Search for a heavy neutral lepton that mixes predominantly with the tau neutrino

Sumitted to PubDB: 2023-05-24

Category: Master Thesis, Visibility: Public

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Authors	Ori Fogel, Abner Soffer
Date	Jan. 1, 2023
Belle II Number	BELLE2-MTHESIS-2023-016
Abstract	Heavy neutral leptons (HNLs) are highly motivated as a solution to the problems of neutrino masses, dark matter and the baryon asymmetry of the universe. In light of tight limits set by previous searches for HNLs that mix with electron and muon neutrinos, we search for an HNL that mixes predominantly with the tau neutrino. Such an HNL can be produced in tau decays, which are best studied in B-factory experiments. We search for the HNL in a sample of 8.8x10^8 e+e− → τ +τ − events collected by the Belle experiment at center-of-mass energies around 10.58 GeV. The search focuses on long-lived HNLs with mass in the range 0.3-1.6 GeV exploiting the displaced-vertex signature for suppressing background. We set a new expected limit on the mixing between the HNL and ντ .
Conference	Tel Aviv