What is Annihilation: Definition and 260 Discussions

In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total energy and momentum of the initial pair are conserved in the process and distributed among a set of other particles in the final state. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all quantum numbers of such an original pair are zero. Hence, any set of particles may be produced whose total quantum numbers are also zero as long as conservation of energy and conservation of momentum are obeyed.During a low-energy annihilation, photon production is favored, since these particles have no mass. However, high-energy particle colliders produce annihilations where a wide variety of exotic heavy particles are created.
The word "annihilation" takes use informally for the interaction of two particles that are not mutual antiparticles – not charge conjugate. Some quantum numbers may then not sum to zero in the initial state, but conserve with the same totals in the final state. An example is the "annihilation" of a high-energy electron antineutrino with an electron to produce a W−.
If the annihilating particles are composite, such as mesons or baryons, then several different particles are typically produced in the final state.
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  1. 4

    I Creation and annihilation operator commutation confusion

    In Quantum Field Theory by Lancaster, equation 3.14 $$ [\hat{a_i},\hat{a_j}^\dagger]=\delta{ij}$$ is introduced as "we define". Yes, example 2.1, where the creation and annihilation operators applied to harmonic operator states, there is a nice simple proof that this is true (although...
  2. F

    B Particle antiparticle collide, teleportation?

    Hi physicists! When a particle and antiparticle collide, (annihilation) as i understand, it in some cases transform and radiate light, which I can buy. But what happen in the teleportation part, where the particle antiparticle pair accurs in an other part in the universe? Do someone have some...
  3. S

    A Annihilation creation operators in case of half H.oscillator

    I'm trying to check if Ehrenfest theorem is satisfied for this wave function, |Y>=(1/sqrt(2))*(|1>+|3>), where |1> and |3> are the ground and 1st exited state wave functions of a half harmonic oscillator. When I'm calculating the expectation values of x and p using annihilation creation...
  4. B

    A Interpreting the K-G Annihilation Operator Expression

    I can derive $$a(k) = \int d^3 x e^{ik_{\mu} x^{\mu}} (\omega_{\vec{k}} \psi + i \pi)$$ for a free real scalar Klein-Gordon field in three ways mathematically: the usual Fourier transform way in Peskin/Srednicki, an awesome direct a = ½(2a) = ... way (exercise!), and as a by-product of a clever...
  5. Michael Netzer

    I Reconsidering Matter/Anti-Matter Annihilation

    Considering the overall behavior of the particle system, I'm wondering whether others might also agree that the case for matter/antimatter annihilation cannot be considered as open and shut as we presently assume. Why should a positron and electron annihilate each other? What additional...
  6. F

    B Matter and antimatter annihilation quarks

    So I'm wonder How does the annihilation occur? Does the quarks pair up like magnets for matter and antimatter? Do matter and antimatter have the same quarks?
  7. S

    Anticommutation relations Fermion creation and annihilation

    Homework Statement This problem is from Lahiri and Pal (2nd edition) Exercise 1.4: Suppose in a system there are operators which obey anticommutation relations ##[a_{r},a^{\dagger}_{s}]_{+}\equiv a_{r}a^{\dagger}_{s}+a^{\dagger}_{s}a_{r}=\delta_{rs}## and ##[a_{r},a_{s}]_{+}=0,## for...
  8. C

    Electron-positron annihilation diagram

    Just a quick question regarding the tree level Feynman diagram(s) contributing to this process - I am wondering if I wanted to compute the unpolarised transition amplitude for the annihilation ##e^+ e^- \rightarrow \gamma \gamma##, are there two tree level diagrams that contribute or just one...
  9. S

    Electron-positron annihilation

    I am presently slogging through an introductory text on QFT (a Christmas present - does that officially make me a nerd?) and I have gotten as far as the Dyson expansion of the S operator and Wick's Theorem. The author dismisses all first-order terms of the expansion as being represented by...
  10. Stephanus

    Anti Proton vs Neutron annihilation

    Dear PF Forum, Just out of curiosity. What happens when an anti proton hits a 'normal' neutron? According to this: https://en.wikipedia.org/wiki/Proton https://en.wikipedia.org/wiki/Neutron A proton has 2 up quarks, 1 down quark A neutron has 1 up quark, 2 down quarks. 1. Does anti proton has 2...
  11. G

    Anti hydrogen - hydrogen annihilation

    I would like to know what exactly hydrogen and anti hydrogen decay products are. Thanks
  12. Andrea M.

