Annihilation Definition and 253 Threads

How does this annihilation process play in semiconductors? Initially i thought that as long as the an electron gets enough energy to move into conduction band (in an energy diagram) - it will move and wander within the Conduction band. However, i have a slide notes about annihilation that talks...

Suppose I want to find the minimum velocity of the electron and positron required to make a Z boson during annihilation. How would I go about this? I had an attempt which came out at 422ms^-1. This doesn't really seem right... so I'm guessing i made a big mistake...

Hello, I have one question. The most probability annihilation is e+ + e- -> y + y with spins -1/2+1/2=-1+1. But I heard, so, there exist with small probability other combinations of spin. yy is general spin-2 and e+e- is spin-1 and now there is something purportedly with orbitals s, p, d, but I...

sorry for this elementary question. when an electron (matter) and a positron (anitmatter) collide, they annihilate, releasing high energy photons/gamma rays - correct? so, when particle pairs are created within the quantum foam, which pop into and out of existence within the Planck time...

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...

Hello, I was studying about the effect of a beam splitter in a text on quantum optics. I understand that if a and b represent the mode operators for the two beams incident on the splitter, then the operator for one of the outgoing beams is the following, c = \frac{(a + ib)}{\sqrt{2}}...

Homework Statement A proton and antiproton at rest in an S-state annihilate to produce \pi0\pi0 pairs. Show that this reaction cannot be a strong interaction. Homework Equations I interpret this problem as: p + p_bar -> \pi0 + \pi0 The Attempt at a Solution If this were a strong...

In Antimatter production in a labratory, does anyone know the principle element used to generate antimatter such as anti-protons?

When looking for antimatter, we generally look for the electron vs. positron signature of 511 keV. It is my understanding that quarks are always confined in hadrons, and that they are held together by gluons. My questions: - Can quarks be removed from their confinement so that they may...

I posted this question in the general physics section and the physics part has been answered somewhat. However the cosmological components remain un-answered. Would someone be kind enough to comment on those aspects please? Here is the question; Matter and Antimatter, I have always...

Imagine you have electron and positron (leptons) falling towards each other. The interaction between these two is electromagnetic at long distances. It is well established that this reaction eventually leads to annihilation of these two particles. Now consider electron and proton(hadron) falling...

Hi, I don't think I understand why antimatter annihilates when it touches matter, should I picture has it as if it was a wave that canceled an other one? Or is it something else entirely? Thanks.

Hello, everyone. I have searched google and wiki, but have not been able to find the solution to my question. I was wondering why do antiparticles annihilate on contact with normal matter? If someone could help explain this to me or send me a link on where i can get this information it...

lets simulate this simple experiment: creation followed by annihilation of 2 equal particles of type P, here named P1 and P2. (*) assuming the precursors before creation as usual, and also residuals as usual after annihilation. The question is about the remaining fields, gravitational...

Hello, I have the missfortune of having to calculate a commutator with some powers of the creation and the annihilation operators, something like: \left[ a^m , (a^{\dagger})^n \right] I have managed to derive \left[ a^m , (a^{\dagger})^n \right]= m a^{m-1} \left[ a , a^{\dagger}...

particle/antiparticle "annihilation" This has been bugging me for quite some time now. Why is it called "annihilation" when a particle and an antiparticle collide, when in fact they don't annihilate at all, but simply transform into photons with the original energy conserved? Since...

http://agenda.albanova.se/contributionDisplay.py?contribId=389&sessionId=257&confId=355 This came out at the Identification of Dark Matter (IDM-2008) meeting in Stockholm on 18-22 August PAMELA - an experiment searching for dark matter with cosmic antiparticles "The PAMELA satellite...

I'm a little unsure about a certain part of this shown in a book. There is an electron and a positron moving in the +x direction. They annihilate each other and release 2 photons. to conserve momentum 1 moves in the -x and one in the +x direction. So then the first step is to do conservation...

Although this question is simple it's been bugging me: If you were to take one kilo of antimatter and annihilate it with one kilo of matter is the energy (using E=mc^2) released proportional simply to the mass of the matter or to the sum of the masses of both the matter and antimatter? So...

[SOLVED] Annihilation, perhaps a defination problem Problem: An electron and an anti-electron undergo mutual annihilation. Which of the following does not have to be conserved? A. Electric charge B. Kinetic energy C. Lepton number D. Momentum Attempt to question: The answer is B but...

When electrons collide with positrons, we get gamma-rays and other particles. Keeping in mind E=mc^2, is the result better called "annihilation" or "conversion"?

Is there set formulas on how exactly this works. We learned in class very very quickly about how a electron and positron collide and form two photons. There has to be a direct relation between the photons properties and the electron/positron. Thanks

Do the gamma rays (from positron-electron annihilation) must interact to have reversible reaction? I read in my textbook that this reaction is reversible? Is that true? The reaction: ^{0}_{-1}e+ ^{0}_{+1}e \rightarrow 2 \gamma

Why, or perhaps how, is 100% of the mass in matter-antimatter annihilation turned into energy? I thought no reaction could be 100% efficient, i.e. 2nd law of thermodynamics? Isn't the Carnot heat engine or the conversion of matter into energy in the accretion disk of a black hole the most...

Hi, We are learning particle physics at the moment in school. My teacher was telling me that when matter meets anti matter, they annihilate each other out. My question is what happens when an anti proton meets a positron or when an anti neutrino meets an electron. Would they annihilate each...

