The Free Press, Mankato, MN

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October 2, 2013

Nobel speaker discusses Large Hadron Collider and universe

Professor discusses Large Hadron Collider

(Continued)

The nature of antimatter is one of the unanswered questions being studied at the collider, Shears said. The search is hard because if there were lots of it around, you’d know.

If a quarter gram of antimatter meets the same amount of matter, the explosive force equals that of 5,000 tons of TNT. That’s about one-third the power of the atomic bomb dropped on Hiroshima.

The key to antimatter lies in some minuscule difference between it and regular matter, Shears said, something like one part in a billion. If there were equal amounts of antimatter and matter at the big bang, as scientists theorize, then they would have annihilated each other and left no matter.

“But that very tiny difference is the reason why we’re here,” Shears said. “We’re the leftovers.”

It is being investigated in a project called LHCb, which studies the type of quark, called the “b” or “bottom” quark, that is most different in its matter and antimatter forms.

Earlier this year, experimenters made their first measurement of the difference in the number of “b” antimatter and matter quarks produced in a series of proton collisions. It is this difference, again, that researchers are searching for. In the search for this type of antimatter, researchers looked at 70 trillion proton-on-proton collisions and only found the anti-matter particle 1,000 times.

They found about 25 percent more matter than antimatter.

“And that was great,” she said. And it was troubling at the same time because researchers couldn’t explain it with the standard model.

“It means, essentially, we have to patch up this very beautiful, elegant theory with something quite ugly to just try and fit what we see,” Shears said.

And that has happened, but the explanation doesn’t account for nearly enough antimatter.

“We’ve made progress in understanding this question, but there’s more to it,” she said.

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