Pair production Definition and 112 Threads

Pair production is the creation of a subatomic particle and its antiparticle from a neutral boson. Examples include creating an electron and a positron, a muon and an antimuon, or a proton and an antiproton. Pair production often refers specifically to a photon creating an electron–positron pair near a nucleus. As energy must be conserved, for pair production to occur, the incoming energy of the photon must be above a threshold of at least the total rest mass energy of the two particles created. (As the electron is the lightest, hence, lowest mass/energy, elementary particle, it requires the least energetic photons of all possible pair-production processes.) Conservation of energy and momentum are the principal constraints on the process.
All other conserved quantum numbers (angular momentum, electric charge, lepton number) of the produced particles must sum to zero – thus the created particles shall have opposite values of each other. For instance, if one particle has electric charge of +1 the other must have electric charge of −1, or if one particle has strangeness of +1 then another one must have strangeness of −1.
The probability of pair production in photon–matter interactions increases with photon energy and also increases approximately as the square of atomic number of (hence, number of protons in) the nearby atom.

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  1. 7

    Pair production - which theory does it belong to

    I am wondering in which theory pair productioon is described? Is it field theory, particle physics or quantum physics? I am sorry for such a basic question, but i need this info to find some books which will explain pair production mathematically and not by waving hands... (like allover the web)...
  2. Q

    Can someone explain how pair production happens?

    I know that if a photon has enough energy, it can split off into a particle and anti-particle. But how does that happen exactly? Does the photon just randomly decides to split off? With annihilation (opposite of pair production), the process is much easier to visualize for me, because you...
  3. A

    Feynman diagramms for Photoelectric, Compton, Pair Production

    Hello to everyone! What are the feynman diagramms for the three basic photon interactions? Photelectric Compton(compton, Rayleigh and Thomsom scattering) Pair Production Thank you in advance!
  4. R

    What is the maximum charge limit for an electron-positron pair creation?

    Calculate the energy is takes to create a positron-electron pair and place the electron in the lowest energy state of a nucleus of charge 푍푒 and the positron infinitely far away. Show that for a sufficiently high charge the creation of the electron-positron pair gives a net release of energy and...
  5. L

    Pair Production: Creating Matter from Light

    Pair production interests me - create matter from electromagnetic waves. So far I have read that a Positron-Electron pair can be created by photons having energy exceeding twice the rest energy (m * c ^ 2) of an electron (1.022 MeV). So, if you have photons exceeding the energy of an up...
  6. F

    Pair Production in static fields

    Hello, I have a [probably silly] question regarding particle pair production in strong static fields. Take for instance the finite Coulomb field (of say an extended nucleus) and the Dirac equation. One can compute the bound states of such a system and see that at a certain value of Z the...
  7. M

    How successful is pair production?

    when a photon interacts with a nucleus, a positron and an electron are created, provided the photo has enough energy. But what is the probabilty of this occurring? If i fire 100 photons at a nucleus, how many electron-positron pairs will i create? Also, has anyone ever succeeded in...
  8. S

    Regarding pair production and annihilation

    Hi, i have a few questions about these two processes. Now, I am only 16 years old, in my last year of school, so I am not so familiar with physics, if you could put terms simple enough for an average 16 year old to understand, i'd much appreciate it :) my question is: If e‾ + e+ → γ + γ and γ →...
  9. Z

    Neutron-Antineutron pair production

    I think its true that you cannot use a bubble chamber to identify the pair production of a neutron-antineutron pair, but how (maybe if) is that studied? Is that reaction common in a proton collider?
  10. I

    Exploring Entanglement in Quantum Collisions

    Hi, I was reading some novice stuff about quantum entanglement and I was wondering if entanglement occurs in either of these two scenarios: 1. electron and positron entangled as a result of being created by a photon passing over a heavy nucleus 2. two free electrons entangled with...
  11. S

    Question about momentum of pair production

    I am learing the particle physics bit of my physics course and don't understand how momentum is conserved when a photon produces an electron/positron pair. In the bubble chamber chamber picture here...
  12. F

    Prediction of pair production via WIMP decay? (Layman question)

    Hello, This may sound silly, don't be afraid to let me know just how silly though! I've read that predictions are made using the standard model. I do not know the details of this process. I understand pair production occurs randomly in a vacuum, but I wondered if there was an underlying...
  13. B

    Why are some nuclei more resistant to pair production?

