Neutrinoless double beta decay and chiral SU(3)

TeV-scale lepton number violation can affect neutrinoless double beta decay through dimension-9 Delta L = AI = 2 operators involving two electrons and four quarks. Since the dominant effects within a nucleus are expected to arise from pion exchange, the pi(-) -> pi(+) ee matrix elements of the dimension-9 operators are a key hadronic input. In this letter we provide estimates for the pi(-) -> pi(+) matrix elements of all Lorentz scalar Delta I = 2 four-quark operators relevant to the study of TeV-scale lepton number violation. The analysis is based on chiral SU(3) symmetry, which relates the pi(-) -> pi(+) matrix elements of the Delta I = 2 operators to the K-0 -> (K) over bar (0) and K -> pi pi matrix elements of their Delta S = 2 and Delta S =1 chiral partners, for which lattice QCD input is available. The inclusion of next-to-leading order chiral loop corrections to all symmetry relations used in the analysis makes our results robust at the 30% level or better, depending on the operator. (C) 2017 The Author(s). Published by Elsevier B.V.