# Particles connected to Antiparticles

Consider a particle-antiparticle creation, lets say an electron and a positron.

I am curious if there is any lasting connection* between particles and the antiparticles that they were born with (in terms of the physics of their interaction).

Has anyone ever predicted or observed such a lasting connection? Has it already been ruled out by experiment?

*In an E&M book I read, they mentioned the idea that charge particles were connected to their corresponding birth-antiparticles by a topological handle. Then electric field lines never end. (Imagine a smooth sphere with a handle, the points of contact between handle and sphere are what we call particles and antiparticles. Draw electric field lines on the handle as if those spots were the charges, and you will see what I am talking about).

dextercioby
Homework Helper
What exactly are u suggesting through this ambiguous "lasting connection"...?And why do you provide a classical example,when it has nothing to do with particle-antiparticle theory...?

Daniel.

mathman
I am curious if there is any lasting connection* between particles and the antiparticles that they were born with (in terms of the physics of their interaction).

Charged particles in general are "connected" with other charged particles by em force. In electron-positron production, the particles go off in opposite directions and the positron is quickly killed by interacting with another electron.

Sterj
If there is created a virtual electron positron pair and they have to annihilate after a time d(t) (Heisenberg's uncertainty principle). How does the electron find the positron?

Sterj
Don't know anyone this question?

I think paritcles and antiparticles are the same except for the fact that the charges is the opposite w/ the antiparticles. go to www.cern.ch for an answer, they were the first to make antiparticles.

Fibonacci

Staff Emeritus
Gold Member
Dearly Missed
Sterj said:
If there is created a virtual electron positron pair and they have to annihilate after a time d(t) (Heisenberg's uncertainty principle). How does the electron find the positron?

"The" electron doesn't have to find "the" positron. Any antiparticle will do, the difference in momentum and energy will be folded into the properties of the resulting virtual photon.

Sterj said:
If there is created a virtual electron positron pair and they have to annihilate after a time d(t) (Heisenberg's uncertainty principle). How does the electron find the positron?

The electron does not find the positron. There has to be this pair because there is just enough energy available to create such a pair. Also if there were no charge present prior to this creation then there must be a positron and an electron because of charge conservation.

regards
marlon

dextercioby
Homework Helper
"The" electron doesn't have to find "the" positron. Any antiparticle will do, the difference in momentum and energy will be folded into the properties of the resulting virtual photon.

It needn't be a virtual photon.It can be very real.Light on light scattering proves it.

Daniel.

dextercioby said:
It needn't be a virtual photon.It can be very real.Light on light scattering proves it.

Daniel.

Only if enough energy was available prior to the actual virtual pair creation, which is indeed the case in your given example. Otherwise energyconservation would be violated.

marlon

Sterj

Lets say (only imagine) there are only these 2 particles (anti particle and its particle). The other space is emtpy. And a particle has a lifetime of d(t) (HUP). How can they annihilate after this time. It seems not logically that they collide after d(t).

Sterj said:

Lets say (only imagine) there are only these 2 particles (anti particle and its particle). The other space is emtpy. And a particle has a lifetime of d(t) (HUP). How can they annihilate after this time. It seems not logically that they collide after d(t).

Sterj,

Didn't i already explain this to you ?

They MUST 'collide' because they can only exist for this certain amount of time dt, predicted by the HUP.

Suppose the initial state has energy-value A and the final state has also energy-value A. In between those two states, the energy value A can become uncertain (dE) during a time-interval dt. that is what happens, during this dt there is more energy and thus, 'spectacular' things can happen, like the vaccuum fluctuations. the term fluctuations really denotes the dE part of my explanation. The question as to whether the two virtual particles collide is not that important. All we know is that after a time dt they MUST BE gone and the energy that is left behind must be equal to the energy prior to the virtual pair creation because of energy conservation. Just look at my A ----> A example

regards
marlon

Besides, let me drive you more crazy with this...

The actual creation of the virtual pair can occur anywhere in space time, this is proven QFT. The annihilation can occur somewhere else on a very remote spot from where the creation occured.

As a force carrier, a virtual particle carries a definite momentum value and due to HUP, it must be ANYWHERE in space time, the field expressing this particle is spread out over an infinite distance.

When the transported momentum-vector points from the emitting matter particle to the receiving matter particle, you have a repulsive force. When the momentum is pointed from the receiving particle to the emitting particle (momentum is transported backwards, if you will) you have an attractive force. In QFT a force is not F = ma, but it really is the transportation of a definite momentum-value

regards
marlon

Sterj
thanks. @marlon: you can explain very well. thanks.
and also thanks to theother

mathman
One bit of confusion in the discussion so far is between (a) the virtual electron-positron production in the vacuum and (b) real electron-positron production by gamma rays (energy above 1.022 Mev) passing near nuclei, especially heavy (like lead). (a) is a result of Heisenberg's principle, while (b) is straightfoward quantum electrodynamics.

reilly
Elelectron-Positron pairs created in scattering experiments are correlated through standard conservation laws -- tightly if they are the only final state, loosely if other particles are involved in the final state.

For virtual pairs the same is true, except for energy -- they are governed by the free, not the exact Hamiltonian.

Regards,
Reilly Atkinson

mathman said:
(b) real electron-positron production by gamma rays (energy above 1.022 Mev) passing near nuclei,

But aren't these pairs on mass shell ? Therefore they cannot be virtual

regards
marlon

reilly said:
Elelectron-Positron pairs created in scattering experiments are correlated through standard conservation laws -- tightly if they are the only final state, loosely if other particles are involved in the final state.

Yes indeed, however, these pairs are not virtual but they exist on their mass shell

marlon

mathman
To Marlon
But aren't these pairs on mass shell ? Therefore they cannot be virtual

regards
marlon

I specifically said they were real (not virtual). I don't understand your question.

mathman said:
To Marlon

I specifically said they were real (not virtual). I don't understand your question.

Well, i was refering to the remark you made about the pairs created out of the vacuum and the pairs created by gamma rays...

Forget what i said about being on or off mass shell but what i don't see why you talk about confusion between these two options. I don't see no confusion and to be exact both processes inherently work the same. The only difference is the initial and final state but the actual electron-positron pair is always virtual an initio. In the second case, though, there is enough energy available so that this pair can become on mass shell and thus 'real' in terms of field theory. It's energy has no uncertainty...

regards
marlon