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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Particle production in an expanding universe?

I was reading this interesting article which talks about particle production in an expanding universe. Usually this process is proposed to have occurred in the early universe, when the expansion was ...
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What frequency is needed for pair production?

I'd like to know exactly what frequency of a photon produces a pair e+/ e- , is it 2,4712x 10^20: must the photon have exactly that frequency or is there a range of tolerance? When the 2 particles ...
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In David Griffiths Elementary Particles Question 7.27, why do the spinors and Bjorken and Drell gamma tensor commute?

So, I have been trying to teach myself out of the David Griffiths Elementary Particles textbook, and I am trying my best to understand the conventions. I am looking at question 7.27 (found on page 270 ...
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Logarithmic behavior in pair annihilation cross section?

I am calculating a tree-level annihilation cross section ($\chi\chi\rightarrow \gamma \gamma$) for a certain model and am getting logarithmic behavior in the cross section, which I've never seen so it ...
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Can Coulomb force of repulsion split two photons into positron and electron?

imagining a nano device which have ability to squeeze two repelling protons to a point that coulombic force of repulsion is near the maximum, then you direct two photons with energy of 1.0mev at the ...
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Free energy from the vacuum?

An electric field with an intensity of the Schwinger limit $$E=\frac{m_e^2c^3}{e\hbar} \approx 10^{18} \hbox{ V/m}$$ is strong enough to create electron-positron pairs out of the vacuum by separating ...
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Why does production of electron come with either electron neutrino or positron?

I read that when an electron is produced, it always comes either with an electron neutrino or with a positron. Why is that so? Why doesn't an electron come instead with say a muon neutrino or antimuon?...
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Lowering the Schwinger limit with superconductors while considering the Unruh effect?

Unruh Effect is often left out in calculations regarding the Schwinger limit. I've been looking at different mechanisms for more easily attaining the Schwinger limit. So far, the only thing I have ...
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Hawking radiation: how can gravity rip a pair of virtual particles apart without creating another pair of virtual particles in the process?

To the best of my (limited) knowledge of theoretical physics you cannot rip a pair of virtual particles apart without investing enough energy to create another pair of virtual particles... If Hawking ...
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In Hawking's original Hawking radiation paper, how can we understand where the radiation comes from in the collapsing star spacetime?

In the original Hawking's paper "Particle creation by black holes" he first studies the collapsing star spacetime, and then the quasi-stationary phase of the black hole. In the collapsing ...
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Chemical Potential of an electron or positron in a pair production reaction

In the Thorne and Blandford Modern Classical Physics text there is an exercise that walks you through deriving the density-temperature limit for pair production in plasmas. To do this they consider a ...
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Pair production and recombination with a more energetic beta particle

Can gamma particles with sufficient energy for pair production gain energy by recombining their positron with a more energetic beta particle than the one they produced? If yes, is this something that ...
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Can a particle anti-particle pair be created with initial particles conserved?

Is it possible to have a particle collision between 2 particles, have those 2 particles structures conserved, but also create a particle-antiparticle pair in the process? For example, you have a Pion ...
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Can real particles be annihilated with virtual antiparticles and the other virtual particle pair replaces the real? Can this explain uncertainty?

Time goes from left to right. An electron is staying still, so from left to right, it's a straight line. A virtual photon got emitted from it, becomes a virtual pair of positron, electron, the virtual ...
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Is pair production possible in Classical Field Theory?

It is often said that quantum effects only become manifest in loops, and all tree-level calculations are classical. I am trying to figure out to what extent this claim is true. I know the claim arises ...
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Does the Schwinger effect prove matter and antimatter can be created from a vacuum?

Virtual particles or vacuum fluctuations are the pair annihilation/creation of matter and antimatter particles in and out of the vacuum. Theses particles are virtual, but we know they exist because of ...
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Can the Maximon Equation be adapted to calculate the pair production cross section for different particles?

The Maximon equation describes the cross section for pair production near matter. It takes the form ${\displaystyle \sigma _{pair}=Z^{2}\alpha r_{e}^{2}{\frac {2\pi }{3}}{\biggl (}{\frac {k-2}{k}}{\...
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How to calculate pair production cross section?

I've adapted the following equation from Wikipedia to calculate the pair production cross section $\sigma_x$ for a photon decaying into a pair of particles $x^+ x^-$ : $\sigma_x = \alpha \times(r_x)^2\...
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What is the minimum speed at which the proton has to move for antiproton production? [duplicate]

In a collision between 2 protons. Do each of them have to move at 1c, 0.5c.. ? The lower the speed, the less likely the production of the antiproton?
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At what speed do newly created protons move after a proton-proton collision?

I read that when 2 protons travelling at near the speed of light collide with each other, they create 3 protons and 1 antiproton. At what approx. speed those 3 new protons usually move once they are ...
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Can radio waves be converted to positron and electron when placed in weak electric field?

In particle physics, gamma rays can be converted to positron and electron when placed in strong electric field. My question is: What will happen if radio waves are placed in weak electric field? Will ...
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Can the time interval between measurements A and B be arbitrarely small?

If we make two measuraments of a particle-antiparticle spin should the interval between the two measuraments be so small that no signal emitted by one particle can have effect on the measueament of ...
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Is there anything that can be created from absolutely nothing? [closed]

Is there anything at all that can be created from nothing? Maybe on the quantum level? I’m aware of pair production but even that requires a photon with energy equal to the 2 particles.
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Why does pair production happen?

When a photon that has an energy of at least twice the rest energy of an electron passes by an atomic nucleus, it turns into an electron and a positron. But why? Nothing I know about quantum/particle ...
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Was the off-shell mass of photons measured in the recent Breit-Wheeler experiment?

Premise: The Breit–Wheeler process is a pair production process in which a positron–electron pair is created from the collision of two photons. Background: In relativistic QFT, solutions that obey the ...
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Why does pair production only occur in an electric but not a magnetic field?

I recently read that the photon "decay" (if you can call it that) in an external field occurs only in an electric field but not in a magnetic field. The reason being that the Euler-...
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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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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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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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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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