Are bound states of color-excited leptons responsible for anomalouse + e ? production in heavy ion collisions?

Abstract

A model for the anomalouse+e− production in heavy ion collisions is proposed. The model is based on the hypothesis thate+e− production derives from the decay of “leptopions,” pionlike bound states of colored excitations ofe+ ande−. Order-of-magnitude estimates for the mass scale of the radial excitations and lifetime of the leptopion obtained by extrapolation from the case of the ordinary pion are in accordance with data. The model for leptopion production is based on the electromagnetic anomaly term. In the classical treatment of the nucleus-nucleus collision the leptopion production amplitude is essentially the Fourier transform of the scalar product of the electric field of the stationary target nucleus and the magnetic field of the colliding nucleus. The production amplitude becomes singular for certain values of the kinematical variables and in singularity the velocity of the leptopion is a definite function of the production angle measured with respect to the direction of the collision velocity. Due to the weak dependence of the velocity of the production angle in the forward direction the leptopions are apparently produced at rest in center-of-mass coordinates in accordance with the data. The observed peak ofe+e− production amplitude (in fact two peaks in some cases) is explained as a quantum diffraction effect resulting from the finite size of the colliding nuclei, when the collision velocity exceeds the velocity needed to overcome the Coulomb barrier. The production amplitude oscillates as a function of collision velocity and the period of oscillation is in accordance with the width of the observed velocity peak. In principle, several diffraction peaks are possible for elastic collisions in a plane, but the effects of strong interactions are expected to lead to the disappearence of the peaks at velocities larger than that needed to overcome the Coulomb barrier. An explanation for the unobservability of lepton color via strong interactions is proposed.