Precision measurements of the total and partial widths of the ψ(2S) charmonium meson with a new complementary-scan technique in p¯p annihilations

We present new precision measurements of the ψ(2S) total and partial widths from excitation curves obtained in antiproton-proton annihilations by Fermilab experiment E835 at the Antiproton Accumulator in the year 2000. A new technique of complementary scans was developed to study narrow resonances with stochastically cooled antiproton beams. The technique relies on precise revolution-frequency and orbit-length measurements, while making the analysis of the excitation curve almost independent of machine lattice parameters. We study the ψ(2S) meson through the processes p¯p→e+e− and p¯p→J/ψ+X→e+e−+X. We measure the width to be Γ=290±25(sta)±4(sys)keV and the combination of partial widths Γe+e−Γp¯p/Γ=579±38(sta)±36(sys)meV, which represent the most precise measurements to date.