    Calculate Baryons Annihilation Cross Sections

    I was wondering if there is a way of calculate the annihilation cross section for two baryons, say ##p\bar p\to\pi\pi## or ##p\bar p\to\gamma\gamma##. The problem here is that we cannot use the usual chiral theory because the energy transfer is of the same order of the cutoff ##\Lambda\sim 1...
  13. Einstein's Cat

    Energy released from annihilation

    Hypothetically, say there were two bodies, both with a mass of 1kg, and these bodies were to anhilliate as one body was an anti-version of the other body then would the energy released equal the speed of light (due to E= mc squared; the bodies are stationary) or twice the speed of light? In...
  14. Buzz Bloom

    I Question about relative abundance of particles before annihilation

    I am looking to correct my understanding about the relative abundance of particles and antiparticles created before the two periods of annihilation: (1) protons/neutrons and anti-protons/anti-neutrons, and (2) electrons and positrons. In a previous thread...
  15. gjonesy

    Matter Antimatter Annihilation event?

    I was watching a documentary on this subject that I found quite interesting. They put forth an explanation of why we see mostly matter in the universe. That after the big bang equal amounts of both matter and antimatter were created and that the decay rate of antimatter was responsible for the...
  16. Buzz Bloom

    Questions re: Matter-Antimatter Annihilation

    I am having trouble getting my head around several of the concepts related to the very early activities of the universe expansion. For this thread in particular, what are the assumptions regarding the relative number of particles of different species before and after annihilation. First, I am...
  17. Chip

    Annihilation of shifted gaussian vs. nonshifted gaussian

    Maybe a picture will help. http://chipreuben.com/annihilation-of-shifted-Gaussian.jpg I get zero, both with the shifted and the non-shifted. Can anyone tell why the nonshifted should yield the ground state eigenfunction multiplied up by a constant? It seems the answer has to do with expanding...
  18. P

    The physical derivation of annihilation operator?

    From P. Meystre's book elements of quantum optics (Many labels of equations are wrong:H) Page 83, the annihilation operator and creation operator, which are helpful to discuss harmonic oscillator, are defined as ## a=\frac{1}{\sqrt{2\hbar\Omega}}(\Omega q+ip),\\...
  19. S

    Matter/antimatter annihilation and conservation of mass

    I was hoping to learn a little bit more about matter-antimatter annihilation. As I understand it, when a particle meets an antiparticle, they are both annihilated and energy is produced. Does this contradict the laws of conservation of energy and conservation of matter? I haven't had much luck...
  20. F

    Exploring Matter-Antimatter Annihilation: Distance and Probability Factors

    Hello all. I had some questions on some of the specifics of matter-antimatter annihilation. I've tried looking this up but haven't had much success. If you guys know of any textbooks or journal articles that dig deep into the mechanics I'd be grateful if you'd post them. Anyway, my basic...
  21. Justice Hunter

    Particle/antiparticle annihilation problem near blackholes

    So around the time of the Big Bang, Particle and antiparticle pairs were created and annihilated. I believe one out of every 100 million(?) particle pairs actually didn't have an accompanying antiparticle, and survived the maelstrom, giving us the galaxies and stars we have today. Now, at the...
  22. G

    Electron-positron annihilation

    I need help with a problem and I would appreciate if you help me with it... An electron with kinetic energy K=1Mev collides with a positron at rest. In the collision, both particles mutually annihiliate, creating two gamma rays with equal energy, each of them traveling in equal angles θ in the...
  23. K

    Proton Proton Annihilation: The Energy Behind Fusion

    How much force (<10kN) is needed to compress two protons into each other? When it happens, when they are annihilated, the energy of the released gamma rays E=Mp *c^2 ? or some are carried away by short-lived byproducts? Regards Karoly
  24. S

