Revolutionary result: researchers unravel the mysteries of the long-theorized fifth force of nature

A research team led by the National Institute of Standards and Technology (NIST) has unraveled the mysteries of the fifth force of nature

He is about to end up run over, his mother saves him

There is a fifth force in nature, long theorized but never "seen". Today a research team led by the National Institute of Standards and Technology (NIST) have unraveled some of its mysteries and at the same time managed to measure a key property of neutrons for the first time in history.





The work was conducted by targeting neutrons, subatomic particles located in atomic nuclei and devoid of charge, in particular those of silicon crystals, and monitoring the result with a sensitivity never achieved before, with the aim of verifying whether the fifth force of nature, theorized for some time but never measured in any way, really existed.

To obtain information about crystalline materials on an atomic scale, scientists generally point a beam of particles (such as X-rays, electrons, or neutrons) at the crystal and detect the properties of the material as that beam passes through or bounces off the lattice planes, the architecture of base of the crystal.

Such information is critically important for characterizing the electronic, mechanical and magnetic properties of microchip components and various new nanomaterials for next generation applications, includingquantum computer science. Which, even if it sounds like science fiction, is already a reality.

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A vastly improved understanding of the crystalline structure of silicon, the 'universal' substrate, the basic material upon which everything is built, will be crucial to understanding the nature of the components operating near the point where the accuracy of measurements is limited by effects. quantum

explains Michael Huber, senior scientist on the project.

What happens at the quantum level

Revolutionary result: researchers unravel the mysteries of the long-theorized fifth force of nature

©NIST

At the subatomic level, in fact, the laws of classical physics no longer apply and there is a real limit imposed by nature that prevents us from continuing. Just to cite an example, one of the fundamental laws of this fascinating branch of physics is in fact the Heisemberg Uncertainty Principle which establishes, "by law", how it is impossible to determine simultaneously the speed and mass of an electron.



What man can do is to get closer and closer to these limits. And that's what the NIST researchers managed to do, improving accuracy by four times of the measures on the structure of the silicon crystal.

Like all quantum objects, neutrons have properties of both point particles and waves. So when a neutron, which is a particle with a mass, albeit very small, travels through the crystal, it generates waves (like a plucked guitar string), and, when the waves coming from each of the two routes combine (technically "they interfere ”), Create particular oscillations called pendellösung that they provide information on forces that neutrons experience inside the crystal.

Imagine two identical guitars - Huber explains - take them the same way, and while the strings vibrate, guide one along a road with bumps - that is, along the planes of the atoms in the lattice - and guide the other along a road of the same length without bumps. - analogous to the displacement between the planes of the lattice. Comparing the sounds of both guitars tells us something about the bumps: how big they are, how smooth they are and if they have interesting shapes

The results

Scientists in this way managed to achieve three extraordinary results: the first measurement of a key property of neutrons, the highest-precision measurements of the effects of heat-related vibrations in a silica crystal, and the "boundaries" of a possible fifth force of nature.

Revolutionary result: researchers unravel the mysteries of the long-theorized fifth force of nature

©NIST

  1. Neutrons aren't exactly neutral

It seems a contradiction in terms, yet it is true. Scientists have in fact measured the 'radius of electric charge' with much greater precision than in the past, demonstrating that these particles, although electrically neutral on the whole, have an internal distribution of charge that makes them inhomogeneous in this sense.



This is because neutrons are composite objects made up of three charged elementary particles called quark with different electrical properties which are not exactly uniformly distributed.

  1. Watch out for vibrations

A valid alternative to neutrons for crystal property measurements is X-ray scattering. But its accuracy has been limited by the atomic motion caused by heat. Thermal vibration, in particular, continuously changes the distances between the crystal planes and thus the interference patterns measured.

But now we know more: Scientists have in fact measured the pendellösung neutron oscillations themselves to test the predicted values ​​of the X-ray scattering patterns and have found that some significantly underestimate the magnitude of the vibration. This result provides valuable complementary information for both X-ray and neutron scattering.

  1. The fifth force of nature

The scientific community has long suspected that current theories on forces and in general on the mechanisms of nature are incomplete, assuming that there is much more of the universe than is currently described in the so-called Standard Model.

This theoretical framework describes three fundamental forces in nature: electromagnetic, strong nuclear and weak nuclear, each of which operates through the action of "carrier particles", the exchange of which generates the reference force.

On this we know that the photon is the vector for the electromagnetic force, but no one has ever found the particle that "carries" the force of gravity in his description of nature (what someone has tried to call "graviton", but never found it ). Furthermore, some experiments and theories suggest the possible presence of a fifth force.

NIST-led researchers have now managed to determine the "boundaries" of action of this fifth force, narrowing the search field (as if they had found the "fence" where someone is hiding).

Generally, if there is a force vector, the length scale on which it acts is inversely proportional to its mass - explains Benjamin Heacock, first author of the work - which means that it can only affect other particles in a limited range. But the photon, which has no mass, can act on an unlimited radius. So, if we can limit the range within which it could act, we can limit its strength

The results of the scientists they have improved the limits on the potential fifth force tenfold on a length scale of 0,02 to 10 nanometers (billionths of a meter), giving fifth-force hunters a narrow range in which to look.

Hunters among whom they themselves apply, planning measurements on the pendellösung oscillations of neutrons in both silicon and germanium, and aiming for a possible reduction factor of five in their uncertainties, which could yield the most accurate measurement of the radius of the charge of neutrons to date and further limit (or perhaps really discover) a fifth force.

They also plan to run a cryogenic version of the experiment, which would provide information on how crystal atoms behave in their so-called 'quantum ground state', which explains the fact that quantum objects are never perfectly still, even at temperatures. that approach absolute zero (temperature at which, theoretically, matter disappears, obviously never reached experimentally).

NIST's work is indeed much more than a scientific curiosity. In fact, silicon is of fundamental importance for many industrial and technological applications, present, just to cite an example, in electronic circuits. The study, therefore, opens many doors on quantum communications and on innovative materials for any use.

The research was published in Science.

Sources of reference: NIST / Science

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