# The State of Energy to Matter Experimentation

1. Nov 20, 2014

### NavalPhysicist

I have been researching energy to matter conversion experiments, and the only information that i have been able to find of a successful experiment is from 1997, when the University of Rochester was able to make a terawatt glass laser send photons into a stream of energized electrons from the SLAC, which resulted in the photons and electrons colliding, producing positrons and electrons. i have not been able to find any, more current, research being conducted on this subject. Have the energy to matter experiments been abandoned?

ref: University Of Rochester. "Out Of Pure Light, Physicists Create Particles Of Matter." ScienceDaily. www.sciencedaily.com/releases/1997/09/970918045841.htm

2. Nov 20, 2014

### ofirg

Collisions where energy ( kinetic energy) is converted to mass (energy of a particle at rest) happen all the time at particle colliders.
What exactly are you looking for ? processes where photons are converted into massive particles?
These also happen at particle colliders. Either in photon photon collisions in electron positron colliders (such as LEP) or in conversions which happen when a photon goes through particle detectors.

What would you call energy to matter conversion?

3. Nov 20, 2014

### ChrisVer

4. Nov 20, 2014

### NavalPhysicist

I am specifically looking for photon to massive particle conversion, with any advances in the ability to create specific molecules of matter (hydrogen would be the easiest to produce, as it needs only one electron and one proton). Are there any ongoing experiments to introduce a proton into the photon-electron collision, producing an atom of matter?

5. Nov 20, 2014

### ChrisVer

it won't save much...even if the electron will be attached to some ionized atom and avoid annihilation, the positron coming from the photons will eventually ionize another atom... So you won't see the creation of any new atom.....or at least that's how I see it.

In general the photon to matter/antimatter and vice versa (due to symmetries) has of course been studied a lot...

6. Nov 20, 2014

### Staff: Mentor

"Energy to matter conversion" does not happen - energy before the process is the same as afterwards. You are looking for "photon to matter conversions". This has been shown, see your link in post 1.

There are proposals for a dedicated photon-photon collider, e.g. http://www.nature.com/nphoton/journal/v8/n6/full/nphoton.2014.95.html, but nothing advanced yet.
That does not work - the produced particles are high-energetic, you won't capture them in a controlled way. Also, what would be the point? Formation of hydrogen atoms has been studied in detail in much more precise experiments.

Producing baryons like the proton in light/light-collisions is unrealistic - the probability to get those in a collision is negligible.

If you would see it at all, you would see both processes happen at different positions.

Last edited by a moderator: May 7, 2017
7. Nov 20, 2014

### ChrisVer

why do you say that the resulted particles are highly energetic? a photon of energy ~1.03 MeV can give pretty low energetic positron+electron...

I don't think you can track back to the position that this occured, at best you can obtain this result into a scintillator ?

(I'm thinking too much about the Na22 spectrum today....)

8. Nov 20, 2014

### ofirg

protons are also produced in photon photon collisions, see http://arxiv.org/pdf/hep-ex/0306017v1.pdf.

However, why would you wan't to make atoms this way? The particles produced have high energies and won't form atoms and all the building blocks of these atoms are readily available without producing them in these collisions.

9. Nov 20, 2014

### Staff: Mentor

A single photon cannot do anything, and pair production at nuclei is not what we are looking at.

The cross-section for photon/photon collisions depends on the energy. I don't have numbers, but directly at threshold it should be quite small. And then you have the additional challenge to produce photons with an energy very close to 511 keV.

Well you can track particles with a reasonable energy. If the energy is too low, every material will stop them in the first layer.

@ofirg: Those are virtual photons, they are not real. The actual process is $e^- e^+ \to p \bar p$.[/quote]

10. Nov 20, 2014

### ofirg

The actual process is $e^{−}e^{+}→p\bar{p}e^{−}e^{+}$, However the electrons are mainly spectators to the collision and the two photons are almost real.
This is quite similar to sea quarks and gluons colliding at a hadron collider, in which the other constitutes of the proton are mainly spectators to the hard collision. In these cases, It is useful to think of the sea quarks, gluons or photons as the colliding particles, which are drawn from the initial state using a certain distribution (PDF's for hadron collisions)