Muon Neutrino Disappearance
Cambridge works on several aspects of the MINOS experiment. We are currently involved in the main Charged Current analysis. This analysis looks for charged current muon neutrino interactions, in which a muon neutrino interacts with a quark via a W-boson to produce a recognizable signal in the detector. The Near Detector Charged Current spectrum can then be extrapolated to the Far detector. The oscillation equations predict that a certain number of Near Detector muon neutrinos will have oscillated (ie, disappeared) into tau neutrinos. The predicted Charged current spectrum can be compared to the measured one to test these assumptions and to constrain the parameters. As of Spring 2008, the analysis had obtained oscillation parameter best fit points of sin2(2θ23)=1.00±0.05 and Δm2=(2.43±)×10-3.
Electron Neutrino Appearance
The Cambridge group also is involved in the MINOS νe appearance analysis. This research group attempts to constrain or measure the mixing angle θ13. This is done by looking for the appearance of a surplus of electron neutrinos in the Far Detector. This analysis requires accurate determination of the background spectra present in both detectors, as well as the creation of a reliable particle identification scheme to identify νe charged current events. A non-zero value of θ13 would both be interesting in its own right, and have important implications for the wider field of particle physics. For instance, it could permit the observation of CP violation in neutrino oscillations.