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

TL;DR

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

Contribution

First search for charge-parity-even charmonium states in $
S$ radiative decays, establishing upper limits and exploring potential new states.

Findings

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

Set 90% C.L. upper limits on branching fractions.

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

Abstract

Using a sample of 102 million $\Upsilon(1S)$ events collected with the Belle detector, we report on the first search for charge-parity-even charmonium and charmonium-like states in $\Upsilon(1S)$ radiative decays. No significant $\chi_{cJ}$ or $\eta_c$ signal is observed and 90% C.L. limits on $\BR(\Upsilon(1S)\to \gamma \chi_{c0})<6.5 \times 10^{-4}$, $\BR(\Upsilon(1S)\to \gamma \chi_{c1})<2.3\times 10^{-5}$, $\BR(\Upsilon(1S)\to \gamma \chi_{c2})<7.6 \times 10^{-6}$, and $\BR(\Upsilon(1S)\to \gamma \eta_c)<5.7\times 10^{-5}$ are obtained. The product branching fraction limits $\BR(\Upsilon(1S)\to \gamma X(3872)) \BR(X(3872)\to\pi^+\pi^-\jpsi)< 1.6 \times 10^{-6}$, $\BR(\Upsilon(1S)\to \gamma X(3872)) \BR(X(3872)\to\pi^+\pi^-\pi^0 \jpsi)< 2.8\times 10^{-6}$, $\BR(\Upsilon(1S)\to \gamma X(3915)) \BR(X(3915)\to\omega \jpsi)< 3.0\times 10^{-6}$, and $\BR(\Upsilon(1S)\to \gamma Y(4140)) \BR(Y(4140)\to \phi \jpsi)<2.2\times 10^{-6}$ are obtained at the 90% C.L. Furthermore, no evidence is found for excited charmonium states below 4.8 GeV/$c^2$.