Search for the baryon number and lepton number violating decays ${\tau }^{-}\to \Lambda {\pi }^{-}$ and ${\tau }^{-}\to \bar{\Lambda }{\pi }^{-}$ at Belle II

Abstract

We present a search for the baryon number $B$ and lepton number $L$ violating decays ${\tau }^{-}\to \Lambda {\pi }^{-}$ and ${\tau }^{-}\to \bar{\Lambda }{\pi }^{-}$ produced from the $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ process, using a 364 fb${}^{-1}$ data sample collected by the Belle~II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have $|\Delta (B-L)|$ equal to $2$ and $0$, respectively. Upper limits at 90\% credibility level on the branching fractions of ${\tau }^{-}\to \Lambda {\pi }^{-}$ and ${\tau }^{-}\to \bar{\Lambda }{\pi }^{-}$ are determined to be $4.7\times 10^{-8}$ and $4.3\times 10^{-8}$, respectively.

8 pages, 4 figures

References in corpus (11)

• An Introduction to PYTHIA 8.2
• Matching perturbative and Parton Shower corrections to Bhabha process at flavour factories
• Photon pair production at flavour factories with per mille accuracy
• Tau and muon pair production cross-sections in electron-positron annihilations at sqrt{s} = 10.58 GeV
• Neutrino Masses, Grand Unification, and Baryon Number Violation
• Searches for the baryon- and lepton-number violating decays $B^0\to {\Lambda }_c^{+}{\ell }^{-}$, $B^{-}\to \Lambda {\ell }^{-}$, and $B^{-}\to \bar{\Lambda }{\ell }^{-}$
• Measurement of the integrated luminosity of data samples collected during 2019-2022 by the Belle II experiment
• Standard Model Baryon Number Violation Seeded by Black Holes
• The Electroweak Sphaleron in a strong magnetic field
• On the phenomenology of sphaleron-induced processes at the LHC and beyond
• Search for lepton-flavor-violating ${\tau }^{-}\to {\mu }^{-}{\mu }^{+}{\mu }^{-}$ decays at Belle II