Annihilation Definition and 260 Threads

This is Feynman diagram of annihilation I get from wikipedia https://en.wikipedia.org/wiki/Annihilation I don't understand what the middle line with arrow to the right is. If I consider the left vertex and conservation of charge, it means the horizontal line with arrow to the right should carry...

I was researching on the Anderson cloud chamber that discovered the positron in 1932. I couldn't help but wonder, if positron annihilates upon contact with an electron, how was it able to get till the cloud chamber without annihilation? Shouldn't the 2 photons be the only thing observed in the...

In the Dodelson's textbook, the author introduce the Boltzmann equation for annihilation. ##a^{-3} \frac{d(n_1 a)}{dt} = \int \frac{d^3 p_1}{(2 \pi)^3 2E_1} \int \frac{d^3 p_2}{(2 \pi)^3 2E_2} \int \frac{d^3 p_3}{(2 \pi)^3 2E_3} \int \frac{d^3 p_4}{(2 \pi)^3 2E_4} \times (2 \pi)^4 \delta^3 (p_1...

Dear PF Forum, It's been a while since I logged in PF Forum. And wish you a good health. I'd like to ask a question concerning anti matter. I read in Dan Brown's Angel and Demon that anti matter can be used as energy source. A ha, I said to myself. There were you went wrong mr. Author. The...

This question is related to equation (1),(3), and (4) in the [paper][1] [1]: https://arxiv.org/abs/2002.12252

I read somewhere that when, say, an electron and positron annihilate, they create two photons which travel in opposite directions in order to conserve linear momentum. Is this true? What about pair production. Do you likewise need two photons to do this? Or, can you do it with one photon...

I’m not super familiar with the physics of this but, from a statistical standpoint it would make sense since so much annihilation was taking place after the Big Bang, and most of our universe is dark energy and matter. Further we know annihilation creates energy why not the opposite of energy...

So, I have a hamiltonian for screening effect, written like: $$ H=\sum_{k}^{}\epsilon_{k}c_{k}^{\dagger}c_{k}+ \frac{1}{\Omega}\sum_{k,q}^{}V(q,t)c_{k+q}^{\dagger}c_{k} $$ And I have to find an equation for the time evolution of the expected value of the operator ##c_{k-Q}^{\dagger}c_{k}##. I...

When an electron meets an anti-electron which is also known as positron and collide, the particles will become photons. But where did the photons go after the electron-positron annihilation happened?

I don't really know what I'm doing, I'd appreciate some nudges in the right direction. We defined ##\mathcal{S}## as the space of complex solutions to the Klein-Gordon equation, and for any ##\alpha, \beta \in \mathcal{S}## that ##(\alpha, \beta) =-\int_{\Sigma_0} d^3 x \sqrt{h} n_a j^a(\alpha...

hello Does special relativity entail matter annihilation ?

I set up this problem this way: ##p_a^{\mu}=(E, \sqrt{E^2-m^2}, 0, 0)## ##p_b^{\mu}=(m, 0, 0, 0)## ##p_c^{\mu}=(2E_\gamma, 2E_\gamma, 0, 0)## I have chosen to consider the two photons as a single particle of energy equal to ##2E_\gamma##. At this point I applied conservation of the...

I consider the laboratory system. The four momentums in this reference system are respectively: ##p^\mu = \big(\sqrt{|p|^2+m^2}, 0, 0, |p| \big)## ##p'^\mu= \big(m, 0, 0, 0 \big)## ##k^\mu = E\big(1, 0, 1, 0\big)## ##k'^\mu = E'\big(1, 0, -\sin \varphi, \cos \varphi \big)## I used conservation...

During particle annhilation the rest mass of the particle pair gets converted into momentum with zero time component ie. light. As the pair is colliding do their rest masses decrease and get converted to momentum as a function of distance? Or do they instantaneous annihilate in a discrete interval?

I was reading about electron-positron annihilation. Typically it results in two photons, each with an energy of 511 keV, that go shooting out in opposite directions. But I read that in some instances three photons can result. Electrons have an intrinsic spin of ½, while photons have a spin of 1...

Hello everyone, I'm new here and I'm struggling with the mathematical formalities in quantum mechanics. $$\langle n+1|b^\dagger bb^\dagger + \frac 12 |n \rangle = \langle n+1|b^\dagger bb^\dagger |n \rangle + \langle n+1| \frac 12 |n \rangle $$ $$ = \langle n+1|b^\dagger b \sqrt{n+1} |n+1...

