[en] A new radiation imager is proposed, which is based on the recent detector technique in high-energy physics experiments; the wavelength shifter coupled to the position-sensitive photomultiplier. The concept model using a CsI(Na) crystal was successfully tested, and a remarkable space resolution, 1.0 mm in FWHM, with detection efficiency of ∼70% has been confirmed for 122 keV gamma rays of ⁵⁷Co. Improvement in time resolution and possible application of the device to high-flux X-ray imaging are discussed

[en] Fast and precise scintillating fiber detectors using KURARAY fibers and HAMAMATSU multianode H6568 tubes were constructed for new experiments (DIRAC and COMPASS) at CERN. Tests of the DIRAC detector and COMPASS prototype show high detection efficiency, good time and space resolution. (author)

[en] A fast and precise scintillating fiber (SciFi) hodoscope based on KURARAY SciFi and HAMAMATSU multianode H6568 tubes was constructed to be used in DIRAC experiment (PS-212) at CERN for tracking and topological triggering information. The front-end electronics was custom developed to allow on-line discrimination after built-in dynamic cross-talk rejection. Preliminary tests of the detector using more than 300 read-out channels have shown an excellent stability and optimum performance for this system: a uniform detection efficiency of 98%, a 125 μm single hit and ∼0.5 mm two-hit space resolution, 0.6 ns time resolution

[en] The DIRAC experiment aims to measure the lifetime of π+π- atoms in the ground state with 10% precision, using the 24 GeV/c proton beam of the CERN Proton Synchrotron. As the value of the above lifetime of order 10-15s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables to determine a combination of S-wave pion scattering lengths to 5%. Pion scattering lengths have been calculated in the framework of chiral perturbation theory with high precision. Thus the accurate measurement of these values would submit the understanding of chiral symmetry breaking of QCD to a crucial test. Some preliminary results from the analysis of a 2000 data sample are presented

[en] The main objective of DIRAC experiment is the measurement of the lifetime τ of the exotic hadronic atom consisting of π⁺ and π^- mesons. The lifetime of this atom is determined by the decay mode π⁺ π^- → π⁰ π⁰ due to the strong interaction. Through the precise relationship between the lifetime and the S-wave pion-pion scattering length difference |a₀ - a₂| for isospin 0 and 2 (respectively), a measurement of τ with an accuracy of 10% will allow a determination of |a₀ - a₂| at a 5% precision level. Pion-pion scattering lengths have been calculated in the framework of chiral perturbation theory with an accuracy below 5%. In this way DIRAC experiment will provide a crucial test of the chiral symmetry breaking scheme in QCD effective theories at low energies

[en] The DIRAC spectrometer has been commissioned at CERN with the aim of detecting π⁺π^- atoms produced by a 24 GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very detector efficiency.ation of the imaging sof the latter with resolution around 0.6 MeV/c. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and set-up performances are also given