P. Rumerio

New measurements of the resonance parameters of the χc0(13P0) state of charmonium

Abstract The resonance parameters of the χ c 0 , the 1 3 P 0 state of charmonium, have been measured at the Fermilab Antiproton Accumulator in the reaction p p→χ c0 →γJ/ψ→γ(e + e − ) . A large data sample collected during the year 2000 run yields the results: M ( χ c 0 )=3415.4±0.4±0.2xa0MeV/ c 2 , Γ ( χ c 0 )=9.8±1.0±0.1xa0MeV, B (χ c0 → p p)× B (χ c0 →γJ/ψ)× B (J/ψ→(e + e − ))=(1.61±0.11±0.08)×10 −7 . Taking B (χ c0 →γJ/ψ) and B (J/ψ→e + e − ) from the literature, we obtain B (χ c0 → p p)=(4.1±0.3 +1.6 −0.9 )×10 −4 and Γ(χ c0 → p p)=(4.0±0.4 +1.6 −0.9 ) xa0keV.

Precision measurements of the total and partial widths of the ψ (2 S) charmonium meson with a new complementary-scan technique in over(p, ̄) p 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. It relies on precise revolution-frequency and orbit-length measurements, while making the analysis of the excitation curve almost independent of machine lattice parameters. For the {Psi}(2S) meson, by studying the processes {bar p}p {yields} e{sup +}e{sup -} and {bar p}p {yields} J/{Psi} + X {yields} e{sup +}e{sup -} + X, we measure the width {Gamma} = 290 {+-} 25(sta) {+-} 4(sys) keV and the combination of partial widths {Gamma}{sub e{sup +}e{sup -}}{Gamma}{sub {bar p}p}/{Gamma} = 579 {+-} 38(sta) {+-} 36(sys) meV, which represent the most precise measurements to date.

Measurement of the resonance parameters of the χ1(13P1) and χ2(13P2) states of charmonium formed in antiproton–proton annihilations

The authors have studied the {sup 3}P{sub J} ({chi}{sub e}) states of charmonium in formation by antiproton-proton annihilations in experiment E835 at the Fermilab Antiproton Source. The authors report new measurements of the mass, width, and B({chi}{sub cJ} {yields} {bar p}p) x {Lambda}({chi}{sub eJ} {yields} J/{psi} + anything) for the {chi}{sub c1} and {chi}{sub c2} by means of the inclusive reaction {bar p}p {yields} {chi}{sub cJ} {yields} J/{psi} + anything {yields} (e{sup +}e{sup -}) + anything. Using the subsample of events where {chi}{sub cJ} {yields} {gamma} + J/{psi} {yields} {gamma} + (e{sup +}e{sup -}) is fully reconstructed, we derive B({chi}{sub cJ} {yields} {bar p}p) x {Lambda}({chi}{sub cJ} {yields} J/{psi} + {gamma}). They summarize the results of the E760 (updated) and E835 measurements of mass, width and B({chi}{sub cJ} {yields} {bar p}p){Lambda}({chi}{sub cJ} {yields} J/{psi} + {gamma}) (J = 0,1,2) and discuss the significance of these measurements.

Study of (p)over-bar-p -> two neutral pseudoscalar mesons at the chi(c0)(1(3)P(0)) formation energy

Fermilab experiment E835 has studied reactions bar{p}p -> pi0 pi0, pi0 eta, eta eta, pi0 eta and eta eta in the energy region of the chi_c0(1^3P_0) from 3340 MeV to 3470 MeV. Interference between resonant and continuum production is observed in the pi0 pi0 and eta eta channels, and the product of the input and output branching fractions is measured. Limits on resonant production are set for the pi0 eta and pi0 eta channels. An indication of interference is observed in the eta eta channel. The technique for extracting resonance parameters in an environment dominated by continuum production is described.

Measurement of the branching ratios ψ′→e+e-, ψ′→J/ψππ, and ψ′→J/ψη

We have measured several branching ratios for

E835 at FNAL: Charmonium Spectroscopy in p̄p Annihilations

psi^prime

Measurement of the angular distribution in p¯p→ψ(2S)→e+e−

decay using the data collected by FNAL E835 experiment during year 2000, obtaining

Measurement of the angular distribution in p̄p→ψ(2S) →e+e-

{cal B}(psi^prime to e^+ e^-) = 0.0068pm0.0001pm0.0004

Interference Study of the χc0(13P0) in the Reaction p¯p→π0π0

,

E835 at FNAL: Charmonium Spectroscopy in Annihilations

{cal B}(psi^prime to J/psi pi^+ pi^-) = 0.292pm0.005pm0.018