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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Probability density of an accelerating charge?
Is the probability density of an accelerating charge in free-space spherically-symmetric? If not, is it possible to produce charge acceleration-induced short range oscillations of charge probability ...
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${}$Higgs mechanism
Is is correct to say that, elementary particles have different masses, because they have different coupling strengths to Higgs field? And if yes. Does it make sense to question, why they have ...
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Spin correlations of identical leptons in a Z-boson decay
In 2012, the CMS experiment observed a decay of the $Z$ boson into four leptons: https://inspirehep.net/literature/1190671
The Feynman diagram for this process is shown in this Figure:
Its final ...
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K-Shell, Low-Energetic Photons & Photoelectric effect
At low photon energies, the probability of the photoelectric effect to occur increases, but the probability of the photoelectric effect to happen also increases when going towards most inner shells ...
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Why are particles still a thing? [closed]
Couldn't we just assume that waves have mass and momentum and can become localized? Dirac Deltas can be given a rigorous mathematical foundation but physicist do not use the Gelfand triple. Why not ...
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What is a particle according to quantum field theory? [duplicate]
I don't know what to say but... I just want a brief discussion about quantum field theory and how can you describe a particle according to this theory...
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What led physics to "anticipate" the tau particle?
Wikipedia writes
The tau was independently anticipated in a 1971 article by Yung-su
Tsai.[8] Providing the theory for this discovery, the tau was detected
in a series of experiments between 1974 and ...
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How Fast Can Toponium Form?
I understand that Toponium is only theoretical because the T quark decays too quickly.
My question is this, would a right handed T quark live long enough to form a meson? If not, how long would it ...
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Collision of two positrons: Is there any "strong force" that binds two positrons together to produce a positron-positron pair with $+2e$?
I want to know if it is possible to hardly collide two positrons with each other to produce a pair with $+2e$. Indeed, I want to know if there is a strong force, similar to those binding protons ...
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Energies less than 511 KeV [closed]
I have an equation to calculate the antineutrino spectra which is as $$P=KE2n(Eo−En)[(Eo−En)2−me]1/2.$$
I have got some energy values which are less than 511 KeV so I am assuming that those are not ...
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Can either of LISA, NanoGrav or LIGO measure the polarization of gravitational wave background(GWB)?
Polarization in GWB should carry as much important information as in CMB. However, I've done some superfluous literature research and found little discussion. Is there any planned project for ...
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Does quantum mechanics say anything about whether the universe could have been otherwise? [closed]
From what I can understand about quantum mechanics, the notion of “probability” is still ultimately a frequentist notion. When we say that there is a 40% probability that a photon will be detected at ...
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Thomson Scattering when low intensity light meets an orbital electron
Can you explain to me the reason why Thomson Scattering can not explain what happens when light meets an electron at low intensity, and what does that have to do with light being a wave or particle or ...
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What force is the axion the mediator of? [closed]
I keep seeing in the literature that the axion is a force-carrier. I assume this is because it has spin 0, and all integer-spin particles are force-carriers. But I cannot find anywhere what force ...
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Decay rate with specific helicity in rest frame and lab frame
Consider a two-body decay, such as the pion decay: $\pi^+\to \mu^+ + \nu_\mu^{}$. In the Standard Model, as there only exits left-handed massless neutrinos, the helicities of final particles are known....
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What is a particle in the context of QFT with interactions?
This is a crossposting of the same question from mathoverflow: https://mathoverflow.net/q/454768/
It seems that this question was not received well there, claiming that this question is not ...
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Can charged boson be emergent?
Dirac's initial interpretation of antimatter is the existence of Dirac Sea. However, it doesn't work for bosons since we can't invoke Fermi's exclusion principle. Goldstone boson can be emergent but ...
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Are neutrinos being scattered frequently?
I'm no more than a passive enjoyer of physics, and have come across humanity's latest neutrino detection method known as CEvNS. I found a slideshow that explains the process very well, especially for ...
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How should we imbed massive spin-3 in a Lorentz covariant tensor? (degree of freedom-wise)
I'm not asking for Weinberg's systematic approach. Rather, I'm more concerned with how to get the correct degrees of freedom(dof) slickly for the moment.
I believe it should be imbedded in the rank 3 ...
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All possible models to explain the hierarchy problem?
There is an interesting paper by Arkani-Hamed and collaborators (https://arxiv.org/abs/1607.06821) to address the hierarchy problem.
There, they consider many possible models of fundamental particle ...
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Does NFW profile work for any galaxy?
We use Navarro–Frenk–White (NFW) to calculate Dark Matter (DM) density. Can we use it for DM halo in any galaxy or is it used only for Milky Way (MW)?
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Electroweak Interaction and SSB
I read that above unification energy, on the order of 100 GeV, electromagnetic force and weak force would merge into a single electroweak force.
I do not really understand how and when exactly two ...
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The difference between High energy SUSY and low energy SUSY
In the literature and comments, I have met two pieces of jargon:
Low energy SUSY,
High energy SUSY
I'm confused about the technical and well-defined conceptual differences between the two type of ...
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What are the properties of an unknown object that guarantee that it has mass?
During JJ thomson experiment and similiar other experiments,they found that cathode rays were deflecting from its direction under magnetic fields and electric field,also the gold leaf attached to co-...
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Project for Elementary Particle Physics Course
Good day! Are there any publicly available dataset in the field of particle physics that can be treated as time series? I am hoping to use methods in white noise analysis to somehow determine ...
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Isn't heating insulator enough for sufficient electrons to escape valence band and conduct electricity?
Diamond has about 5.5eV of energy gap, So If I heat diamond it will get atleast 1J energy which is enough to excite about 10^18 electrons, But Diamond still not conduct electricity, Why?
