Constraining neutrino mass from neutrinoless double beta decay

Abstract

We study the implications of the recent results on neutrinoless double beta decay (0νββ) from GERDA-I (⁷⁶Ge ) and KamLAND−Zen+EXO−200 (¹³⁶Xe) and the upper limit on the sum of light neutrino masses from Planck. We show that the upper limits on the effective neutrino mass from ¹³⁶Xe are stronger than those from ⁷⁶Ge for most of the recent calculations of the nuclear matrix elements (NMEs). We also analyze the compatibility of these limits with the claimed observation in ⁷⁶Ge and show that while the updated claim value is still compatible with the recent GERDA limit as well as the individual ¹³⁶Xe limits for a few NME calculations, it is inconsistent with the combined ¹³⁶Xe limit for all but one NME. Imposing the most stringent limit from Planck, we find that the canonical light neutrino contribution cannot saturate the current limit, irrespective of the NME uncertainties. Saturation can be reached by inclusion of the right-handed (RH) neutrino contributions in TeV-scale left-right symmetric models with type-II seesaw. This imposes a lower limit on the lightest neutrino mass. Using the 0νββ bounds, we also derive correlated constraints in the RH sector, complimentary to those from direct searches at the LHC.