Boosting background suppression in the NEXT experiment through Richardson-Lucy deconvolution

The NEXT collaboration aims to observe neutrinoless double beta decay in gaseous 136Xe using a high pressure gaseous Xe time projection chamber with signal amplification by means of electroluminescence (EL). One of the advantages of the technique is that it allows for track reconstruction making use of a sensor plane equipped with SiPMs located nearby the EL region. However, the signals recorded in the TPC are degraded by electron diffusion and spread of light produced in the EL process, limiting the potential of the detection scheme. We have recently developed an improved reconstruction procedure based on the Richardson-Lucy deconvolution [1], an iterative algorithm well-known in image processing and de-blurring. Deconvolution allows reversing the smearing mechanisms in the NEXT TPC and significantly enhances the definition of reconstructed tracks. Consequently, detector performance is strongly boosted, with a five-fold improvement in background rejection demonstrated on experimental data. The algorithm application in the context of the NEXT experiment is detailed with a focus on the performance in NEXT-White, a 50 cm TPC which operated underground at Laboratorio Subterráneo de Canfranc until July 2021. The procedure applied to characterize the optical response of the chamber and obtain the point spread function that best describes the observed signals is described.