Fermilab experiment E835 has measured the cross section for the reaction p̄p→e+e− at s=11.63, 12.43, 14.40 and 18.22 GeV2. From the analysis of the 66 observed events new high-precision measurements ...of the proton magnetic form factor are obtained.
We 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.
Fermilab experiment E835 has observed (-)pp annihilation production of the charmonium state chi(c0) and its subsequent decay into pi(0)pi(0). Although the resonant amplitude is an order of magnitude ...smaller than that of the nonresonant continuum production of pi(0)pi(0), an enhanced interference signal is evident. A partial wave expansion is used to extract physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate the expansion. Both are accessed by L=1 in the entrance (-)pp channel. The product of the input and output branching fractions is determined to be B((-)pp-->chi(c0))xB(chi(c0)-->pi(0)pi(0))=(5.09+/-0.81+/-0.25)x10(-7).
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.
The resonance parameters of the χc0, the 13P0 state of charmonium, have been measured at the Fermilab Antiproton Accumulator in the reaction p̄p→χc0→γJ/ψ→γ(e+e−). A large data sample collected during ...the year 2000 run yields the results: M(χc0)=3415.4±0.4±0.2 MeV/c2, Γ(χc0)=9.8±1.0±0.1 MeV, B(χc0→p̄p)×B(χc0→γJ/ψ)×B(J/ψ→(e+e−))=(1.61±0.11±0.08)×10−7. Taking B(χc0→γJ/ψ) and B(J/ψ→e+e−) from the literature, we obtain B(χc0→p̄p)=(4.1±0.3+1.6−0.9)×10−4 and Γ(χc0→p̄p)=(4.0±0.4+1.6−0.9) keV.
Experiment E835 at Fermilab Garzoglio, G.; Gollwitzer, K.; Hahn, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2004, Letnik:
519, Številka:
3
Journal Article
Recenzirano
We provide a comprehensive description of experiment E835 at Fermilab, a high-precision experimental study of charmonium bound states. The
c
̄
c
states are formed in
p
̄
p
annihilations of cooled ...antiprotons stored in the Fermilab Antiproton Accumulator using a dense internal hydrogen gas-jet target. We describe the experimental strategies adopted for detecting the tiny
c
̄
c
resonant signals in the huge non-resonant hadronic background, and for measuring resonance parameters with high precision.
We present the first measurement of the angular distribution for the exclusive process p¯p→ψ(2S)→e+e− based on a sample of 6844 events collected by the Fermilab E835 experiment. We find that the ...angular distribution is well described by the expected functional form dNdcosθ∗∝1+λcos2θ∗, where θ∗ is the angle between the antiproton and the electron in the center of mass frame, with λ=0.67±0.15(stat)±0.04(sys). The measured value for λ implies a small but non-zero ψ(2S) helicity 0 formation amplitude in p¯p, comparable to what is observed in J/ψ decays to baryon pairs.
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