Speaker
Ori Fogel
(Tel Aviv University)
Description
The Belle and Belle~II experiment have collected samples of $e^+e^-$ collision data at centre-of-mass energies near the $\Upsilon(nS)$ resonances. These data have constrained kinematics and low multiplicity which allow searches for new long-lived particles in the mass range from a few MeV to 10~GeV. Belle II has searched for a long-lived scalar particle $S$ produced in $B\to KS$ decays using $189~\mathrm{fb}^{-1}$ of data. Using tau-lepton decays in a 915~fb$^{-1}$ sample, Belle has searched for a long-lived heavy neutral lepton that mixes primarily with the tau neutrino.
