Lattice Calculation of Short-Range Contributions to Neutrinoless Double-Beta Decay $\pi^-\to\pi^+ ee$ at Physical Pion Mass

Boyle, Peter and Erben, Felix and Feng, Xu and Flynn, Jonathan and Garron, Nicolas and Izubuchi, Taku and Jin, Luchang and Mukherjee, Rajnandini and Tsang, J. Tobias and Tuo, {Xin-Yu (2025) Lattice Calculation of Short-Range Contributions to Neutrinoless Double-Beta Decay $\pi^-\to\pi^+ ee$ at Physical Pion Mass. Arxiv. (Accepted for Publication)

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Abstract

Neutrinoless double-beta (\(0\nu\beta\beta\)) decays provide an excellent probe for determining whether neutrinos are Dirac or Majorana fermions.
The short-range matrix elements associated with the \(\pi^- \rightarrow \pi^+ ee\) process contribute at leading order in the \(0\nu\beta\beta\) decay channel \(nn \to ppee\) through pion exchange between nucleons.
However, current lattice calculations show notable discrepancies in predicting these short-range contributions.
To address this issue, we perform a lattice QCD calculation of the \(\pi^- \rightarrow \pi^+ ee\) matrix elements using domain wall fermion ensembles at the physical pion mass generated by the RBC/UKQCD Collaboration. To mitigate contamination from around‑the‑world effects, we develop a new method to reconstruct and subtract them directly from lattice data.
We then perform a nonperturbative renormalization using the RI/SMOM approach in \((\gamma_\mu,\gamma_\mu)\) and \((\slashed{q},\slashed{q})\) schemes.
Compared with previous studies, this work reduces the uncertainties in the matrix elements and provides an independent cross-check that helps to reconcile the discrepancies among previous lattice calculations.

Item Type:	Article
Faculty / Department:	Faculty of Human and Digital Sciences > School of Computer Science and the Environment
Depositing User:	Nicolas Garron
Date Deposited:	01 Sep 2025 13:45
Last Modified:	01 Sep 2025 13:45
URI:	https://hira.hope.ac.uk/id/eprint/4738

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