Speaker
Description
Neutrinoless double-beta ($0\nu\beta\beta$) decay is a beyond-Standard-Model process in which two neutrons decay into two protons and two electrons, without any neutrinos in the final state. If this process is observed experimentally, this would violate lepton number conservation and demonstrate that the neutrino is a Majorana fermion, i.e., its own antiparticle. In order to interpret experimental searches, accurate calculations of $0\nu\beta\beta$ decay nuclear matrix elements (NMEs) are essential, and recent advances in first-principles, or \textit{ab initio}, methods now allow calculations of NMEs with reduced uncertainty [1]. Additionally, a recent study demonstrated that $0\nu\beta\beta$ decay and double Gamow-Teller (DGT) transition NMEs, calculated using phenomenological techniques, exhibit a strong linear correlation [2].
In this presentation, I will discuss the correlation between $0\nu\beta\beta$ and DGT NMEs calculated using the \textit{ab initio} valence space in-medium similarity renormalization group (VS-IMSRG) approach. In particular I calculate NMEs for lower fp-shell isotopes with $20 < Z < 24$ and $44 < A < 62$, and for select heavier isotopes including $^{76}$Ge, $^{82}$Se, $^{130}$Te, and $^{136}$Xe using several $NN + 3N$ interactions. These results show a strong, linear correlation between DGT decay and $0\nu\beta\beta$ decay NMEs, indicating that DGT decay, a process that is allowed by the Standard Model, can be used to experimentally constrain the NMEs of $0\nu\beta\beta$ decay, a beyond-Standard-Model process.
References
[1] A. Belley, C. G. Payne, S. R. Stroberg, T. Miyagi, and J. D. Holt, “Ab Initio Neutrinoless Double Beta Decay Matrix Elements for $^{48}$Ca, $^{76}$Ge, and $^{82}$Se”, Phys. Rev. Lett. 126, 042502 (2021).
[2] N. Shimizu, J. Menéndez, and K. Yako, “Double Gamow-Teller Transitions and its Relation to Neutrinoless $\beta\beta$ Decay”, Phys. Rev. Lett. 120, 142502 (2018).
