Sling effect in AA-interactions and its implication for UHECR

Abstract

The 'Sling effect' appears when a fragment of a projectile nucleus emitted after a peripheral collision of the latter with a target nucleus is caused to rotate with a high spin. The spinning fragment has a deformed shape and looks like an oblate ellipsoid. Due to the virtual non-compressibility of nuclear matter and the polarization of the spin in the plane transverse to the input momentum of the projectile nucleus such an ellipsoid has a reduced mean interaction cross-section compared with a non-spinning fragment which has a spherical shape. Due to purely geometrical arguments, such an ellipsoidal nucleus should have additional fluctuations of the cross-section even at the fixed impact parameter dependent on the orientation angle between the axis of the ellipsoid and the vector connecting centers of projectile and target nucleus. The number of wounded nucleons in the projectile nucleus participating in the interaction correlates strongly with the interaction cross-section. All these reasons lead to a non-exponential attenuation of fragments and an increased probability of finding the fragment at a large depth in the absorber. If the sling effect appears in the interaction of a primary cosmic ray nucleus with nuclei in the atmosphere the induced atmospheric cascade will have a slower attenuation, and thereby can help to reduce some inconsistencies in the interpretation of the existing experimental data on extensive air showers, observed in the lower half of the atmosphere. It will also have an implication on the development of nucleus-induced cascades at ultra high energies.