Γγ Decay Channels Research Articles

Two photon decay widths of charmonium resonances

E835 studies resonant charmonium formation in the Fermilab Antiproton Accumulator. Preliminary measurements of the ground state η c (1 1 S 0) and the γγ partial width of the χ 2 ( 3 P 2) are presented. Also reported are the preliminary results of the search for the η c ′ (2 1 S 0) in the γγ decay channel.

Production of η mesons in e +e − annihilations at √ s=29 GeV

Data from e +e − annihilations at 29 GeV have been used to measure the production cross section and fragmentation function of η mesons. The signal is observed in the η→ γγ decay channel. The fragmentation for p η >1.5 GeV/ c agrees well with the prediction of the Lund model, whereas the prediction of the Webber model lies above the data. The mean multiplicity is measured to be 〈 n η 〉=0.58±0.10 η mesons per hadronic event, of which 0.51 represents the direct production of η and η′ mesons in the fragmentation chain.