Neutrinos at the Main Injector, orNuMI, is a project atFermilab which creates an intensebeam ofneutrinos aimed towards the Far Detector facility near Ash River, Minnesota for use by severalparticle detectors.[1] As of June 2010[update], theMINOS,MINERνA andNOνA experiments use the NuMI beam.[2][3]
The first step in the production of the NuMI beam is to direct a beam ofprotons from Fermilab'sMain Injector onto a carbon target. Interactions of the proton beam in the target producemesons, primarilypions andkaons, which are focused toward the beam axis by twomagnetic horns. The mesons then decay intomuons and neutrinos during their flight through a long decay tunnel. Ahadron absorber downstream of the decay tunnel removes the remaining protons and mesons from the beam. The muons are absorbed by the subsequent earth shield, while the neutrinos continue through it to theMINERνA,MINOS, andNOvA near detectors on-site atFermilab. The neutrinos then travel through the Earth to theMINOS far detector cavern in theSoudan Mine 735 km away and theNOvA far detector 810 km away at Ash River, MN, then onwards into space.
Because of the close relationship between NuMI and theMINOS experiment, MINOS is sometimes conflated with NuMI. For instance, the MINOS webpage was at www-numi.fnal.gov instead of www-minos.fnal.gov.