Is Cen A surrounded by tens-EeV UHECR multiplet?

Abstract

Ultra High Energy Cosmic Rays (UHECR) at GZK cut off energy (E≥5.5⋅1019eV) may keep sharp or diffused directionality wherever their composition is made by nucleon or light nuclei. Auger experiment UHECR (2007–2010) did show a mild clustering around Cen A. Two over three of the recently discovered AUGER multiplet (a dozen of events each) tails clustering at twenty EeV are pointing to primary sources very near the same UHECR crowded Cen A region. These twin tens-EeV UHECR tail is aligned with the same UHECR events. We foresaw such a possibility as fragment tails of lightest UHECR nuclei. We discuss the relevance of this correlation within a model where UHECR clustering along extragalactic Cen A are mostly lightest He like nuclei. UHECR fragment multiplet clustering aligned along higher Cen A events (above 5.5⋅1019 eV energy) probe and reinforce our interpretation with an a priori probability to occur below 3⋅10−5.