Speaker
Description
The exploration of physics Beyond the Standard Model within nuclear physics is closely tied to the investigation of rare electroweak transitions. The most promising process correspond to the neutrinoless double-beta decay ($0\nu\beta\beta$) which is a transition in nuclei where two neutrons simultaneously transform into two protons, accompanied by the emission of only two electrons [1]. This second-order decay, if observed, would prove that neutrinos are Majorana particles (their own antiparticles), shed light on the existence of massive neutrinos, and help explain the predominance of matter over antimatter in the universe.
The half-lives depend on the square of the nuclear matrix elements (NMEs), which must be computed since $0\nu\beta\beta$ has not been observed yet.
In this talk, I will discuss computations of the NMEs at the next-to-next-to-leading order (N$^2$LO) [2] corrections within the nuclear shell model (NSM) and quasi-particle random phase approximation frameworks. These calculations aim to reduce the uncertainty surrounding the NMEs. Then, I will briefly present new predictions for two-neutrino $\beta\beta$ half-lives from $0^+$ ground state to the first $0^+$ excited state [3] with novel next-to-leading order (NLO) terms [4] at the NME level.
M. Agostini et al. Rev. Mod. Phys. 95, 025002 (2023)
L. Jokiniemi, D. Castillo, P. Soriano, J. Menéndez, Phys. Lett. B 860, 139181 (2025).
D. Castillo, D. Frycz, B. Benavente, J. Menéndez, arXiv:2507.21868
S. el Morabit et al. JHEP 06, 082 (2025)
