Imagine two flashlights aimed at each other; do their beams collide? Nope! In everyday physics, light is too chill for drama. Beams glide through one another without so much as a “hey,” overlapping like ghostly whispers. So if you’re dreaming of a real-life lightsaber duel, prepare for some anticlimactic swishing in the void.
But quantum physics loves a plot twist. It predicts that under extreme conditions, light can nudge light, a rare effect called light-on-light scattering. You won’t see this with regular lasers; they’re too gentle. But at CERN, where particles race at near-light speeds, things get spicy. Invisible “virtual particles” pop into existence for the briefest blink, meddling with photons and slightly shifting their path.
The effect is minuscule, barely a blip, but it’s vital. Scientists need to understand it precisely to test theories about particles like the muon, where even the tiniest glitch can hint at new physics.
Researchers at TU Wien have uncovered that tensor mesons, a type of particle made of a quark and an antiquark, play a much bigger role in light-on-light scattering than previously thought.
During photon-photon interaction, virtual particles are created that can’t be measured directly due to their quick disappearance.
In the quantum world, particles can be in two opposite states at once, like being here and not here at the same time. It’s like they’re undecided, floating between possibilities until something forces a choice. This strange behavior, called superposition, totally breaks the rules we’re used to in everyday life, where something has to be either one thing or the other.
Jonas Mager from the Institute of Theoretical Physics at TU Wien, lead author of the study, said, “Even though these virtual particles cannot be observed directly, they have a measurable effect on other particles. If you want to calculate precisely how real particles behave, you have to take all conceivable virtual particles into account correctly. That’s what makes this task so difficult – but also so interesting.”
Usually, photons (light particles) are like dancers who never touch—they glide past each other in graceful silence. But in rare moments, under intense energy, a photon can do something wild: shape-shift into an electron and a positron, a pair of particles with opposite charge.
For a fleeting instant, this duo takes center stage. Other photons waltz in and interact with them, creating a mini-quantum dance-off. But the performance is short-lived—the electron and positron eventually reunite and vanish, releasing a fresh photon like a cosmic encore.
Now, cue the complexity: sometimes, instead of that lightweight duo, the photon transforms into mesons, chunkier particles made of a quark and an antiquark. These aren’t just dancers; they bring strong nuclear forces into the mix, turning the elegant ballet into chaotic choreography. Mesons make photon interactions richer, messier, and much more fascinating to study.
Jonas Mager said, “There are different types of these mesons,” says Jonas Mager. “We have now been able to show that one of them, the tensor mesons, has been significantly underestimated. Through the effect of light-light scattering, they influence the magnetic properties of muons, which can be used to test the Standard Model of particle physics with extreme accuracy.”
Tensor mesons appeared in earlier models, but scientists didn’t take them seriously; they were treated with rough shortcuts. Now, a fresh look reveals they’re far more influential than expected. Even more surprising? They don’t just boost the effect—they reverse it, like pushing the results in the opposite direction.
Last year, scientists noticed a mismatch between two ways of studying particle physics—traditional math-based calculations and computer simulations. The issue? Standard calculations struggle to handle the messy, strong forces between quarks except in extreme cases.
To fix this, the team at TU Wien tried something bold: holographic quantum chromodynamics. It’s like solving a puzzle by stepping into a higher dimension. They took our usual 4D world (three dimensions of space plus time) and mapped it into a 5D space where gravity helps simplify the math. In this new space, tricky particles like tensor mesons behave like 5D versions of gravity particles, called gravitons, which Einstein’s theory can predict.
The Standard Model is like physics’ master recipe; it explains nearly everything about particles and forces… except gravity. But even the best recipes need testing, and one of the sharpest tools for that is the muon’s magnetic moment, a tiny twist in how this particle spins in a magnetic field.
For years, scientists noticed a mismatch between what the Standard Model predicted and what experiments measured. Was this a hint of new physics, undiscovered particles, or forces? Or just a glitch in the math?
Recently, that mismatch has shrunk, thanks to better experiments and smarter calculations. But to honestly know if the Standard Model is missing ingredients, researchers must iron out every last wrinkle in the theory. That’s where the latest work comes in, refining the details to help us spot whether the universe is hiding something beyond the known.
Journal Reference:
- J. Mager et al., Longitudinal short-distance constraints on hadronic light-by-light scattering and tensor-meson contributions to the muon g-2, Physical Review Letters. DOI: 10.1103/dxwr-gpsl