How long-baseline neutrino experiments, like MINOS, analyze detector data to extract neutrino oscillation parameters

2015 Summer QuarkNet MINOS Research Project

Theodore Baker (Walnut Hills High School)
Panos Manganaris (Anderson High School)
Mentor Alex Sousa

The purpose of my research this summer was to understand how long-baseline neutrino experiments, like MINOS, analyze detector data to extract neutrino oscillation parameters. By utilizing the ROOT Data Analysis Framework, I first learned basic properties and differences of different types of neutrino interactions through Monte Carlo (simulated) data. Neutrinos interact with other subatomic particles through the weak force. Charged current (CC) interactions occur when a neutrino of any flavor converts to its partner charged lepton (e.g.) through exchange of a boson. Neutral Current (NC) interactions take place when a neutrino interacts with a Z⁰boson yet does not convert into a charged lepton. Unlike CC events observed in the detector, NC events all look the same no matter the neutrino flavor and therefore are insensitive to neutrino oscillations and are removed from the oscillation analysis. I developed a selection method based on the event length of separate NC and CC events. I then fit the MINOS data reconstructed energy spectrum to a Monte Carlo spectrum oscillated with different sets of values for the oscillation parameters. The best-fit value for sin( Ø₂₃ ) is almost 1 and the best-fit parameter for Δm_2/23 is 0.0022, closely matching the MINOS published results. The study of these neutrino oscillations could potentially help us solve the long-standing puzzle of matter-antimatter asymmetry.