IU physicists lead world's most precise measurement of neutron lifetime

https://news.iu.edu/stories/2021/10/iub/13-physics-neutron-lifetime-measurement-study.html

The process by which a neutron ‘decays’ into a proton — with an emission of a light electron and an almost massless neutrino — is of great interest to physicists. “...understanding the precise lifetime of the neutron can shed light on how the universe developed ... and show flaws in our model of the subatomic universe that we know exist but nobody has yet been able to find.” The neutron source was the Ultracold Neutron source at Los Alamos. The experiment captures these neutrons, whose temperatures are lowered to nearly absolute zero, inside a “bathtub” lined with about 4,000 magnets. After waiting 30 to 90 minutes, researchers count the surviving neutrons in the tub as they’re levitated against gravity by the force of the magnets. The trap allows neutrons to remain stored for more than 11 days. This is significantly longer than earlier designs, minimizing the need for systematic corrections that could skew the results of the lifetime measurements. Over two years, they counted 40 million neutrons captured this way. Will help physicists confirm or deny the validity of the “Cabibbo-Kobayashi-Maskawa matrix,” “The underlying model explaining neutron decay involves the quarks changing their identities, but recently improved calculations suggest this process may not occur as previously predicted,” “Our measurement of the neutron lifetime will provide an independent assessment to settle this issue, or provide much-searched-for evidence for the discovery of new physics.”