Posted on behalf of Devin Powell.

According to a new prioritization, the Neutrino Factory, a proposed multibillion-euro facility, is the best long-term European option for testing whether neutrinos and antineutrinos behave differently, a step towards understanding why the Universe contains primarily matter instead of antimatter.

The recommendation comes from a report, four years in the making, that looks ahead to Europe’s future in high-intensity neutrino research. Paid for by the European Commission’s Seventh Framework Programme and presented on 10 June at CERN, Europe’s largest particle physics laboratory, in Switzerland, the EUROnu project weighed the pros and cons of three candidate neutrino machines.

Costing between €4.6 billion (US$6.1 billion) and €6.5 billion, the Neutrino Factory would generate an especially intense beam of neutrinos and send them on an underground journey of about 2,000 kilometres. At the source end, probably at CERN, the neutrino beam would be created by smashing protons into a solid target, producing muons that in turn break down into neutrinos. At the receiving end, perhaps in Finland’s Pyhäsalmi mine, a 100-kilotonne detector made of iron could spot the arrival of neutrinos and detect whether the particles had ‘oscillated’ during flight, transforming from one of the three types of neutrinos to another.

This setup could measure how often neutrinos and antineutrinos change form with less error than the other two options considered by the report: Beta Beam, powered by the breakdown of ions, and Fréjus Super Beam, which would employ a water-based detector. The Neutrino Factory would be significantly more expensive, though, so its architects are exploring ways to scale it down or implement it in stages.

Whether the facility will ever be funded and built, in its entirety or in stages, remains an open question, especially in light of the CERN Council’s recent update to the European strategy for particle physics. It indicates a willingness to back large projects abroad, such as the Long-Baseline Neutrino Experiment (LBNE), which intends to send neutrinos on a 1,300-kilometre trip from Fermilab in Batavia, Illinois, to a mine in South Dakota.