Charmonium Production at FNAL-E835 - Triplet P States

Fermilab experiment E835 has done an extensive set of studies on charmonium triplet P states. The most precise measurements on mass and total width come indeed from charmonium spectroscopy by direct formation of $c\bar{c}$ states in $\bar{p}p$ annihilations. Results on both partial widths and higher multipoles radiative transitions $\chi_{cJ} \to J/\psi \gamma \to \gamma e^+ e^-$ are given, together with the $\gamma \gamma$ widths of $\chi_{c0}$ and $\chi_{c2}$. For the first time in hadronic charmonium production, hadronic annihilation channels ($\pi^0 \pi^0$ and $\eta \eta$) have been clearly identified at the $\chi_{c0}$ resonance.