Simulation and background characterisation of the SABRE South experiment
E. L. Barberio, Ti. Baroncelli, L.J. Bignell, I. Bolognino, Geoffrey Brooks, F. Dastgiri, G. D’imperio, A. Di Giacinto, Alan R. Duffy, M.B. Froehlich, Guang-Yong Fu, M. S. M. Gerathy, G. C. Hill, S. Krishnan, G. J. Lane, G. Lawrence, K. T. Leaver, I. Mahmood, A. Mariani, P. McGee, L.J. McKie, P. C. McNamara, M. Mews, W. J. D. Melbourne, G. Milana, L. J. Milligan, J. R. Mould, F. Nuti, V. Pettinacci, F. Scutti, Z. Slavkovská, N.J. Spinks, Matthew Stanley, A. E. Stuchbery, G. N. Taylor, C. Tomei, P. Urquijo, C. Vignoli, Anthony G. Williams, Yang Zhong, M. J. Zurowski
Abstract
Abstract SABRE (Sodium iodide with Active Background REjection) is a direct detection dark matter experiment based on arrays of radio-pure NaI(Tl) crystals. The experiment aims at achieving an ultra-low background rate and its primary goal is to confirm or refute the results from the DAMA/LIBRA experiment. The SABRE Proof-of-Principle phase was carried out in 2020–2021 at the Gran Sasso National Laboratory (LNGS), in Italy. The next phase consists of two full-scale experiments: SABRE South at the Stawell Underground Physics Laboratory, in Australia, and SABRE North at LNGS. This paper focuses on SABRE South and presents a detailed simulation of the detector, which is used to characterise the background for dark matter searches including DAMA/LIBRA-like modulation. We estimate an overall background of 0.72 cpd/kg/ $$\hbox {keV}_{\hbox {{ee}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>keV</mml:mtext> <mml:mtext>ee</mml:mtext> </mml:msub> </mml:math> in the energy range 1–6 $$\hbox {keV}_{\hbox {{ee}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>keV</mml:mtext> <mml:mtext>ee</mml:mtext> </mml:msub> </mml:math> primarily due to radioactive contamination in the crystals. Given this level of background and considering that the SABRE South has a target mass of 50 kg, we expect to exclude (confirm) DAMA/LIBRA modulation at $$4~(5)\sigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>4</mml:mn> <mml:mspace/> <mml:mo>(</mml:mo> <mml:mn>5</mml:mn> <mml:mo>)</mml:mo> <mml:mi>σ</mml:mi> </mml:mrow> </mml:math> within 2.5 years of data taking.