In 1934, American theoretical physicists Dr Gregory
Breit and Dr John A. Wheeler suggested that it
should be possible to turn light into matter by
smashing together only two particles of light –
photons, to create an electron and a positron.
“Despite all physicists accepting the theory to be
true, when Dr Breit and Dr Wheeler first proposed
the theory, they said that they never expected it
be shown in the laboratory,” Prof Rose explained.
But a new experiment conducted by his team shows
for the first time how the Breit and Wheeler’s
theory could be proven in practice.
“Today, nearly 80 years later, we prove them
wrong. What was so surprising to us was the
discovery of how we can create matter directly
from light using the technology that we have today
in the UK. As we are theorists we are now talking
to others who can use our ideas to undertake this
landmark experiment,” said Prof Rose, the senior
author of a paper published in the journal Nature
Photonics.
The photon-photon collider experiment that the
physicists have proposed involves two steps.
First, they would use a powerful high-intensity
laser to speed up electrons to just below the speed
of light.
They would then fire these electrons into a slab of
gold to create a beam of photons a billion times
more energetic than visible light.
The next stage of the experiment involves a tiny
gold can called a hohlraum. The scientists would fire
a high-energy laser at the inner surface of this
gold can, to create a thermal radiation field,
generating light similar to the light emitted by
stars.
They would then direct the photon beam from the
first stage of the experiment through the center of
the can, causing the photons from the two sources
to collide and form electrons and positrons. It would
then be possible to detect the formation of the
electrons and positrons when they exited the can.
“Although the theory is conceptually simple, it has
been very difficult to verify experimentally,” said
Oliver Pike, a PhD student at Imperial College and
the first author on the study.
“We were able to develop the idea for the collider
very quickly, but the experimental design we
propose can be carried out with relative ease and
with existing technology.”
“Within a few hours of looking for applications of
hohlraums outside their traditional role in fusion
energy research, we were astonished to find they
provided the perfect conditions for creating a
photon collider. The race to carry out and complete
the experiment is on!”
Demonstrating the Breit-Wheeler theory would
provide the final jigsaw piece of a physics puzzle
which describes the simplest ways in which light and
matter interact.
