Search for the baryon number and lepton number violating decays $\tau^{\mathstrut -} \to \Lambda \pi^{\mathstrut -}$ and $\tau^{\mathstrut -} \to \bar\Lambda \pi^{\mathstrut -}$ at Belle II
Abstract
We present a search for the baryon number $B$ and lepton number $L$ violating decays $\tau^- \rightarrow \Lambda \pi^-$ and $\tau^- \rightarrow \bar{\Lambda} \pi^-$ 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 $\tau^- \rightarrow \Lambda\pi^-$ and $\tau^- \rightarrow \bar{\Lambda}\pi^-$ are determined to be $4.7 \times 10^{-8}$ and $4.3 \times 10^{-8}$, respectively.
@article{Belle-II:2024ynh,
author = "Adachi, I. and others",
collaboration = "Belle-II",
title = "{Search for the baryon number and lepton number violating decays {\ensuremath{\tau}}-{\textrightarrow}{\ensuremath{\Lambda}}{\ensuremath{\pi}}- and {\ensuremath{\tau}}-{\textrightarrow}{\ensuremath{\Lambda}}{\textasciimacron}{\ensuremath{\pi}}- at Belle II}",
eprint = "2407.05117",
archivePrefix = "arXiv",
primaryClass = "hep-ex",
reportNumber = "Belle II Preprint 2024-020; KEK Preprint 2024-17",
doi = "10.1103/PhysRevD.110.112003",
journal = "Phys. Rev. D",
volume = "110",
number = "11",
pages = "112003",
year = "2024"
}