[Andeh]

Correct me if I'm wrong, but--
>>>Antimatter and matter annihilate to yeild energy.
>>>high velocity collisions of particles ("normal" matter, not antimatter), i.e. in a collider, momenterilly annihilates them, yeilding energy, which quickly reforms into matter again.

What intrigues me are the behaviors of these two energies, how the energy yeilded from matter and antimatter is stable and can exist in that state, but the energy emmited from a collision of like matter only exists for an instant before re-forming into matter. What causes them to behave so different from each other? Why is one stable, but the other so short-lived? Any ideas?

[timo]

Andeh, on 13 October 2011 - 09:42 PM, said:

Correct me if I'm wrong, but--
>>>Antimatter and matter annihilate to yeild energy.
>>>high velocity collisions of particles ("normal" matter, not antimatter), i.e. in a collider, momenterilly annihilates them, yeilding energy, which quickly reforms into matter again.

Here's your correction: You are wrong. Energy is conserved in all know particle physics processes. What happens is that particles can transform into other particles within some constraints (such as the just-mentioned conservation of energy). "Energy" itself is not a particle.

What people often mean by "annihilate into energy" is that the particles transform into particles with very little mass (e.g. light, or "photons" if you want to impress people with scientifically-sounding terms). There is also light being produced in the particle physics processes at particle colliders, just not exclusively.

There are two main parameters (that I can think of at the moment) that influence the amount of light yield (compared to the production rate of other particles):
- There can be constraints that at least forbid a complete transformation in only light (e.g. the baryon number conservation forbids two protons to transform into only light, electron and positron may annihilate into only light).
- The higher the total energy, the more likely non-light products become. Keep in mind that the total energy of a proton-proton collision at LHC is roughly ten million times the total energy of an annihilation of an electron and a positron at low energies.

[IM Egdall]

Here's how I think it works. A photon is not a particle with "very little mass". It is a particle with zero mass. The conservation law is conservation of mass/energy.

Mass is converted to energy by E = mc^2. So say an electron and anitelectron(positron) collide, annihilate each , and produce photons. The total mass/ energy of the electron and positron before the collision equals the total energy of the photons after the collision. Mass/energy is conserved.

And of two photons have enough energy, when they collide, they can produce an electron and a positron. Again the energy of the photons before collision has to be enough to equal the mass/energy of the electron and positron after.

This mass/energy consrevation works for all particle interactions.

This post has been edited by IM Egdall: 14 October 2011 - 06:55 PM

[Mystery111]

IM Egdall, on 14 October 2011 - 06:54 PM, said:

Here's how I think it works. A photon is not a particle with "very little mass". It is a particle with zero mass. The conservation law is conservation of mass/energy.

Mass is converted to energy by E = mc^2. So say an electron and anitelectron(positron) collide, annihilate each , and produce photons. The total mass/ energy of the electron and positron before the collision equals the total energy of the photons after the collision. Mass/energy is conserved.

And of two photons have enough energy, when they collide, they can produce an electron and a positron. Again the energy of the photons before collision has to be enough to equal the mass/energy of the electron and positron after.

This mass/energy consrevation works for all particle interactions.

If it had a mass, surely it would be to small to compare it to the mass of other particles...? I do believe that the mass of the photon would be around grams... however saying this, certain field theories can treat a neutrino (which we all know to have a very small mass) as being negligable, meaning certain restrictions can treat a neutrino as acting like a massless particle.

So maybe a photon does have mass... unlikely, but I am open to the suggestion. It would certainly remove the complicated symmetry-breaking hypothesis.

[Genius13]

can any1 pls tell me how r they abel to make some antimatter in CERN??

[imatfaal]

Genius13, on 17 October 2011 - 11:02 AM, said:

can any1 pls tell me how r they abel to make some antimatter in CERN??

They slam a beam of very high energy protons into slab of metal and then hive off using magnets any antiprotons that have been created as part of a proton/anti-proton pair

Quote

The starting point, surprisingly, is a beam of protons from the Proton Synchrotron (PS), which is fired into a block of metal. The energy of the collisions is enough to create a new proton-antiproton pair about once in every million collisions. The antiprotons are produced travelling at almost the speed of light and have too much energy to be useful for making anti-atoms. They also have a range of energies and move randomly in all directions. The job of the AD is to tame these unruly particles into a useful, low-energy beam.

http://user.web.cern...arch/AD-en.html