Neutrinos more reactive than once thought

Neutrinos detected in ‘weird reaction’ with the nucleus of particles.

Research from the University of Rochester suggests that an odd little particle which goes by the name of neutrino is involved in a reaction that even physicist Kevin McFarland describes as “weird.”

This new research shows that it is possible for these particles to occasionally interact with a nucleus while inflicting next to no damage. This phenomenon is possible due to the creation of a charged substomic particle that is able to defend the nucleus from the reaction. Without the creation of this new particle, the nucleus would receive extreme damage.

Professor McFarland uses the example of a bubble being shot by a bullet.

“The bubble – a carbon nucleus in the experiment – deflects the neutrino ‘bullet’ by creating a particle from the vacuum,” McFarland said. “This effectively shields the bubble from getting blasted apart, and the bullet instead only delivers a gentle bump to the bubble.”

Previous studies have observed the creation of these charged pions, but the results had been plagued by inconsistencies. Even results of theoretical calculations were “all over the map” according to McFarland. With new technology, it has now become possible to measure not only the momentum and energy transfers that are placed on the nucleus, but also the distribution of the pions.

The nature and the frequency of these “weird” reactions surprised physicists. Neutrinos, in fact, rarely react – so rare that even with ten trillion neutrinos passing through your hand every second, there is a chance that only one of those neutrinos will react. Out of those occurring reactions, only a portion will be of the variety illustrated in this experiment.

This study, however, managed to accumulate so much data that a student of McFarland’s, Aaron Mislivec, was recruited to generate a computer code to sift through the data accumulated under the supervision of Aaron Higuera, a postdoctoral fellow. The code searches for the signature intact nuclei that marked this specific reaction. Once the intact nuclei is located, it is possible to then look at the resultant particles. The resulting data gave a clearer picture of the processes within the reaction.

“Our detectors,” said Mislivec, “gave us access to the full information of exactly what was happening in this reaction.”

Although neutrino reactions may not have direct implications on our everyday lives, even McFarland admits that “it is exciting to learn that this weird reaction really does take place.”

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