M. Uhrmacher

Hypernuclei with sigma particles

Abstract The production of Σ particles in the (K − , π − ) on 9 Be at 720 MeV/ c has been studied at the CERN proton synchrotron (PS). The missing-mass spectrum shows structures in the Σ region, which have been interpreted as belonging to hypernuclei with sigma particles. An upper limit of 8 MeV for the width of these states has been estimated.

Spin-orbit interaction of lambda particles in nuclei

Abstract In the strangeness exchange reaction (K − , π − ) on 12 C and 16 O the most prominent transitions to hypernuclear states produced in recoilless and quasi-free Λ production have been identified. The analysis of the spectra shows that in the Λ-nucleus interaction the spin-orbit coupling is at least one order of magnitude smaller than for the nucleon-nucleus interaction.

Σ hypernuclear states in (K−, π±) reactions on 12C

Abstract Using negative kaons of momenta 400 and 450 MeV/c, Σ hypernuclear states have been produced in (K−, π−) and (K−, π+) reactions on 12C. The observed states are interpreted as the recoilless production of Σ particles on carbon. The upper limit for the widths of these states is estimated to be 5 MeV, independent of the charge of the Σ particle.

The (K−, π+) strangeness exchange reaction on 16O

Abstract Using negative kaons of 450 MeV/c momentum, Σ hypernuclear states have been produced in the (K−, π+) reaction on 16O. The observed states are interpreted as the recoilless production of Σ− particles in the p 3 2 and p 1 2 orbits of the Σ16C hypernucleus. Their energy splitting gives a constraint to the magnitude of the spin-orbit coupling for the Σ− particles in the nucleus.

The nuclear response in high-energy hadron-nucleus interactions

In an experiment at the CERN Super Proton Synchrotron (SPS) studying hadron-nucleus interactions, slow particles which are mainly knockout protons were measured with an electronic detector. Their dependence on the target mass, incoming energy, and projectile is shown. We discuss the use of the number of protons as a measure for the number of interactions of the projectile and conclude that the emitted protons measure the impact parameter of the reaction.

Search for narrow baryonium states near the NN threshold

Abstract The reactions p p →π − X and p d → pX earch for narrow baryonium states in the mass region between 1.6 and 2.0 GeV/c2. No such state has been observed. In the first reaction the upper limit for the production of narrow baryonium states is 8μb/sr for a 3 standard deviation signal with 4 MeV/c2 width. In the second reaction this limit is 10 μb/sr. The second reaction is rather insensitive for observation of baryonium states as it is dominated by quasi-free contributions.

Particle production in high-energy hadron-nucleus interactions

The pseudorapidity (η) distributions of fast particles (β>0.7) emitted in inelastic hadron interactions with carbon, copper and lead were measured for incoming energies from 50 to 150GeV at the CERN Super Proton Synchrotron. Their dependence on target mass (A) and projectile (h) obeys -scaling as expected. Their energy dependence is in contrast with most model predictions.

Observation of a set of nuclear shell orbitals for the Λ particle in 32ΛS and 40ΛCa

Energy excitation spectra have been obtained for hypernuclei in the s-d shell from (K/sup -/,..pi../sup -/) reaction in flight on /sup 32//sub ..lambda../S and /sup 40//sub ..lambda../Ca. The analysis is carried out in a simple particle hole model and leads to the results that the ..lambda.. behaves in the nucleus like an independant particle in a harmonic oscillator potential well with no significant spin orbit term.Energy excitation spectra have been obtained for hypernuclei in the s‐d shell from (K−,π−) reaction in flight on 32ΛS and 40ΛCa. The analysis is carried out in a simple particle hole model and leads to the results that the Λ behaves in the nucleus like an independant particle in a harmonic oscillator potential well with no significant spin orbit term.

A New Measurement of pp̄ Excitation Functions

In a recent experiment at the CERN Proton Synchrotron (PS) the proton-antiproton excitation functions of the annihilation as well as of the elastic channel have been measured in the laboratory momentum range from 370 to 1000 MeV/c. The experiment was characterized by an r.m.s. mass resolution of 0.4 MeV/c2 and a statistical accuracy of 1.2% for the annihilation channel. With this precision a narrow structure, about 4 MeV/c2 wide, at a mass of 1936 MeV/c2 is observed in the annihilation channel.