Search for the exotic states at Belle

TL;DR

This paper reviews recent Belle experiment results on charmonium-like exotic states, including searches for Y(4140) and X(4350), with some new potential resonance signals observed in two-photon processes.

Contribution

It reports new measurements and searches for exotic charmonium-like states, including the observation of a narrow peak at 4350.6 MeV/c^2, expanding the understanding of these states.

Findings

No signal for Y(4140) in $ o \, o \, o$

Observation of a narrow peak at 4350.6 MeV/$c^2$

Resonant structures in $ o VV$ decays

Abstract

We review recent results on charmonium-like exotic states from the Belle experiment. The two-photon process $\gamma \gamma \to \phi \jpsi$ is measured to search for Y(4140). No signal for the $Y(4140) \to \phi \jpsi$ is observed. But a narrow peak with a significance of 3.2$\sigma$ deviations including systematic uncertainty is observed at 4350.6 MeV/$c^2$ that we named X(4350). We also search for charmonium-like states, including X(3872), Y(4140), X(3915) and X(4350), in $\Upsilon(1S)$ and $\Upsilon(2S)$ radiative decays. No significant signal of any charmonium-like state is observed. The processes $\gamma \gamma \to VV$ ($V=\omega$ or $\phi$) are also measured to search for the possible exotic states in low mass region. There are clear resonant structures in all the decay modes.