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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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Is pair production a type of elastic scattering?

Pair production is the creation of a subatomic particle and its antiparticle from a boson. Pair production often refers specifically to a photon creating an electron–positron pair near a ...
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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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Gamma radiation incident on material generating $e^+/e^-$ pair and Schwinger Limit

Does a gamma photon incident upon a material creating an electron-positron pair plus kinetic energy transfer momentum to an EM field and if so does the intensity approach the Schwinger Limit during ...
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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 ...
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Does the Uehling potential have any observable effect?

Uehling potential is the correction made to the coulomb potential due to vacuum polarization (electron-positron pair creation and annihilation). How big is this correction compared to the coulomb ...
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Why do we always choose centre-of-mass frame to study particle physics problems (e.g. Feynman diagrams)? Even in non-relativistic regimes (v<0.3c)

Example: electron positron annihilation forbids a single photon production, and searching through this forum (Why can't a single photon produce an electron-positron pair?) and a few books, they ...
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How can one of the particles on a pair of virtual particles created by vacuum fluctuations have negative energy? How does it lower black hole mass?

Assuming Stephen Hawking’s 1975 “Particle Creation by Black Holes” : “One might picture this negative energy flux in the following way. Just outside the event horizon there will be virtual pairs of ...
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Is there a simple rule connecting all indirect semiconductors band gaps to their electron-hole pair generation average energy?

The band gap of Diamond, Silicon and Germanium is 5.5, 1.12, 0.66 eV while the average energy to produce an electron-hole pair for the same semiconductor is namely 13, 3.6 and 2.9 eV. This ratios are ...
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Spaghettification on quarks?

Imagine a nucleon falls into a black hole, I would expect the gravitational force acting on each quark to be drastically different but due colour confinement wouldn't there more pairs of quarks being ...
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How far the pairs emitted by the photon has to be?

An electron-positron pair can be emitted by a photon having enough energy. Can one say the pairs are already inside the photon (like an atom), and when got the right energy they fly off? If this ...
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What is negative energy as used by Dirac to explain pair production? [duplicate]

While reading about pair production, I came across the concept of negative energy. What is negative energy exactly? And can there be negative mass corresponding to this energy?
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Why does pair production produce an electron and positron with opposite spin?

So I was trying to understand quantum entanglement and the example that was used to describe an entangled pair of particles was of an electron and positron after it is formed from a photon in pair ...
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Why does a particle-antiparticle collision produce $2$ photons instead of $1$?

In one of the questions that I did, it asked: What is produced when an electron and positron collides with each other? The answer is $2$ photons. Why doesn't it merge into one? After all, the photon ...
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How can a Kugelblitz form because pair production will occur before that

I might be incorrectly mixing up two separate theories - quantum physics and general relativity but from what I've studied, a Kugelblitz is a black hole that is formed from condensing large amounts of ...
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What happens to pressure exerted by photons in pair production?

Photons exert (positive) pressure which is a source of gravity. What happens to pressure exerted by a photon after converting into an electron-positron pair or a proton-antiproton pair? Does it still ...
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What is the most massive symmetric black hole pair that can pair produce during their collision?

Gravitational waves produced by inspiraling black holes have a similar inverse dependence on mass that the strength of the gravitational field outside of the event horizon has. For example, look at ...
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Endless electron-positron annihilation/creation?

We start the process with gamma rays collision that produces positron electron pair, the pair then annihilates when hit each other and gamma rays are produced again and everything repeats. Sure, in ...
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reading the bubble chamber image

I have a bubble chamber image and some explanation from the textbook, however, I was still not sure how to read it clearly. From What are the "x" marks in a bubble chamber image? I ...
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If photons have no mass, how they create electrons and positrons on colliding? [duplicate]

How are electrons and positrons formed when photons collide, as photons are massless?
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Pair production near an electron

A high energy photon (E>~MeV) after interacting with an atomic nucleus produces an electron positron pair. The threshold of this process is the sum of the rest mass energies of these two leptons. My ...
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Electron-positron annihilation/creation

I understand that gamma-rays can produce positron-electron pairs and positrons and electrons can annihilate to two gamma-rays. My question is: If a gamma-ray photon creates a positron-electron pair, ...
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Can photons take momentum from a nearby photon during pair production?

