Description
T2K (Tokai to Kamioka) is a Japan-based long-baseline neutrino oscillation experiment designed to measure (anti)neutrino flavor oscillations. T2K is taking data in neutrino and antineutrino mode with a primary goal to improve the constraint on the phase $\delta_{CP}$, an unknown element of the Pontecorvo-Maki-Nakagawa-Sakata matrix, that can provide a test of whether CP symmetry is violated in the neutrino sector. To reach this goal T2K performs frequentist and bayesian analyses. In the frequentist analyses the flux and cross-section prior models are fit to the near detector data. Since the previous oscillation analysis the near detector fit has incorporated significant updates to the flux and cross-section models. In particular, the analysis now uses the Benhar Spectral Function model as a nuclear ground-state model. The latter takes into account the shell structure of the nucleus, and dedicated systematic uncertainties have been introduced to account for this. In order to help constrain systematic effects related to the neutrino flux and interactions, new samples have been introduced to the neutrino mode event selections using photon and proton information. The results of this fit are propagated to the far detector as a multivariate normal distribution described by a covariance matrix and the best-fit values for each parameter associated to flux and cross-section systematic uncertainties. In this poster the methodology employed to perform the near detector fit is presented, along with the improvements made with respect to the previous iteration of the oscillation analysis.
| Collaboration | T2K |
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