Questions tagged [pair-production]

Pair production is the creation of an elementary particle and its antiparticle out of a neutral boson, typically a photon, but sometimes a gluon.

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What does it mean for an electron and positron to be in thermal equilibrium?

My question refers to the following from this source: Within this context, what does it mean for a positron and electron to be in thermal equilibrium and why would that mean the process is reversible?...
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Entropic factor of electron-positron annihilation [closed]

In this question, user Nicolau Saker Neto states that "The distinction between enthalpy and Gibbs free energy in such subatomic reactions is completely negligible, as the entropic factor is ...
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Pair production from one gamma photon to an electron and positron

According to this Wikipedia article, the Electron–positron annihilation forms two gamma photons from an electron and a positron collision. However, according to this other article from Wikipedia, pair ...
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Can photons turn into neutrinos, similar to 'pair production' of electrons and positrons?

Since neutrinos ate much lighter, and are their own antiparticles (Majorana), it should be much 'easier' than turning a photon into an electron-positron pair, correct?
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Is electron-positron annihilation time reversible?

Consider that a low energy electron and positron annihilate creating two 511keV photons with no other particles around. To time reverse this process, we send two 511eV photons to collide hoping that ...
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Cross section using dimensional analysis

I am interested in finding the Tau pair production cross-section from electron-positron annihilation. The mediator is $Z$-boson. In a normal scenario using Feynman Rule, we can find the cross-section. ...
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Does quantum entanglement necessitate that two particles communicate their state with one another?

I often hear it said that quantum particles, like an electron-positron pair or two entangled photons, which are entangled with one another communicate or transfer information about their state ...
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Pair production in presence of charges

I have multiple questions here: When electron and positron are created, do the electric (Coulomb) field change in that region of space ? There is in fact an electric dipole, so my guess is yes. But ...
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Maxwell's equations and pair production

If a photon can create a particle and an antiparticle pair. then the result is that a changing $E, B$ field creates an actual charge density. why is this not reflected in Gauss law? with a combination ...
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Is it possible to create protons from photons?

I've read a few pages on related topics (e.g., here) but not found this question. Is this type of reaction theoretically possible that we know of? I know pair production creates electron and positrons,...
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Pair Production invariant

I am having trouble understanding what the fixed quantity in pair production is. A photon hits a nucleus and based on the photon's minimum energy relative to the nucleus, we get pair production. Is ...
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Can you measure the actual wavelength depending on if pair production occurs or not?

We know that pair production only occurs when the photon when the photon wavelength is 1.21 picometers or higher (or higher than the sum of the rest frame energies of the electron positron pair). ...
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Center of momentum frame for two dimensions

I have been investigating the scenario of two photons traveling in space (in a lab frame of reference) of different frequencies are about to collide with an angle $\theta$ between them. I set their 4-...
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Can Friedmann equations take in account positron-electron pair formation? How?

In Friedmann equations, $\rho$ described matter, radiation or cosmological constant. If it is matter, then $\rho ∝ a^{-3}$ and it is radiation, then $\rho ∝ a^{-4}$. But matter can be described in ...
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Vacuum pair-production and energy conservation

As far as I have seen it is assumed that the universe's energy is conserved or at least every reference agrees that pair production doesn't violate the conservation of energy as there is, ultimately, ...
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What does the inter-photon force look like (as mediated by electrons)?

Most often we think of photons mediating a force between charged particles (e.g. electrons and positrons), and it's a standard exercise in QFT to do the computation and find that, to leading order in $...
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Electron leaving the atom

From the photoelectric effect, we know that a photon can kick an electron outside the atom if it has the right amount of energy ($E_{\gamma} \geq W_0$). On the other hand, pair production tells us ...
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Does QED evolve unitarily after the Schwinger limit?

If QED becomes nonlinear after the Schwinger limit, shouldn't QED no longer be unitary (above the limit) since linearity is a requirement of a unitary operator (and vice versa)? Does this mean that ...
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Can Schwinger effect occur in electric field of a nucleus?

I know that electron-positron pairs can be produced within a uniform electric field with electric field strength above $10^{18}V$. Electric field of such strength can be found near atomic nuclei. So ...
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Pair production in vacuum

So , everywhere I have looked for pair production it is stated that it cannnot happen in vacuum . Most proofs I have seen for that , state that the conservation of energy and momentum cannot be true ...
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Pair-instability supernovae: a thermodynamic perspective

The discovery of a black-hole pair with "forbidden" masses has gotten me trying to understand pair-instability supernovae. A well-crafted sentence from a recent paper gives the explanation ...
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Why does pair production of an electron and positron only needs 1 photon whereas their annihilation releases 2 photons? [duplicate]

I know that in particle annihilation, for momentum to be conserved, we have to create a minimum of 2 photons moving in the opposite direction. According to Wikipedia: Pair production often refers ...
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Meson could include both matter and antimatter?

I wonder eta and pion could exist containing up quark (anti up quark)? Isn't there pair annihilation in this meson?
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Can Chirped Pulse Amplification (CPA) be used for creating antimatter?

