A new particle
Such splitting would depend on the presence of a theorized particle that has gone undetected so far: a so-called heavy Majorana neutrino. Neutrinos are fundamental particles that come in three flavors (electron, muon and tau). A fourth neutrino might also exist, however, that is expected to be much heavier than the others and thus more difficult to detect (because the heavier a particle is, the more energy a collider must produce to create it). This particle would have the strange virtue of being its own antimatter partner. Instead of a matter and antimatter version of the particle, the matter and antimatter Majorana neutrinos would be one and the same.
This two-faced quality would have made neutrinos into a bridge that allowed matter particles to cross over into antimatter particles and vice versa in the early universe. Quantum laws allow particles to transform into other particles for brief moments of time. Normally they are forbidden from converting between matter and antimatter. But if an antimatter particle, say, an antielectron neutrino turned into a Majorana neutrino, it would cease to know whether it was matter or antimatter and could then just as easily convert to a regular electron neutrino as turn back into its original antielectron neutrino self. And if the neutrino happened to be lighter than the antineutrino back then, because of the varying Higgs field, then the neutrino would have been a more likely outcome—potentially giving matter a leg up on antimatter.
“If true, this would solve a big mystery in particle physics,” says physicist Don Lincoln of the Fermi National Accelerator Laboratory in Illinois, who was not involved in the study. Yet the Majorana neutrino “is entirely speculative and has eluded discovery, even though the LHC experiments have a vigorous research program looking for it. Researchers will certainly keep this idea in mind as they dig through the new data the LHC will begin generating in the early summer this year.”
Kusenko and his colleagues also have another hope for finding additional support for their theory. The Higgs field process they envision could have created magnetic fields with particular properties that would still inhabit the universe today—and if so, they might be detectable. If found, the existence of such fields would provide evidence that the Higgs field really did decrease in value long ago. The scientists are trying to calculate just what the magnetic field properties would be and whether experiments have a plausible hope of seeing them, but the option raises the tantalizing hope that their theory could have testable consequences—and maybe a chance to solve the antimatter mystery after all.