The E760 Collaboration performed an experiment in the Antiproton Accumulator at Fermilab to study the two photon decay of the ηc(1 1S0) charmonium state formed in p̄p annihilations. This resulted in a new measurement of the mass Mηc=2988.3-3.1+3.3 MeV/c2 and of the product B(ηc→p̄p)×Γ(ηc→γγ) =(8.1-2.0+2.9) eV. We performed a search for the process p̄p→ηc′(2 1S0)→γγ over a limited range of center-of-mass energies. Since no signal was observed, we derived upper limits on the product of branching ratios B(ηc′→p̄p)×B(ηc′→γγ) in the center-of-mass energy range 3584≤ s ≤3624 MeV. We observed no signal for the nonresonant process p̄+p→γ+γ and obtain upper limits.
ASJC Scopus subject areas
- Nuclear and High Energy Physics