    I've gotten interested in this pair production stuff, and I'm wondering: Why is it that some nuclei can absorb more energy than the energy needed for pair production, while other nuclei result with the incoming energy creating pair production? Is it because heavier nuclei can distribute the...
  14. B

    Electron Capture in Pair Production

    During electron-positron pair production, does electron capture always happen? Gracias
  15. J

    1 MV electrode limited by vacuum pair production?

    Hi, Someone told me that a potential of 10^6 volts is not stable because it would cause spontaneous electron-positron creation from the vacuum. Is this true? I thought one could reach higher potentials than 1000000 volts.
  16. L

    Pair Production and Mass Energy Equivalence

    Hello, In a previous discussion of Pair production I was shocked by what I heard and I have some questions from the general explanation of the subject. So you can make fermions out of bosons? You can make rest mass out of energy? Does this mean that not just relativistic mass, but...
  17. D

    Pair production: Has it been observed experimentally?

    I was reading about electron-positron annihilation and I got to the part where it says that this is a reversible process, meaning that an electron and a positron could be created from photons. About this reverse process the article says "In nuclear physics, this occurs when a high-energy photon...
  18. S

    Possible Particle Pairs in Gravitational Pair Production: A Speculative Inquiry

    Although there is no experimental evidence or QG theory, it is not unreasonable that very strong gravitational fields or very high energy gravitons would cause pair production of real particles. In view of the spin-2 nature of gravity, what might these pairs be? One electron, one positron and...
  19. M

    Pair production in boson-boson collision

    Homework Statement I'm given this interaction Lagrangian: L_I (x) = -g \overline{\psi}(x) \psi (x) \phi (x) where g is the coupling constant, \psi is an electron and \phi is a neutral scalar field. I have to calculate the amplitude for process \psi + \psi \rightarrow e^- + e^+ that...
  20. B

    What Is the Minimal Wavelength for Electron-Positron Pair Production?

    Homework Statement what is the minimal wavelength of electromagnetic radiation to pair-produce an electron-positron pair? Homework Equations ~ = wavelength hc/~ = 2MeC^2 + K The Attempt at a Solution hc/~ = 2MeC^2 = 2(9.11x10^-31)(3x10^8)^2 ~ = 8.24x10^-11m is tis correct?
  21. L

    Gamma - when is pair production dominant

    hi, am i right in saying that for gamma rays of energies above 10MeV, the main interaction mechanism is pair production? and this is independent on energy? (or is it compton scattering for example?) thanks
  22. N

    [particle physices] pair production not possible in absence of matter?

    Homework Statement "Prove that pair production is not possible in the absence of matter." Homework Equations / The Attempt at a Solution First of all, I'll assume a photon is considered matter, cause two photons can create a pair. Second: I thought pairs pop into and out of existence all the...
  23. C

    Exploring Pair Production: Rules and Resources

    Hey all, Just like to prefix this question with the statement that I am a computer scientist with a strong interest and passion for physics, so please forgive me if this question is a tad naive. With that out of the way, I have a general question about this image: It's from "The Little...
  24. A

    Effect of magnetic field on pair production

    Homework Statement Hi Its just me again! I kindly need help on this question. Its as follows: The tracks of a positron and an electron created by pair production in a magnetic field curve in opposite directions. a) Why do they curve in opposite directions b)Both particles spiral...
  25. S

    What Does It Mean for a Fireball to Be Opaque to Pair Production?

