Cosmic rays from primordial black holes in the Randall-Sundrum braneworld

Abstract

We present a method to probe the Randall‐Sundrum type‐2 (RS2) braneworld with the Hawking radiation of small, five‐dimensional primordial black holes (PBHs). There are three important effects originating from the nature of braneworld; (i) Slow expansion rate in the earliest radiation dominated era makes the mass spectrum of PBHs soft, (ii) but, at the same time, accretion of surrounding radiation fluid may occur and lead to relative enhancement of the PBH abundance, (iii) Moreover, the large extra dimension lowers the Hawking temperature of each hole and the spectra of emitted particles via Hawking radiation are drastically changed. Applying the above effects to two distinctive astrophysical observations, the diffuse X‐ray/γ‐ray background and the cosmic‐ray antiproton in sub‐GeV region, we constrain the PBH abundance and/or braneworld parameters such as the size of the extra dimension and the efficiency of accretion.