Ultrahigh energy cosmic rays: a window to post-inflationary reheating epoch of the universe?
Kuzmin, V. A.; Rubakov, V. A.
Yadernaya Fizika (1998), 61(6), 1122-1124
CODEN: IDFZA7; ISSN: 0044-0027. Russian.
The authors suggest the highest energy cosmic rays, E > EGZK, where EGZK .apprx. 5 .times. 1019 eV is the Griesen-Zatsepin-Kuzmin cut-off energy of the cosmic ray spectrum, may provide a unique window into the very early epoch of the Universe, namely that of reheating after inflation, provided these cosmic rays are due to decays of parent superheavy long-lived X particles. These particles may constitute a considerable fraction of cold dark matter in the Universe. It is argued that the unconventionally long lifetime of the superheavy particles, which should be in the range of 1010-1022 yr, might require novel particle physics mechanisms of their decays, such as instantons. A toy model illustrating the instanton scenario is proposed. Generic expected features of ultra-high energy extensive air showers in this scenario are similar to those of other top-down scenarios. However, some properties of the upper part of the cosmic ray spectrum make the instanton scenario distinguishable, at least in principle, from other ones.
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