Manifestation of $s\to \Lambda$ fragmentation matrix elements via   transverse $\Lambda$ polarization in unpolarized $e^-e^+$ annihilation
  Making use of the collinear expansion technique developed by Ellis, Furmanski and Petrozio, and the special propagator concept invented by Qiu, we present a factorization approach to the photon fragmentation tensor for the inclusive Lambda hyperon production. As a result, the structure function $\tilde F$, which is related to the transverse polarization of the inclusive Lambda hyperon in unpolarized electron-positron annihilation, is expressed as a combination of four parton fragmentation matrix elements. Since the inclusive $\Lambda$ production we considered is theoretically the simplest, our study can be taken as a question to the operatability and practability of the first nonleading QCD factorization theorem in the transverse $\Lambda$ polarization phenomena. 
Wei Lu, Xue-Qian Li, Hai-Ming Hu