Lightest and heaviest nuclei as keys to the origin of ultrahigh energy cosmic rays
Abstract
The origin of ultrahigh energy cosmic rays (UHECRs) has been a long-standing mystery. A unique feature of UHECRs originating in binary neutron star mergers (BNSMs) is two distinct populations of light elements -- those directly accelerated in the jets, and photo-disintegration products of massive nuclei accelerated in the bulk outflow. We show that Pierre Auger Observatory spectrum and composition data confirm the existence of the predicted two populations at ≥ 7.2σ significance, having rigidity (R≡ E/Ze) cutoffs agreeing with prior estimates. The data also favor 5-10% of UHECRs originating as r-process nuclei, a signature of a BNSM origin. Our results provide strong evidence that UHECRs are produced by merging neutron stars, and show how UHECRs and UHE-neutrinos elucidate otherwise inaccessible aspects of neutron star mergers.
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BibTeX
@misc{suliga2026lightest,
title = {{Lightest and heaviest nuclei as keys to the origin of ultrahigh energy cosmic rays}},
author = {Anna M. Suliga and Glennys R. Farrar},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.00205},
eprint = {2611.00205},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.00205},
}
RIS
TY - UNPB
TI - Lightest and heaviest nuclei as keys to the origin of ultrahigh energy cosmic rays
AU - Anna M. Suliga
AU - Glennys R. Farrar
PY - 2026
DA - 2026/11/01
PB - arXiv
DO - 10.48550/arxiv.2611.00205
UR - https://arxiv.org/abs/2611.00205
AB - The origin of ultrahigh energy cosmic rays (UHECRs) has been a long-standing mystery. A unique feature of UHECRs originating in binary neutron star mergers (BNSMs) is two distinct populations of light elements -- those directly accelerated in the jets, and photo-disintegration products of massive nuclei accelerated in the bulk outflow. We show that Pierre Auger Observatory spectrum and composition data confirm the existence of the predicted two populations at ≥ 7.2σ significance, having rigidity (R≡ E/Ze) cutoffs agreeing with prior estimates. The data also favor 5-10% of UHECRs originating as r-process nuclei, a signature of a BNSM origin. Our results provide strong evidence that UHECRs are produced by merging neutron stars, and show how UHECRs and UHE-neutrinos elucidate otherwise inaccessible aspects of neutron star mergers.
ER -