Measurement of the Resonance Parameters of the $\chi_{1}(1^3P_1)$ and $\chi_{2}(1^3P_2)$ States of Charmonium formed in Antiproton-Proton Annihilations

TL;DR

This paper reports precise measurements of the mass, width, and decay properties of the $ ext{chi}_c1$ and $ ext{chi}_c2$ charmonium states formed in antiproton-proton annihilations, advancing understanding of charmonium spectroscopy.

Contribution

The study provides new experimental measurements of resonance parameters for $ ext{chi}_c$ states, including mass, width, and branching ratios, using data from Fermilab's E835 experiment, improving previous results.

Findings

Measured mass and width of $ ext{chi}_c1$ and $ ext{chi}_c2$ states.

Determined product of branching ratios and decay widths for these states.

Updated previous measurements with higher precision.

Abstract

We have studied the $^3P_J$ ($\chi_c)$ states of charmonium in formation by antiproton-proton annihilations in experiment E835 at the Fermilab Antiproton Source. We report new measurements of the mass, width, and $B(\chi_{cJ} \to \bar{p} p) \times \Gamma(\chi_{cJ} \to J/\psi + anything)$ for the $\chi_{c1}$ and $\chi_{c2}$ by means of the inclusive reaction $\bar{p}p \to \chi_{cJ} \to J/\psi + anything \to (e^{+}e^{-}) +anything $. Using the subsample of events where $\chi_{cJ} \to \gamma + J/\psi \to \gamma + (e^{+}e^{-}) $ is fully reconstructed, we derive $B(\chi_{cJ} \to \bar p p)\times \Gamma(\chi_{cJ} \to J/\psi + \gamma) $. We summarize the results of the E760 (updated) and E835 measurements of mass, width and $ B(\chi_{cJ} \to \bar{p}p) \Gamma(\chi_{cJ} \to J/\psi+\gamma)$ (J=0,1,2) and discuss the significance of these measurements.