During pair production, a photon steals momentum from a nearby nucleus so that momentum is conserved. My question is: whether the photon can take the momentum from a nearby photon or not?
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Baryon asymmetry still going on

I read these questions and answers and it made me curious. Baryon asymmetry Why do we believe baryon asymmetry? Why does matter-antimatter asymmetry only refer to baryon asymmetry? How does ...
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In pair production does gamma rays actually strike a nucleus?

I think the quetion is vagueless.I simply want to ask it is often printed that there must be a heavy nucleus present for pair production.It is answered that its needed to make electron and positron ...
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Can pair production produce any particle/anti-particle pair?

Hopefully this one'll be a fairly easy answer. My understanding of pair production is that it is a simple transfer of momentum/energy in which an incident particle looses energy after a scattering ...
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Pion pion collision

I am following a course on subatomic physics and I was asked this question Consider the interaction $\gamma\to\pi^++\pi^-$. Which conservation law prohibits this reaction? And modify this reaction ...
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Why electron positron pair move oppositely inspite of attraction?

In pair production the two antiparticles always move in opposite direction I wonder why is that so though I know it is to conserve energy but the basic principle unlike charged particle attract should ...
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Why is the production cross section for 3rd generation squarks (stops) so much smaller than for 1st and 2nd generation?

In the plot below we see that the production cross section for 3rd generation squarks (i.e. top squarks) at a hadron collider is about a factor 10 smaller than that for 1st and 2nd generation squarks (...
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Is pair production instantaneous?

I was just reading this question and I didn't understand the question at first. But I think I understood it after a bit of thought. Here is my question inspired from that question: Are the processes ...
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Why is the proton anti-proton annihilation and pair production asymmetric?

This is a follow up question to this question. The process of annihilation is very well explained. However while the annihilation is a step-by-step process the pair production does not seem to follow ...
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Virtual and Real particles

In a discussion with my astrophysics lecturer, we ended up talking about virtual particles. One of the most astonishing phenomena he pointed out was the fact that annihilation of virtual particles ...
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Can all light-matter interactions be reduced to the photoelectric effect, the Compton scattering, and pair production?

My book says that all interaction of light and matter can be reduced to the photoelectric effect, the Compton scattering and pair production. How true is this? What about reflection and absorption ...
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Lasers so powerful they could rip apart empty space

An article in Science says: According to the theory of quantum electrodynamics (QED), which describes how electromagnetic fields interact with matter, the vacuum is not as empty as classical ...
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Energy in an electron/positron electric field shortly after pair production

Just a quick thought, I was considering the energy contained within the electric field and was curious about the following situation: Consider you create an electron/positron pair (using a third body ...
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Electron-positron pair production requiring a nucleus

I was told that a nucleus is required to be present to allow the conservation of energy and momentum in the production of an electron and positron from a high energy photon, during pair production. ...
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The wavelength of a photon after pair production

The book that I am using says that the total energy of an electron positron pair before they happen to collide is equal to $$ 2mc^² + 2K.E$$ where K.E is kinetic energy. They then say that this energy ...
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Is it possible to have a non mathematical explanation of the dependence of Pair Production cross section with energy?

Cross section of pair production with interaction of photon increases with energy. But why does that happen? I want a non mathematical answer on this.
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Why does pair production have a minimum energy?

This was an exam question I recently encountered, and it sparked my interest. To me, the following makes sense: Given that pair production has no maximum energy (since $E_{min} \geq 2E_o$), the ...
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Helicity conservation in QED

In QED, suppose I talk of annihilation of electron and positron, is it right to say that if the electron is right handed then the positron is left handed and so the total $S_z=0$ (Assuming they have ...