Liquid Scintillator Neutrino Detector

LSND (Liquid Scintillator Neutrino Detector, engl. For " liquid scintillator neutrino detector " ) was a physics experiment at the Los Alamos National Laboratory. It was used for the study of neutrino oscillations and ran from 1993 to 1998. The result was interpreted as an indication of previously unknown sterile neutrinos beyond the standard model of particle physics, but was highly controversial from the start.

The experiment

LSND was at the 800 - MeV linear accelerator of the LAMPF (Los Alamos Meson Physics Facility, engl. "Los Alamos meson physics facility " ) connected. The protons of the beam hit on a water target. The collision created pions, who came still in the target to rest and fell into muons and neutrinos, the muon neutrinos with emission further also disintegrated. By residing residues of other particles shielding the neutrinos reached the detector. This was a 8.3 m long and 5.7 m by measuring cylinders with a filling of 167 t mineral oil. Here the neutrinos with protons, electrons and atomic nuclei could react. Resulting scintillation and Cherenkov light detected by photomultipliers. The detector was 30m away from the target, which is a very small distance for oscillation experiments.

Result

By the reactions in the target of the neutrino beam should consist mainly of muon antineutrinos and have an electron antineutrino fraction of at most. In order to observe a neutrino, has now been increased by event numbers for reactions that were only possible with electron antineutrinos searched. In fact, the LSND collaboration came to the conclusion to have a significantly increased proportion of such events measured. However, the observation of neutrino oscillation on such a short route can not explain why so-called sterile neutrinos, a fourth neutrino places were postulated without weak charge and leptonic partner, as the simplest explanation in the framework of the usual Oszillationstheorien and other experiments.

Controversy and control experiments

Thanks to its upright to other experiments and the current theory contradicts results was often suspected, the LSND results were statistically insignificant, mishandled or just measurement error. The KARMEN experiment from 1999 to 2001, the results could not be confirmed, but also not sure because not exclude congruent parameters. This finally succeeded in 2007 with Mini Boone, whose first publications KARMEN confirmed and exclude the LSND Declaration by sterile neutrinos. So now either found alternative explanations or experimental errors must be assumed for the LSND results.