'Perfect' Electron Roundness Established! A Blow To 'Popular Theories Beyond Higgs'
Scientists have established a new benchmark for the electron's almost perfect roundness and, as a result, have raised "severe" doubts about several popular theories of what lies beyond the Higgs boson.
The study's findings are described in detail in the journal Science Express.
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"We are trying to glimpse in the lab any difference from what is predicted by the Standard Model, like what is being attempted at the LHC," said John Doyle, Professor of Physics at Harvard, in a statement.
"It is unusual and satisfying that the exquisite precision achieved by our small team in its university lab probes the most fundamental building block of our universe at a sensitivity that compliments what is being achieved by thousands at the world's largest accelerator," added Gerald Gabrielse, the George Vasmer Leverett Professor of Physics at Harvard.
"Given that the Standard Model is not able to explain how a universe of matter could come from a big bang that created essentially equal amounts of matter and antimatter the Standard Model cannot be the final word."
To search for particles that might fall outside the Standard Model, the scientists precisely measures how particles effect on the shape of electrons.
Under the Standard Model, electrons are predicted to be nearly perfectly round, but most new theories of what lies beyond the Standard Model also predict the electron to have a much larger departure from a perfect roundness.
Scientists have recorded the most sensitive measurement to date of the electron's deformation. Their results demonstrate that the particle's departure from spherical perfection, if it exists at all, must be smaller than predicted in many theories that include new particles.
This includes many variants of the theories known as Supersymmetry.
Supersymmetry proposes new types of particles that enlarge those in the Standard Model. It may help to account, for example, for dark matter-a mysterious substance estimated to make up most of the universe.
It may also provide an explanation for why the Higgs particle's mass turn out to have the value seen at the Large Hadron Collider. These are the facts about the universe that cannot be explained by the Standard Model, scientists say.
"It is amazing that some of these predicted supersymmetric particles would squeeze the electron into a kind of egg shape," Doyle said. "Our experiment is telling us that this just doesn't happen at our level of sensitivity," noted Doyle.
To test for electron deformation, the scientists hunt for a particular deformation in the electron's shape called as an electric dipole moment.
"You can picture the dipole moment as what would happen if you took a perfect sphere, then shaved a thin layer off one hemisphere and laid it on top of the other side," said David DeMille of Yale.
"The thicker the layer, the larger is the dipole moment."
The scientists measured the electron's electric dipole moment using electrons inside the polar molecule thorium monoxide, which intensifies the deformation. Moreover, they reduce the possibility of false effects that might suggest at the deformation of the electron when none exists.
The tests were more than ten times more sensitive than any earlier test for the effect.
"We are optimistic that we can probe ten times more deeply in the next several years," added Gabrielse.
"If so, the ACME experiment will remain a strong contender in the race to find the first particles that lie beyond the Higgs boson."
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