Search for Ultra-High-Energy Neutrinos at the Pierre Auger Observatory: New Triggers, Methods, and Constraints

Abstract

The Pierre Auger Observatory has the capability to identify neutrino-induced extensive air showers above $10^{17}$ eV by using its large Surface Detector (SD) array. Data from the Observatory have been used to set some of the most stringent upper limits to the neutrino flux in the ultra-high energy (UHE) range. The data have also been used for follow-up detection of transient events in the context of multi-messenger astrophysics. In mid-2013, two additional SD triggers (Time-over-Threshold-deconvolved (ToTd) and Multiplicity-of-Positive Steps (MoPS)) were shown to increase the detection capability for the neutrino-induced air showers in the energy regime below $10^{19}$ eV by a factor of 5-10. This contribution will give an overview of the ongoing work regarding the searches for UHE neutrinos at the Pierre Auger Observatory. The impact of the ToTd and MoPS triggers for neutrino search in the zenith angle range of $60^{\circ} < \theta < 75^{\circ}$ is discussed. A novel neutrino identification method, which integrates these triggers, is applied to observational data to look for neutrino-like events using a $\textit{blind}$ search strategy. New constraints to point-like sources of UHE neutrinos will be presented for the angular range explored.