[ExI] Government Scientists Are Creating Matter From Pure Light

Dave Sill sparge at gmail.com
Wed Sep 22 16:04:14 UTC 2021


Scientists at Brookhaven National Laboratory turned light into electrons,
validating a theory that dates back nearly a century.

By Becky Ferreira
September 20, 2021, 1:30pm

In a U.S. government laboratory on Long Island, scientists have forged
matter out of pure light using a sophisticated particle accelerator, while
also demonstrating an elusive phenomenon for the first time ever on Earth.

The experimental breakthrough validated predictions made by influential
physicists nearly a century ago and sheds new light on mysterious processes
that occur on both quantum and cosmic scales.

This conversion of photons, which are massless light particles, into
electrons, an elementary form of matter, was achieved by a team of
researchers working with the Relativistic Heavy Ion Collider (RHIC) at the
U.S. Department of Energy’s Brookhaven National Laboratory. Though the
theoretical groundwork of the new research has its origins in the early
20th century, it took special upgrades to an experiment called the
Solenoidal Tracker at RHIC (STAR) detector to finally make it a reality.

“All the stars lined up for us to get this right,” said Zhangbu Xu, a
member of the STAR collaboration and the lead author of a recent study
about the experiment in Physical Review Letters, in a joint call with
fellow STAR members Lijuan Ruan and Daniel Brandenburg.

Ruan, a physicist at Brookhaven and a co-spokesperson for STAR, added that
the kinematics of the experiment sit “right in the sweet spot” for this
type of ground-breaking transformation of energy into matter.

Achieving this star-aligned sweet spot is a dream that dates back to 1934,
when physicists Gregory Breit and John Wheeler suggested that smashing
photons together could produce a matter-antimatter pair composed of
electrons, which are negatively charged particles of matter, and positrons,
which are antimatter counterparts of electrons that carry a positive

The idea, now known as the Breit-Wheeler process, was inspired in part by
the dawn of quantum mechanics during this period, which revealed that
photons could interact on quantum levels in ways that are not predicted by
classical mechanics. The physicists were also building on Albert Einstein’s
famous mass-energy equivalence, written as E=mc2, which demonstrates that
mass and energy are two sides of the same coin.

That said, it is much trickier to transform energy into matter than it is
to convert matter into energy. It would have seemed especially
inconceivable back in the 1930s. As a credit to their foresight, Breit and
Wheeler speculated that a device that could accelerate ions, which are
atoms stripped of electrons, might be able to do the trick, even though no
such machine existed at the time.

“It shows some of their brilliance because this was in the early 30s,
before many of the modern experiments that we have,” said Brandenburg, who
is a Goldhaber Fellow at Brookhaven. “But they already predicted, in the
last paragraph of their paper, how you could actually achieve this really
difficult process, and they discuss exactly the experiment that we finally
have been able to do.”

“I find it very amazing that they had the insight to predict not only this
theory calculation, but that they predicted experimentally how it would
come about nearly 100 years before we had the technology to do it,” he

The experiment that Breit and Wheeler envisioned, and that the STAR
collaboration has now successfully conducted, requires shooting heavy ions
(in this case gold) past each other at 99.995 percent the speed of light.
The strong positive charge and extremely high speeds of the ions create a
circular magnetic field and a cloud of photons that travel with the
particles through the collider.

As the gold ions skim each other, their halos of light particles interact
and produce the matter-antimatter pairs that were predicted so many decades
ago. While RHIC was able to demonstrate the Breit-Wheeler process, the STAR
detector was the instrument that actually observed, measured, and confirmed
the achievement.

Though the milestone is the result of a century of theoretical groundwork,
there was also an element of serendipity involved, as STAR researchers only
recently realized their setup could experimentally prove this otherworldly
conversion of energy into matter.

“It's actually only a few years back, in 2018, that we started to see
something interesting, but at that time we didn't realize it was the
Breit-Wheeler process,” said Ruan. “We saw something different from what we
regularly expected from heavy ion collisions, but it was really when Daniel
[Brandenburg] started to do the data analysis with STAR-caliber precision,
with all the differential kinematics measurements, that we could say: ‘Oh,
this is really the Breit-Wheeler process.’”

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