F. Bradamante

Transverse-spin and transverse-momentum effects in high-energy processes

The state of the art concerning transverse-spin and transverse-momentum phenomena in hard hadronic reactions is reviewed. An account is given of single-spin and azimuthal asymmetries in semiinclusive deep inelastic scattering, e + e − annihilation, Drell-Yan production, and hadroproduction. The ongoing experiments and the main theoretical frameworks are described in the first part of the paper. The second part is devoted to the experimental findings and their phenomenological interpretations. A brief discussion of the perspectives of future measurements is finally presented.

Antinucleon nucleon interaction at low energy: Scattering and protonium

We present nucleon–antinucleon scattering experiments performed at the Low Energy Antiproton Ring (LEAR) of CERN. The data are reviewed and the underlying physics is discussed, in particular by comparison with the predictions of current models based on meson exchange and short-range absorption. A detailed description is given of protonium, which gives information on the interaction at zero energy and is the initial state when annihilation occurs at rest.

Development of THGEM-based photon detectors for Cherenkov Imaging Counters

The development of a large size gaseous detector of single photons, able to stably operate at high gain and high rate, and to provide good time resolution and insensitivity to magnetic field would be beneficial to future Cherenkov Imaging Counters. The detector could be based on the use of a multilayer architecture of THGEM electron multipliers coupled to a solid state CsI photocathode. A systematic study of the response of THGEM-based counters versus the geometrical parameters has been performed and the main results will be presented. Small photon detector prototypes have been built and preliminary data obtained detecting single photoelectrons are presented as well. The key aspect of photoelectron extraction from the photocathode is illustrated presenting both simulation and dedicated measurement results.

Differential cross sections and analysing powers for PP → π−π+ and K−K+ from 360 to 1550 MeV/c

Abstract Analysing powers and differential cross sections for p p → π − π + and p p → K − K + have been measured over the full angular range using a polarised target at LEAR at 20 beam momenta from 360 to 1550 MeV/c. Discrepancies in the normalisation of earlier d σ/ d Ω data at low momenta are clarified. Above 1000 MeV/c, A0N results confirm values close to +1 over most of the angular range for both reactions, in excellent agreement with earlier data of lower statistics. Below 1000 MeV/c, where the analysing power is measured for the first time, large variations of A0N with energy and angle are present.

p̄p total cross sections below 420 MeV/c

Abstract pp total cross sections have been measured from 220 to 413 MeV/ c in small (⩽ 10 MeV/ c ) steps of momentum with statistics of ± 0.5 %. There is no evidence for structure in the cross section, and a limit of 8 mb MeV/ c 2 is set with 90% confidence on the strength of any narrow resonance down to 250 MeV/ c .

Evidence against the S-meson

Abstract Measurements are reported of pp total cross sections from 388 to 599 MeV/c in small momentum steps. Statistical errors are typically ±0.4%and the normalisation uncertainty is ±0.7%. There is no evidence for the “S-meson”.

Measurement of the analysing power and the differential cross section of the pp charge-exchange reaction at LEAR

Abstract As part of a programme to study the spin structure of the p p→ n n channel, we have measured the analysing power A 0 n and the differential cross section at an incident antiproton beam momentum of 704 MeV/ c . The analysing power exhibits a remarkable angular dependence, which is poorly reproduced by the existing potential models.

The mirror system of COMPASS RICH-1

The architecture and the properties of the mirror system of the COMPASS RICH-1 detector, composed by 116 spherical VUV reflecting units supported by a lightweight mechanical structure, are described.

The radiator gas and the gas system of COMPASS RICH-1

The design of the COMPASS RICH-1 gas system, its operational modes, the cleaning setups for the preparation of the radiator gas and transmission measurement installations are described. The gas system in presently fully operational and satisfactory transmission of VUV light through the radiator gas has been reached.

Plastic detectors for medium energy neutrons

Abstract Three neutron detectors made up of a total of fifty-three vertical plastic scintillator bars BC412 (equivalent to NE110) with 8 × 20 cm2 section and a sensitive height varying from 40 to 130 cm are used in the PS199 experiment at the CERN Low Energy Antiproton Ring (LEAR). Monitoring of the stability of the counters during data taking is done by a laser system. The TOF is calibrated with γ rays from the p p → π 0 ′s → γ′s reaction. A new method to calibrate the amplitude of the counters at low energy using 4.4 MeV gamma rays from an 241Am/Be source is described, as well as a high energy calibration using cosmic muons. The absolute neutron detection efficiency of the counters is measured for neutron energies varying from 33 MeV to 204 MeV. Measurements are performed at five counter thresholds of 1.5, 2.5, 4.5, 6.5 and 8.5 MeVee. A comparison of the experimental measurements with the predictions of a Monte Carlo computer code is presented.