XENONnT Analysis: Signal Reconstruction, Calibration and Event Selection

TL;DR

The paper details the XENONnT detector's signal reconstruction, calibration, and event selection methods, establishing a framework for analyzing rare events like dark matter interactions with low background noise.

Contribution

It introduces the signal processing and calibration techniques specific to XENONnT, enabling precise detection of rare phenomena and setting the stage for future physics analyses.

Findings

Achieved an exceptionally low background level of 15.8 events/(tonne·year·keV).

Described the detector response calibration process.

Established a framework for blind analysis of dark matter search data.

Abstract

The XENONnT experiment, located at the INFN Laboratori Nazionali del Gran Sasso, Italy, features a 5.9 tonne liquid xenon time projection chamber surrounded by an instrumented neutron veto, all of which is housed within a muon veto water tank. Due to extensive shielding and advanced purification to mitigate natural radioactivity, an exceptionally low background level of (15.8 $\pm$ 1.3) events/(tonne$\cdot$year$\cdot$keV) in the (1, 30) keV region is reached in the inner part of the TPC. XENONnT is thus sensitive to a wide range of rare phenomena related to Dark Matter and Neutrino interactions, both within and beyond the Standard Model of particle physics, with a focus on the direct detection of Dark Matter in the form of weakly interacting massive particles (WIMPs). From May 2021 to December 2021, XENONnT accumulated data in rare-event search mode with a total exposure of one tonne $\cdot$ year. This paper provides a detailed description of the signal reconstruction methods, event selection procedure, and detector response calibration, as well as an overview of the detector performance in this time frame. This work establishes the foundational framework for the `blind analysis' methodology we are using when reporting XENONnT physics results.