Sensitivity of NEXT-100 to neutrinoless double beta decay

TL;DR

NEXT-100 is a high-pressure xenon gas detector with excellent energy resolution and track reconstruction, designed to search for neutrinoless double beta decay of Xe-136 with high sensitivity and low background.

Contribution

This paper demonstrates the expected sensitivity of NEXT-100 to neutrinoless double beta decay, including detailed background estimates and detector performance predictions.

Findings

Background rate predicted at most 4×10⁻⁴ counts keV⁻¹ kg⁻¹ yr⁻¹

Sensitivity to decay half-life of 2.8×10²⁵ years after 1 year of data

Potential to reach 6.0×10²⁵ years after 3 years

Abstract

NEXT-100 is an electroluminescent high-pressure xenon gas time projection chamber that will search for the neutrinoless double beta ($\beta \beta 0 \nu$) decay of Xe-136. The detector possesses two features of great value for $\beta \beta 0 \nu$ searches: energy resolution better than 1\% FWHM at the $Q$ value of Xe-136 and track reconstruction for the discrimination of signal and background events. This combination results in excellent sensitivity, as discussed in this paper. Material-screening measurements and a detailed Monte Carlo detector simulation predict a background rate for NEXT-100 of at most $4\times10^{-4}$ counts keV$^{-1}$ kg$^{-1}$ yr$^{-1}$. Accordingly, the detector will reach a sensitivity to the \bbonu-decay half-life of $2.8\times10^{25}$ years (90\% CL) for an exposure of 100 $\mathrm{kg}\cdot\mathrm{year}$, or $6.0\times10^{25}$ years after a run of 3 effective years.