We investigate constraints on primordial black holes (PBHs) as dark matter candidates that arise from their capture by neutron stars (NSs). If a PBH is captured by a NS, the star is accreted onto the PBH and gets destroyed in a very short time. Thus, mere observations of NSs put limits on the abundance of PBHs. High DM densities and low velocities are required to constrain the fraction of PBHs in DM. Such conditions may be realized in the cores of globular clusters if the latter are of a primordial origin. Assuming that cores of globular clusters possess the DM densities exceeding several hundred $\mathrm{GeV}/{\mathrm{cm}}^3$ would imply that PBHs are excluded as comprising all of the dark matter in the mass range $3\times {10}^{18}\lesssim m_{\mathrm{BH}}\lesssim {10}^{24}\mathrm{g}$. At the DM density of $2\times {10}^3\mathrm{GeV}/{\mathrm{cm}}^3$ that has been found in simulations in the corresponding models, less than 5% of the DM may consist of PBH for these PBH masses.

• Received 13 May 2013

DOI:https://doi.org/10.1103/PhysRevD.87.123524