Researchers from Stony Brook University’s Department of Physics and Astronomy have participated in a joint analysis with international teams from the T2K (Tokai to Kamioka) and NOvA (NuMI Off-axis νe Appearance) experiments. Both projects study long-baseline neutrino oscillations, using data collected over several years with advanced detectors and accelerators.
By combining the different baselines and energy spectra from both experiments, the team achieved more precise measurements of neutrino oscillations. Their findings were published in Nature on October 22. The joint effort reduced uncertainty in differences between neutrino masses to below 2%. While the exact ordering of the three neutrino masses remains unknown, the results indicate that depending on this ordering, the degree of Charge Conjugation and Parity (CP) symmetry violation—an important difference in behavior between particles and antiparticles—would be strongly limited.
This collaboration marks a significant step toward understanding CP symmetry violation in neutrinos and could help explain why there is more matter than antimatter in the universe. The analysis combined ten years of T2K data starting from 2010 and six years of NOvA data beginning in 2014, highlighting the benefits of cooperation between two competitive but complementary international research groups.
Chang Kee Jung, Distinguished Professor and chair of the Department of Physics and Astronomy at Stony Brook University, said: “I truly commend both NOvA and the T2K collaborations seeing this through despite many technical and political challenges during the joint analysis process. The initial discussion of a possible joint analysis started more than 10 years ago and the first NOvA-T2K meeting was held in March 2016. Thus, it has been a really long process. The outstanding and informative results obtained from this joint analysis are products of strong desires of both collaborations to maximize the scientific output from their experiments in advancing human knowledge. It is an exemplary model of inter-experimental collaboration. Stony Brook has been the Principal Investigator institution for the T2K United States group since the inception of the T2K experiment and has made numerous and significant contributions to the experiment, including this joint analysis.”
Although these first results do not fully resolve remaining questions about neutrinos, they provide scientists with improved information about these particles. The outcome also demonstrates effective collaboration between two major experimental teams.
The T2K collaboration includes over 560 members from 75 institutions across 15 countries, including Stony Brook University as well as other US institutions such as Boston University; Duke University; Lawrence Berkeley National Laboratory; Louisiana State University; Michigan State University; South Dakota School of Mines and Technology; Stanford Linear Accelerator Center (SLAC); University of California, Irvine; University of Colorado, Boulder; University of Houston; University of Minnesota; University of Pennsylvania; University of Pittsburgh; and University of Rochester. The US group’s participation is supported by the US Department of Energy.
The NOvA project is managed by Fermi National Accelerator Laboratory and consists of more than 250 scientists and engineers from 49 institutions in eight countries. Collaboration on this joint analysis began actively in 2019, with both experiments continuing to collect new data for future updates.
Currently, NOvA and T2K are the only operational long-baseline neutrino experiments worldwide. Their initial combined findings set a foundation for future research aimed at answering unresolved questions about neutrinos.