A Search for the Singlet-P State hc(1 1P1) of Charmonium in Proton-Antiproton Annihilations at Fermilab Experiment E835p

TL;DR

This study searched for the elusive hc(1 1P1) charmonium state in proton-antiproton annihilations at Fermilab, setting upper limits on its production and decay channels without observing a significant signal.

Contribution

It provides the first experimental upper limits on the production and decay of the hc(1 1P1) state in specific channels at Fermilab energies.

Findings

No evidence for hc(1 1P1) was observed in the studied channels.

Upper limits on branching ratios were established at 90% confidence level.

The results constrain theoretical models of charmonium states.

Abstract

We present the results of a search for the spin-singlet P-wave state hc(1 1P1) of charmonium formed through proton-antiproton annihilation at Fermilab experiment E835. The decay channels whjich were studied were ppbar -> J/psi + X -> e^+e^- + X, ppbar -> J/psi + pi0 -> e^+e^- + 2gamma, ppbar -> J/psi + pi0pi0 -> e^+e^- + 4gamma, and the neutral channel ppbar -> eta_c gamma -> (2gamma) gamma. The decay ppbar -> J/psi gamma -> e^+e^- gamma, into which 1P1 decay is forbidden by C-parity conservation, was also examined for comparison The 90% confidence upper limits for the decay channels studied in the mass range 3525.1-3527.3 MeV for a 1P1 resonance with a presumed width of 1.0 MeV were determined to be B(ppbar->1P1)xB(1P1->J/psi+X) <= 1.8x10^-7, B(ppbar->1P1)xB(1P1->J/psi+pi0) <= 1.2x10^-7, and B(ppbar->1P1)xB(1P1->J/psi+gamma) <= 1.0x10^-7. No evidence for a 1P1 enhancement was observed in either of the two additional reactions studied.