2023-07-03 06:00:04
One of the simplest elements of nature gives scientists a hard time. New research shows that the protons and neutrons in helium atoms do not behave as predicted by theory. This discrepancy could reveal a physique beyond the Standard Model, the dominant model describing subatomic particles. Scientists can’t figure out why the forces within the atom’s nucleushelium continue to challenge the theory after decades of experience.
A study published in April in the journal Physical Review Letters shows an inconsistency between theory and experiment. The researchers subjected a container of helium atoms to an electron beam, inducing a temporary excited state of the helium nucleus. They found that the reaction of protons and neutrons diverged significantly from theoretical predictions, confirming the conclusions drawn from previous experiments.
The helium nucleus is made up of two protons and two neutrons. Resolving this discrepancy could help us understand other exotic phenomena, such as fusion taking place at the core of neutron stars.
The first discrepancy between theory and experimentation appeared in 2013. Sonia Bacca led the calculations on the helium nucleus. She and her colleagues found results that diverged strongly from the experimental data. However, the experimental data used for the comparison dated back to the 1980s and had large uncertainties.
Simon Kegel, lead author of the new study, pointed out that the current facilities at his university in Mainz, Germany, are capable of performing these same measurements but with very high precision.
The complex problem of nuclear interactions is usually simplified by Effective Field Theory (EFT). However, when the researchers used an enhanced version of EFT, the theoretical predictions diverged even more from the observed phenomena.
To verify the extent of this divergence, Simon Kegel and his team used the MAMI electron accelerator to bombard a container with helium atoms. Two parameters made it possible to improve the precision of the measurements: the density of the helium atoms in the container and the intensity of the electron beam at low energy.
The results did not solve the riddle. The arrival in 2024 of the MESA superconducting accelerator in Mainz could offer a more detailed vision of the low-energy frontier of the Standard Model.
1688364422
#mystery #Helium #defies #scientists