Study of nucleon spin structure by using transversely polarized nucleon targets at HERMES experiment

In this paper, the nucleon spin structure studies made by using transversely' polarized nucleon target at DESY in Hamburg, Germany is reported. Asymmetry of hadron generation, which is called Sivers, Collins asymmetry, was successfully separated for the first time in the world. At the HERMES experiment, deep inelastic scattering was measured using the 27.5 GeV positron beam and transversely polarized hydrogen target, to obtain the degree of asymmetry for the generation of π+, π- and π0. The results are summarized as follows. Sivers asymmetry; π+: positive value with 3σ statistical accuracy, π0: positive value with 2σ statistical accuracy, and π-: zero within statistical error. Collins asymmetry; π-: negative value with 3σ statistical accuracy, π+: positive value with 2σ statistical accuracy, and π0: zero within statistical error. The paper [A.Airapetian et al., HERMES, Phys.Rev.Lett. 94('05)012002] is recommended to be referred to. (S. Funahashi)