avatar
1 vote
1 answer
26 views

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 ...
Xiaan YuanTian's user avatar
1 vote
0 answers
33 views

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-...
Clara's user avatar
  • 95
0 votes
2 answers
110 views

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 ...
Noumeno's user avatar
  • 4,484
0 votes
0 answers
21 views

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 ...
Developer's user avatar
1 vote
1 answer
105 views

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: ...
blacktopshaman's user avatar
1 vote
0 answers
87 views

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 ...
10GeV's user avatar
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