P. Birien

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.

Hypernuclear production in the

Abstract Cross sections for the production of hypernuclei were measured in the reaction A(K − , π − ) Λ A. on light and heavy nuclear targets, using a separated K − beam at the CERN Proton Synchrotron. The pions were detected in the forward direction. The results are compared with cross sections calculated under the assumption that the reaction took place on a single neutron. The good agreement between the measured and the calculated cross sections justifies the use of the (K − , π − ) reaction in order to obtain spectroscopic information on hypernuclei.

(K^−, π^−)

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.

reaction

Abstract Neutron hole states in the 1s shell have been studied in the n(K−, π−)Λ strangeness-exchange reaction on 6Li, 7Li, 9Be, and 12C targets at the CERN Proton Synchrotron. The excitation energy and the width of the states as well as the differential cross section have been determined. The clear similarity with the 1s proton hole states observed in (p, 2p) reactions indicates that the presence of the Λ-particle can be taken into account within the weak-coupling model. In this way the (K−, π−) reaction can be used for the study of Λ -states as well as for the investigation of neutron hole states produced at very low momentum transfer.