A new complementary-scan technique for precise measurements of resonance parameters in antiproton-proton annihilations

A new technique for precision measurements of resonance widths in antiproton-proton annihilations is presented. It is based on the analysis of excitation curves obtained by scanning the resonance twice, at constant orbit and at constant magnetic bend field, in an antiproton storage ring. The technique relies on precise revolution- frequency and orbit-length measurements, while making the results almost independent of the machine´s phase-slip factor. The uncertainty is dominated by event statistics. The technique was recently applied by Fermilab experiment E835 at the Antiproton Accumulator to obtain the most precise measurements to date of the total and partial widths of the psi(2S) charmonium meson.