= Lederman-Schwartz-Steinberger two-neutrino beam experiment
{c}
{title2=1962}
= Two-neutrino beam experiment
{synonym}
In 1962, <Leon Max Lederman>, <Melvin Schwartz>, <Jack Steinberger> and collaborators distinguished <muon neutrinos> from <electron neutrinos> using a <neutrino beam>.<1988 Nobel Prize by Brookhaven National Laboratory>[Discovery of the Muon Neutrino]{ref}
The <Alternating Gradient Synchrotron> delivered $15\,\mathrm{GeV}$ <protons> onto <beryllium>. <Particle decay> of <pions> and <kaons> supplied <neutrinos>; a $13.5\,\mathrm m$ <iron> shield preceded a ten-ton <aluminium> <spark chamber>.<Observation of High-Energy Neutrino Reactions and the Existence of Two Kinds of Neutrinos by G. Danby and others>[pp. 37–38, Figs. 1–3]{ref}
Production and detection are separate. In modern <neutrino flavour> notation,
$$
\pi^+\longrightarrow\mu^++\nu_\mu.
$$
Shielding suppresses the daughter <muon>; a newly produced <muon> inside the <spark chamber>'s <aluminium> marks an interaction.<1988 Nobel Prize by Brookhaven National Laboratory>[Decay and aluminium readout]{ref}
\Image[/two-neutrino-beam-shield-and-spark-chamber.png]
{title=Production, shielding and charged-particle readout in a <neutrino beam> experiment}
{description=Original functional schematic, not a scale reconstruction. Only a rare interaction is drawn; most neutrinos traverse the detector. The lower patterns explain classification, rather than reproducing photographs.}
Beam-timed <coincidence circuits> and veto counters rejected entering tracks. Machine-off runs measured <cosmic ray> contamination; shield-thickness changes tested <neutrons>. Placing <lead> near the target shortened the <meson> decay path and reduced events. Cosmotron <Electron> calibration established <particle shower> recognition.<Observation of High-Energy Neutrino Reactions and the Existence of Two Kinds of Neutrinos by G. Danby and others>[pp. 38–42, Table II, Figs. 8–9]{ref}
The paper compared $34$ single-<muon> candidates, including $5$ estimated <cosmic ray> events, with six shower candidates unlike calibrated <Electron> showers. <Kaon> decays could supply genuine <electron neutrinos>. The deficit favored distinct <neutrino flavours> under <lepton universality>.<Observation of High-Energy Neutrino Reactions and the Existence of Two Kinds of Neutrinos by G. Danby and others>[p. 42, Figs. 8–9]{ref}
The inference concerns production and detection channels. It does not measure <neutrino> <mass> or establish permanently fixed <neutrino flavour>. Later <neutrino oscillation> experiments address changes during propagation.<Brookhaven Neutrino Research by Brookhaven National Laboratory>[Discovery of the Muon Neutrino; Super-Kamiokande]{ref}
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