Scientists on an experiment at the MATTER OF LIGHT BY HADRON COLLIDER see massive W particles emerging from collisions with electromagnetic fields. How can this happen?
The Large Hadron Collider plays with Albert Einstein’s famous equation, E = mc²,
to rework matter into energy then back to different sorts of matter.
But on rare occasions, it can skip the first step and collide pure energy—in the form of electromagnetic waves.
Last year, the ATLAS experiment at the HADRON COLLIDERobserved two photons, particles of sunshine, ricocheting off each other
and producing two new photons.
This year, they’ve taken that research a step further and discovered photons merging and reworking into something even more interesting:
W bosons, particles that carry the weak interaction, which governs nuclear decay.
This research doesn’t just illustrate the central concept of governing processes inside the HADRON COLLIDER:
that energy and matter are two sides of an equivalent coin.
It also confirms that at high enough energies, forces that appear separate in our everyday lives—electromagnetism
therefore the weak force—are united.
From massless to massive
If you are trying to duplicate this photon-colliding experiment reception by crossing the beams of two laser pointers,
you won’t be ready to create new, massive particles.
Instead, you’ll see the 2 beams combine to make a good brighter beam of sunshine.
“If you return and appearance at Maxwell’s equations for classical electromagnetism,
you’ll see that two colliding waves sum up to a much bigger wave,” says Simone Pagan Griso,
a researcher at the US Department of Energy’s Lawrence Berkeley National Laboratory. “We only see these two phenomena recently observed by ATLAS once we put together,
Maxwell’s equations with the special theory of relativity and quantum physics within the so-called theory of QED .”
Inside CERN’s accelerator complex, protons are accelerated on the brink of the speed of sunshine. Their normally rounded forms squish along the direction of motion as the special theory of relativity supersedes
the classical laws of motion for processes happening at the LHC.
The two incoming protons see one another as compressed pancakes amid an equally squeezed electromagnetic field
(protons are charged, and everyone charged particles have an electromagnetic field).
The energy of the LHC combined with the length contraction boosts
the strength of the protons’ electromagnetic fields by an element of 7500.
When two protons graze one another, their squished electromagnetic fields intersect. These fields skip the classical “amplify” etiquette that applies at low energies and instead follow the principles outlined by QED. Through these new laws, the 2 fields can merge and become the “E” in E=mc².
“If you read the equation E=mc² from right to left,
you’ll see that a little amount of mass produces an enormous amount of energy due to the c² constant,
which is the speed of sunshine squared,” says Alessandro Tricoli,
a researcher at Brookhaven National Laboratory—the US headquarters for the ATLAS experiment, which receives funding from DOE’s Office of Science.
“But if you look at the formula the other way around,
you’ll see that you need to start with a huge amount of energy
to produce even a tiny amount of mass.”
The LHC is one of the few places on Earth which will produce and collide energetic photons,
and it’s the sole place where scientists have seen two energetic photons merging and transforming into massive W bosons.
Unification of forces
The generation of W bosons from high-energy photons exemplifies,
the discovery that won Sheldon Glashow, Abdus Salam, and Steven Weinberg the 1979 Nobel Prize in physics:
At high energies, electromagnetism and the weak interaction are one within the same.
Electricity and magnetism often feel like separate forces. One normally doesn’t worry about getting shocked while handling a refrigerator magnet. And light bulbs, even while lit up with electricity, don’t stick with the refrigerator door. So why do electrical stations sport signs warning about their high magnetic fields?
“A magnet is one manifestation of electromagnetism, and electricity is another,” Tricoli says.
“But it’s all electromagnetic waves and that we see this unification in our everyday technologies,
like cell phones that communicate through electromagnetic waves.”
At extremely high energies, electromagnetism combines with yet one more fundamental force: the weak interaction. The weak interaction governs nuclear reactions, including the fusion of hydrogen into helium that powers the sun
therefore the decay of radioactive atoms.
Just as photons carry the electromagnetic force, the W and Z bosons carry the weak interaction. The reason photons can collide and produce W bosons within the LHC is that at the very best energies,
those forces combine to form the electroweak force.
“Both photons and W bosons are force carriers, and that they both carry the electroweak force,” Griso says. “This phenomenon is basically happening because nature is quantum mechanical.”