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

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.Comment: 17 pages, 3 figures, 3 tables. Final manuscript accepted for publication in Phys. Lett. B. Parts of the text slightly expanded or rearranged; results are unchange

Measurement of the two photon decay of the χc0(13P0) state of charmonium

AbstractWe report on the decay to two photons of the χc0(13P0) charmonium resonance formed in p̄p interactions at Fermilab experiment E835. We have measured the product of branching ratios BR(χc0→p̄p)×BR(χc0→γγ)=(6.52±1.18(stat)+0.48−0.72(sys))×10−8. Using values from the 2002 PDG, this measurement leads to the partial width Γ(χc0→γγ)=2.9±0.9 keV

Measurement of the Resonance Parameters of the χ1(13P1)\chi_{1}(1^3P_1) and χ2(13P2)\chi_{2}(1^3P_2) States of Charmonium formed in Antiproton-Proton Annihilations

We have studied the $^3P_J$ ($\chi_c)$ states of charmonium in formation by antiproton-proton annihilations in experiment E835 at the Fermilab Antiproton Source. We report new measurements of the mass, width, and $B(\chi_{cJ} \to \bar{p} p) \times \Gamma(\chi_{cJ} \to J/\psi + anything)$ for the $\chi_{c1}$ and $\chi_{c2}$ by means of the inclusive reaction $\bar{p}p \to \chi_{cJ} \to J/\psi + anything \to (e^{+}e^{-}) +anything$. Using the subsample of events where $\chi_{cJ} \to \gamma + J/\psi \to \gamma + (e^{+}e^{-})$ is fully reconstructed, we derive $B(\chi_{cJ} \to \bar p p)\times \Gamma(\chi_{cJ} \to J/\psi + \gamma)$. We summarize the results of the E760 (updated) and E835 measurements of mass, width and $B(\chi_{cJ} \to \bar{p}p) \Gamma(\chi_{cJ} \to J/\psi+\gamma)$ (J=0,1,2) and discuss the significance of these measurements

E835 at FNAL: Charmonium Spectroscopy in Annihilations

I present preliminary results on the search for hc in its ηcγ and J/ψπ0 decay modes. We observe an excess of ηcγ events near 3526 MeV that has a probability P ∼ 0.001 to arise from background fluctations. The resonance parameters are M = 3525.8±0.2±0.2 MeV, Γ ≤ 1 MeV, and 10.6±3.7±3.4(br) < Γp̄pBηcγ < 12.8±4.8±4.5 (br) eV. We find no event excess within the search region in the J/ψπ0 mode. © 2005 Elsevier B.V. All rights reserved

Results of a search for the hc(1P1) state of charmonium in the \u3b7c\u3b3 and J/\u3c8\u3c00 decay modes

We report evidence for the hc state of charmonium in its \u3b7c\u3b3 decay mode and lack of evidence in the J/\u3c8\u3c00 mode. We studied these channels in p\u304p annihilations near the center of gravity of the PJ3 states, where the hc was reported in the J/\u3c8\u3c00 mode by E760, our previous experiment, at 3526.2\ub10.15\ub10.2MeV, with \u393R 641MeV. We observe an event excess in the \u3b7c\u3b3 mode near 3526 MeV. Testing the null hypothesis of a linearly varying background cross section against the alternate hypothesis that includes a resonance near 3526 MeV, we reject the null hypothesis with P 3c0.001. The resonance mass is 3525.8\ub10.2\ub10. 2MeV and the resonance width 641MeV. We estimate 10.0\ub13. 5<\u393p\u304pB\u3b7c\u3b3<12.0\ub14.5eV, corresponding to fixed values 0.5<\u393R<1.0MeV. We find no event excess within the search region in the J/\u3c8\u3c00 mode. \ua9 2005 The American Physical Society