How do I write a nuclear equation representing the annihilation of a positron with an electron? Do they just cancel out? or do I write energy on the left hand side of the equation?

Why can't we use electron-positron annihilation as an energy source? Unlike antiprotons, positrons sometimes pop out of beta decay and positron-producing isotopes with short half lives are routinely produced in cyclotrons around the world for hospital PET-scanners. Positrons and electrons...

If you have a proton and an anti-proton traveling in the same direction with momentum from A to B but during the flight time they become attracted due to their opposite charges and annilhilate, the momentum I would guess is transferred to the resulting unstable K particles mesons etc, which, as...

I have seen some seemingly differing statements in various sources about the dynamics of annihilation when the positron has some kinetic energy and is traveling through a medium. Two sources I've read state or imply that a positron in motion through matter must first lose it's kinetic...

Here is a question, which may seem dumb: Consider an electron and a positron that annihilate, both of which are non-relativistic (taking the observer's frame of reference to be the center of mass frame of the electron-positron pair) so that we only consider their electric fields for simplicity...

How did they experimentally verify that there is pair creation and annihilation in the vacuum? What kind of particles usually pops in and out of the vacuum?

Homework Statement state why p + p_bar --> 1 photon is forbidden Homework Equations The Attempt at a Solution I have checked all quantum numbers and they are okay. I wondering altough if p_bar has intrinsic parity -1 (p has parity +1)?? According to the soloution, it is...

Homework Statement A positron having a kinetic energy equal to its rest mass energy mec^2 collides with a stationary electron. The positron and the electron annihilate in the process and two photons are created. What is the maximum possible energy of a photon produced in the...

Problem:An electron flies toward +x direction with velocity of 0.9c, while a positron flies toward -y direction with the same velocity. Assuming their speed is so fast that they collide and annihilate at the origin, what will be the magnitude and the direction of the wave vector of the generated...

Homework Statement How do I show that the annihilation operator \hat{a} is hermitian WITHOUT explicitly using the condition where an operator X is hermitian if its adjoint is also X ie. X=X^+ Homework Equations none. The Attempt at a Solution I could show \hat{a} \hat{x}...

Homework Statement Wavefunction: \psi(x) = N\sum_{n=0}^\infty \frac{\beta^n}{\sqrt{n!}}\psi_n(x) And \psi_n(x) has eigenvalue E_n = (n + 1/2)\hbar\omega . - Determine N (normalisation constant). - Show \psi(x) is an eigenstate of 'a' (annihilation operator). The attempt at a...

Does QM tell us that photons are actually electrons and positrons goign through a cycle of annilation and creation?

In as few words as possible, could someone refresh my memory as to why in the Big Bang there was a slight excess of matter that survived the matter-antimatter annihilation? And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?

Mater Annihilation --matter v.s. anti-matter-- hey all, in the study of "massless particles" such as the electron and the and the positron. in beta decay (beta plus) there is an emission of a subatomic particle called the positron (the anti-particle of the electron) my thought is...

Hey, I am calculating the expectation value of the position x. I have the wave function psi(x) = |1> + |2> so I use the equation <x> = <psi|(a+a^+|psi> to calculate the mean value. So I get (<1| + <2|)(a+a^+)(|1> + |2>) which I reduce to <1|a|1> + <1|a|2> + <2|a|1> +...

When an electron and a positron, for instance, annihilate, do their fields disappear away at c from the point of the annihilation, letting their former influence still apply beyond the vanishing line? If the energy of these particles is entirely in their fields, as I sometimes read, how can...

As far as I know the usual extension of the standard model to include a massive neutrino implies a violation of the conservation of quantum numbers, this means the lepton number (since the neutrino is uncharged). During its propagation a massive left-handed neutrino can be regarded as a massive...

Hey i am doing some studying and when it comes to the subject of nuclear decays it says that when an electron and positron annihilate at rest they produce two photons with equal energys. Can someone try to explain to me why the photons have equal energies and how come there must be two photons...

If we could produce the highest order of Gamma Ray energy of a single photon and bombarded an Atom with direct precision, Would the Atom be Annihilated? If the Atom is Annihilated then would the release of Energy of the Atom be greater than the Single High Energy Gamma Photon? Assume that...

Greetings--what is meant by "s-wave" or "p-wave" annihilation? I've been trying to figure out what this refers to by looking through the standard QM and QFT texts, but I keep missing this. Does anyone have a handy reference I can look up? Thanks, Flip

I read a book and there it is written something as following: "By the lifetime of a virtual pair (e-e+) (that is given by the HUP) a virtual e- can remove with the distance s from the e+ that is given by: s=c*d(t) (d(t) from HUP)." My question: How can they annihilate if they are away at a...

Why do proton and anti-proton annihilation can produce extra pions, in addition to the photons; whereas the electron and positron interaction only gives photons?

I have a question regarding particle-antiparticle annihilation, such as electron-positron, proton-antiproton, etc. Can the annihilation still occur if the two particles are in opposite spin eigenstates, i.e. if the pair has zero net spin?

A 5MeV electron undergoes annihilation with a positron that is at rest, producing two photons. One of the photons travels in the direction of the incident electron. Calculate the energy of each photon. So the 5 MeV electron undergoes annihilation with a positron and from that 2 separate...

Well, I've been trying to figure out how to prove that when a positron and an electron annihilate and two photons are produced, the addition of their wavelengths equals L1+L2=Lcompton(1-cos(theta)) where theta is the angle that separates both photons. It's a relativity problem I guess. I...