A new method has been designed for dealing with precession of spin and corr
ecting polarization of boolean AND in magnetic fields. Using this method, t
he direction of spin could be obtained at any position where the lambda is
and where the polarization is corrected automatically. We obtained the resu
lts by analysing the data from both a Monte-Carlo generator and a real expe
riment using the method described in this paper. (C) 2001 Elsevier Science
B.V. All rights reserved.