Spin effects in the fragmentation of transversely polarized and   unpolarized quarks
  We study the fragmentation of a transversely polarized quark into a non collinear (k_T not= 0) spinless hadron and the fragmentation of an unpolarized quark into a non collinear transversely polarized spin 1/2 baryon. These nonperturbative properties are described by spin and k_T dependent fragmentation functions and are revealed in the observation of single spin asymmetries. Recent data on the production of pions in polarized semi-inclusive DIS and long known data on Lambda polarization in unpolarized p-N processes are considered: these new fragmentation functions can describe the experimental results and the single spin effects in the quark fragmentation turn out to be surprisingly large. 
M. Anselmino (1), D. Boer (2), U. D'Alesio (3) and F. Murgia (3) ((1)   University and INFN, Torino, Italy, (2) RIKEN-BNL Re...