    What does "to be opaque to pair production" mean? (I'm talking about fireball). I know what a pair production is but I can't get the crucial point: does it mean the photons don't collide? If it is so that means an opaque-to-p.p.- source have a greater luminosity (emits more photons) than a non...
  26. A

    Energy and Wavelength of a photon in pair production

    Homework Statement Electron and positron each have a kinetic energy of 220 keV even when far apart. Homework Equations The Attempt at a Solution I have no idea. My book says the answer 1.46 MeV, 8.49 x 10^-13 m but I don't know how to get that.
  27. S

    Differential cross section formula of electron-positron pair production.

    Homework Statement I need to calculate the differential cross section in order of Mandelstam variable t, instead of the angle \theta. My problem is with the change of variable not the amplitude of the process. I'm getting a global minus sign which can only be wrong. It seems I'm making a very...
  28. Matterwave

    Energy variance, and pair production

    Ok, so here's a question. The energy of say photons is frame-dependent. Photons are blue-shifted or red-shifted depending on my velocity towards or away from the source. However, what happens when I apply this to pair-production? For example, if my photons are energetic enough, they may create a...
  29. K

    Can Pair Production Occur if Positron and Electron Have the Same Rest Energy?

    Homework Statement If positron and electron have the same rest energy can pair production occur?Homework Equations E=hc/λ Plancks equation E=mc^2The Attempt at a Solution so i found the E of the photons using Plancks equation and found the photon E to be 6.83x10^-14 ( should I double this...
  30. F

    Best, -Your Quantum Mechanics Tutor

    Hey Guys, Am working through Relativistic Quantum Mechanics: Wave equations by W.Greiner and have a simple question about the Klein-Gordon equation: is it fair to say that bound states only occur between -m<=E<=m? (c=1). There are a few problems where they show that you can get pair...
  31. H

    Pair Production Energy: Formula & Wavelength

    In pair production, what is the formula for the energy of an electron or positron of this conversion. Also, what is the wavelength of a photon that can create an electron positron pair.
  32. B

    Probability of Spin Polarization in Pair Production

    Hi, I have a question which sounds like : Particle with spin 0 annihilates in two particles with spin one. What is the probability their spin polarization will in the same direction in short time? I think is 0 because of argument saving spin of the system and correlation function of two...
  33. P

    How Accurate is the Uncertainty in the Lifetime of Electron-Positron Pairs?

    Homework Statement What is the uncertainty in the life time of an electron and positron produced in a vacuum?Homework Equations \Delta E\Delta t=\frac{\hbar}{2}The Attempt at a Solution \Delta E\approx1.6\times10^{-13}J \Delta t\geq\frac{\hbar}{2\Delta E}\approx 3ps (edited for Tex) This...
  34. C

    A Query about Pair Production and Electron-Positron Annihilation

    After an electron-positron pair is produced by a high-energy photon hitting the nucleus of an atom, is it possible for the produced positron to annihilate with a bound electron from the very same atom it was produced in? In this situation, what would happen to the produced electron--would it be...
  35. R

    Is there an intermediate 'particle' to pair production?

    This question was brought to mind while reading other threads. I didn't think it was appropriate to diverge those threads off their subjects, so I started a new one. (hope this is right). I'm specifically thinking about the extremely rare event of the interaction of two gamma rays as the...
  36. B

    Vacuum Energy - Pair Production Confusion

    So, let's get this straight :smile:. Black hole evaporation is, by the layman's version, supposedly due to a negative mass particle entering the black hole, while it's counterpart leaves, as radiation. These particles are formed near the black hole by vacuum fluctuations (i.e. pair...
  37. R

    Pair Production and Annihilation

    When a photon, with the help of a nucleus experiences pair production to make a positron and an electron, the energy of the photon will equal the rest mass of both the electron and positron together right? Then when the electron and positron annihilate, the two photons produces will each have...
  38. Z

    Pair Production: Electron/Positron from Photon Collisions?

