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DOE OSTI ยท 3024492

Lattice calculation of short-range contributions to neutrinoless double-beta decay ๐œ‹ โˆ’ โ†’ ๐œ‹ + โข๐‘’โข๐‘’ at physical pion mass

Boyle, Peter [Brookhaven National Laboratory (BNL), Upton, NY (United States); University of Edinburgh, Scotland (United Kingdom)] (ORCID:0000000289601587)ยทErben, Felix [European Organization for Nuclear Research (CERN), Geneva (Switzerland)] (ORCID:0000000284061307)ยทFeng, Xu [Peking University, Beijing (China)] (ORCID:0000000208560649)ยทFlynn, Jonathan M. [University of Southampton (United Kingdom)] (ORCID:0000000262801677)ยทGarron, Nicolas [Liverpool Hope University (United Kingdom); University of Liverpool (United Kingdom)] (ORCID:0000000244283984)ยทIzubuchi, Taku [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000304575322)ยทJin, Luchang [University of Connecticut, Storrs, CT (United States)] (ORCID:0000000308064183)ยทMukherjee, Rajnandini [University of Edinburgh, Scotland (United Kingdom); University of Southampton (United Kingdom)] (ORCID:0000000310158533)ยทTsang, J. Tobias [European Organization for Nuclear Research (CERN), Geneva (Switzerland); University of Liverpool (United Kingdom)] (ORCID:0000000187783543)ยทTuo, Xin-Yu [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000310273283)
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Abstract

Neutrinoless double-beta (0โข๐œˆโข๐›ฝโข๐›ฝ) decays provide an excellent probe for determining whether neutrinos are Dirac or Majorana fermions. The short-range matrix elements associated with the ๐œ‹ โˆ’ โ†’ ๐œ‹ + โข๐‘’โข๐‘’ process contribute at leading order in the 0โข๐œˆโข๐›ฝโข๐›ฝ decay channel ๐‘›โข๐‘› โ†’ ๐‘โข๐‘โข๐‘’โข๐‘’ 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 ๐œ‹ โˆ’ โ†’ ๐œ‹ + โข๐‘’โข๐‘’ 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 nonperturbative renormalization in the regularization-independent symmetric momentum-subtraction scheme (RI/SMOM), using the (๐›พ ๐œ‡ , ๐›พ ๐œ‡ ) and ($\not{๐‘ž}$, $\not{๐‘ž}$) projectors. 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.

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Boyle, Peter [Brookhaven National Laboratory (BNL), Upton, NY (United States); University of Edinburgh, Scotland (United Kingdom)] (ORCID:0000000289601587), Erben, Felix [European Organization for Nuclear Research (CERN), Geneva (Switzerland)] (ORCID:0000000284061307), Feng, Xu [Peking University, Beijing (China)] (ORCID:0000000208560649), Flynn, Jonathan M. [University of Southampton (United Kingdom)] (ORCID:0000000262801677), Garron, Nicolas [Liverpool Hope University (United Kingdom); University of Liverpool (United Kingdom)] (ORCID:0000000244283984), Izubuchi, Taku [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000304575322), Jin, Luchang [University of Connecticut, Storrs, CT (United States)] (ORCID:0000000308064183), Mukherjee, Rajnandini [University of Edinburgh, Scotland (United Kingdom); University of Southampton (United Kingdom)] (ORCID:0000000310158533), Tsang, J. Tobias [European Organization for Nuclear Research (CERN), Geneva (Switzerland); University of Liverpool (United Kingdom)] (ORCID:0000000187783543), Tuo, Xin-Yu [Brookhaven National Laboratory (BNL), Upton, NY (United States)] (ORCID:0000000310273283). 2026-03-04. Lattice calculation of short-range contributions to neutrinoless double-beta decay ๐œ‹ โˆ’ โ†’ ๐œ‹ + โข๐‘’โข๐‘’ at physical pion mass. https://doi.org/10.1103/pf3g-kmcr

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