‘Ghost particles’ may be the secret behind the heaviest elements

Large atoms require a lot of energy to build. A new model of quantum interactions now suggests that some of the lightest particles in the Universe may play a critical role in how at least some heavy elements form.

Physicists in the US have shown how ‘ghost’ subatomic particles known as neutrinos can force atomic nuclei to become new elements.

Not only would this be a completely different method for building elements heavier than iron, but it could also describe a long-hypothesized ‘intermediate’ pathway that lies at the boundary between two known processes, nuclear fusion and nucleosynthesis.

For most elements larger than hydrogen, the warm embrace of a large, bright star is enough for protons and neutrons to overcome their strong need to break apart enough to take on other radiative interactions short. This embrace of fusion releases extra energy, helping the stars’ cores stay warm.

Once atoms grow to about 55 nucleons in size—the mass of an iron nucleus—adding extra protons requires more energy than the fusion process can pay.

This change in thermonuclear economics means that the heavyweights of the periodic table can only form when extra neutrons climb into the compaction mass of nuclear particles long enough for one to decay and vomit out an electron and a neutrino, transforming it into the extra proton required to qualify as a new element.

Usually, this process is painfully slow, unfolding on the scale of decades or even centuries, as the cores inside massive stars oscillate, gaining and losing neutrons frequently, with few ever making it to the proton hood at the critical moment.

With enough impact, this growth can also be surprisingly fast—within minutes in the hot mess of collapsing and colliding stars.

But some theoretical physicists have wondered whether there are other, intermediate paths between the slow or ‘s’ process and the fast or ‘r’ process.

“It’s not clear where the chemical elements are made, and we don’t know all the possible ways they could be made,” says the study’s lead author, University of Wisconsin-Madison physicist Baha Balantekin.

“We believe some were made in supernova explosions or neutron star mergers, and many of these objects are governed by the laws of quantum mechanics, so then you can use stars to explore aspects of quantum mechanics.”

A solution may simply be found in the quantum nature of the floods of neutrinos – the most abundant particles with mass in the Universe – pouring into the cosmic medium.

Although virtually massless, with almost no means of making their presence known, their sheer numbers mean that the random emission and absorption of these transient ‘ghost particles’ still exert an influence on the budgets of protons and neutrons buzzing around deep within the massive and cosmically cataclysmic stars. events.

A strange feature of the neutrino is its habit of oscillating within a quantum ambiguity, going through several flavors of identity as it flies through empty space.

Modeling large numbers of flavors of neutrinos spinning and falling inside a chaotic nucleon shoulder is easier said than done, so physicists often treat them as a single system, where the properties of the individual particles are considered as a big, entangled superparticle.

Balantekin and his colleagues at George Washington University and the University of California, Berkeley, used the same approach to better understand how neutrino winds emitted by a newborn neutron star colliding with the surrounding medium could serve as a process of nucleosynthesis intermediate.

By determining the extent to which the quantum identity of individual neutrinos depends on the extent of this entangled state, the team found that a significant amount of new elements could be generated from this ghost storm.

“This paper shows that if neutrinos are entangled, then there is a new improved process of producing the elements, the i process,” says Balantekin.

While the numbers add up in theory, testing the idea is another matter entirely.

The study of “ghost” neutrino interactions on Earth is still in its infancy, leaving researchers looking into the distance of space for evidence of new ways larger elements come together.

This research was published in The Astrophysical Journal.