We search for lepton-flavor-violating τ→eα and τ→μα decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8 fb-1, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ→eν_{e}ν_{τ} and τ→μν_{μ}ν_{τ} decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ→eα)/B(τ→eν_{e}ν_{τ}) in the range (1.1-9.7)×10^-3 and on B(τ→μα)/B(τ→μν_{μ}ν_{τ}) in the range (0.7-12.2)×10^-3 for α masses between 0 and 1.6 GeV/c2. These results provide the most stringent bounds on invisible boson production from τ decays.
Search for Lepton-Flavor-Violating τ Decays to a Lepton and an Invisible Boson at Belle II
Bettarini, S;Casarosa, G;Corona, L;Forti, F;Massaccesi, L;Paoloni, E;Rizzo, G;Tenchini, F;
2023-01-01
Abstract
We search for lepton-flavor-violating τ→eα and τ→μα decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8 fb-1, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ→eν_{e}ν_{τ} and τ→μν_{μ}ν_{τ} decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ→eα)/B(τ→eν_{e}ν_{τ}) in the range (1.1-9.7)×10^-3 and on B(τ→μα)/B(τ→μν_{μ}ν_{τ}) in the range (0.7-12.2)×10^-3 for α masses between 0 and 1.6 GeV/c2. These results provide the most stringent bounds on invisible boson production from τ decays.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
