Exploring Cosmic Background Events Appearning in NOνA Far Detector Neutral Current Selection

The NOνA (NuMI Off-axis ν Appearance) experiment measures neutrino oscillations in a nearly pure muon neutrino beam over a 810 km baseline. In order to detect any behavior beyond the Standard Model, we look at neutral current (NC) events since any NC disappearance would indicate oscillation between active flavors and sterile neutrinos. The NOνA Far Detector (FD) is situated on the surface and is exposed to 140 kHz of cosmic rays. Therefore, the current FD NC selection includes additional cosmic rejection cut. However, after a hands-on analysis of 564 event displays (EVD) of out-of-time cosmic events, we found many cosmic events that the new cuts may be able to reject. In order to reduce the number of cosmic events in the NC selection, we are exploring principle component analysis (PCA) which would eliminate any very long and narrow events potentially due to cosmic tracks. Additionally, we are examining ways to reduce activity near the top and walls of the detector. In this talk, we will show how these new cuts change the expected signal and background in the NC event selection.