Test of non-perturbative QCD by means of the measurement of Kπ scattering length -Extension of DIRAC experiment-

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The principal objective of this study is to carry out PS212 (DIRAC) experiment at CERN to test the non-perturbative QCD in the low-energy region. It is essential to test the theory experimentally to understand thoroughly the hadron interactions. Although is difficult to carry out reliable calculations in this region, the π-π scattering length is predicted with an exceptional precision, better than 2%. DIRAC experiment aims at measuring the pi-pi scattering length with a precision of 5% by measuring the life-time of the A_<2π> atom.During the period of this project, the Japanese group pursued the experiment by improving the experimental setup. Parts of the experimental result have been already analyzed and published.The collaboration undertakes a measurement of the life time of atoms formed with K and π by applying the same technique used in DIRAC. The production cross section of such atoms, however, is much smaller, and the measurement requires the development of detectors efficient in much larger beam intensities.To solve the saturation problem of the current dE/dx counter, a fast silicon strip counter which allows a use in triggering is developed, and now it is ready. Also a scintillating fiber hodoscope using 0.28 mmΦ scintillator in stead of current 0.5 mmΦ one, and a fast readout system using F1-TDC have been developed. The detector has now an efficiency of 98%, spatial resolution of 64 μm together with a time resolution better than 500 ps, and it can be used as a tracking device as well as a triggering device.With the development of these counters together with micro drift chamber developed by the Russian group, the detection of A_<Kπ> became possible, and the project to carry out this experiment as an extension of DIRAC has been approved in December 2005. A serious preparation is in progress.