    Electron-Positron Annihilation Conservation Laws

    What ensures conservation of energy and conservation of momentum in Electron-Positron annihilation? If e=mc2 and momentum = mass*velocity, couldn't the energy equivalence of the electron and the positron be converted to make one photon, or more that 2 photons? I've read that two photons are...
  25. Stephanus

    Matter - anti matter annihilation

    Dear PF Forum, Can proton be annihilated by anti neutron? Can proton be annihilated by positron? Can neutron be annihilated by positron? Does every particle has to match its antiparticle to be annihilated, example: Proton must be annihilated by anti-proton, not by anti neutron. I've heard that...
  26. AlanKirby

    How can e-e+ possibly go to ZZ?

    Hi there, my question is the following. If an electron and positron annihilate, how can they result in ZZ? The issue I'm having is that due to charge conservation, the exchange particle can't be W- or W+. It also can't be a photon since the Z's don't have electrical charge to couple to. It...
  27. kq6up

    Can antiparticles annihilate different types of particles?

    The title says it all. For example can an anti-neutron annihilate with an electron? Thanks, Chris
  28. SU403RUNFAST

    Does the annihilation of a proton always result in gamma radiation emission?

    When a proton is annhilated, is there gamma radiation emitted?
  29. A

    Proving Coherent States are Eigenfunctions of Annihilation Operators

    Look at the following attached picture, where they prove the coherent states are eigenfunctions of the annihiliation operators by simply proving aexp(φa†)l0> = φexp(φa†)l0>. I understand the proof but does that also prove that: aiexp(Σφiai†)l0> = φiexp(Σφiai†)l0> ? I can see that it would if you...
  30. itssilva

    Creation and annihilation as measuring processes?

    From a purely theoretical standpoint, I'm quite comfortable with the concept of particle creation/annihilation, but, as a chemist, I cannot but feel that there's something missing in the way of interpretation, so I came up with the following 'explanation' of the phenomenon based on the measured...
  31. V

    Dark matter annihilation into gamma rays

    This question straddles this forum and the "Beyond the Standard Model" one a bit, so if a mentor thinks it belongs better elsewhere, please feel free to move it. I've seen references in the "popular science" press about the possibility of indirectly detecting dark matter by looking for gamma...
  32. T

    Creation and annihilation operators

    - a|n>=C|n-1> - a+|n>=D|n+1> And because |n-1> is normalized, <n-1|n-1>=1: (<n|a+)(a|n>)=C2 Thus, <n|a+a|n>=C2 Where a is the annihilation operator and a+ is the creation operator I don't understand this as...
  33. ryanuser

    Is Quantum Teleportation Possible Through Electron-Positron Annihilation?

    Hi Would it be possible to force an electron and a positron to meat each other and annihilate, then the gamma beam created is to be directed some distance away and passed next to an atom for pair production to occur. ( I dismissed complications related to the vacuums and the magnetic fields)...
  34. J

    Muon Speed Calculation After Photon Collision

    Homework Statement Two equal-energy photons collide head-on and annihilate each other, producing a u+ and u- pair. The muon mass is about 207 times the electron mass. Calculate the maximum wavelength of the photons for this to occur. If the photons have this wavelength, describe the motion of...
  35. DiracPool

    Proton creation and annihilation

    1. Can a proton be created in a particle accelerator that doesn't use protons? For instance, an "electron-positron" collider? I understand baryon number needs to be conserved, so this would necessitate the accompanying creation of an anti-proton, but I'm wondering if these colliders have...
  36. F

    Distribution of energy after matter/antimatter annihilation

    Hi all Maybe a quick question! After the big bang and inflation, a little while later there is the mass annihilation event where 10 billion matter particles and 10 billion anti matter particles annihilate, sending out energetic photons. For each 10 billion annihilation events there is one...
  37. H

    Anti-matter annihilation and the CMBR

    Recently I watched a lecture on Anti-matter and the Standard Model... ...At one point Dr. Quinn, makes the statement that the CMB is the resulting energy left over from the annihilation of the matter and anti-matter which arose during cosmic inflation (leaving behind only one part in 30 million...
  38. Larry Pendarvis

    Is photon-photon annihilation possible in an optical fiber?

