InterLeptons News & Co

Z′ in a final state with two muons and missing energy at Belle II -> Submitted

After an intense period of data analysis and of internal review within the Belle II Collaboration, we have submitted for publication to the Physical Review Letters the results of our search for invisible Z' boson, in events containing two muons and missing energy in the final state. This search is one of the pillars of the InterLeptons project, for which we have some time ago developed a dedicated machine learning tool, a neural-network-based method that allows to search for the Z' boson by optimizing the selection of signal and rejection of backgrounds available here. Unfortunately, no excess of events was observed, but we could exclude a large region of the parameter space hence improving by orders of magnitude our knowledge of this physics model.
A preprint of the research paper is available here.
It is also important to mention two other results that were released by the Belle II Collaboration with a significant contribution of members of our group.
- The search for an invisible alpha boson, produced in tau decays was also submitted for publication to the Physical Review Letters, the day after the Z' paper, and a preprint is available here.
- The search for an invisible (or very long-lived) dark Higgs boson produced in association to a dark photon decays to a pair of muons. A preprint is available here and the paper was recently accepted for publication in PRL.