Two research teams have found new evidence of
transformations in elusive elementary particles called neutrinos. The findings
may finally help explain why the universe didn’t vanish shortly after its
birth.
“These results are just the beginning of the story for
neutrinos,” said physicist Robert Plunkett of
Fermilab in Chicago. “They could lead to
clues … and tell us why there’s now far more matter than antimatter.”
Most neutrinos are emitted by the sun, and are so small and
ghostly that billions pass through our bodies every second. Most go right
through Earth without hitting anything. But some human-built devices — slabs of
iron and plastic, big
chambers of oil or water lined with photon detectors, or
detector arrays
plunged into seawater or
Antarctic ice — can record the blip of light when a
neutrino occasionally slams into an atom.
Using these detection events, physicists have identified
three types of neutrino, called muon, tau and electron neutrinos. Further
discoveries suggested that each type can transform into another, with
muon-to-tau neutrino transformations being dominant, at least in
particle-accelerator-powered experiments.
Researchers proposed a third and weaker change, that of
muon-to-electron neutrinos, but until now lacked evidence for its existence.
On June 14, the Japanese
Tokai-to-Kamioka experiment reported the significant
detection of muon-to-electron neutrino changes. On June 24, the
Main Injector
Neutrino Oscillation Search (MINOS) experiment at Fermilab reported on the
same phenomenon. While the ranges of their data varied, the basic claims
jibed.
“[The values] differ because we used different techniques
and distances, but they overlap at one part. They’re complementary,” said
Plunkett, a co-spokesperson of MINOS. They may differ only because of
statistical fluctuations, he said.
With a more complete understanding of neutrino
transformation in hand, Plunkett said physicists can now design experiments to
investigate larger questions about the universe. The largest among them: Why
there’s far more matter than antimatter.
Matter and antimatter particles annihilate when they meet.
Each type is thought to have appeared in equal proportions shortly after the Big
Bang, yet the matter-rich universe as we know it still exists. As a result,
physicists are seeking evidence of “asymmetries,” in which matter-antimatter
encounters end up emitting more matter particles.
Some matter-favoring asymmetry shows up in the annihilation
of quarks, though the effect is relatively meager. But physicists say a
muon-to-electron neutrino transformation supports the possibility of more
significant asymmetries.
“We now have a good enough handle on neutrinos to design
experiments and try to address such a big mystery,” Plunkett said.
Originally Posted by Khendraja'aro
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