Light nuclei solving the AUGER puzzles: the Cen-A imprint

Abstract

Ultra-high-energy cosmic rays' (UHECR) maps at 60 EeV have been found recently by the AUGER group to be spreading anisotropy signatures in the sky. The results have been interpreted as a manifestation of AGN sources ejecting protons at GZK (Greisen–Zatsepin–Kuzmin) edges, around or below 80 Mpc distances, mostly from Supergalactic (SG) plane. The result is surprising due to the lack of correlation with the much nearer Virgo cluster. Moreover, early GZK cutoff in the spectra may be better reconciled with light nuclei (than with protons). In addition, a large group (of nearly a dozen) of events cluster suspiciously along Cen-A. Finally, proton UHECR composition nature is in sharp disagreement with the earlier AUGER claim of a heavy nuclei dominance at 40 EeV, within 13 extreme events (ln A=2.6±0.6). Therefore, we interpret here the signals as mostly UHECR light nuclei (He, Be, B, C and O) ejected from nearest Cen-A, UHECR smeared by galactic magnetic fields, whose random vertical bending is overlapping with SG arm. The (possible) AUGER misunderstanding took place because of a rare coincidence between the SG plane (arm) and the smeared (randomized) signals from Cen-A, bent orthogonally to the galactic fields. Our derivation verifies the consistency of the random smearing angles for He, Be, B, C and O range, respectively, ≳2.7°–11° in reasonable agreement with the AUGER main group event around Cen-A. Only a few other rare events are spread elsewhere. The more collimated from Cen-A, the lighter (lnAHe⩽2). The more spread, the heavier (lnA⩾2). Consequently, Cen-A is probably one of the best candidate UHE neutrinos at tens–hundreds of PeVs. This solution may be tested soon by future (and may even have already been recorded) clustering around the Cen-A barycenter, events smeared by vertical galactic magnetic forces on the lightest nuclei.