MOTIVATION

In the Standard Model of particle physics, there are three kinds of neutrinos, electron neutrinos, muon neutrinos, and tau neutrinos. These neutrinos have no charge and very little mass, hardly interacting with other matter. Nevertheless, neutrinos are a very important part of the Universe, which consists of a billion times more neutrinos than atoms. If neutrinos had mass, quantum mechanics would allow them to morph into one another. For example, a muon neutrino moving through space could oscillate into a tau neutrino. The characterization of neutrino oscillations may provide the key to the nature of mass and existence of a universe that can support life. NuMI/MINOS is designed to detect these oscillations and measure their properties.

NuMI/MINOS

The NuMI/MINOS project is a collaboration of some thirty-two institutions and almost two hundred members. The overarching goal of NuMI/MINOS is to observe muon neutrino oscillations and, if all goes as planned, make the most sensitive measurement of the corresponding oscillation parameters to date. To this end, NuMI/MINOS will employ a neutrino beam and two particle detectors.

NuMI (Neutrino Main Injector), a neutrino beam generated at Fermilab and aimed at the MINOS detector, will, when completed, be the most intense neutrino beam ever generated. The NuMI beam is expected to be finished by the end of 2004.

The Near Detector, currently in the final stages of construction, is located at the end of the NuMI beamline. This roughly one kiloton detector will monitor the beam content and energy spectrum. Because the Near Detector is so close to where the neutrino beam originates, all neutrino interactions it contains will be unoscillated, giving the collaboration an accurate account of what the beam initially contains.

MINOS (Main Injector Neutrino Oscillation Search) is located roughly 700 kilometers from the Near Detector and 2,341 feet underground in the Soudan Underground Mine State Park, which is in northern Minnesota. This mine was also the site of the Soudan 2 proton-decay experiment, which is currently standing idle in an adjacent cavern. MINOS is a five kiloton magnetized tracking calorimeter designed to observe neutrino events from the NuMI beam. If the beam is different at MINOS from what it was at the Near Detector, the neutrinos oscillated in transit. Observation of these oscillations would be conclusive evidence that neutrinos have mass.

Groundbreaking on the MINOS hall took place on July 20, 1999, and the detector was completed in August of 2003. While waiting for the beam, MINOS has been taking cosmic ray data and will publish results soon.

For more information on NuMI/MINOS, see the NuMI/MINOS page maintained by Fermilab.

The finished detector, veto shield, and coil.