Exploration for degradation of Lambda polarization produced in relativistic nucleus-nucleus collisions

The degradation of Lambda transverse polarization produced in S + Pb central collisions at energy 200 GeV per nucleon has been studied in detail. The S + Pb central collision events have been generated using Monte-Carlo generator-LUCIAE at 200 GeV per nucleon, The various factors degrading Lambda transverse polarization have been analysed quantitatively. The ratios of Lambda's produced from rescattering, secondary production and decays of Sigma, Xi hyperons to the total measurable Lambda's in experiment have been investigated and the degradation effect of these Lambda on the total polarization has been determined. The simulation and calculation show that above three factors decrease the Lambda transverse polarization strongly, however, can not eliminate the polarization completely when the Lambda's are assumed to be produced from hadronic gas in the final stale. To explain the experimental data of vanished Lambda polarization, it probably needs to consider new mechanisms of Lambda production, including a weak effect of QGP formation.