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History of Neutrinos at Lab E

Home has a different meaning for different people. For a select few graduate students, home was a building and a set of portakamps in the fixed-target area at Fermilab: Lab E. The Lab E building itself and the detector within it have a history and utility that go beyond neutrino physics. However, this page focuses on the story of the Lab E detector in the high-energy neutrino era of Fermilab. Those who seek a general history of particle physics must look elsewhere.

E616, run in 1979, was the first experiment to take advantage of the high-energy neutrino beam in Lab E. Back then the collaboration was called "CCFRR", the initials of the institutions that funded the experiment: California Institute of Technology, Columbia University, Fermilab, University of Rochester, and Rockefeller University.

At the time, the Fermilab accelerator fed 400 GeV protons to the fixed-target line, which limited the upper neutrino energy to about 300 GeV. The neutrino beamline was configured in a "narrow-band" mode, which meant that the neutrino energy was restricted to a relatively narrow range -- this allowed for a better measurement of the beam flux, but cut down on the number of neutrinos that reached the Lab E detector. The number of neutrino events observed was further restricted by the detector itself: the charged particles that emerged from a neutrino event were recorded using spark chambers, which were limited to recording one event per "ping" (a fast extraction of protons during the accelerator cycle).

E701 took data in 1982 and was similar to E616, but it had a different purpose: to search for neutrino oscillations. A portion of the Lab E detector's apparatus was moved upstream to another detector in the (now demolished) Wonder Building. Although no oscillations were observed, analyses were performed on the combined E616/E701 data sample for cross-sections, structure functions, and other phyics results.

By this time the group had become the "CCFR" collaboration: University of Chicago, Columbia University, Fermilab, and the University of Rochester.

The Lab E neutrino era hit its stride with E744, run in 1985, and E770, run in 1987 and 1988. By the time of these experiments, the Tevatron was in operation, which accelerated protons up to 800 GeV. Also, the neutrino beamline had been changed to a quadrupole-triplet wide-band beam, which greatly increased the number of events reaching the detector. Finally, the spark chambers in the detector were replaced with drift chambers, which could record several events per ping.

The big advantage of this new set-up was that over ten times more events were collected in the E744+E770 data sample compared to the E616+E701 data sample, with neutrino energies ranging up to about 600 GeV. Indeed, until NuTeV almost a decade later, the E744+E770 data sample remained the highest-energy highest-statistics sample of neutrino data in the world. A minor disadvantage of the new beam setup was that no measure of the absolute flux was possible, so cross-sections could not be measured. However, the CCFR data provided a wealth of other physics results. Among the most important results were measurements of the structure of the proton and the electroweak mixing angle.

The latest neutrino experiment in Lab E, E815, (run by the "NuTev" collaboration) maintains the high standards established by the earlier experiments. The neutrino beamline is now a "sign-selected" quadrupole-triplet beam, which allows separate high-statistics neutrino and anti-neutrino beams. The test beam program to calibrate the detector is greatly improved over the previous experiments. An additional decay channel was built in front of the Lab E detector to search for neutral heavy leptons. The primary physics goal of E815 is to measure the electoweak mixing angle to a greater precision than any other deep-inelastic scattering experiment.

Alas, the days of neutrinos at Lab E are coming to an end. The neutrino detector will be shoved aside and Lab E will be used for testing modules for other experiments. But those of us who worked there will always remember the thrill of being drenched with scintillator oil, the grime we inhaled as we crawled underneath the detector, the gentle thrill as 1725 volts passed through our bodies. The legacy of Lab E lives on.


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