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Is Our Universe Supersymmetric?

Scientists hope the rebooted Large Hadron Collider could find supersymmetric particles—the next frontier of particle physics

(Mark Thiessen/National Geographic Creative/Corbis)
smithsonian.com

The Large Hadron Collider, the world’s biggest and most famous particle accelerator, will reopen in March after a years-long upgrade. So what’s the first order of business for the rebooted collider? Nothing less than looking for a particle that forces physicists to reconsider everything they think they know about how the universe works.

Since the second half of the twentieth century, physicists have used the Standard Model of physics to describe how particles look and act. But though the model explains pretty much everything scientists have observed using particle accelerators, it doesn’t account for everything they can observe in the universe, including the existence of dark matter.

That’s where supersymmetry, or SUSY, comes in. Supersymmetry predicts that each particle has what physicists call a “superpartner”—a more massive sub-atomic partner particle that acts like a twin of the particle we can observe. Each observable particle would have its own kind of superpartner, pairing bosons with “fermions,” electrons with “selectrons,” quarks with “squarks,” photons with “photinos,” and gluons with “gluinos.” 

If scientists could identify a single superparticle, they could be on track for a more complete theory of particle physics that accounts for strange inconsistencies between existing knowledge and observable phenomena. Scientists used the Large Hadron Collider to identify Higgs boson particles in 2012, but it didn’t behave quite as they expected. One surprise was that its mass was much lighter than predicted—an inconsistency that would be explained by the existence of a supersymmetric particle.

Scientists hope that the rebooted—and more powerful—LHC will reveal just such a particle. “Higher energies at the new LHC could boost the production of hypothetical supersymmetric particles called gluinos by a factor of 60, increasing the odds of finding it,” reports Emily Conover for Science.

If the LHC were to uncover a single superparticle, it wouldn’t just be a win for supersymmetry as a theory—it could be a step toward understanding the origins of our universe. But it could also create a lot of work for scientists—after all, a supersymmetric universe is one that would hold at least twice as many particles. Michael Williams of the Massachusetts Institute of Technology tells the BBC he’s ready for the challenge but admits it could be tricky:

Finding any particle that could be a dark matter candidate is nice because we could start to understand how it affects the galaxy and the evolution of the universe, but it also opens the door to whatever is on the other side, which we have no idea what is there.

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