The enigmatic neutrino, often considered a ghostly particle, could be reshaping our understanding of all particles and forces in the universe.

The Standard Model of particle physics stands as a monumental achievement in contemporary science, meticulously cataloging known particles and forces. However, physicists have long been aware of its deficiencies and are eager to establish a more cohesive model. Notably, it fails to tie gravity to the other three fundamental forces.

During stress tests that expose weaknesses in the Standard Model, researchers can pinpoint areas in need of further exploration. Francesca Dorday and her team at the National Institute of Nuclear Physics (INFN) in Cagliari, Italy, have identified a potential flaw by investigating the mysterious behaviors of neutrinos.

“In every assessment of the Standard Model over the past two decades, we’ve consistently confirmed its predictions. This necessitates the derivation of more precise outcomes, especially since neutrinos exhibit unique characteristics,” Dorday explains.

Neutrinos possess an extraordinarily small mass—so insignificant that they were once considered massless. They interact so weakly with matter that they pass through substances undetected—akin to tiny phantoms. Nonetheless, recent investigations have managed to quantify some minimal electromagnetic interactions of neutrinos using a measurement known as the charge radius. Neutrinos can also engage with other particles via the weak nuclear force.

Dorday and her team have meticulously examined the nuances of neutrino interactions and charge radius through numerous experiments, gathering data from neutrinos produced by nuclear reactors, particle accelerators, and even the nuclear fusion activities within the Sun. Additionally, by utilizing detectors created for dark matter, they found sensitivity to neutrinos.

Team member Nicola Calgioli remarked that compiling this data was challenging but ultimately offered a comprehensive overview of our understanding of neutrinos. “We essentially integrated all available data,” added Christoph Ternes from Italy’s Gran Sasso Scientific Institute, who collaborated on this project.

While the value of the neutrino’s charge radius matched Standard Model expectations, researchers uncovered an intriguing phenomenon concerning the particles’ weak interactions. They observed “mathematical degeneracy,” meaning that both the Standard Model and a slight variant could explain the findings equally well. Strikingly, further examination revealed that the alternative model might fit the data even more closely, hinting at a long-anticipated crack in our current grasp of particle physics.

Despite the new analysis not achieving a definitive statistical breakthrough, it represents an initial foray into rigorously evaluating the Standard Model through neutrinos. Researchers aspire to gather additional data to substantiate or refute their findings as new detection technologies emerge. If these discrepancies persist, the implications could be profound.

“Identifying flaws may necessitate a complete re-evaluation of established principles,” cautions Calgioli. New models beyond the Standard Model might postulate entirely new particle types with interactions congruent with the neutrino dynamics revealed in the research.

Omar Miranda underscores that capturing neutrino interactions, particularly at ultra-low energies, is exceedingly complex, now made feasible thanks to advancements in detector technology, including those designed for dark matter research. He emphasizes the significance of neutrino detection as a litmus test for the Standard Model.

The new findings call on particle physicists to conduct ultra-precise neutrino experiments across various settings in the coming years, assert the authors. As Jose Valle from the University of Valencia, Spain points out, better measurements of neutrinos’ electromagnetic properties are still essential to uncover their internal structure.

CERN and Mont Blanc: Unraveling Dark Matter

Discover CERN, Europe’s leading hub for particle physics, situated near the picturesque city of Geneva, where researchers operate the renowned Large Hadron Collider.