First extraction of the Λ polarizing fragmentation function from Belle e+e− data

We present a thorough phenomenological analysis of the experimental data from Belle Collaboration for the transverse Lambda and (Lambda) over bar polarization, measured in e(+ )e(-) annihilation processes, for the case of associated (with a light charged hadron) and inclusive (plus a jet) production. Within a transverse momentum dependent (TMD) approach we show how this intriguing phenomenon can be accounted for. This allows for the first ever extraction of the quark polarizing fragmentation function for a Lambda hyperon, a TMD distribution giving the probability that an unpolarized quark fragments into a transversely polarized spin-1/2 hadron.