Search for charmonium and charmonium-like states in $\Upsilon(1S)$ and $\Upsilon(2S)$ radiative decays

TL;DR

This study searches for charmonium and charmonium-like states in radiative decays of $
S$ and $
2S$ using large data samples, finding no significant signals but setting upper limits on various decay branching fractions.

Contribution

First search for charge-parity-even charmonium states in $
S$ and $
2S$ radiative decays, providing the first limits on these processes.

Findings

No significant $cJ$ or $c$ signals observed.

Set 90% C.L. upper limits on branching fractions for multiple states.

No evidence for excited charmonium states below 4.8 GeV/$c^2$.

Abstract

Using samples of 102 million $\Upsilon(1S)$ and 158 million $\Upsilon(2S)$ event samples collected with the Belle detector, we report on the first search for charge-parity-even charmonium and charmonium-like states in $\Upsilon(1S)$ and $\Upsilon(2S)$ radiative decays. No significant $\chi_{cJ}$ or $\eta_c$ signal is observed and 90% C.L. limits on $\BR(\Upsilon(nS)\to \gamma \chi_{cJ})$ ($n=1,2$ and $J=1,2,3$) are obtained. No significant signal of any charmonium-like state is observed. The product branching fraction limits $\BR(\Upsilon(nS)\to \gamma X(3872))$ $\BR(X(3872)\to\pi^+\pi^-\jpsi)$, $\BR(\Upsilon(nS)\to \gamma X(3872))$ $\BR(X(3872)\to\pi^+\pi^-\pi^0 \jpsi)$, $\BR(\Upsilon(nS)\to \gamma X(3915))$ $\BR(X(3915)\to\omega \jpsi)$, and $\BR$ $(\Upsilon(1S)\to \gamma Y(4140))\BR(Y(4140)\to \phi \jpsi)$ ($n=1,2$) are obtained at the 90% C.L. At the same time, $\BR(\Upsilon(2S) \to \gamma X(4350))\BR(X(4350)\to\phi\jpsi))$ is also determined at the 90% C.L. Furthermore, no evidence is found for excited charmonium states below 4.8 GeV/$c^2$.