Speaker
Description
This talk reports the first measurement using the NOvA detectors of
$\nu_{\mu}$ disappearance in a $\nu_{\mu}$ beam. Oscillation parameters
$\Delta m_{32}^{2}$ and $\sin^{2}\theta_{23}$ are measured as function
of the count and energy spectrum of $\nu_{\mu}$ interactions at a
Near and Far Detector, separated by a distance of $810\text{ km}$.
High-statistics Near Detector energy spectra are compared to Monte
Carlo predictions, and discrepancies used to perform a data-driven,
bin-by-bin ``Far/Near extrapolation'' correction to the predicted
Far Detector energy spectrum. The corrected spectrum is fit to data
in $\Delta m_{32}^{2}$ and $\sin^{2}\theta_{23}$, marginalizing
over systematic uncertainties and the remaining oscillation parameters
(excepting $\delta_{CP}$, which is left unconstrained) to produce
best fit points and $90\%$ confidence level contours. Systematic
uncertainties considered cover particle simulation, cross-sections,
detector calibration, and differences in exposure and performance
between the Far and Near Detectors. This analysis uses a 14 kton-equivalent
exposure of $2.74\times10^{20}$ protons-on-target from the Fermilab
NuMI beam. Assuming the normal neutrino mass hierarchy, we measure
$\Delta m_{32}^{2}=(2.5_{-0.18}^{+0.20})\times10^{-3}\text{ eV}^{2}$
and $\sin^{2}\theta_{23}$ in the range $0.38-0.65$, both at the
$68\%$ confidence level, with two statistically-degenerate best fit
points at $\sin^{2}\theta_{23}=0.43$ and $0.60$. Results for the
inverted mass hierarchy are also presented.
