Measurements of the Mass, total Width and Two-Photon Partila Width of the $\eta_{c}$ Meson

TL;DR

This study precisely measures the mass, total width, and two-photon partial width of the $$ meson using data from the CLEO detector, providing important parameters for understanding charmonium states.

Contribution

First precise measurement of the $$ meson parameters including mass, width, and two-photon partial width using a large dataset from the CLEO detector.

Findings

$$ mass measured at 2980.4 MeV

Total width of $$ is 27.0 MeV

Two-photon partial width is 7.6 keV

Abstract

Using 13.4 $fb^{-1}$ of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudo-scalar charmonium in the decay $\eta_c$ -> $K_S K^{\mp} \pi^{\pm}$. We have measured the $\eta_c$ mass to be (2980.4 +- 2.3 (stat) +- 0.6 (sys)) MeV and its full width as (27.0 +- 5.8 (stat) +- 1.4 (sys)) MeV. We have determined the two-photon partial width of the $\eta_c$ meson to be (7.6 +- 0.8 (stat) +- 0.4 (sys) +- 2.3 (br)) keV, with the last uncertainty associated with the decay branching fraction.