Constraining the Local Burst Rate Density of Primordial Black Holes with HAWC

TL;DR

This paper reports a search for primordial black hole bursts using HAWC data, setting the strongest limit to date on their local burst rate density in the gamma-ray energy range.

Contribution

The study provides the first all-sky search for PBH bursts with HAWC and establishes the most stringent electromagnetic constraint on their local burst rate density.

Findings

Excluded PBH burst rate density above 3400 pc^{-3} yr^{-1} at 99% confidence.

Utilized 959 days of HAWC data with high sensitivity to gamma rays in the GeV-TeV range.

Demonstrated HAWC's capability for all-sky PBH burst searches.

Abstract

Primordial Black Holes (PBHs) may have been created by density fluctuations in the early Universe and could be as massive as $> 10^9$ solar masses or as small as the Planck mass. It has been postulated that a black hole has a temperature inversely-proportional to its mass and will thermally emit all species of fundamental particles via Hawking Radiation. PBHs with initial masses of $\sim 5 \times 10^{14}$ g (approximately one gigaton) should be expiring today with bursts of high-energy gamma radiation in the GeV--TeV energy range. The High Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays with energies of $\sim$300 GeV to past 100 TeV, which corresponds to the high end of the PBH burst spectrum. With its large instantaneous field-of-view of $\sim 2$ sr and a duty cycle over 95%, the HAWC Observatory is well suited to perform an all-sky search for PBH bursts. We conducted a search using 959 days of HAWC data and exclude the local PBH burst rate density above $3400~\mathrm{pc^{-3}~yr^{-1}}$ at 99% confidence, the strongest limit on the local PBH burst rate density from any existing electromagnetic measurement.