Neutrinos are fundamental particles with no electric charge and as-yet-unmeasured masses, allowing them to travel unimpeded through enormous amounts of material. Despite their elusiveness, a lot of compelling evidence shows that neutrinos have non-zero masses and change from one flavor to another. Intense neutrino beams generated by particle accelerators are now being used in order to more precisely probe the physics of neutrino masses and mixing.
This talk will briefly review the experimental evidence and the framework that describes neutrino oscillations. As an example of a man-made neutrino beam, it will focus on the Tokai-to-Kamioka (T2K) experiment, which creates a beam of muon neutrinos at J-PARC on the east coast of Japan. With two neutrino detectors, one located near the origin of the beam, and another located 295 km away, T2K has seen the disappearance of muon neutrinos and the appearance of electron neutrinos. The talk will conclude with a brief discussion of future long-baseline neutrino experiments, especially the efforts in the US to send a high-intensity beam of neutrinos from Fermilab to a former gold mine in South Dakota.