Light - cone behavior of the pion Bethe - Salpeter wave function in the ladder model *

The Bethe-Salpeter wave function X( q v + P v, q •) for two spin-l/2 quarks bound by the exchange of a scalar meson is examined in the ladder model. We seek the behavior <if X as the squared momentum, (q + P)2, on one leg becomes infinite while the squared momentum, q 2, on the other leg remains fixed. This behavior is investigated by making a Wick rotation, expanding x in partial-wave amplitudes x}(q 2) of the group 0(4), and then looking for the rightmost poles of x}(q 2) in the complex J plane. Our results verify (in the ladder model) the useful hypothesis that the locations of these poles are independent of q 2 and can thus be computed in the q 2-+ oo limit by using conformal in variance.