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.