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In Cyclical Cosmology (Big Bounce) is it possible the new universe will be different or the same? [closed]
Could it be a universe with similar laws to ours but a different configuration of matter, so there may be another earth like planet in this new universe?
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Atomic Fission & Nuclear Force
If the strong interaction force between the quarks that make up protons & neutrons get stronger with distance, and if the gluons enabling that force split up if enough energy is applied to them, ...
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Every possible QFT from positive geometry?
Physicist Nima Arkani-Hamed has taken an interesting approach to understand fundamental physics based on geometry (specifically, positive geometry constructions). This started with his work with ...
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Interactions between Protons, Neutrons & Electrons [closed]
I'm curious to learn more about the way that protons, neutrons and electrons interact. Specifically, about how the forces that attract and repel them work.
While I don't have a background in physics ...
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What exactly are resonances in particle physics?
I am very confused about this, are they an excited state of a particle where an electron is excited to an upper energy level, which seems less likely to be the case since the resonant states of ...
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How does a photon interact with EM field of a nucleus thus exchange momentum and recoil the nucleus when pair production happens? [duplicate]
The photon must be near a nucleus in order to satisfy conservation of momentum, as an electron–positron pair produced in free space cannot satisfy conservation of both energy and momentum.[4] Because ...
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Predicted Mass of Hypothetical Graviphoton
In (some) supersymmetry theories, a spin-1 gravivector or graviphoton is predicted (but has not yet been observed) to exist. My question: is there a consensus among theorists as to the mass (if any) ...
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Could the LHC create a strangelet by creating another multi-strange particle that then interacts with a nucleus?
I became interested in the discussions about potential catastrophic risk from colliders and I have some questions about it.
I am particularly interested in the strange matter scenario, and there is ...
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What problems might somebody encounter when trying to use the Breit-Wheeler process to produce positron gas?
Let's take a hypothetical an experimental scenario where a stream of high-energy photons from a powerful source is directed via a system of mirrors and lenses in a two coherent rays to a vacuum camera....
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The chirality of the standard model fermions
I read 'The Standard Model Effective Field Theory at Work' by Isidor, Wilsch, and Wyler. In a footnote, they say that, in principle, right-handed neutrinos could be included in the Standard Model by ...
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What would happen if a multi-strange particle were absorbed by an atomic nucleus?
I have been reading about the hypothetical possibility of "strange matter consuming the Earth" and there is one thing I don't understand. I understand that it has been shown that it is ...
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Why is there a $u$ in the middle of the feynman diagram for a quark and an antiquark annihilating?
There is a feynman diagram in chapter 2 of Griffiths Introduction to elementary particles, where a pair annihilation is taking place. I am confused as before it was written that internal lines are ...
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Why can't $uus$ and $uds$ quark content have $I = 1$ Isospin?
Well, I know the isospin singlet with $I=0$ and isospin triplet with $I = 1$. But for $I = 0$, why it must be $uds$ quark content rather than other assembly like $uus$ or $dds$? $ud$ can have $I = 0$ ...
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Slope in interaction strength vs mass for QCD axion
The theory models of QCD axion, i.e. those who solve the strong CP problem, all have a prediction that follows a band with a slope in the space interaction strength vs. axion mass.
(1) What does cause ...
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How does parity conservation follow from the Wu experiment?
The Wu experiment shows how parity symmetry does not hold for the weak force. However, how does this proof that parity conservation also doesn't hold?
If my understanding is correct, the absence of ...
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$\pi ^+$ decay to $e^+ +e^+ +e^- +\nu_e$
I was asked to give the Feynman diagram of the following weak interaction: $\pi ^+(u\bar d) \rightarrow$$e^+\nu_e e^+e^-$. I was asked to do this on the level of leptons and quarks. However, I could ...
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When to consider and when not to consider the loop contributions from light quarks?
Consider the following Lagrangian:
$$
\tag 1 \mathcal{L} = \frac{\partial_{\mu}a(x)}{f}\sum_{q}\bar{q}\gamma^{\mu}\gamma_{5}q
$$
This is a Lagrangian of the axion-like particles (ALPs) $a$ interacting ...
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Why take into account deceleration radiation only, but not acceleration radiation when Bremsstrahlung happens?
Why only take into account deceleration radiation rather than the radiation caused by acceleration when going tangent towards the nucleus and acceleration caused by the change in direction when flyby ...
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Why is the electromagnetic force not an emergent property of the strong force? [closed]
Two up quarks in a proton lead to an imbalance, which results in the proton having the ability to attract electrons. Two down quarks in a neutron lead to balance in the electromagnetic force, leading ...
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Why were multiple layers of absorbers and scintillators used in the CMS HCAL?
Why were multiple layers of absorbers and scintillators used in the CMS HCAL? Couldn't they have used just one absorber and one scintillator layer? Why was the choice made to have multiple layers?
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Can energy of one field be converted to another?
From school we know examples of energy conversions: from electromagnetic to electric, from electric to heat, from heat to electromagnetic, etc.
However, obviously this almost has nothing to do with ...
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About particle number non-conservation in Quantum Field Theory
There are already similar topics with interesting answers such as When particle number can change in quantum physics? but I still don't understand much.
I often read about the non-conservation of ...
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Calculating Cross Section in terms of barns (help with converting from natural units)
I am trying to calculate the Glashow resonance to get something in terms of barns but I am getting confused switching between natural units and non-natural units. The Glashow Resonance is given by the ...
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When is the OZI rule applicable?
According to wikipedia, the OZI rule states that any strongly occurring process will be suppressed if, through only the removal of internal gluon lines, its Feynman diagram can be separated into two ...
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