Pretty much in a nutshell... fielded a question about how spin affects electron positron annihilation... ie do the spins have to be opposite in order to conserve angular momentum for two-photon annihilation to happen? Intuitively I figured that looks reasonable ... but decided to check, and...

π+ + π- → γ + γ How do you represent this in a Feynman diagram showing the individual quark? I am very confused please help! [Moderator's note: Moved from a technical forum and thus no template. Own effort below.]

IfA=cd, where c and d are annihilation operators of two different types of Fermions, then {A,A°}is? A.1+n1+n2 B.1-n1+n2 C.1-n2+n1 D.1-n1-n2 Where,n1 and n2 are corresponding number operator, A° means A dagger or creation operator,as the particles are fermions they will obey anti-commutation I think

Does anti-matter and matter annihilate each other even if they are not same "type" (eg. neutron and positron) and they meet each other?

Doom: Annihilation 2019 has just been released October 1, 2019 and I just watched it. I think it is better than the Original Doom flick by the Rock. What is your thought? This is the synopsis (it's not a spoiler): "Follows a group of UAC Marines as they respond to a distress call from a top...

[Moderator's note: Post edited to remove the homework header.] High school physics demonstrations teach and show us that a positron and an electron must be at rest with their environment before they can join together and annihilate. The process makes them disappear and they are replaced by two...

I'm unclear on what exactly an annihilation or creation operator looks like in QFT. In QM these operators for the simple harmonic oscillator had an explicit form in terms of $$ \hat{a}^\dagger = \frac{1}{\sqrt{2}}\left(- \frac{\mathrm{d}}{\mathrm{d}q} + q \right),\;\;\;\hat{a} =...

The pure energy released from antimatter annihilation can there be any use of this clean energy for research purposes like the use of light in LIGWO for gravitational waves study can we use it efficiently like light in LIGWO I think we can and it could lead us to reveal mysteries of universe

Hello everybody! I have a question regarding the process ##e^+ e^- \rightarrow Z/\gamma \rightarrow f \bar{f}##, where ##f## is a fermion and ##\bar{f}## is an antifermion. I am studying the process to understand LEP measurements. Supposing of being in ultrarelativistic regime, so helicity and...

The definition of coherent state $$|\phi\rangle =exp(\sum_{i}\phi_i \hat{a}^\dagger_i)|0\rangle $$ How can I show that the state is eigenstate of annihilation operator a? i.e. $$\hat{a}_i|\phi\rangle=\phi_i|\phi\rangle$$

Everyone knows that matter and antimatter annihilate upon contact. But exactly WHY this should happen is not at all obvious, at least to me. So what exactly happens when two such particles encounter one another that leads them to disappear in a large release of photons? And for that matter...

Cohererent states are defined as eigenstates of the annihilation operator. Never the creation operator is referred to. Is this just a convention or is more behind? What is the essential difference between eigenstates of the annihilation- versus the creation operator? Thank you very much in...

Electrons and positrons are assumed to be point masses. Two points presumably can never actually touch. How close do they have to be before they annihilate each other?

Homework Statement Consider the state $$\psi_\alpha = Ne^{\alpha \hat a^\dagger}\phi_0, $$ where ##\alpha## can be complex, and ##N = e^{-\frac{1}{2}|\alpha|^2}## normalizes ##\psi_\alpha##. Find ##\hat N \psi_\alpha##. Homework Equations $$\hat N = \hat a^\dagger \hat a$$ $$\hat a\phi_n =...

Hi, When one quantizes EM the resulting gauge boson, the photon, ends up being its own antiparticle. From what I read of gluons, they have anti particles. I can follow how anti particles come about quantizing a complex-valued field like that for electrons. For the spin 1/2 case non-interacting...

Homework Statement After proving the relations ##[\hat{b}^{\dagger}_i,\hat{b}^{\dagger}_j]=0## and ##[\hat{b}_i,\hat{b}_j]=0##, I want to prove that ##[\hat{b}_j,\hat{b}^{\dagger}_k]=\delta_{jk}##, however I'm not sure where to begin. 2. The attempt at a solution I tried to apply the...

I was recently reading about annihilation and creation operators in particle physics using the model of an harmonic oscillator, and then quantizing it. This is fine. I can understand it. But how does this quantization of the energy of the harmonic oscillator manifest physically? Is it that only...

