"Buddha's Light" of Cumulative Particles

Abstract

We show analytically that in the cumulative particles production off nuclei multiple interactions lead to a glory-like backward focusing effect. Employing the small phase space method we arrived at a characteristic angular dependence of the production cross section $d\sigma \sim 1/ \sqrt {\pi - \theta}$ near the strictly backward direction. This effect takes place for any number $n\geq 3 $ of interactions of rescattered particle, either elastic or inelastic (with resonance excitations in intermediate states), when the final particle is produced near corresponding kinematical boundary. Such a behaviour of the cross section near the backward direction is in qualitative agreement with some of available data. Explanation of this effect and the angular dependence of the cross section near $\theta \sim \pi$ are presented for the first time.