Intrinsic charm contribution to the proton spin

M. V. Polyakov, A. Schäfer, O. V. Teryaev
1999 Physical Review D, Particles and fields  
The charm quark contribution to the first moment of g_1(x,Q^2) is calculated using a heavy mass expansion of the divergence of the singlet axial current. It is shown to be small.
doi:10.1103/physrevd.60.051502 fatcat:lhickiixvbecfn4ysw63pb7szy