Homework Statement The possible (normalized) eigenstates of a photon in a given system are written as: $$|\psi_1>,|\psi_2>,...|\psi_m>$$ Let another state be $$|\phi> = \frac{|\psi_1>+|\psi_2>+...+|\psi_m>}{\sqrt{m}}$$ and denote: $$|n>=|\psi_1>|\psi_1>...|\psi_1>$$ which represent a state...

Homework Statement An antiproton of energy 35 ##GeV## from a source outside the solar system interacts with a proton in the upper atmosphere traveling on a trajectory which is radial with respect to the centre of the Earth. The antiproton annihilates the proton with the final outcome that two...

Hello! I am a bit confused about the idea of spin. Let's say we have spin ##1/2## particles. This means that the spin along a random axis is ##\pm 1/2##, right while the values of the particle spin (i.e. the module) is actually ##\sqrt{1/2(1+1/2)}##? Also I am a bit confused about combining...

I have been trying to understand the implications of a thought experiment and am interested to know either where it's going off course or what those implications might be. Through some reading of earlier threads on this forum I have verified my starting hunch that photons bend spacetime despite...

I am confused about entanglement, but I am not a physicist. The concept sounds cool and I want to understand in a way so that it is familiar with what I already know. I want to know if I am interpreting this right: 1) If we have a photon that produces a pair of electron and positron, the...

<Moderator's note: Two threads on the same topic merged in order to have arguments and sources at one place.> Can antimatter-matter be used as a fuel for a rocket? There are various problems for anti-matter to be used as a fuel as it produces a lot of gamma rays. Gamma rays are not healthy to...

Let's assume an electron and an anti-electron are in a gravitational field so they both have potential energy. What will become of this energy if they annihilate? Will the momentum of the photons after the annihilation will increase so the total energy will be conserved? Thanks for answering!

In the calculation of R=σ(e+e-→hadrons)/σ(e+e-→μ+μ-) from BaBar experimental data at a center of mass energy of √s≈10 GeV i obtain R=5. Theoretically I should get a value of R=10/3. I know it has something to do with the resonances of ϒ mesons shown in the plot attached, but I don't know how to...

Homework Statement Suppose V=U⊕W. Prove that V0=U0⊕W0. (V0= annihilator of V). Homework Equations (U+W)0=U0∩W0 The Attempt at a Solution Well, I don't see how this is possible. If V0=U0⊕W0, then U0∩W0={0}, and since (U+W)0=U0∩W0, it means (U+W)0={0}, but V=U⊕W, so V0={0}. I don't think this...

I am confused about the production of bosons in annihilation processes. If we have a positron and an electron coming together and annihilating, we can always find a frame in which the net momentum is zero, which would suggest that a single photon can never be produced in such an interaction...

Homework Statement [/B] The problem is as follows: in a reference frame there is one electron at rest and one incoming positron which annihilates with the electron. The positron energy is E and two gamma rays are produced. Find first the energy of the photons in the center of mass frame as...

The youngest epoch of the universe we can observe so far is the CMB. It is theorized that systematic and accurate measurement of gravitational waves could allow us to "see" events from even earlier cosmic epochs. If we go to even earlier cosmic epochs we have what must have been a very singular...

I have seen several estimates that the period during the early universe in which almost all the protons, neutrons, anti-protons, and anti-neutrons (P, N , AP, AN) were annihilated occurred about 1 second after the big bang. I conceptualize this as a period in which as the temperature cooled...

How can a couple of W bosons annihilate each other, if both are left-handed particles? (there are no right handed Ws)

Is there any link between the energy released from the annihilation of matter-antimatter during baryogenesis and cosmic inflation or expansion/dark energy? This question came up when reading: https://www.nasa.gov/mission_pages/chandra/news/08-160.html

Consider the following u-channel diagram (on the right) in the link below. https://www.physicsforums.com/attachments/diphoton-png.95147/ Let the polarization vectors of ##k_1## and ##k_2## be ##(\epsilon^{\mu}_{1})^{*}## and ##(\epsilon^{\mu}_{2})^{*}## respectively. Do you label the incoming...

Hi! We have a projekt at the university and I have been thinking of creating a tiny tiny black hole after I've read some articles. I know one can create an artificial black hole with polarized laser pulses at a block of glass. And then one can measure a lot of things, usually hawkingradiation...