Study of a spherical Xenon gas TPC for neutrinoless double beta detection

Abstract

A: Several efforts are ongoing for the development of spherical gaseous time projection chamber detectors for the observation of rare phenomena such as weakly interacting massive particles or neutrino interactions. The proposed detector, thanks to its simplicity, low energy threshold and energy resolution, could be used to observe the ββ0ν process i.e. the neutrinoless double beta decay. In this work, a specific setup is presented for the measurement of ββ0ν on 50 kg of 136 Xe. The different backgrounds are studied, demonstrating the possibility to reach a total background per year in the detector mass at the level of 2 events per year. The obtained results are competitive with the present generation of experiments and could represent the first step of a more ambitious roadmap including the ββ0ν search with different gases with the same detector and therefore the same background sources. The constraints in terms of detector constructions and material purity are also addressed, showing that none of them represents a show stopper for the proposed experimental setup.

R2D2 spherical TPC: first energy resolution results

“…Concerning energy resolution, high pressure gas TPC could in principle achieve a sub-percent energy resolution at the relevant Q ββ , which was demonstrated so far in ionization mode up to 60 bar [13]. Assuming an energy resolution of 1% FWHM at the xenon Q ββ of 2.458 MeV, the sensitivity of a detector filled with 136 Xe at a pressure of 40 bars was investigated [14], and the obtained results are indeed the origin of the R2D2 R&D effort. A detector of 200 kg of 136 Xe could reach values of effective neutrino mass in the range 35 -70 meV, improving the current world best sensitivity by a factor of two [7], whereas a ton scale detector could cover the inverted mass hierarchy region, measuring a neutrino effective mass of the order of 10 meV.…”

“…Expected sensitivity for neutrinoless double beta decay search using a SPC in terms of its mass assuming the parameters of Ref. [14] for one year of operation (left). The width of the blue band is due to the uncertainty on the nuclear matrix elements which are used to convert the limit on the lifetime to the limit on the effective mass.…”

Preliminary results of the R2D2 project

“…A dedicated simulation was developed to assess the detector sensitivity [2]: with 50 kg xenon at 40 bars in a sphere of 37 cm radius, in one year a limit on the 0ν ββ half life of 2.5 × 10 25 years can be obtained, corresponding to an effective mass m ee smaller than 160 -330 meV depending on the matrix element values. The estimated efficiency is at the level of 64% and the expected number of background events in the ROI is 2 events per year.…”

A simulation framework for Spherical Proportional Counters

“…R2D2 (Rare Decays with a Radial Detector) [3] aims to use SPCs in the search for neutrinoless double beta decay (0ν ββ). Such a search requires excellent energy resolution of order 1% full-width…”

“…Spherical proportional counters [1] (SPCs), are novel gaseous detectors with multiple applications including searching for low-mass dark matter [2], neutrinoless double beta decay measurements [3,4] and neutron spectroscopy [5,6]. A simulation framework has been developed to study SPCs [7] by combining the Geant4 [8] and Garfield++ [9] toolkits.…”