In this excellent answer by Emilio Pisanty, he states that: Of course, all the cool laser-driven QED stuff at the top of that second diagram: if your laser is strong enough that, if you release an ...
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Pair production through massless gauge mediator

I am wondering if it is possible for a massless boson to change the particle interacting with it, into another type of particle. In other words, is it possible to have a pair production process (in S ...
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Pair production in more detail

I have stumbled upon pair production recently and it intrigued me,but i need help understanding the subject further. If i understood correctly you can produce a pair of a particle and an anti-particle ...
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Pair production problem

Can you explain me why in the pair production process we need a minimum energy $E_\gamma=2m_e$ in terms of invariant mass? I tried to calculate it but I get another result like $E_\gamma=2m_e+\frac{...
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Pair production: photon collides with an electron

During pair production, a high energy photon collides with an electron which then creates an electron–positron pair, but what happens to the electron that the photon collides with? I am asking ...
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How is momentum conserved in pair production?

I saw today in book that the momentum in pair production is conserved. My question is, how could it be possible that the momentum is conserved?
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Pair production mass

I’ve read other questions on here, but I still don’t have the answer that I need. In pair production, where does the mass come from that’s found in the electron-positron pair? I’m extremely novice and ...
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Why does electron/positron pair production form a fractal?

The wikipedia page for electron/positron pair production from photons has a weird section titled "aestheticity", which says that the symettry of the phenomenon meets the definition of a fractal, but ...
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Pair production limit

We know that a gamma photon with energy that is higher than 1.02 MeV produce electron and positron when its close to the nucleus. So, my question is if the photon has a very high energy, lets say 70 ...
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How are proton-antiproton pairs produced?

The production of electron-positron pairs occurs if a photon with high enough energy passes near a nucleus so that the energy of the photon is converted into particle mass, in accordance with the mass-...
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Differential cross section for muon pair production?

I derived the following QED probability density for $e^+e^-\rightarrow\mu^+\mu^-$ \begin{equation*} \langle|\mathcal{M}|^2\rangle =e^4\left(1+\cos^2\theta+\frac{m^2+M^2}{E^2}\sin^2\theta+\frac{m^2M^2}{...
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Real particles gets replaced by virtual ones all the time?

If virtual particles arises all the time, everywhere, wouldn’t an virtual electron-positron pair arise near an real electron; the virtual positron annihilate the real electron (as opposed to the ...
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How do photons create matter?

How exactly do photons create matter? I really have a hard time understanding this. I've seen an explanation where they use other, virtual particles to create electron and positrons, but even then, I ...
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Minimum energy for pair production near charge $eZ$

According to the text "On the Production of the Positive Electron" by Oppenheimer and Plesset, from 1933, the authors give a lower bound for the energy $E$ for the pair production near a nucleus of ...
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Why are there two photons in pair production Feynman diagram? [duplicate]

Given I wonder why are there two photons entering in a) pair production? Isn't it one photon resulting in $e^+e^-$ ?
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Pair production form high energy cosmic microwave background photons and related calculations

If assume that fluctuating fermion-antifermions pairs in space are products of photon-photon fusion reactions. Thus their total electric charge and total color are null. And the pairs spins are ...
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Electron and positron pair production and annihilation

An electron and a positron arise from an energetic gamma photon. However during annihilation of an electron and positron, two gamma photons are released. Is this a violation of law of ...
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Does pair production happen even when the photon is around a neutron?

In order for a photon to decay into a pair of $e^+ e^-$, it must have at least $E_{\gamma}=1.022$ MeV and must be near a nucleus in order to satisfy the conservation of energy-momentum. But would ...
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Question about pair production

Pair production can't occur in vaccum because momentum cannot be conserved because the photon does not have a rest frame of reference, that means that the produced pair has a center of mass frame of ...
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Pair production problem, how is energy not conserved here?

The problem is asking me to find the minimum photon energy that would produce an electron-positron pair when it collides with a free electron at rest. This is my attempt at trying to conserve both ...
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Are 40 Kelvin interstellar gas clouds evidence of virtual positron and real electron annihilation

Given that Hawking radiation includes separation of a virtual electron-positron pair, then why cannot it be the case that in the vicinity of a real electron it annihilates with the virtual positron? ...
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Can an electron inside an atom annihilate? [duplicate]

We know that in QFT, all particles are being created and annihilated, and because of the conservation laws, on average the number of particles remains constant. Suppose we have an electron in an atom....
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Can vacuum fluctuations change the position of an electron?

According to QFT, virtual electron-positron pairs are created everywhere in the space, and more frequently near electric charges. Suppose that one such a pair is created in the proximity of an ...
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What parameters determine the amount of Uehling potential and self-energy correction effects?

Uehling potential correction and electron self-energy correction are the two most important factors contributing to the lamb shift in the hydrogen atom, by "smearing" the wavefunction of the electron. ...
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Does the Compton wavelength put a limitation on how precise we can measure the position of a particle?

I have read on Wikipedia (https://en.wikipedia.org/wiki/Compton_wavelength) that we cannot measure the position of a particle more precise than half of its Compton wavelength, since the photon we ...
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Photo pair production: differential cross section

In a scientific paper, I need for my Bachelor thesis, the differential cross section for photo pair production $\gamma\gamma\to e^{+}e^{-}$ is given as follow: $\mathrm{d}\sigma = \frac{r_{0}^{2}\...
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Pair creation and annihilation and Wheeler's one electron universe

I stumbled upon Wheeler's idea that there could be only one electron. If I understood correctly, basically the idea is that one electron moves forward and backward in time such that it appears as if ...