The measure shows the stubborn roundness of the electron

The electrons are extremely round and some physicists are not satisfied.

A new experiment has captured the most detailed view of electrons to date, using lasers to highlight particles surrounding particles, a new study has announced. By illuminating molecules, scientists have been able to interpret how other subatomic particles change the charge distribution of an electron. [The 18 Biggest Unsolved Mysteries in Physics]

The symmetrical roundness of the electrons suggests that the invisible particles are not big enough to skew them into oblong or oval crushed shapes. These findings once again confirm a long-standing theory of physics, known as the Standard Model, which describes the behavior of particles and forces in the universe.

At the same time, this new discovery could upset several alternative theories of physics that attempt to fill gaps in phenomena that the standard model can not explain. This refers to the drawing board some probably very dissatisfied physicists, said David DeMille, co-author of the study, professor at the Department of Physics at Yale University in New Haven, Connecticut.

"It certainly will not please anyone," DeMille told Live Science.

A proven theory

Since subatomic particles can not yet be observed directly, scientists discover objects through indirect evidence. By observing what is going on in the void around negatively charged electrons, supposedly teeming with still-invisible particle clouds, researchers can create models of particle behavior, DeMille said.

The standard model describes most of the interactions between all the constituent elements of matter, as well as the forces acting on these particles. For decades, this theory has successfully predicted the behavior of matter.

However, there are some stubborn exceptions to the explanatory success of the model. The standard model does not explain dark matter, a mysterious and invisible substance that exerts gravitational attraction without emitting light. And the model ignores gravity alongside other fundamental forces that influence matter, according to the European Organization for Nuclear Research (CERN).

Theories of alternative physics offer answers where the standard model is insufficient. The standard model predicts that particles surrounding electrons affect the shape of the electron, but on a scale so small that it is virtually undetectable with existing technology. But other theories suggest that there are heavy particles not yet discovered. For example, the supersymmetric standard model indicates that each particle of the standard model has an antimatter partner. These hypothetical heavy particles would deform electrons to a degree that researchers should be able to observe, according to the authors of the new study.

Illuminating electrons

To test these forecasts, new experiments scrutinized electrons with a resolution ten times greater than previous efforts, completed in 2014; both surveys were conducted by the Advanced Cold Molecule Research Project Electron Electric Moment Dipole Search (ACME).

The researchers looked for an elusive (and unproven) phenomenon called electric dipole moment, in which the spherical shape of an electron seems deformed – "dented at one end and swollen at the other," explained DeMille, because of particles heavy influence on the charge of the electron.

These particles would be "much larger than the particles predicted by the standard model". "So it's a very clear way of saying if something new is happening beyond the standard model," DeMille said.

For the new study, ACME researchers directed a bundle of cold thorium oxide molecules at the rate of 1 million per pulse, 50 times per second, in a relatively small chamber located in a basement from Harvard University. Scientists zapped molecules with lasers and studied the light reflected by molecules; curvatures in the light would indicate an electric dipole moment.

But there was no distortion in the reflected light and this result casts a dark shadow on the physical theories that predicted heavy particles around the electrons, the researchers said. These particles could still exist, but they would be very different from the way they were described in existing theories, DeMille said in a statement.

"Our result indicates to the scientific community that it is necessary to seriously rethink some of the alternative theories," DeMille said. [Strange Quarks and Muons, Oh My! Nature’s Tiniest Particles Dissected]

Dark discoveries

While this experiment evaluated the behavior of particles around electrons, it also has important implications for dark matter research, DeMille said. Like subatomic particles, dark matter can not be observed directly. But astrophysicists know it because they have observed its gravitational impact on stars, planets and light.

"A bit like us, [astrophysicists] look at the heart of what many theories have predicted – for a long time and for very good reasons – a signal should appear, "said DeMille. "And yet, they see nothing and we do not see anything."

Dark matter and new subatomic particles not foreseen by the standard model have yet to be detected directly; however, a growing body of convincing evidence suggests that these phenomena do exist. But before scientists can find them, some long-standing ideas about their appearance will probably have to be dropped, DeMille added.

"Expectations for new particles are looking more and more wrong," he said.

The results were published online today (October 17) in the journal Nature.

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