Columbia University REU at Fermilab

The final stages of the MiniBooNE neutrino oscillation analysis made an exciting backdrop for my REU working with Columbia Professor Janet Conrad at Fermilab this summer. MiniBooNE is a νμ → νe oscillation search designed to check to controversial LSND [1] result. My work focused on isolating neutral current delta baryons which undergo the rare electromagnetic decay. When deltas decay via the strong force, they can be easily identified in the MiniBooNE detector because of the pions they produce. Likewise, deltas which are produced by charged-current interactions are easily identified by the muon which comes out as the delta is produced, so even if they decay radiatively (producing photons instead of pions) they can be identified. This leaves the problem of identifying deltas produced by neutral current (NC) interactions which then decay radiatively. If the photons produced in such a decay form an electron-positron pair, this could look very similar to the MiniBooNE oscillation signal: an excess of νe interactions, which only produce electrons. One purpose of my analysis is to help identify NC deltas to eliminate them from the oscillation signal. Based on estimates from the run plan [2], MiniBooNE expects about 300 oscillation events and about 80 NC delta radiative decays, making this a significant background. Another goal is to optimize the purity of the sample enough to report a direct observation of neutrino scattering producing radiative delta decays. A positive identification of radiative delta decays would be a first for neutrino physics. NuMI (Neutrinos at the Main Injector) is another beamline of neutrinos at Fermilab looking for oscillations. Two detectors, collectively called MINOS (Main Injector Neutrino Oscillation Search) watch this beamline. It runs from the main injector at Fermilab, through a “near detector” at Fermilab, all the way to Soudan in Minesota, where there is a similar “far detector.” The NuMI beamline runs about 7◦ off from the MiniBooNE beamline, and