Second dip as a signature of ultrahigh energy proton interactions with cosmic microwave background radiation.
We discuss as a new signature for the interaction of extragalactic ultrahigh energy protons with cosmic microwave background radiation a spectral feature located at E= 6.3 x 10(19) eV in the form of a narrow and shallow dip. It is produced by the interference of e+e(-)-pair and pion production. We show that this dip and, in particular, its position are almost model-independent. Its observation by future ultrahigh energy cosmic ray detectors may give the conclusive confirmation that an observed steepening of the spectrum is caused by the Greisen-Zatsepin-Kuzmin effect.
Berezinsky
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V
INFN, Laboratori Nazionali del Gran Sasso, I-67010 Assergi (AQ), Italy.
Gazizov
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A
Kachelrieb
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M