Probing νSMEFT at Belle II with displaced dilepton vertices
Abstract
The existence of right-handed (RH) neutrinos is strongly motivated by the observation of small neutrino masses and as a means to shed light on the origin of parity violation in the Standard Model (SM). Experimental searches for the corresponding mass eigenstates, referred to as heavy neutral leptons (HNLs), have been carried out in a variety of experiments and within different HNL models. In the current work we use the SM effective field theory with added RH neutrinos, known as νSMEFT, to study GeV-scale HNL production in e+e- collisions at the Belle~II experiment. We focus on leptonic decays of long-lived HNLs that produce a displaced vertex in the Belle~II detector. Accounting for detection efficiency and backgrounds, we estimate the sensitivity of Belle~II to the new-physics scale of four-fermion, Higgs-current, and dipole operators in νSMEFT. We find that for most operators, the search we propose probes large regions of parameter space that are not excluded by other searches.
Related
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- Forward decay chain reconstruction with displaced vertices in intense magnetic fields
- Probing dark-matter scenarios of Belle II excess in B+→ K+MX with K+→ π+ MX decays
- Probing neutrino compositeness with invisible and displaced signals
BibTeX
@misc{bolton2026probing,
title = {{Probing $ν$SMEFT at Belle II with displaced dilepton vertices}},
author = {Patrick D. Bolton and Fabian Esser and Lukáš Gráf and Juraj Klarić and Suchita Kulkarni and Abner Soffer},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04332},
eprint = {2609.04332},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04332},
}
RIS
TY - UNPB
TI - Probing νSMEFT at Belle II with displaced dilepton vertices
AU - Patrick D. Bolton
AU - Fabian Esser
AU - Lukáš Gráf
AU - Juraj Klarić
AU - Suchita Kulkarni
AU - Abner Soffer
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.04332
UR - https://arxiv.org/abs/2609.04332
AB - The existence of right-handed (RH) neutrinos is strongly motivated by the observation of small neutrino masses and as a means to shed light on the origin of parity violation in the Standard Model (SM). Experimental searches for the corresponding mass eigenstates, referred to as heavy neutral leptons (HNLs), have been carried out in a variety of experiments and within different HNL models. In the current work we use the SM effective field theory with added RH neutrinos, known as νSMEFT, to study GeV-scale HNL production in e^+e^- collisions at the Belle~II experiment. We focus on leptonic decays of long-lived HNLs that produce a displaced vertex in the Belle~II detector. Accounting for detection efficiency and backgrounds, we estimate the sensitivity of Belle~II to the new-physics scale of four-fermion, Higgs-current, and dipole operators in νSMEFT. We find that for most operators, the search we propose probes large regions of parameter space that are not excluded by other searches.
ER -