K. Gollwitzer

Evidence for ηη resonances in antiproton-proton annihilations at 2950 < s < 3620 MeV

Abstract We present the first high-statistics study of the ηη system over the mass range 1000–3000 MeV/c2. The experiment was performed at the Fermilab Antiproton Accumulator, and the data sample consists of six-photon final states produced in antiproton-proton annihilations at s in the range 2950–3620 MeV. We find evidence for three states with masses 1488 ± 10 MeV/c2, 1748 ± 10 MeV/c2 and 2104 ± 20 MeV/c2 respectively.

Study of the χ1 and χ2 charmonium states formed in pp annihilations

We report on a study of the χ1(3P1) and χ2(3P2) states of charmonium formed in antiproton-proton annihilations. An energy scan through the resonances, performed with a very narrow momentum-band beam of antiprotons intersecting a hydrogen jet target, enables us to perform very precise measurements of the mass and the total width of the two resonances. From a sample of 513 χ1 and 585 χ2 events we find Mχ1 = (3510.53±0.13) MeV/c2, Mχ2 = (3556.15±0.14) MeV/c2, Γχ1 = (0.88±0.14) MeV and Γχ2 = (1.98±0.18) MeV. From our measurement of the quantity Γ(R → pp) × BR(R → Jψ → e+ e−), using known branching ratios, we obtain Λ(χ1 → pp) = (69±13) eV and Λ(χ2 → pp) = (180±31) eV.

Precision measurements of antiproton-proton forward elastic scattering parameters in the 3.7 to 6.2 GeV/c region

Abstract Differential cross sections for p p elastic scattering have been measured for very small momentum transfers at six different incident antiproton momenta in the range 3.7 to 6.2 GeV/c by the detection of recoil protons at scattering angles close to 90°. Forward scattering parameters σ T , b , and ϱ have been determined. For the ϱ-parameter, up to an order of magnitude higher level of precision has been achieved compared to that in earlier experiments. It is found that existing dispersion theory predictions are in disagreement with our results for the ϱ-parameter.

Production of the f2 (1520) resonance in antiproton—proton annihilations at s = 2980 and MeV☆

Abstract We present measurements of the 2π0 mass spectrum in proton—antiproton annihilations. The f2 (1520) resonance is strongly produced in the 3π0 channel. Its production along with an η is observed, but strongly suppressed. Other features are seen in the data, including the f2 (1270) and structures at 2000 MeV/c2 and above.

Evidence for ηη resonances in antiproton-proton annihilations at

Abstract We present the first high-statistics study of the ηη system over the mass range 1000–3000 MeV/c2. The experiment was performed at the Fermilab Antiproton Accumulator, and the data sample consists of six-photon final states produced in antiproton-proton annihilations at s in the range 2950–3620 MeV. We find evidence for three states with masses 1488 ± 10 MeV/c2, 1748 ± 10 MeV/c2 and 2104 ± 20 MeV/c2 respectively.

Experimental determination of the proton electromagnetic form factor at Q2=12.4(GeV/c)2

The value of the proton form factor in the time‐like region has been determined at Q2=12.4(GeV/c)2. We have selected events pp→e+e− from the data collected in an experiment performed at the Antiproton Accumulator Ring at Fermilab and, assuming the validity of the ‖GE‖≊0 hypotesis, we have found ‖GM‖=.034±.017 and σTOT(pp→e+e−)=10±5pb.

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

We present the first measurement of the angular distribution for the exclusive process

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

\bar p p \to \psi(2S)\to e^+e^-

Study of the angular distribution of the reaction p̄p→χc2→Jψγ→e+e-γ

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

STUDY OF THE ANGULAR-DISTRIBUTION OF THE REACTION (P)OVER-BARP-]CHI-C2-]J/PSI-GAMMA-]E+E-GAMMA RID C-5223-2009

\frac{dN}{d\cos\theta^{*}}