Measurement of $\mathcal B(\psi(3770)\to\gamma \chi_{c1})$ and search for $\psi(3770)\to\gamma \chi_{c2}$

TL;DR

This paper precisely measures the branching fraction of $oxed{ ext{psi(3770) to gamma chi_c1}}$ decay and sets an upper limit for the $oxed{ ext{psi(3770) to gamma chi_c2}}$ transition, providing key data for charmonium state studies.

Contribution

It presents the most precise measurement to date of the $oxed{ ext{psi(3770) to gamma chi_c1}}$ branching fraction and establishes an upper limit for the $oxed{ ext{psi(3770) to gamma chi_c2}}$ transition.

Findings

Branching fraction of $ ext{psi(3770) to gamma chi_c1}$ is $(2.48 imes 10^{-3})$

Upper limit for $ ext{psi(3770) to gamma chi_c2}$ is $<0.64 imes 10^{-3}$

Partial widths are $(67.5 ext{ keV})$ for $ ext{chi_c1}$ and $<17.4 ext{ keV}$ for $ ext{chi_c2}$.

Abstract

We report a measurement of the branching fraction of $\psi(3770)\to\gamma\chi_{c1}$ and search for the transition $\psi(3770)\rightarrow \gamma \chi_{c2}$ based on 2.92~fb$^{-1}$ of $e^+e^-$ data accumulated at $\sqrt{s}=3.773$~GeV with the BESIII detector at the BEPCII collider. The measured branching fraction of $\psi(3770) \rightarrow \gamma \chi_{c1}$ is $\mathcal B(\psi(3770) \rightarrow \gamma \chi_{c1})=(2.48 \pm 0.15 \pm 0.23) \times 10^{-3}$, which is the most precise measurement to date. The upper limit on the branching fraction of $\psi(3770)\rightarrow \gamma \chi_{c2}$ at a $90\%$ confidence level is $\mathcal B(\psi(3770) \rightarrow \gamma \chi_{c2})<0.64 \times 10^{-3}$. The corresponding partial widths are $\Gamma(\psi(3770) \to \gamma \chi_{c1}) =(67.5\pm 4.1\pm 6.7)$~keV and $\Gamma(\psi(3770) \to \gamma \chi_{c2}) < 17.4$~keV.