Backgrounds and sensitivity of the NEXT double beta decay experiment

M Nebot-Guinot,P Ferrario,J Martín-Albo,J Muñoz Vidal,J.J Gómez-Cadenas

doi:10.1016/j.nuclphysbps.2015.10.006

Abstract

NEXT (Neutrino Experiment with a Xenon TPC) is a neutrinoless double-beta (ββ0ν) decay experiment that will operate at the Canfranc Underground Laboratory (LSC). It is an electroluminescent high-pressure gaseous xenon Time Projection Chamber (TPC) with separate read-out planes for calorimetry and tracking. Energy resolution and background suppression are the two key features of any neutrinoless double beta decay experiment. NEXT has both good energy resolution (<1% FWHM) at the Q value of 136Xe and an extra handle for background identification provided by track reconstruction. With the background model of NEXT, based on the detector simulation and the evaluation of the detector radiopurity, we can determine the sensitivity to a measurement of the ββ2ν mode in NEW and to a ββ0ν search in NEXT100. In this way we can predict the background rate of 5×10−4 counts/(keV kg yr), and a sensitivity to the Majorana neutrino mass down to 100 meV after a 5-years run of NEXT100.

Highlights

Background modelA detailed simulation of the detector performance has been implemented in NEXUS, the Geant4-based simulation program of the experiment
Considering the finite energy resolution (∆E) of any detector, other processes occurring in the detector, as the tail of the ββ2ν mode, can fall in the region of energies around Qbb becoming background
The NEXT-100 detector will search for the neutrinoless double beta decay of 136Xe at the Laboratorio Subterraneo de Canfranc

Summary

Neutrinoless double beta decay

Neutrinoless double beta decay (ββ0ν) is a postulated nuclear transition in which two neutrons undergo β decay simultaneously without the emission of neutrinos. Evidence of this process would establish that massive neutrinos are Majorana particles, provide a hint of a new physics scale beyond the Standard Model and prove the violation of total lepton number, a key element to explain the observed asymmetry between matter and antimatter in the universe. The measurement of the ββ0ν-decay rate would provide information on the absolute scale of neutrino masses [1], as shown in Eq.: T

Double beta decay experiments

NEXT-100

Background model

Analysis and Sensitivity