Milagro Limits and HAWC Sensitivity for the Rate-Density of Evaporating Primordial Black Holes

TL;DR

This paper reports new upper limits on the rate of evaporating primordial black holes based on Milagro data and discusses HAWC's sensitivity to such events, advancing the search for these elusive objects.

Contribution

It provides the first constraints on PBH burst rate density from Milagro data and evaluates HAWC's potential for detecting PBH evaporation events.

Findings

Established new upper limits on PBH burst rate density.

Demonstrated HAWC's improved sensitivity to PBH evaporation.

Provided observational constraints relevant to early universe models.

Abstract

Primordial Black Holes (PBHs) are gravitationally collapsed objects that may have been created by density fluctuations in the early universe and could have arbitrarily small masses down to the Planck scale. Hawking showed that due to quantum effects, a black hole has a temperature inversely proportional to its mass and will emit all species of fundamental particles thermally. PBHs with initial masses of ~5.0 x 10^14 g should be expiring in the present epoch with bursts of high-energy particles, including gamma radiation in the GeV - TeV energy range. The Milagro high energy observatory, which operated from 2000 to 2008, is sensitive to the high end of the PBH evaporation gamma-ray spectrum. Due to its large field-of-view, more than 90% duty cycle and sensitivity up to 100 TeV gamma rays, the Milagro observatory is well suited to perform a search for PBH bursts. Based on a search on the Milagro data, we report new PBH burst rate density upper limits over a range of PBH observation times. In addition, we report the sensitivity of the Milagro successor, the High Altitude Water Cherenkov (HAWC) observatory, to PBH evaporation events.