  Spontaneous polarization of $\Lambda/\bar{\Lambda}$ in unpolarized hadron
interactions has been observed experimentally for nearly half a century and
still eludes a definitive explanation. One possible origin is the effect
arising from polarizing fragmentation functions (pFFs), which describe the
production of polarized hadrons from the fragmentation of an unpolarized
parton. Recently, significant transverse polarization of
$\Lambda/\bar{\Lambda}$ has been observed in unpolarized $e^{+}e^{-}$
annihilation at Belle experiment, along the normal to the plane defined by the
thrust axis and $\Lambda$ momentum. In unpolarized $pp$ collisions, the
measurement of transverse polarization of $\Lambda$/$\bar{\Lambda}$ within jet
could also provide important constraints and universality test for the pFFs. In
this contribution, preliminary results on the first measurement of
$\Lambda$/$\bar{\Lambda}$ polarization within a jet in $pp$ collision at
$\sqrt{s}$ = 200 GeV are reported. The data used for this measurement were
taken by the STAR experiment at RHIC in 2015.
