Simulating Trident Events in the NOvA Detector

Trident events are a rare neutrino interaction where a charged lepton and antilepton pair is generated by a neutrino interacting with a heavy nucleus. These interactions are allowed by the Standard Model but may have information about beyond the Standard Model. The NOvA experiment has been running at Fermilab since 2014 and may have recorded approximately 100 trident events out of 100 million total events. The first step in finding these events out of the larger sample is to have accurately simulated trident events in the detector to use as examples when building analyzers. In order to accurately simulate the trident events the events need to be overlaid with other neutrino interactions and they need to occur at a properly calibrated flux rate. The method we used was to take real detector events and replace them with Trident events while reweighting their frequency according to the cross section of the trident event. The reweighting was done through the rejection sampling method. The resulting simulations contained both the trident events and the original detector events to accurately represent the way that trident events would appear in the detector. These tagged events can then be used to build analyzers to identify real trident events in the NOvA data.