Single Transverse-Spin Asymmetry in Large $P_T$ Open Charm Production at   an Electron-Ion Collider
  We discuss the single transverse-spin asymmetry (SSA) to be observed in the $D$-meson production with large transverse-momentum in semi-inclusive deep inelastic scattering, $e p^\uparrow \rightarrow e D X$. This contribution is embodied as a twist-3 mechanism in the collinear factorization, which is induced by purely gluonic correlation inside the transversely-polarized nucleon, in particular, by the three-gluon correlation effects. The complete formula for the corresponding SSA in the leading-order QCD is expressed in terms of the four independent gluonic correlation functions and reveals the five independent structures with respect to the dependence on the azimuthal angle for the produced $D$-meson. We present the numerical calculations of the SSA formula at the kinematics relevant to a future Electron Ion Collider. 
Hiroo Beppu (1), Yuji Koike (1), Kazuhiro Tanaka (2), Shinsuke Yoshida   (1) ((1) Niigata Univ., (2) Juntendo Univ.)
hep-ph nucl-th