M. Roy-Stephan

Spin structure of the Δ excitation

Spin structure and cross section data for Δ production in the (n, p-like reaction (d, 2p[1S0]) on p, d and 12C targets are presented. At laboratory kinetic energies 2 GeV and 1.6 GeV, and forward scattering angles, we find dominance of spin transverse over spin longitudinal cross section for free Δ production. On the nucleus 12C we find significant enhancement of the transverse dominance, and a large downwards shift in the peak position of the laboratory energy transfer associated with the production of the Δ.

A detection system using drift chambers for the SPES4 spectrometer at Laboratoire National Saturne

Abstract We describe the “drift chamber” detection setup of SPES4, the 4 GeV/c spectrometer at Laboratoire National Saturne. The particle identification is performed by combining magnetic rigidity selection with energy loss and time of flight measurements. This allows to separate analysed isotopes from Z = 1 to at least Z = 10 up to a rigidity of 4 GeV/c. A charge resolution of ΔZrms = 0.1 and a time resolution of Δtrms = 120 ps for 18Ne at about 3 GeV/c per Z are easily obtained. Two sets of multiwire drift chambers are used to measure and reconstruct the particle trajectories at the output of the system. A position resolution better than Δxrms = 160 μm can be achieved in the focal plane. This corresponds to a momentum resolution of Δδrms = 0.22 × 10−4. The performances of SPES4 (Δδrms = 2.2 × 10−4) can then be wholly exploited.