The physicists observed a similar trend in analogous reactions involving antineutrinos-the particles’ antimatter counterpart. “Twenty-five percent of the time, with some uncertainties, protons are traveling around with neutrons,” Harris says. The appearance of an extra proton alongside a neutron-turned-proton indicates that neutrinos tend to strike particle pairs. “Some fraction of the time, it looks like more than just one proton comes out.” “It spits out a proton, and leaves the rest of the nucleus basically undisturbed,” Harris says. The interaction of those two electrically neutral particles yields two oppositely charged particles, a positively charged proton and a negatively charged muon, which scatter outward like billiard balls struck by a cue ball. The analyses focus on so-called quasi-elastic scattering, which in the simplest case involves a neutrino colliding with a neutron in one of the carbon atoms. In two new studies that will appear in the journal Physical Review Letters, the MINERvA collaboration reports on several months of experimental operation in 20.
“One of the goals is to measure the neutrino interaction on several different nuclei.” Now the experiment has produced its first physics results, an analysis of neutrino interactions with carbon nuclei in the plastic portion of the detector. “It’s chewy on the inside and crunchy on the outside,” says Deborah Harris, a Fermilab physicist and co-spokesperson for the MINERvA collaboration. MINERvA’s detector contains a variety of different materials, including layers of lead and iron fronting the hydrocarbon plastic material of the inner detector. MINERvA, an apparatus about the size of a bread truck, is parked in the path of a Fermilab neutrino beam, nearly all of which passes cleanly through the detector and into another neutrino experiment called MINOS. The results will have implications for precision neutrino measurements, which often rely on carefully reconstructing the physics of rare collisions between neutrinos and atoms.
Neutrino vs neutron free#
Some of the particles within the atomic nuclei, it appears, are pairing up rather than moving about independently, only to be sprung free in twos when a neutrino strikes. Neutrinos are notoriously antisocial, nearly always slipping past atoms of matter without so much as a “how do you do.” But new research indicates that on the rare occasion a neutrino and an atomic nucleus do make contact, the interaction is surprisingly involved.īy training a beam of neutrinos on a plastic target, researchers at the MINERvA experiment at Fermi National Accelerator Laboratory in Batavia, Ill., have found that when a neutrino collides with an atom it often knocks free not just one proton or neutron, but two.
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