Particles are constantly appearing and annihilating, even in front of your face right now. It's called vacuum energy.

https://en.m.wikipedia.org/wiki/Vacuum_energy

>Vacuum energy can also be thought of in terms of virtual particles (also known as vacuum fluctuations) which are created and destroyed out of the vacuum. These particles are always created out of the vacuum in particle–antiparticle pairs, which in most cases shortly annihilate each other and disappear. However, these particles and antiparticles may interact with others before disappearing, a process which can be mapped using Feynman diagrams.

The process involving black holes is called hawking radiation.

https://en.m.wikipedia.org/wiki/Hawking_radiation