C. Lechanoine

Elastic scattering of π−p, K−p and pp at 25 and 40 GeV/c

Elastic diffraction scattering of π−, K− and pon protons has been measured at 25 and 40 GeV/c at the Serpukhov Proton Accelerator. Differential elastic cross sections and diffraction slopes are presented in the momentum-transfer interval 0.07–0.80 (GeV/c)2 and compared with existing data at lower energies.

Elastic scattering of pi- p, K- p and anti-p p at 25-GeV/c and 40-GeV/c

Elastic diffraction scattering of π−, K− and pon protons has been measured at 25 and 40 GeV/c at the Serpukhov Proton Accelerator. Differential elastic cross sections and diffraction slopes are presented in the momentum-transfer interval 0.07–0.80 (GeV/c)2 and compared with existing data at lower energies.

Evidence for a two-peak structure in the A2 meson

Abstract The missing-mass spectrum of the A 2 meson [ M = 1297 ± 16 MeV, Γ = 95 ± 15 MeV] obtained in the reaction π − p → pX − in three independent runs at 6 and 7 GeV/ c shows a narrow dip of 6 standard deviations in the centre of the A 2 peak at 1297 MeV, thus suggesting a two-peak structure.

The reaction π−p → π−π−π+p at 25 and 40 GeV/c

The reaction pp→pπ−π+p has been studied at 25 and 40 GeV/c at the Serpukhov proton synchroton using the CERN-IHEP spectrometer. The differential cross section has been determined as a function of four-momentum transfer to the proton (0.05–0.30 (GeV/c)2) and pππ mass (up to 2.2 and 2.6 GeV/c2). At both energies there is a broad low-mass maximum with an enhancement at 1.6–1.8 GeV/c2. The cross section in a given mass band falls rapidly with |t|, with an exponential slope that decreases with increasing mass. In both the background and the 1.7 GeV/c2 peak there is a strong Δ−−π+ component. Possible spin-parity (JP) contributions to it are discussed. Throughout the range 1.5–2.2 GeV there is at least one state of J ⩾ 32 and there is interference between states of opposite P, |ΔJ| ⩽ 1. At the peak there is a J ⩾ 52 component. There are striking parallels between this reaction and the boson reactions π−p→π−π−π+p and K− → K−π−π+p.

Confirmation of the A2 splitting near threshold

Abstract The shape of the A 2 resonance has been measured in π p → pA 2 at 2.6 GeV/ c , i.e. near threshold, with A 2 produced at minimum momentum transfer. The results confirm, with a new method and instrument, the A 2 splitting found previously with the Jacobian-peak method.

Missing-mass spectra observed in π- + p → p + X- at 25 and 40 GeV/c

Abstract Missing-mass spectra were obtained in the reaction π − p → p X − at 25 and 40 GeV/ c at the Serpukhov Accelerator. At low masses a strong peak at 1.3 and a smaller one near 1.7 GeV are observed. In the mass region above 2 GeV no structure exceeding 3μb/(geV/ c 2 is seen.

A2 splitting in the decay channel A2− → K10K− produced in the reaction π−p → pA2− at 7 GeV/c

Abstract A K10K− mass spectrum in the A2 region has been obtained in the reaction π−p → p K10K− at 7 GeV/c. The double peak structure of the A2 meson, observed in the earlier missing mass spectra, is found to be present also in the decay channel A2− → K10K−.

Spectrum of charged non-strange bosons in the mass region 2.5–3.0 GeV

Abstract The CERN boson spectrometer shows significant enhancements in the spectrum of charged non-strange bosons near 2.6 GeV and 2.8 GeV mass values.

SPECTRUM OF CHARGED NON-STRANGE BOSONS IN THE MASS REGION FROM 3.0 TO 3.8 GeV.

Abstract With the CERN Boson Spectrometer five new resonances have been found in the spectrum of charged non-strange bosons with masses between 3.0 and 3.8 GeV.

Experimental confirmation of R-meson structure

Abstract Experimental confirmation of the structure in the region of the R(1700) meson, in the reaction π − + p → p + R − reported earlier at incident pion momenta of 7 and 12 GeV/ c , has been obtained at 11.5 GeV/ c with the missing-mass spectrometer. The peaks R 1 (1630), R 2 (1700) and R 3 (1748) have been observed; in addition a peak at 1830 ± 15 MeV, reported by the CERN-Liverpool bubble chamber group, is indicated. Speculative comparison of our peaks and bubble chamber data with the L -excitation quark-antiquark model predictions gives a suggestive agreement in both mass separations and G -parities; however, we cannot exclude this as being coincidence.