English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Up to date, there is no consensus regarding the origin of ultra-high energycosmic rays (UHECR) beyond the Greisen--Zatsepin--Kuzmin (GZK) limit. In orderfor these UHECRs to reach the Earth, an extremely suppressed interactionbetween them and the cosmic microwave background (CMB) is required, which isimpossible for standard model (SM) particles, except neutrinos. In this letter,we present constraints on the parameter space of models involving axion-likeparticles and dark photons, as candidates for UHECRs, by assuming that theseparticles can traverse the visible Universe without decaying. In the case ofaxion-like particles, the constraints are tighter than those given in previousworks. We present for the first time constraints on the parameter space of darkphoton models, by considering their kinetic term mixing with SM photons.

Limits on beyond standard model messengers as ultra high energy cosmic rays