Nitrogen dilution effect for small angle GDH experiment in JLab Hall-A

[1]
. Chupp T E et al. Phys. Rev. C, 1987, 36: 22442. Romalis M V. Phys. Rev. D, 1998, 58: 15983. Happer W. Rev. Mod. Phys., 1972, 44: 1694. Appelt S et al. Phys. Rev. A, 1998, 58: 14125. Gerasimov S. Yaz., 1965, 2: 598; Drell S D, Hearn A C.Phys. Rev. Lett., 1966, 16: 9086. Alcorn J et al. (JLab Collaboration). NIM A, 2004, 522:2947. LU Hai-Jiang, YE Yun-Xiu, YAN Xin-Hu et al. HEP NP, 2007, 31(8): 764-768 (in Chinese)