LSND

The LSND, or Liquid Scintillator Neutrino Detector, was an experiment located at Los Alamos National Laboratory in New Mexico. Its primary goal was to search for evidence of neutrino oscillations, a phenomenon where neutrinos change flavor as they travel. LSND was designed to detect a specific type of neutrino oscillation: the conversion of muon neutrinos ($\nu_\mu$) into electron neutrinos ($\nu_e$).

The experiment used a large tank filled with a liquid scintillator, a material that emits light when struck by particles. This tank contained a significant volume of mineral oil doped with a scintillator cocktail. A beam of muons was stopped in a target at Los Alamos, producing a beam of muon neutrinos. These neutrinos then traveled through the Earth to the LSND detector.

LSND looked for the distinctive signature of an electron neutrino interacting with the scintillator. Specifically, it searched for events consistent with a $\nu_e$ interacting with a proton to produce a positron and a neutron. The positron would then annihilate with an electron, producing gamma rays, and the neutron would be captured by other elements in the scintillator, also producing a detectable signal.

The LSND experiment reported evidence for oscillations of $\nu_\mu$ to $\nu_e$. This result was statistically significant but also generated considerable debate within the particle physics community due to discrepancies with other neutrino experiments at the time, particularly those searching for oscillations of muon neutrinos into muon antineutrinos ($\bar{\nu}_\mu$) or electron neutrinos into electron antineutrinos ($\bar{\nu}_e$). Subsequent experiments, such as MiniBooNE, were designed to either confirm or refute the LSND findings.