Axionlike particles as ultrahigh energy cosmic rays? art. no. 096005

If ultrahigh energy cosmic rays (UHECRs) with E> 4 x 10(19) eV originate fr om BL Lacertae at cosmological distances as suggested by recent studies, th e absence of the GZK cutoff cannot be reconciled with standard-model partic le properties. Axions would escape the GZK cutoff, but even the coherent co nversion and back conversion between photons and axions in large-scale magn etic fields is not enough to produce the required flux. However, one may co nstruct models of other novel (pseudo)scalar neutral particles with propert ies that would allow for sufficient rates of particle production in the sou rce and shower production in the atmosphere to explain the observations. As an explicit example for such particles we consider SUSY models with light sgoldstinos.