Measurements of φdecay in nuclear matter

in qcd,hadrons are described as a bound state of confined valence quarks which obtained the effective massdue to the spontaneous breaking of the chiral symmetry. This mechanism determines the properties ofhadrons in free space，such as the mass and the decay width. If the vacuum structure was changed from in space那些properties应该也改变. this project aims to obtain the first experimental results whichcan answer whether such theoretical expectations from the chiral symmetry restorationare exist or not.We have completed the spectrometer construction in 1998 by installing the lastdetectors, the rear gas-Cherenkov counters and the rear EM-calorimeters. In 1997，we have performed the test run focusing only to the φ→K we have performed the test run focusing only to the φ→K we have performed the test run focusing only to the φ→K we have decay mode.自1998年，we have started simultaneous data taking runs for both φ→e - D1+ e - D1- D1 and φ→K - D1- D1- D1 decay modes.The analysis of the 1997 data was completed. the results are报告several international conferencesand the PhD thesis of Dr. Yokkaichi and the associated paper have bean published. the 1997 data wasnot statistically enough so that we只能报告the nuclear mass-dependence of the φproduction. From the 1998-1999 data, however，we could obtain the signature of in-medium decay of φ meson which carries the information ofmedium width and shift of the vector mesons. results are being reported in severalconferences.This report includes the scientific materials which been reported so far，也可以包括在这个项目中开发特殊的detectors的发展。

In QCD, hadrons are described as a bound state of confined valence quarks which obtained the effective mass due to the spontaneous breaking of the chiral symmetry. This mechanism determines the properties of hadrons in free space, such as the mass and the decay width. If the vacuum structure was changed from that in free space those properties should also change.This project aims to obtain the first experimental results which can answer whether such theoretical expectations originated from the chiral symmetry restoration are exist or not.We have completed the spectrometer construction in 1998 by installing the last detectors, the rear gas-Cherenkov counters and the rear EM-calorimeters. In 1997, we have performed the test run focusing only to the φ → KィイD1+ィエD1KィイD1-ィエD1 decay mode. Since 1998, we have started simultaneous data taking runs for both φ → eィイD1+ィエD1eィイD1-ィエD1 and φ → KィイD1+ィエD1KィイD1-ィエD1 decay modes.The analysis of the 1997 data was completed. The results are reported in several international conferences, and the PhD thesis of Dr. Yokkaichi and the associated paper have bean published. The 1997 data was not statistically enough so that we could only report the nuclear mass-dependence of the φ production. From the 1998-1999 data, however, we could obtain the signature of in-medium decay of φ meson which carries the information of in-medium width and shift of the vector mesons. The results are being reported in several conferences.This report includes the scientific materials which have been reported so far, and also includes outcomes from the developments of special detectors developed in this project.