Speaker
Description
Neutrinoless double beta decay ($0\nu\beta\beta$) is the most promising low-energy probe of physics beyond the Standard Model (BSM). If experimental searches which are underway detect such decays, understanding which BSM theory best fits the data will require theoretical work to disentangle Standard Model contributions to the process from experimental measurements. The only known way to determine QCD contributions to the process is with lattice methods. While methods exist to calculate long-range contributions to the process without placing full nucleons on the lattice, no method has yet been demonstrated which can overcome the signal-to-noise problem for heavy-physics contact interactions between nucleons. We explore a Feynman-Hellmann (FH) method adapted for four-quark matrix elements. FH methods have previously been used to boost the signal for nuclear matrix elements with bilinear currents. Naive calculation of the summed sequential two block propagators necessary for the method are at present computationally intractable at lattice sizes which approach the physical limit. We investigate four-quark matrix elements on small lattice sizes in order to determine whether further development is justified to optimize the necessary calculations for FH at adequate sizes.