J.-C. Brient

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.

Precision measurements of the antiproton-proton elastic scattering cross section at 90° in the incident momentum range between 3.5 GeV/c and 5.7 GeV/c

Abstract The high antiproton-proton luminosity obtained by using a target system consisting of a hydrogen gas-jet crossing a coasting beam of cooled antiproton circulating in one of the rings of CERNs ISR provides the possibility to measure low cross section reactions with very high precision. We present measurements of the antiproton-proton elastic cross section at 90° CM at incident momenta between 3.5 GeV/ c and 5.7 GeV/ c . The precision of these measurements is much higher than previously reported results. The data show that the cross section of this reaction decreases faster than s −12 over this momentum range.

CHI formation by antiproton annihilations on hydrogen: Results from experiment R704 at the CERN ISR

Recent measurements of masses, total widths and branching ratios to pp of χ1 and χ2 charmonium states are reported: a novel experimental technique (circulating p beams+gas jet target) has provided excellent energy resolution, together with small background and reduced systematics.

Angular distributions in the reactions

Abstract In the experiment R704 at the CERN Intersecting Storage Rings, the two p-wave charmonium states χ1 and χ2 were formed directly in proton-antiproton annihilation, and detected through the decay chain χ j →γ+J ψ→ψ+ e + e − . The angular d istributions of the events found are studied here. A maximum likehood analysis shows that χ1 radiative transition to the J ψ is compatible with a pure dipole. Indications of a nonzero, positive quadropole contribution to the χ2 radiative transition are found. Finally, it is found that the χ2 data are consistent with the conventional assumption that a single quark radiates the photon in the transition from the χ2 to the J ψ .

Angular-distributions In the Reactions Ppbar-]chi-1,2-]gamma-psi-]gamma-ete-

Abstract In the experiment R704 at the CERN Intersecting Storage Rings, the two p-wave charmonium states χ1 and χ2 were formed directly in proton-antiproton annihilation, and detected through the decay chain χ j →γ+J ψ→ψ+ e + e − . The angular d istributions of the events found are studied here. A maximum likehood analysis shows that χ1 radiative transition to the J ψ is compatible with a pure dipole. Indications of a nonzero, positive quadropole contribution to the χ2 radiative transition are found. Finally, it is found that the χ2 data are consistent with the conventional assumption that a single quark radiates the photon in the transition from the χ2 to the J ψ .