Erratum to: Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of 136 Xe

We correct an overestimation of the production rate of 137 Xe in the DARWIN detector operated at LNGS. This formerly dominant intrinsic background source is now at a level similar to the irreducible background from solar 8 B neutrinos, thus unproblematic at the LNGS depth. The projected half-life sensitivity for the neutrinoless double beta decay (0 νββ ) of 136 Xe improves by 22% compared to the previously reported number and is now T 0 ν 1 / 2 = 3 . 0 × 10 27 yr (90% C.L.) after 10 years of DARWIN operation.


Abstract
We correct an overestimation of the production rate of 137 Xe in the DARWIN detector operated at LNGS.This formerly dominant intrinsic background source is now at a level similar to the irreducible background from solar 8 B neutrinos, thus unproblematic at the LNGS depth.The projected half-life sensitivity for the neutrinoless double beta decay (0νββ) of 136 Xe improves by 22% compared to the previously reported number and is now 0ν 1/2 = 3.0 × 10 27 yr (90% C.L.) after 10 years of DARWIN operation.
Erratum to: Eur.Phys.J. C https://doi.org/10.1140/epjc/s10052-020-8196-zDetailed MC simulation studies of muon-induced neutrons [1] revealed our initial overestimation of the 137 Xe activation by neutron capture on 136 Xe in the DARWIN TPC located at LNGS.The in-situ 137 Xe production rate must be corrected to (0.82 ± 0.10) atoms/(t•yr), a factor of 8.4 lower than the initially estimated value.This reduces the previously-dominant intrinsic background contribution from 137 Xe to a level similar to the 8 B neutrino background via ν-e − scattering.This increased importance of the formerly subdominant 8 B background calls for a revision of its initially simplified calculation.The neutrino flux spectrum is now convolved with the energy-dependent electron neutrino survival probability P ee (E ν ), according to the MSW-LMA solution [2].Accordingly, Table 3 and Figures 6, 7 and 8 of the initial manuscript are corrected.
The DARWIN sensitivity to the 0νββ decay of 136 Xe is recalculated with the updated background rates.The figureof-merit estimator (section 6.1 of the original manuscript) projects a half-life sensitivity at 90% confidence level (C.L.) of T 0ν 1/2 = 2.7 × 10 27 yr (1.7 × 10 27 yr) after 10 (4) years of exposure.The frequentist profile-likelihood analysis (section 6.2) yields a T 0ν 1/2 sensitivity limit of 3.0 × 10 27 yr for a 10 year exposure with 5 t fiducial mass.The corresponding 3 σ discovery potential after 10 years is 1.3 × 10 27 yr.
The now corrected intrinsic background is dominated by the β-decay of 214 Bi in the baseline scenario (black in Figure 8).Reducing the BiPo tagging inefficiency to 0.1% leads The original article can be found online at https://doi.org/10.1140/epjc/s10052-020-8196-z. a e-mail: Fabian.Kuger@physik.uni-freiburg.deb e-mail: patricia.sanchez@physik.uzh.chc e-mail: darwin@lngs.infn.itd Also at University of Banja Luka, Bosnia and Herzegovina e Now at SLAC, Menlo Park, CA 94025, USA f Also at Institute for Subatomic Physics, Utrecht University, Utrecht, The Netherlands g Also at Coimbra Polytechnic-ISEC, Coimbra, Portugal h Also at SISSA, Data Science Excellence Department, Trieste, Italy   Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material.If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.To view a copy of this licence, visit http://creativecomm ons.org/licenses/by/4.0/.Funded by SCOAP 3 .SCOAP 3 supports the goals of the International Year of Basic Sciences for Sustainable Development.

Fig. 6
Fig. 6 Background rate in the ROI versus fiducial mass.External contributions are combined.Fiducial volume independent intrinsic sources are shown per contribution.Bands indicate ±1 σ uncertainties

Fig. 7
Fig. 7 Predicted background spectrum around the 0νββ-ROI for the 5 t fiducial volume.A hypothetical signal of 0.5 counts per year corresponding to T 0ν 1/2 ≈ 2 × 10 27 yr is shown for comparison.Bands indicate ±1 σ uncertainties

Table 3
Expected background index averaged in the 0νββ-ROI of [2435-2481] keV, the corresponding event rate in the 5 t FV and the relative uncertainty by origin