Physicists from the USA have theoretically demonstrated the fundamental possibility of building a neutrino laser. The idea is based on the phenomenon of superradiance in a radioactive Bose-Einstein condensate. Scientists have calculated that in a condensate of about a million rubidium-83 atoms, the half-life will be reduced from 86 days to two and a half minutes. The article was published in Physical Review Letters.
Neutrinos hardly interact with matter, which makes them extremely difficult to study, although they play an important role in both astrophysics (for example, in the dynamics of supernovae) and fundamental particle physics. Today, researchers have learned to record only some processes involving them, and parameters such as the exact masses or nature (Majorana or Dirac) remain unknown. Scientists solve the problem of rare events by building giant detectors containing tons of recording matter, or by placing detectors near intense neutrino sources, such as a nuclear reactor. However, creating a compact intense neutrino source still remains an important task.
Ben Jones (BJP Jones) of the University of Texas at Arlington and Joseph Formaggio (JA Formaggio) of the Massachusetts Institute of Technology have proposed a mechanism similar to Dicke superradiance, in which collective decay is accelerated by coherent quantum correlations in the medium. In the ordinary case, this amplifies photon radiation, but in a Bose condensate, all the atoms share the same spatial wave function, and the proximity condition is satisfied automatically. As a result, each subsequent decay becomes indistinguishable in terms of which atom initiated it, and the amplitudes of such processes add up. This leads to a collective acceleration of decay: the rate increases proportionally to the square of the number of particles in the condensate, and the resulting neutrino flux becomes coherent and amplified.
According to the authors' calculations, in a condensate of 106 rubidium-83 atoms, half of the substance will decay in just 148 seconds instead of tens of days. The scientists note that such a source can be considered an analogue of a laser, but for neutrinos. They suggest rubidium-83 as a real candidate: it can be cooled by laser methods to the state of a condensate, it has suitable properties, and the decay products are easy to register using X-ray quanta. In addition, it is possible to work with a mixture of stable rubidium-87 and radioactive rubidium-83, which should simplify the creation and retention of the condensate.
For now, the idea remains theoretical: it is not yet clear how exactly to cool the radioactive gas to condensate and how to cope with the heating of the trap during decay. Nevertheless, the authors emphasize that they have demonstrated for the first time the possibility of coherent amplification of neutrino radiation, and this opens up a fundamentally new path to the creation of neutrino sources.
Scientists continue to study neutrinos. Recently, physicists have limited the minimum size of their wave packet.
