Study of spin structure of the proton and the neutron with new experimental technique at HERMES

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It was found about 20 years ago by EMC at CERN that the quark spin contribution to the proton spin is small. It is called 'proton spin problem'. The HERMES experiment is an international collaboration from 11 countries to study this problem with unique technical capabilities. Electron or positron beam of DESY-HERA of 27.6 GeV and internal gas targets are used Deep-inelastic scattering of electron off the nucleon is measured. The HERMES detects the scattered electron and also produced hadrons. For the hadron identification, the RICH(ring imaging Cherenkov detector) plays a main role.The HERME started its data-taking in 1995 and the data-taking was completed in July 2007. We have received support by Grant-in-aid continuously for 10 years and this was the last two years. During these two years, we published the result of precision measurement of g1(x) structure functions for proton, neutron and deuteron. Like F2(x) structure function in the unpolarized deep inelastic scattering, g1(x) is the fundamental structure function. We determined the quark spin contribution to the nucleon spin with a good precision using this g1(x).We also published the results of hadronization studied by deep-inelastic scattering. Hadronization is in other words fragmentation. For this we measured the multiplicity which is hadron yield per deep inelastic scattering. The fragmentation function determined in deep inelastic scattering can be compared to the one from electron-positron collider experiments.We published the longitudinal and transverse polarization of produced Lambda particles. It is important to extend the study of baryon spin in a way to include strange quark.Finally, we did theoretical calculation of perturbative QCD for DGLAP evolution equation and analyzed the world data in a consistent way.