Speaker
Description
The neutrinoless double beta decay $0\nu\beta\beta$ is of fundamental importance for particle physics, nuclear physics, and cosmology. The amplitude for the $0\nu\beta\beta$ decay of the two-neutron system $nn\rightarrow ppe^-e^-$ is a key building block to calculate the $0\nu\beta\beta$ decay in nuclei employed in large-scale experimental searches. Assuming that $0\nu\beta\beta$ decay is mediated by a light-Majaorana-neutrino exchange, an analysis based on the standard nonrelativistic chiral effective field theory (EFT) shows that already at leading order (LO) a contact decay operator is required to ensure renormalizability. So far, the size of this contact operator is still uncertain and has only been estimated by a generalized Cottingham model.
In this presentation, we will show that such a LO contact operator is not needed for renormalizability in the manifestly Lorentz invariant formulation of chiral EFT. We will present, for the first time, the predictions of $nn\rightarrow ppe^-e^-$ amplitude up to the next-to-leading order, where to this order no uncertain contact operators appear. We will discuss the validation of the present approach, and compare the results with the previous estimation from the generalized Cottingham model.
