Longitudinal spin transfer of semi-inclusive $\Lambda$ production in deep inelastic scattering

$\Lambda$ particle is an excellent tool for probing spin effects due to its self-analyzing weak decay. We study the longitudinally polarized $\Lambda$ production in semi-inclusive deep inelastic scattering. In particular, we propose a method based on the spectator diquark model to directly calculate the contributions from the target fragmentation region. The results indicate that these contributions significantly suppress the longitudinal spin transfer to $\Lambda$ from the current fragmentation region, thereby describing the experimental data from COMPASS, HERMES and CLAS12 quite well.