T2K Results Restrict Possible Values of Neutrino CP Phase | WPN World People News

New results showing the strongest constraint yet on the parameter that governs the breaking of the symmetry between matter and antimatter in neutrino oscillations has been published in this week's Nature by the T2K Collaboration.

Figure 1: The arrow indicates the value most compatible with the data. The gray region is disfavored at 99.7% (3-omega) confidence level. Nearly half of the possible values are excluded.

"It is wonderful - especially in this time of global stress and uncertainty - to see such an exciting result come from the long-term efforts of an extremely diverse, international team of researchers working together toward a common goal, even while physically separated by great distances," said Kavli IPMU Principal Investigator Mark Vagins, who works on the T2K experiment at the institute.

Using beams of muon neutrinos and muon antineutrinos, T2K has studied how these particles and antiparticles transition into electron neutrinos and electron antineutrinos, respectively. The parameter governing the matter/antimatter symmetry breaking in neutrino oscillation, called δcp phase, can take a value from -180º to 180º.

For the first time, T2K has disfavored almost half of the possible values at the 99.7% (3σ) confidence level, and is starting to reveal a basic property of neutrinos that has not been measured until now. This is an important step on the way to knowing whether or not neutrinos and antineutrinos behave differently.

These results, using data collected through 2018, were published in the multidisciplinary scientific journal, Nature on April 16.

Source: Kavli Institute for the Physics and Mathematics of the Universe