  The light front analysis of pi^{-} mesons in A_{P} (He, C, Mg, O) + A_{T}
(Li,C, Ne, Mg,Cu,Pb) collisions is carried out. The phase space of secondary
pions is naturally divided into two parts in one of which the thermal
equilibration assumption seems to be in a good agreement with data.
Corresponding temperatures are extracted and compared to the results of other
experiments. The dependence of the average temperature T on (A_{P}*A_{T})^{1/2}
is studied.