    Consider this report: http://www.physics-astronomy.com/2015/01/quantum-teleportation-of-subatomic.html "Then, the researchers shot a third particle of light at the photon traveling down the cable. When the two collided, they obliterated each other. Though both photons vanished, the quantum...
  39. 2

    Question about creation and annihilation operators?

    Hello! I am reading about the creation and annihilation operators and I don't get how you find the creation operator from the annihilation one. The creation one is \hat{a}=\sqrt{\frac{m \omega}{2 \hbar}}\left( \hat{x}+\frac{i \hat{p}}{m \omega}\right) and the annihilation operator is...
  40. A

    Why proton and electron collision doesn't result in annihilation?

    I am new to particle physics, but I heard that electron and positron annihilate each other in case of contact mainly because both have opposite charge( even same mass). Consider an electron is given enough kinetic energy such that it compensates mass differentiation between proton and electron...
  41. R

    Electron Positron Annihilation

    What kinds of particles do e- and e+ annihilation make? Where does the higgs boson come into play? And why are the electromagnetic and the weak force so closely related? Thanks peeps
  42. R

    Observing Particle Annihilation: How Anti-Particles Affect Universe Formation

    How do we know/observe a particle annihilating a anti-particle? Is it impossible to theorize that in the early universe atoms of hydrogen were as abundant as anti-hydrogen atoms yet did not annihilate each other? Instead anti-Hydrogen repelled and pushed Hydrogen together to form clumps? In...
  43. S

    Annihilation results in an extreme burst of energy

    Annihilation results in an extreme burst of energy... If enough antimatter is isolated, it can be utilized for annihilation which can converted into useful energy...This can make us approximately half as fast as light... Just wanted to have ur comments ..?? Is it possible...?
  44. D

    Hermitian conjugate of the annihilation operator

    Hi I have been looking at the solutions to a past exam question. The question gives the annihilation operator for the harmonic oscillator as a= x + ip ( I have left out the constants ). The question then asks to calculate the Hermitian conjugate a(dagger). I thought to find the Hermitian...
  45. W

    Antimatter-Matter Annihilation (i.e. antiproton w/ positron)

    I know that a particle's exact anti-counterpart (i.e. an electron and positron) will annihilate into pure energy. But my question is do differing particles and antiparticles (such as an antiproton and positron) annihilate each other, and if so how much so, because I doubt it too would result in...
  46. R

    A Commutator of annihilation operator

    Hi, everybody: I encountered a problem when I am reading a book. It's about the atom-photon interaction. Let the Hamiltonian for the free photons be H_0=\hbar \omega(a^{\dagger}a+\frac{1}{2}). so the commutator of the annihilation operator and the Hamiltonian is [a,H_0]=\hbar\omega a and I...
  47. S

    Minimum distance for annihilation

    How close does does a particle and anti-particle pair have to be with each other in order to achieve annihilation?
  48. K

    Does virtual particle-antiparticle annihilation produce anything?

    My understand is, the virtual particle-antiparticle pairs created under uncertainty principle are not the same as the traditional particle-antiparticle (creates new particle after annihilation), the virtual ones does not produce anything, since they are created from nowhere, which the...
  49. K

    Does annihilation always produce new particles?

    I have some basic confusion on the annihilation, please help me to understand these: 1 Does antiparticles all have negative energy? And the energy we talking about here is the rest mass energy? If it is, does it means antiparticles have negative mass since E=mc^2 ? My understanding on...
  50. P

    Particle annihilation in quantum vacuum

    Well this is a doubt that comes from some time ago and I haven't found the answer on the net. Quantum fluctuations in quantum vacuum create particle-antiparticle pairs for very short periods of time satisfying ΔEΔt≥\frac{\hslash}{2} It is very well known that when a pair particle-antiparticle...
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