Precision measurements of the total and partial widths of the psi(2S) charmonium meson with a new complementary-scan technique in antiproton-proton annihilations

TL;DR

This paper reports highly precise measurements of the psi(2S) charmonium meson's total and partial widths using a novel complementary-scan technique in antiproton-proton annihilations, improving the accuracy of resonance parameters.

Contribution

A new complementary-scan method was developed for studying narrow resonances, reducing dependence on machine lattice parameters and enhancing measurement precision.

Findings

Measured psi(2S) total width as 290 ± 25(stat) ± 4(sys) keV.

Determined the partial width product as 579 ± 38(stat) ± 36(sys) meV.

Achieved the most precise resonance width measurements to date.

Abstract

We present new precision measurements of the psi(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 psi(2S) meson through the processes pbar p -> e+ e- and pbar p -> J/psi + X -> e+ e- + X. We measure the width to be Gamma = 290 +- 25(sta) +- 4(sys) keV and the combination of partial widths Gamma_e+e- * Gamma_pbarp / Gamma = 579 +- 38(sta) +- 36(sys) meV, which represent the most precise measurements to date.