Study of $\bar{\Lambda}$-$p$ Annihilation into Light Mesons

The annihilation of $\bar{\Lambda}$-$p$ into light mesons is studied using $(10.087\pm0.044)\times10^{9}$ $J/\psi$ events collected with the BESIII detector at the BEPCII storage ring. The $\bar{\Lambda}$ baryons are produced in the process $J/\psi\rightarrow\Lambda\bar{\Lambda}$ and interact with the protons in the hydrogen nuclei in the cooling oil of the beam pipe. The reactions $\bar{\Lambda}p\rightarrow K^+\pi^+\pi^-$ and $K^+2\pi^+2\pi^-$ are observed for the first time, evidence for the reaction $\bar{\Lambda}p\rightarrow K^0_S2\pi^+\pi^-$ is found, and no significant signals are seen for the reactions $\bar{\Lambda}p\rightarrow K^0_S\pi^+$, $K^+3\pi^+3\pi^-$ and $2K^+K^-$. The cross sections of these reactions are also measured at $P_{\bar{\Lambda}}\approx 1.074$ GeV/$c$. Furthermore, no significant structures are observed in the combinations of the final state particles for these reactions. The annihilation of $\bar{\Lambda}$-$p$ into light mesons presents the similar behavior as $\bar{n}$-$p$ reactions in this energy region. These new measurements will serve as important inputs for the theoretical understanding of the antihyperon-nucleon interaction, and further contribute to understanding antibaryon-baryon interaction in a unified perspective.