Search for primordial black holes with SGARFACE

The short gamma-ray front air-cherenkov experiment (SGARFACE) uses the Whipple 10 m telescope to search for bursts of γ-rays. SGARFACE is sensitive to bursts with duration from a few ns to ∼20 μs and with γ-ray energy above 100 MeV. SGARFACE began operating in March 2003 and has collected 2.2 million events during an exposure time of 2267 h. A search for bursts of γ-rays from explosions of primordial black holes (PBH) was carried out. A Hagedorn-type PBH explosion is predicted to be visible within 60 pc of Earth. Background events were caused by cosmic rays and by atmospheric phenomena and their rejection was accomplished to a large extent using the time-resolved images. No unambiguous detection of bursts of γ-rays could be made as the remaining background events mimic the expected shape and time-development of bursts. Upper limits on the PBH explosion rate were derived from the SGARFACE data and are compared to previous and future experiments. We note that a future array of large wide-field air-Cherenkov telescopes equipped with a SGARFACE-like trigger would be able to operate background-free with a 20-30 times higher sensitivity for PBH explosions.