Search for Antimatters of Cosmic Origin with the BESS Spectrometer

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1.Three successive balloon-borne experiments with the BESS superconducting spectrometer have been carried out from 1999 to 2001 to serch for cosmic antimatters in cosmic rays.2.Togeter with data taken in the prebious BESS flights, an upper limit on a ratio on antiheliums to helium nuclei was placed to be less than 6.8 x 10-7 at the 95% confidence level. This most stringent upper limit in the world directly indicates that the Universe near our galaxy consists of matters.3.For further search for antimatters with the higher sensitivity, a longer balloon-borne experiment with smaller superconducting spectrometer was discussed in the 7th BESS workshop and planed by a long duration flight in Antarctica.4.Detector R＆D for the cosmic-ray measurement with the long duration balloon has been continued, for example, the improvement of the water-proof of the superconducting magnet, distributed environmental monitor system for the house-keeping and lighter drift chamber with low-material structure.5.A long duration balloon-borne "BESS-Polar" experiment in Antarctica was proposed and is planed to be carried out in December 2003 to January 2004. For this experiment, smaller and lighter new superconducting spectrometer has been developed and constructed.