A. Ceccucci

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. n nFrom 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.

Study of the chi(1) and chi(2) charmonium states formed in anti-p p 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. n nFrom 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.

THE THRESHOLD GAS CHERENKOV COUNTER OF CHARMONIUM EXPERIMENT 835 AT FERMILAB

Abstract A threshold gas Cherenkov counter is used in Fermilab experiment 835 to tag electrons from the decay of charmonium states. It is an improved version of the counter used in a previous charmonium experiment, E760. The new features of the design, the technique used to build a set of ellipsoidal mirrors, and the counter performance are presented.

Measurement of the φφ cross section in pp annihilations at ECM≈3 GeV

In an experiment performed at the CERN Intersecting Storage Rings as a part of an energy scan to detect the ηc formation in pp annihilation, we studied the reaction pp→φφ→K+K−K+K−. The total cross section has been determined to be 25.0± 7.4±3.8 nb.

A large acceptance threshold Cherenkov counter for experiment 760 at Fermilab

Abstract A threshold gas Cherenkov counter is used in Fermilab Experiment 760 to tag electrons in the detection of charmonium states. Mechanical structures and mirrors were built with carbon-fiber-epoxy composites, resulting in a light weight detector covering 2π in azimuthal angle. The counter is operated at atmospheric pressure with different gases, CO 2 and Freon 13, respectively in the two cells at small and large polar angles, to maximize pion rejection. Design considerations, construction details, and performance of the counter are described.

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.

A glass spherical Cherenkov counter based on total internal reflection

We built and tested a Cherenkov counter for particle identification, with spherical shape (R = 600 mm), made of glass. The threshold at β = 0.92 is set by the mechanism of total internal reflection of the Cherenkov light.

Measurement of the

Abstract Data collected in the experiment R704 at the CERN ISR are used to study the annihilation process p p → π 0 π 0 at several centre-of-mass energies between 2.97 and 3.56 GeV. A total sample of 7359 events has been identified, from which cross sections and angular distributions in the interval 0 cos θ ∗ | have been measured.