M. Lamanna

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.

COMPASS RICH-1

RICH-1, one of the key detectors of the COMPASS experiment at CERN SPS, is described. Photon detectors are MWPCs equipped with CsI photo-cathodes.

The COMPASS RICH project

The set-up of the COMPASS experiment (NA58 at CERN SPS) consists of two spectrometers (a large-angle one followed by a small-angle spectrometer) both equipped with a gas RICH (RICH 1 and RICH 2) for hadron identification. RICH 1 is currently under construction, while RICH 2 will be added at a second stage. RICH 1 design parameters and technological choices are discussed

The limited streamer tubes for experiment PS199 at LEAR

Abstract Eight thousand limited streamer tubes have been built for the antineutron detectors of experiment PS199 at LEAR, the Low-Energy Antiproton Ring at CERN. The tubes are arranged in vertical planes and each plane is equipped with two orthogonal sets of strips used as position-sensitive readout elements. The digital readout system is based on the new board “streamer interface” built by SGS. The construction and testing procedure are described, as well as the performances of the detector and the readout system in a test with cosmic rays.

Measurement of the analyzing power of the charge-exchange reaction in the momentum range 546-875 MeV/c at LEAR

Abstract Results are given for the analysing power of the p p→ n n charge-exchange reaction at four incident beam momenta. The measurement is part of an experimental programme to study the spin structure of this reaction at LEAR. The analyzing power shows strong angular and energy dependence, which at present is not reproduced by the existing meson-exchange potential models.

Measurement of the analysing power of the charge-exchange pp → nn reaction in the momentum range 546–1287 MeV/c at LEAR

Final results of the measurement of the analysing power AOn of the pp → nn reaction are presented. Eight measurements in the range 546–1287 MeV/c incoming p momentum have been performed over the full angular range using a solid polarized proton target and the Low Energy Antiproton Ring (LEAR) at CERN antiproton extracted beams.

High-precision measurement of the pp → nn charge-exchange differential cross-section

Abstract The differential p p → n n charge-exchange cross section has been measured at the CERN Low Energy Antiproton Ring (LEAR), at two incident p momenta, 601 and 1202 MeV/c. features of the differential cross-section near the forward direction, i.e. a sharp peak at 0° scattering angle followed by an energy dependent dip-bump structure, are confirmed and measured with good precision and high statistical accuracy. The data show very clearly that the shape of the cross-section is a manifestation of the pion-exchange amplitude, and a simple extrapolation to the pion pole already indicates that the pion-nucleon coupling constant f c 2 can be determined with good precision.

The COMPASS RICH-1 read-out system

This paper describes the reconfigurable read-out system for the 82944 RICH-1 channels of the COMPASS experiment (NA58) at CERN. The system is based on 192 identical large front-end boards (BORA board). BORA was designed for acquiring, digitizing, threshold subtracting and transmitting event data. The overall operation of the board is controlled and supervised by a DSP tightly interacting with an FPGA that acts as a parallel co-processor. The DSP allows characterizing each analog channel by locally calculating noise and pedestal. Each BORA communicates with the outside world through two optical fibers and through a dedicated DSP network. One optical fiber is used to receive event triggers, and the other one is used to transmit event data to subsequent processing stages of the acquisition system. The DSP network allows reconfiguring and reprogramming the DSPs and FPGAs as well as acquiring sample events to visualize the overall operation of the system. The whole RICH has eight DSP networks working in parallel. These networks are handled by DOLINA, a PC resident multiprocessor board containing eight DSPs. Each network is formed by 24 BORA DSPs and 1 DOLINA DSP. The read-out system can steadily work up to a trigger rate of 75 kHz with maximum pixel occupancy of 20%, reaching a transmission data rate of 5.13 Gbytes/s.