    In Pair Production where a high energy photon collides with a nucleus a positron and an electron may result. But I have also come across references that say that two high energy photons can collide with each other to produce an electron and a positron. Is this correct?
  39. J

    Literature on Black Hole Pair Production (?)

    Does anyone could indicate what is the best literature to learn about black hole pair production? Any textbook explaining the instanton derivation in detail for the case of black holes? Jan
  40. P

    Cross Section Difference Bhabha Scattering and Muon Pair Production

    Hello, how do the angular distributions of Bhabha Scattering e^+ e^- \Rightarrow e^+ e^- and Muon pair production e+ e- \Rightarrow \mu^+ \mu^- differ? Regards, Phileas Fogg
  41. malawi_glenn

    Question on differential crossection, pair production

    Hi! I have encountered many differential crossections: \frac{d\sigma}{dE_+d\Omega _+ d \Omega _-} (Pair production of electrons and positrons) Where E+ is energy of positron. However, in all of these crossections, the energy of the electron; E- is included in the formula, e.g eq 2.1.1...
  42. malawi_glenn

    Where Can I Find High-Energy Pair Production Differential Cross Sections?

    Hi I am looking for a source which covers a differential crossection for pair production of electrons and positrons due to photons. \frac{d^2\sigma}{dEd\Omega} I need it to be valid for high relativistic energies of electrons/positrons and for all angels. I can only find formulas...
  43. M

    Kinetic Energy and Photon Energy Calculation in Pair Production

    5. A photon of energy E strikes an electron at rest and undergoes pair production, producing a positron and an electron: photon + e * = e * + Positron + e * The two electrons and the positron move off with identical momenta in the direct ion of the init ial photon. Find the kinet ic...
  44. J

    Pair Production and Momentum Transfer in Photon Interactions

    I read about "pair production" how a photon can create and electron and a positron. I read the calculations and I understand how this is impossible unless something else (a nucleus) is present to take away some of the initial photon momentum, however, the book doesn't say exactly 'how' the...
  45. V

    Pair Production: Why Can't Photon Create Positron+Electron?

    why can't a gamma ray photon -->positron+electron? My notes simply say this would violate momentum conservation (you need a recoiling nucleus), but why? I mean, the photon WOULD have momentum (=E/c), so the sum of momentums of the positron and electron would just have be E/c..
  46. B

    What is the Minimum Energy Required for Photon-Induced Pair Production?

    Homework Statement To show that the minimum energy a photon must have to create an electron-positron pair in the presence of a stationary nucleus of mass M is 2mc^2[1 + (m/M)], m is the electron rest mass. Homework Equations Conservation of energy and momentum.Also the minimum energy a...
  47. J

    Possibility of pair Production without interaction with matter?

    Homework Statement Is it possible for pair production to occur without interacting mwith matter? Homework Equations E+ + E- = E(gamma) - 2*m_e*c^2 The Attempt at a Solution In the Coulomb field of nucleus (or electron), the incident photon energy can be converted to the...
  48. H

    Reference frames for photon collisions (pair production)

    Homework Statement Hi, My question probably has a simple answer, but I've been scratching my head over it a little too long so I thought I would ask it here. I have three initial photons involved in a collision with 4-momenta k1, k2 and k3. I have two reference frames: frame 1: the...
  49. kreil

    Pair production photon electron problem

    Homework Statement A photon of energy E strikes an electron at rest and undergoes pair production, producing a positron and an electron: photon + (e-) = (e+) + (e-) + (e-) The two electrons and the positron move off with identical momenta in the direction of the initial photon. Find...
  50. P

    Pair production and another body?

    Why does pair production cannot occur except in the presence of another body? The explanation is so that linear momentum is conserved but why does a photon must first collide with something? I can see how linear momentum is conserved without a collision first. i.e. the two particles move with...
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