Topical Seminar: Precission of double-beta NMEs

por Daniel Castillo García (Universidad de Barcelona)

jueves 10 jul. 2025 12:00 → 13:00 Europe/Madrid

1001-Primera-1-1-1 - Paterna. Seminario (Universe)

The exploration of physics beyond the Standard Model in nuclear physics is closely tied to investigating rare electroweak transitions. The most promising process is neutrinoless double-beta decay (0vbb), a nuclear transition where two neutrons simultaneously convert into two protons with the emission of only two electrons. If observed, this second-order decay would prove that neutrinos are Majorana particles, shed light on the existence of massive neutrinos, and help explain the matter–antimatter imbalance in the universe. The half-lives depend on the square of the nuclear matrix elements (NMEs), which must be computed since 0vbb has not yet been observed.

In this talk, I will discuss the novel corrections in chiral effective field theory for 0vbb and related second-order weak processes as 2vbb. These calculations aim to reduce uncertainty in the NMEs. First, I will present the contribution of ultrasoft (low-momentum) neutrinos, which can dominate in scenarios involving light sterile neutrinos, then show the full N2LO NME results, and provide further detailed analysis. Finally, I will briefly address the recent addition of novel next-to-leading order (NLO) terms in two-neutrino double-beta decay NMEs within the NSM, focusing on transitions from the ground state to the first 0+ excited states.