Revised performance parameters of the ZEPLIN-III dark matter experiment

TL;DR

This paper revises the detector parameters for the ZEPLIN-III dark matter experiment's 2008 data, highlighting its record electron recoil discrimination in liquid xenon and providing calibrated parameters to improve response models.

Contribution

It introduces updated detector parameters and calibration methods based on 2008 data, enhancing the understanding of liquid xenon responses for dark matter detection.

Findings

Achieved electron recoil discrimination of 1 in 10,000 below 40 keV

Provided calibrated optical parameters for better response modeling

Supported development of liquid xenon response models at high electric fields

Abstract

This note presents revised detector parameters applicable to data from the First Science Run of the ZEPLIN-III dark matter experiment; these datasets were acquired in 2008 and reanalised in 2011. This run demonstrated electron recoil discrimination in liquid xenon at the level of 1 part in 10,000 below 40 keV nuclear recoil energy, at an electric field of 3.8 kV/cm; this remains the best discrimination reported for this medium to date. Building on relevant measurements published in recent years, the calibration of the scintillation and ionisation responses for both electron and nuclear recoils, which had been mapped linearly to Co-57 gamma-ray interactions, is converted here into optical parameters which are better suited to relate the data to the emerging liquid xenon response models. Additional information is given on the fitting of the electron and nuclear recoil populations at low energy. The aim of this note is to support the further development of these models with valuable data acquired at high field.