How round is the electron and why does it matter?

1 May 2012

At the Institute of Physics on the evening of the 25 April 2012 Dr Michael Tarbutt from the Centre for Cold Matter at Imperial College, London explored the connections between the shape of the electron, the direction of time and the existence of antimatter.


Electrons have been conceptualized as point-like objects with negligible dimensions. Meanwhile, the seemingly empty space that surrounds the electron is teeming with pair of particles and antiparticles that fleet in and out of its existence, also called virtual particles. 

Modern physics then sees the electrons as inseparable from the cloud of the virtual particles that surrounds it. Were precisely measuring this cloud is extremely difficult scientists have predicted the electron to be very nearly, but not precisely, a sphere. 

The electron could be thought to be somewhat of a tiny battery, complete with positive and negative poles and this pull from opposite poles would in principle warp the cloud's morphology. 

Although this distortion would be extraordinarily minute, the consequences would be on a cosmic scale, namely account for the fact that the universe is almost entirely made of matter, challenging the current theories of physics that predict that there should be roughly equal amounts of matter and antimatter. 

So, the current model predicts that the electron is slightly aspheric, with a distortion characterized by the electric dipole moment. However no experiment so far has ever detected this deviation.

The electron is a fundamental particle of nature. It has a series of properties. 1-Mass (9.10938215±0.000000450) x10-31Kg, 2-Charge = -1.602176487±0.00000040 x10-19 Coulombs; 3- Magnetism, its magnetic dipole= -928476377± 0.00000023x10-24J/T; 4- Spin= 5.27285814±0.00000026 x10-35J. 

The intrinsic property of spin causes the electron dipole moment. Finally, 5-Roundness; although its size has not been obtained yet.

Measuring its roundness has important consequences. There are four major questions that could be answered with investigating the shape of the electron. 

A- Could measuring the electron's shape provide an answer to explain time-reversal symmetry? What about the origins of the arrow of time? Well, a non-spherical electron breaks time-reversal symmetry. 

B- Where is all the antimatter? There is a matter-antimatter symmetry. Every particle has a corresponding antiparticle, identical except for opposite charge. They were made in equal number in the big bang. However, the universe is made of matter, and matter appears to be ubiquitous. A non-spherical electron breaks the symmetry of matter and antimatter. 

C- Could the research into the shape of the electron suggest and evidence that there are new laws of physics? The Standard Model (SM) gives a prediction that the electron has a deviation from being round, but it may well be the case that there are other theories that could give different answers! 

D- Will then the shape of the electron give us the final answer? Electrons have the property of spin. The electrons display precession when exposed to magnetic and electric fields. And it is by measuring the change on precession when exposed to electric fields that yields the results regarding its shape. If the shape is ovoid, then, the electron would wobble.

Hudson and the team at Imperial College studied the roundness of electrons by measuring the degree of wobbling of the particles in an electric field. The rounder the electron, the reduction of the wobbling displayed. There was no sign of wobbling!!

These results provide a challenge to the established views. The research continues. Those interested can read further by accessing the article below.

Improved measurement of the shape of the electron, J J Hudson, D F M Kara, I J Smallman, B E Sauer, M R Tarbutt, & E A Hinds. Nature 473, 493-96 (26 May 2011)

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