Ghostly particles might just break our understanding of the universe
An analysis of several experiments aimed at detecting the mysterious neutrino has identified a hint of a crack in the standard model of particle physics
Neutrinos rarely interact with normal matter
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Notoriously ghostly particles called neutrinos may have revealed a crack in our understanding of all the particles and forces in the universe.
The standard model of particle physics, which catalogues all the particles and forces we know to exist, is one of the biggest successes of modern physics, but physicists have also spent decades trying to break it. That is because it has enough flaws – notably, it doesn’t connect gravity to any of the three other fundamental forces – for researchers to suspect that they must formulate another, better model.
If the standard model cracks under a stress test, that would point to where we should start building this next model. Francesca Dordei at the Italian National Institute for Nuclear Physics (INFN) in Cagliari and her colleagues have now identified one possible crack by studying the enigmatic neutrino.
“In all the checks [of the standard model] that we did in the last two decades, every time, stubbornly, they confirmed the standard model, which means that we have to go to even more precise results. In this sense, neutrinos are special particles,” says Dordei.
For one, neutrinos have incredibly small masses – so small that physicists once thought they were massless. What’s more, they are weakly interacting, which means they pass through objects and bodies undetected, like tiny ghosts. Yet careful study has pinpointed some small electromagnetic interactions that neutrinos take part in, which can be quantified through a number called charge radius. Neutrinos can also interact with other particles through the weak nuclear force.
Dordei and her colleagues examined the details of that interaction and of the neutrinos’ charge radius across the many experiments that have looked for signs of these elusive particles in recent years. For instance, they combined data from observations of neutrinos created in nuclear reactors, particle accelerators and fusion processes inside the sun. The team also took advantage of the fact that some detectors built for dark matter – the mysterious substance that permeates the cosmos – are sensitive to neutrinos as well.
